Elasmobranchs Flashcards
Describe the unique structure of elasmobranch skin.
What type of scales do they have?
How does skin thickness vary with species?
What about rays? What about Chimaeras?
What defensive mchanisms do they have in the integumentary system?
What sensory organs do they have within their skin?
Integument
- Placoid scales (aka dermal denticles) - formed like teeth (calcified layer, dentin, enamel)
- Silk sharks - denticles minute (softer skin); Blue sharks - females have sig. thicker skin d/t mating trauma
- Many rays have few to no scales - tend to have sig. mucus layer
- Porcupine rays and some others - “armor” on dorsum
- Many batoids, some sharks - sharp spines; venomous spine or barb in most rays (except mantas, mobulas, porcupine rays); can have more than one barb
- Barbs covered by integument including cells for venom production
- Chimaeras - scaleless (except juveniles), very sensitive to skin trauma
- Visible, symmetrical epithelial pores
- Pit organs - free neuromasts; sensory hair cells detect water motion
- Ampullae of Lorenzini - gel-filled tubular structures, detect electric fields for navigation, prey/predator detection, mating
Describe the unique adaptations of the elasmobranch muculoskeletal system.
How does their skeleton differ from other vertebrates?
Describe the feeding mechanisms.
What sharks have red muscle? What is its function?
Musculoskeletal System
- Entire endoskeleton cartilaginous - made of hyaline cartilage-like core supported by mineralized tesserae
- Bone exists - teeth, denticles
- Calcification can occur in vertebrae, jaws; true bone not present
- Centrum of vertebral cartilage can be used for aging
- If cartilage fractures - does not heal fully, fibrous “bandage”
- Prey capture - biting, ram feeding and/or suction feeding
- Permanent jaw protrusion assoc. w/ spinal deformity in sand tiger sharks
- Muscle similar to teleosts (red, white) - most poikilothermic but regional endothermy in some lamniform sharks (mako, white, salmon, porbeagle, thresher sharks)
How do elasmobranchs regulate their buoyancy?
Buoyancy
- Buoyancy d/t cartilaginous skeleton, large lipid-dense liver, urea and methylamine oxides in blood
- No cartilaginous fish have swim (gas) bladders; sand tiger sharks swallow air for additional buoyancy
Describe the anatomy of the elasmobranch eye.
What species have mobile eyes?
Describe the ray iris?
How does the PLR differ across species?
How do sharks adjust their tapetum?
What makes enucleation more challenging in elasmobranchs than in teleosts?
What species have the pinneal eye?
Ocular Anatomy
- Diverse eye anatomy - typically fixed eyelids (mobile in some - nurse and catsharks) - is blink reflex
- 3rd eyelid in some (requiem sharks)
- Pupil type and shape characterizing features in some
- Rays - upper iris modified into operculum pupillare covers iris during light adaptation
- PLR highly variable - diurnal –> rapid constriction, nocturnal –> intermediate, batoids –> slowest
- Dilation can be achieved w/ topical acetylcholine
- Sclera - thick w/ cartilaginous layer; Cornea - same layers as other vertebrates
- Many sharks - partially or totally occlusible tapetum - melanophores can migrate (some have fixed tapetum - catsharks, deep-sea sharks)
- Avascular retina, no choroid gland
- Many can pull globe into socket w/ extraocular muscles
- Optic pedicle - cartilaginous structure - connects globe to cranium
- D/t scleral cartilage, optic pedicle and size of optic nerve/vessels/muscles - enucleation more challenging
- Pineal organ/eye (epiphysis) well-developed in most (except absent in electric rays)
- Photoreceptors superficial on dorsal chondrocranium
Describe the auditory anatomy of sharks?
Auditory Anatomy
- Ears similar to other vertebrates
- Located in cartilaginous otic capsules caudal to large optic capsules; only external indication of position is tiny paired endolymphatic pores on dorsal chondrocranium near medial line
- Each ear - inner ear labyrinth (utriculus, sacculus, lagena) - none of accessory organs seen in teleosts
- W/in endolymphatic duct - no otolith, instead otoconial paste of CaCO3 granules in gel functioning like otoliths in teleosts
- Patches of sensory epithelium (macula neglecta) - vibration detection
- Audiograms - freq. 50-1500 Hz, greatest sensitivity 400-600 Hz (may be sensitive to pump/filters noise)
Describe the olfactory and gustatory anatomy of elasmobranchs?
What portion of the brain is well developed in elasmobranchs for these senses.
Elasmobranchs use olfaction for hunting at what range?
What leads sharks to predation when they are otherwise well fed in aquaria?
Olfactory and Gustatory Anatomy
- Olfactory bulbs w/in rostrum, part of forebrain (telencephalon) - well-developed
- Bulbs detect amino acids, bile salts, pheromones
- Nares (endolymphatic pores) possible entry route for development of meningitis
- Taste buds in oropharyngeal cavity
- Olfaction - used for feeding w/in 3-15 m, vision more important at closer range (<3 m)
- One study showed sharks become conditioned to the odors from normal, healthy fish
- Fish have different odors when frightened, stressed, or excited - can stimulate predation
Describe the dentition of elasmobranchs.
How are their teeth replaced?
How are their teeth attaches?
How often are they replaced?
What is the function of the denticles in the back of some species pharynx.
Oral/Pharyngeal Cavity
- Teeth or dental plates dictated by feeding strategy
- Teeth/plates erupt, roll out continuously w/ Cd.-most gradually replacing front (polyphyodont dentition)
- Lyodont teeth - embedded in oral mucosa, not ankylosed to jaw); have dentine and enameloid
- Tooth replacement rate varies by spp., 8-10 days per row up to 5 weeks per row
- If they typically eat hard-bodied prey (i.e. crustaceans, etc) - overgrowth of plates can occur
- Gingival hyperplasia and neoplasia described in sand tigers
- Denticles - pharynx of most sharks (except carpet sharks) and some others (guitarfish)
- May decrease drag for ram ventilators, prevent trauma, improve predation success
Describe the GI anatomy of elasmobranchs.
What is the function of the spiral valve?
What species have pyloric cecae?
What is the function of the rectal gland?
What are the cloacal pores used for?
Gastrointestinal System
- GI tract short, simple - slightly S- or J-shaped tube
- Ileum includes spiral or valvular intestine - sig. increases surface area (colloquially spiral colon - not technically colonic though)
- 4 variations - spiral winding around central column, cones directed Cd. or Cr., and scroll-shaped
- Empties into short tube (colon/rectum)
- A few have pyloric cecum or ceca (deepwater dogfish)
- Rectal gland - unique intestinal appendage - Cd. to valvular intestine @ colon/rectum
- Osmoregulatory function, secretes Na/Cl rich fluid (~2x plasma concentration) in contrast to urine (not concentrated)
- Sig. reduced in FW elasmobranchs
- Bilateral coelomic (abdominal) pores in cloaca - suspect excretory function (also catheter access point)
Describe the liver of elasmobranchs.
What does a healthy versus an unhealthy liver look like?
What is the hepatosomatic index?
Liver and Gallbladder
- Liver - 1º lipid storage organ, helps maintain neutral buoyancy
- Large volume of lipid must be stored, size and density critical in maintaining position in water column
- Major indicator of general health/caloric intake; size can fluctuate w/ age and repro cycle
- Hepatosomatic index (HIS) - ratio of liver wt to body wt ID’d for many species
- Grossly should be tan, fill a large portion of coelom and float in formalin
- Gallbladder - dynamic in appearance
Describe the respiratory anatomy of elasmobranchs.
How many gill arches do they typically have?
What is the spiracle? What species is it well developed in?
What are the two modes of respiration for sharks?
Respiratory System
- Usually 5 gill arches, may be up to 7 - hemibranch cranially (one filament row) and holobranchs for remaining (2 filament rows)
- Interbranchial septum extends to form gill slits on external surface
- Cranial most gill slit modified to spiracle in some spp.; well developed in skates, rays, slow-moving sharks and absent in pelagic sharks
- Damage to gills affects gas exchange and other physiology; in SW spp. gills have important role in acid-base balance and in FW spp. important salt regulation
- Critical for urea retention, esp. some species (spiny dogfish)
- Oral cavity - orobranchial and parabranchial cavities
- If buccopharyngeal pumping - double pumping action delivering oxygenated water through mouth or spiracles to gills
- In ram-ventilating species - mandibular muscles control opening of mouth
Describe the cardiovascular system of elasmobranchs.
What is the relationship between the percardium and the coelom?
What are the the four parts of the elasmobranch heart?
What is the function of the second vascular system?
Cardiovascular System
- Heart in rigid pericardial chamber w/ large volume pericardial fluid
- Pericardial lumen communicates w/ coelomic cavity via pericardiocoelomic canal (usually closed unless pericardal pressure exceeds coelomic cavity)
- Pericardial cavity fluid reported to be different from plasma, coelomic fluid
- Heart - sinus venosus, atrium, ventricle, conus arteriosus (similar to bulbus arteriosus)
- Sinus venosus - thin walled, very compliant
- Atrium - flaccid, larger volume than ventricle
- Ventricle - thickest myocardial tissue
- Conus arteriosus - tubular and thick w/ prominent valvular structures
- Often synchrony b/w respiratory and cardiac beat - inconsistent, no obvious clinical consequence
- ECG similar to other vertebrates except V-wave (depolarization of sinus venosus) prior to PQRS
- Secondary vascular system (SVS) w/ different blood values than 1º system
What are the lymphoid tissues of sharks?
Where are they located?
Hematopoietic and Immunologic System
- Tissues include epigonal organ, Leydig organ, thymus, meninges of brain, eye orbit, spleen, gut-associated lymphoid tissue (GALT)
- Epigonal organ - physically associated w/ gonads; in some spp. enclosed w/in epigonal organ (common guitarfish, dogfish) or may be attached (stingrays)
- Generally if prominent epigonal organ 🡪 Leydig organ is unapparent or absent
- Leydig organ - in some spp., (not Leydig organ involved in sperm maturation) - sometimes ID by lighter-colored area w/in dorsal (occasionally ventral) submucosa of esophagus (may be raised)
- Spp. - skates, some rays, guitarfish, some shark species (velvet belly lanternshark)
- All have bilateral thymus - dorsal near gills
- Some species (catsharks, nurse sharks) - involution with age
- Others (bullhead sharks, some rays) - remains visible/small through life
- Spleen - dark red, strap-like to oval; lacks marginal zones and germinal centers (like in mammals) - likely b/c no true lymphatic system
- Melanomacrophages in spleen, liver - do not aggregate like in teleosts
Describe the endocrine anatomy of elasmobranchs.
What is the function of the interrenal gland? Where is it located?
Where is the thyroid location?
What is the function of the ultimobranchial bodies? Where are they located?
Endocrine System
- Complex, but organs, stimuli and targets of action similar to other vertebrates
- Pituitary similar to teleosts, slight anatomical variations
- Hypothalamus (w/in diencephalon) well-developed, important for feeding, reproduction, aggression, likely migration
- Interrenal gland (equiv. of adrenal cortex) - grossly visible 🡪 section of yellow b/w each kidney (long thin strip in sharks, smaller oval in skates/rays)
- Chromaffin cells of suprarenal bodies separate, located on dorsal kidneys near dorsal aorta
- Hypothalamo-pituitary-interrenal axis considered endocrine stress axis - not fully characterized
- Single thyroid gland - encapsulated, varies in size/shape
- Batoids - usually ventral to pharynx, near bifurcation of ventral aorta
- Sharks - under commissure of mandible
- Ultimobranchial bodies - produce calcitonin (similar to mammal parathyroid system) - actions of calcitonin in cartilaginous fish less well-understood
- Batoids - paired, found in caudal wall pericardial cavity
- Sharks - only L side of body on dorsal wall of pericardial cavity
- Pancreas (bilobed) and GI tract - produce expected hormone; detail on function and activity limited
- Heart and kidney also produce several natriuretic peptides - have renin-angiotensin system (regulates renal and cardiovascular systems)
- Pineal organ and gonads also have endocrine function
Describe the renal anatomy of elasmobranchs.
Where are the kidneys located?
Describe the flow of urine from the kidney to the urogenital pore?
How can you collect a urine sample?
Urinary System
- Manages osmotic and ionic regulation
- Marine elasmobranchs - maintain high plasma osmolality d/t high Na, Cl, urea, methylamine oxides
- Slightly hyperosmotic 🡪 uptake of water to balance fluid lost in urine
- Drinking negligible (unlike marine teleosts)
- Gills, kidney, rectal gland important for maintaining homeostasis
- Kidney primary urea regulator
- FW elasmobranchs - urea, electrolytes, osmolality much lower
- Kidneys microscopically similar
- Rectal gland significantly reduced
- Kidneys - paired, firmly attached to dorsal wall
- Sharks - midway in coelomic cavity, widen caudally
- Skates, rays - more caudal in coelomic cavity, more lobulated
- Males - ureters leave kidneys medially 🡪 midline 🡪 seminal vesicles 🡪 sperm sacs 🡪 exit through single (sometimes double) urogenital pore/papilla
- Small urine sample - catheter past repro tract; large volume not possible d/t low production
- Semen sample can be collected more distally
- In SW - unable to produce concentrated urine - ionic conc. cannot be higher than that of plasma
- GFRs 0.2-4.0 mL/kg/h - higher than SW teleosts but similar to FW teleosts
- In dilute enviro 🡪 increased urine flow 🡪 decreased urea absorption
- FW stingray have GFR of 8-10 mL/kg/h
Describe the reproductive anatomy of elasmobranchs.
Where does sperm storage occur in males and females?
Describe the flow of sperm in males.
Describe the sections of the oviduct.
Describe the uterine anatomy and function.
Reproductive System
- Diverse anatomy and biology - mode generally split by oviparity or viviparity and fetal nutrition
- Synchrony (seasonal aggregation) important in some species
- Gestation 4.5 months to 2 years (up to 3.5 yr if egg cases included)
- Embryonic diapause confirmed in 3 species (Australian sharpnose sharks, common stingrays, bluntnose stingrays) but may be more common
- Parthenogenesis in many species; polyandry (multiple paternity) also occurs
- Sperm storage in males (ampullae of distal epididymis; weeks to months) and females (oviductal gland; weeks to over a year)
- Fertilization internal in all elasmobranchs; all males have external claspers (part of pelvic fins)
- Tend to increase in size and internally calcify; able to rotate
- Internal paired organs - testes (diametric, radial, compound); genital ducts; Leydig glands (produce sperm maturation substances); alkaline glands (Marshall’s glands - in skates - seminal fluid)
- Genital ducts (efferent ductules, epididymis, ductus deferens, seminal vesicle) - embedded in dorsal abdominal wall
- Epigonal organs can embed testis, incorporate caudal end, or be separate
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Copulation - sperm ejaculate 🡪 urogenital papilla(e) 🡪dorsal groove of clasper
- Batoids - clasper glands w/ many proposed functions
- Sharks - subdermal siphon sacs - either for sperm propulsion or to wash rival sperm out (can be prominent on ultrasound)
- Surgical amputation of claspers when necessary - may not impact repro capacity
- Ovaries - typically paired, may be single (left is dominant in batoids, right in viviparous sharks)
- Developing follicles of various sizes, follicles undergoing atresia, corpora lutea-like tissue
- Can be within or separate from epigonal organ
- Oviduct - differentiated into an ostium (receives the ovum), oviducal (nidamental or shell) gland, isthmus (some spp.), leads to uterus, cervix, common urogenital sinus
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Uterus - single (typ. L side) or paired
- In oviparous - uterus hardens egg capsules and hold until oviposition
- Yolk-sac viviparous - uterus creates intrauterine milieu - supplying O2, water, nutrient to embryo and regulates wastes
- Uterine wall vascular, folded
- Stingrays - secretory cells w/in uterine trophonemata (large villous projections) - produce histotroph
- All placental species have limited histotrophic stage after absorption of yok sac before placental implantation where uterus provides nutrients (complex subject)
Elasmobranchs have many reproductive strategies.
Describe the various strategies and give some example species of each.
Describe the neuroanatomy of elasmobranchs.
What are the parts of their brain?
What is unique about the cerebellum of several species?
How does their blood brain barrier differ from other vertebrates?
Neurologic System
- Cranium encloses brain, olfactory bulbs, optic and otic organs
- Telencephalon (forebrain), diencephalon (epithalamus, thalamus, hypothalamus), mesencephalon (cerebellar body and auricles, medulla)
- Brains vary widely in shape and size; some have obvious asymmetry w/in cerebellum (rays, requiem sharks, hammerhead sharks)
- Notable on gross examination, not think pathologic on necropsy
- Cranial nerves similar
- Choroid plexus forms cerebrospinal fluid (CSF) - large space rostral to brain where can collect
- Electrolyte composition of CSF and plasma differs, independent regulation
- Blood-brain barrier differs from other verts - endothelium permeable but tight junctions b/w glial cells
Describe the generation of electricity in electric (torpedo) rays and skates.
Electric Organs
- Electric (torpedo) rays - large electric organs (electroplaques) on either side of gill arches - derived from branchial musculature - moderate electric discharges
- Skates - weak electric discharges from small bilateral electric organs in tail
- Both can have intermittent and focused discharges; coordination of discharge originates in medulla
- Relatively low amplitude 20-40 mV in skates vs. 30-60 V from electric rays
What is the order of Chimaeras?
What fish are in this group?
Describe their unique anatomy.
What is a concern with their eyes in managed care?
Chimaeriformes (Chimaeras, Ratfish, Ghost sharks)
- Cartilaginous skeleton but upper jaw has grinding tooth plates fused to cranium
- One gill opening, lack spiracle except as embryos; eyes cannot regulate light going onto retina - exposure to bright lights a concernà “bloody eye”, handling induced damage to pseudobranchial artery
- Scaleless except for denticles over pelvic claspers and tenaculum; dorsal spine venomous
- Lack stomach, ribs, epigonal organ, Leydig organ; there is spiral intestine and rectal gland
- Separate anal and urogenital openings; male have claspers and fertilization is internal
What order are the ground sharks in?
What groups are in this order?
What are the defining anatomic features?
Carcharhiniformes (Ground Sharks)
- Largest order of sharks, 2 dorsal fins in most, anal fin, 5 gill slits, 3rd eyelid, mouth extends behind eyes
- Oviparous, ovoviviparous, or viviparous
- Includes requiem, catsharks, hound, hammerhead and bonnethead sharks
- Requiem sharks look like “typical” sharks - internal nictitans and spiracles absent; scroll intestine valve
- Catsharks have rudimentary nictitans, small spiracles, spiral valve
- Hound sharks - spiracles, spiral valve
- Hammerhead/bonnetheads - lateral extension to head (cephalofoil) w/ eyes on lateral aspects; spiracles absent, have spiral valve
What order are mackerel sharks, white sharks, and sand tigers in?
What are the defining anatomic features of this group?
Lamniformes (Mackerel sharks, White sharks, Sand Tigers)
- 2 dorsal fins and an anal fin; 5 gill slits - broad and extend beyond base of pectoral fin
- Sand tiger sharks differ - gills in front of pectoral fin
- Spiracles present behind eyes but are small; eyes lack a nictitating membrane
- Mouth extends behind eyes; ring-type spiral intestine
- Practice of oophagy or adelphotrophy (uterine cannibalism); some practice endothermy
What order are dogfish adn gulper sharks in?
What are the defining anatomic features of this group?
Squaliformes (Dogfish, Gulper sharks)
- Two dorsal fins, may have spines; anal fins absent; 5 gill slits and spiracles present
- Small nictitating membrane in lower lid
What order are carpet sharks, bamboo sharks, and nurse sharks in?
What is the largest shark of this group?
What are teh defining anatomic features of this group?
Orectolobiformes (Carpet sharks, Wobbegongs, Bamboo sharks, Nurse sharks)
- 2 dorsal fins and an anal fin, 5 gill slits w/ spiracles close to eyes; no nictitating membrane, eyes dorsolateral; most have prominent nasoral grooves w/ barbels
- Wobbegong - dorsoventrally flattened head/body, rostral mouths, fang-like teeth
- Also includes whale sharks
What order are skates in?
What are the defining anatomic features of this group?
- Rajiformes (Skates)*
- Skates - dorsoventrally compressed w/ enlarged pectoral fins continuous with their heads; caudal fin and no anal fins; some have dorsal fins; tail has no barbs, oviparous; skin freq. has thorns and some have weak electric organs
What is the order most rays are in?
What are the families of the following commonly kept rays: eagle rays, cownose rays, manta rays, southern rays, river stingrays, whiptail stingrays?
What are the defining anatomic features of this group?
Myliobatiformes (Cownose rays, Stingrays, Manta rays)
- Typical stingrays - dorsoventral compression w/ enlarged pectoral fins continuous w/ head
- 5 gill openings ventral; eyes and spiracles on dorsal surface - water pulled in through spiracles for respiration - jaws protrusible and do not articular w/ neurocranium
- No nictitating membrane, cornea attaches directly to skin; cranial vertebrae fused w/ pectoral girdle (synarcual), no anal fin, most have one or more venomous spines
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Aetobatidae, Myliobatidae, Mobulidae, Rhinopteridae - eagle rays, mobulids, cownose rays - small dorsal fin at base of tail, head elevated, eyes and spiracles lateral on head; tooth-plates made up six-sided teeth in horizontal arrangement; capable of leaping into air. Mobulids have cephalic lobes - cranial extensions of pectoral fins to assist in feeding
- Have gill rakers, mobulids lack venomous barbs
- Dasyatidae - whiptail stingrays - inhabit FW and SW habitats; long, slender tail
- Potamotrygonidae - river stingrays - all FW species, reduced rectal gland, venom more potent
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Aetobatidae, Myliobatidae, Mobulidae, Rhinopteridae - eagle rays, mobulids, cownose rays - small dorsal fin at base of tail, head elevated, eyes and spiracles lateral on head; tooth-plates made up six-sided teeth in horizontal arrangement; capable of leaping into air. Mobulids have cephalic lobes - cranial extensions of pectoral fins to assist in feeding
What order are electric rays in?
What are the defining anatomic features of this group?
Torpeniniformes (Electric rays)
- Strong electric organs derived from branchial musculature; dorsoventrally flattened w/ rounded pectoral fins; slow-moving and do not use pectoral wings much for locomotion
- Skin is soft, no denticles or thorns - eyes very small; well-developed caudal fin
What order are guitarfish and sawfish in?
What is their anatomy like?
Pristiformes (Guitarfish, Sawfish)
- Guitarfish - stout tail, with two dorsal fins, caudal fin w/out a barb
- Bowmouth guitarfish - similar but tail bilobed and rostrum unique
- Sawfish - carpenter sharks - rostrum shaped like flat blade, non-replaceable “teeth” (modified dermal denticles)
- Mouth and nares ventral, oral dentition varies but teeth mostly blunt-edged “cobblestones” in rows; prominent spiracles, no anal fins
Touch pools are common in aquariums.
What are some important considerations to make in planning one of these exhibits?
What species work best? How can stress be reduced?
On a water quality basis, how do touch pools differ from display exhibits?
What contingency planning needs to be in place for these systems?
How should they be monitored?
Fowler 9, Chap 48: Touch-Pools: The Other Side of the Hand
- Touch-pools provide unique immersive experience for guests to interact with collection
- Should be designed to enhance welfare, minimize stressors, while balancing good guest experience
Setting Goals- before design starts to guide habitat plans/species selection- animal welfare, education, conservation
- Animal health/welfare standards compliant with AZA
- Track morbidity/mortality and compare to display only exhibits
- Long-term sustainable population plan
- Meet guest needs and promote conservation discussion
Species Selection - determine early to help optimize habitat, within framework of goals that were set
- Meeting quarantine and environmental needs for all species, management if they outgrow habitat
- Ease of monitoring individual health, mitigating morbidity and mortality, expected lifespan and breeding activity
- Time on exhibit, desired behaviors for exhibit, rotating animals in and out
- Ideal species- stable populations with little turnover- ELASMOBRANCHS (may outgrow), invertebrates > teleosts
- Determine training/enrichment plan early on (desensitize to touch, target feeding, husbandry behaviors
Planning - all groups involved in building and managing should be involved in planning, allow additional time for training
- Requires more space, should provide refugia, use suitable substrate/décor for target species
- Allow interpreters to access animals and be seen by guests, use a cue if entering habitat itself
- Life support system larger/more complex- increased contaminants- high water turnover, biofilter accommodating peak attendance, good foam fractionation (saltwater), UV light + Ozone (monitor nitrate, iodate, iodide)
- Regular period of full darkness, maintain appropriate temperature despite fluctuations in attendance/season
- Off-exhibit holding area improves health/welfare- close to touch-tank to minimize transport time, same water system
- Hand-washing/drying stations- low zoonotic risk, some guests may be immunocompromised, 30-60% compliance
- Contingency planning: human fluid contamination, human injury, zoonotic concerns, life support failure, morbidity/mortality, animal abnormality, welfare concerns
Monitoring- more closely tracked than display-only habitats
- Assess water quality parameters regularly- expect fluctuations in DO2, NH4, temp- include bacterial counts
- Review feeding/behavior records regularly to address health concerns as needed
- Routine exams, routine trimming of stingray barbs
- Ensure collection in touch-pools is doing as well as display-only collection
- 2-3 years to find optimal balance of animal health, life-support systems, guest dynamics
- Extensive training for staff- natural history, conservation/education goals, common questions, animal touch rules
- Positive reinforcement for appropriate guest behavior
- Evaluate guest metrics
What is the most common nutrient deficiency in elasmobranchs? What does this result in?
Describe the role of calcium in elasmobranch health. How are those needs typically met?
What vitamin and mineral deficiencies have been suggested as possible causes of spinal deformities in sand tiger sharks? How did healthy v affected animals differ? What is the proposed mechanism?
What B vitamin is commonly supplemented in elasmobranchs? Why?
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Most common mineral deficiency in elasmobranchs = Iodine.
- Results in goiter.
- Oral supplementation is recommended in systems where levels are below natural seawater and nitrate > 10 mg/L. Commercially available supplementation tablets for elasmobranchs will meet these requirements.
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Ca and P major roles in growth and development of bone, teeth, cartilage, muscle contraction, and blood clotting in teleosts.
- Ca:P ratio in diet should be 1:1 or 2:1.
- Inverted ratios lead to skeletal malformations, poor growth and muscle disorders.
- Dietary Ca minimal contribution to daily requirements in teleosts, as fish have access to ionic Ca in sea water.
- Diets including whole bony fishes generally meet min Ca:P ratio.
- Consider supplementing Ca if feeding chopped fish.
- Ca:P ratio in diet should be 1:1 or 2:1.
- Vitamins
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Nutritional deficiency in Vit C and Zn has been suggested as causative of spinal deformities in sand tiger sharks.
- Health animals higher K, vit C, vit E, and Zn vs affected. Small sample size in that study.
- Vit C and Zn are cofacts involved in collagen synthesis and cartilage development across taxa.
- While teleosts cannot synthesize vit C and require it in the diet, some research shows elasmobranchs may be able to synthesize it in the kidneys. Vit C can be supplemented.
- Vit E declines over time through storage of fish. Elasmobranchs fed thawed fish are susceptible to deficiencies.
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Nutritional deficiency in Vit C and Zn has been suggested as causative of spinal deformities in sand tiger sharks.
- Thiamin (B1) – Integral for carbohydrate metabolism, digestion, growth, fertility, neuro function in fish.
- Thiaminases found in certain fish and shellfish, render thiamin inactive when ingested.
- Thiamin can also be lost by holding diet items too long in storage.
- Wet or frozen diets risk thiamin deficiency.
- Supplement thiamin when feeding frozen thawed fishes and shellfish.
- CS of deficiency – Neuro symptoms, muscle spasms, spinning, jerky movements.
- Supplementation is recommended.
- Vit D and D essential for teleosts, probably also for elasmobranchs.
- Potential accumulation in liver and adipose when over supplemented.
- Excess vit A causes slow growth, anemia, abnormal vertebral growth and mortality.
- Vit A and D likely met in aquarium elasmos that consume whole fatty fish.
- Mollusks, crabs, crustaceans generally low in fat-soluble vitamins.
- Nutrient values in elasmobranch blood:
- Plasma Vit A largely influenced by diet or level of supplementation.
- Plasma or serum vit A (retinol) good indicators of status.
- Plasma vit E (a-tocopherol) may be directly related to diet or level fo supplementation. Variable based on spp.
- Serum Ca generally only changes with prolonged deprivation or pathology. Plasma or serum P are a good determinant of phosphorus status.
- Plasma/serum Mg reflective of dietary status, K may not be.
- At minimum – Supplementation with I, thiamin (B1) is recommended for elasmobranchs. Ca, Zn, Mn, vit C, vit A, and other nutrients can be considered.
- Plasma Vit A largely influenced by diet or level of supplementation.
What are some unique considerations for planning the quarantine of elasmobranchs?
How does tank shape affect them?
How does ozone affect them? Is this an issue with a typically short quarantine period?
How can you encourage them to eat?
Describe a quarantine exit exam and potential diagnostics that might be run.
Quarantine Planning:
- Elasmobranch systems need appropriate space for normal swimming, gliding, and turning.
- Large oval tanks are preferred.
- Jump barriers should be regularly inspected.
-
Ozone and/or UV disinfection can reduce pathogen burdens.
- Goitrogenic effects of ozone use and high nitrates are unlikely to be an issue in short term quarantine periods, supplement diet with iodide anyway.
-
Techniques for encouraging food intake:
- Offer variety of foods – fish, crustaceans, mollusks, cephalopods.
- Offer fresh rather than frozen.
- Add fish blood to water prior to feeding.
- Crushing or cutting stripes into food prior to feeding.
- Using rod, grabber, or line to move food in water.
- Offer live foods that clear quarantine.
- Feed at different times to match feeding times in wild or previous institution.
- Avoid aversive stimuli i.e. loud noises, people leaning over aquarium.
- Isolate animals in suitable systems or parts of the system to reduce competition for food.
Physical Exams – Quarantine:
- Endoscopic or laryngoscopic examination of buccal and branchial cavities can help ID parasites.
- Determine sexual maturity and BCS.
- Morphometrics – Body mass BM, total length TL, precaudal length, snout-to-vent length and/or disc width (DW).
- Remove visible parasites, save images for future.
- Gill biopsies – Potential for hemorrhage, lower diagnostic value vs teleosts, not often performed.
- Fecal samples for helminths and coccidia from water or cloacal wash.
- Coelomic aspirates, flushes recommended in cownose rays for coccidia.
- Blood – Hematology, bioichemistry, blood gases, lactate and ancillary testing i.e. macronutrients, vitamins, hormone assessment.
- Venipuncture – Ventral tail vein, posterior cardinal sinuses, wing or radial veins.
- Venipuncture sites affect PCV – Lower PCV from dorsal sinus (~8%). Sharks more tolerant of anaerobic conditions have lower HCT values, similar differences between the two sites. Ventral tail vein less affected vs the sinus. Total WBC count also affected. Heparin preferred.
- Elasmobranchs – Total dissolved solids = ~2x total protein.
- Sodium, chloride, urea, osmolality high in marine adapted elasmos.
- Serum or plasma may require dilution.
- Sodium, chloride, urea, osmolality high in marine adapted elasmos.
- US – Free fluid may indicate inappropriate salinity, inanition, coelomitis, bacterial or parasitic infection. Female repro ultrasound is essential to check gestational status, ID pathology, and obtain baseline images of ovaries and oviducts.
- Full necropsy for animals that die.
Anesthetic drug effect can vary widely in elasmobranchs.
What are some reasons for this?
WHat species have endothermic capabilities? How does that affect drug uptake?
Do elasmobranchs have a renal portal system?
- Variation in Drug Effects:
-
Body temperature, hepatic biotransformation, renal function, drug receptor type and distribution, injection site. Also gill surface area to BW ratio, lipid content, stress, health status, body condition changes.
- Most elasmobranchs – poikilothermic.
- Endothermic abilities – porbeagle, mako and white shark.
- Regional heterothermy associated with variable vascular densities may result in unpredictable drug uptake.
- Liver size and composition is species dependent.
- Kidneys have higher filtration rate and different selectivity that influence drug elimination rates.
- Renal-portal system may enhance nephrotoxicity or renal excretion of drugs.
- Most elasmobranchs – poikilothermic.
-
Body temperature, hepatic biotransformation, renal function, drug receptor type and distribution, injection site. Also gill surface area to BW ratio, lipid content, stress, health status, body condition changes.
Describe physical restraint of elasmobranchs.
What is tonic immobility?
What are some hazards associated with physically restraining elasmobranchs?
What safety precautions should be in place?
How can stingray envenomation be managed?
How should electric rays be handled?
- Physical Restraint:
- Tonic immobility – Level of restraint highly variable between species, often starts with period of marked excitement, especially in batoids. Not considered to have any analgesic effects, has been linked to hyperesthesia. Additional analgesia required for painful or invasive procedures.
-
Hazards while handling and diving – Teeth, spines, tail barbs, venomous spines at leading edge of first dorsal fin (piked dogfish), abrasive skin, electric shock (Torpediniforme rays), saw blades (Pristiformes, sawfishes).
- Accident prevention – Procedures should be well planned, two operantions commanders (one for human safety, the other for the overall procedure and animal wellbeing). Staff briefing before the procedure.
- Develop SOPs, PPE, emergency protocols, safety equipment (Kevlar, chain mail), safety glasses around rays, practice safety drills.
- All staff should be trained in first aid. Blood loss from shark bites can be significant and must be stopped rapidly.
- Stingray envenomation can be painful, fragments of spine can remain in wounds. Heat labile proteins can be denatured through application of heat (hot water immersion as hot as the patient can tolerate without scalding).
- Diving – Occupational diving regulations (OSHA). DSO (diving safety officer) at each aquarium should understand and enforce relevant regulations. Additional safety divers are recommended for operations that require full attention i.e. repairs. Safety diver encourages elasmos to remain at a safe distance from working divers and maintains non-visual (sound tapping, etc) communication with working divers.
- PVC with electrical tape around it – “shark wand” deterrent.
- Can also isolate the diver from the elasmobranchs with cages, netting, etc.
- Grasp smaller sharks with one hand over top of the body and gripped in the region of the pectoral girdle, posterior to gills and anterior to pectoral fins. Can also hold around or behind the pelvic girdle for additional support.
- Do not hold around the abdomen or coelom.
- Handling electric rays – Keep all parts of body away from water in which rays are maintained, handle with fabricated tools made from electrically insulated materials i.e. wood, plastic. Wear thick rubber gloves with long cuffs.
List several agents used in immersion anesthesia of elasmobranchs. What is typically used?
What injectable anesthetics have been used? What ones are most reliable? What is the route of administration?
- Chemical Restraint:
- Immersion – Disadvantage is drug volume needed. Not usually practical.
- Benzocaine is similar to MS-222 with high potency, quick onset, high margin of safety, low cost, may cause bradycardia and increased resistance to circulatory flow.
- Etomidate and metomidate – Rapid induction and recovery.
- Halothane/O2/NO – Bubbled into water, human exposure hazard.
- O2 narcosis – Short procedures, 100% O2. Sedation likely due to CO2 elevations due to respiratory depression. Prolonged exposure results in hypercapnia and potentially life-threatening acidemia. Gas bubble disease does not occur since not administered under pressure.
- Divers can put MS222 in a spray bottle/syringes and apply directly to gills, use food coloring.
- MS222 75-90 mg/L most spp. Buffer in FW systems. And small SW systems.
- Injectable – IV most reliable, rapid induction and short duration. IM dorsal saddle.
- Ventral coccygeal vein. Spinal needle in large animals to avoid cartilage plug.
- IM injections – Differences between red and white muscle. Erratic/delayed.
- Alfaxalone – Highly variable.
- Azaperone – Reduces response to environment without sedation.
- Carfentanil – No effect even with massive doses.
- Detomidine – Little effect. Reversal split IV and IM smooths recovery.
- Ketamine – Seizure-like muscle spasms occasionally seen. Only used in combos.
- Metomidine – Combo with ketamine.
- Propofol – Works well, IV.
- Sodium pentobarbital – Has been used, may result in death.
- Tiletamine/Zolazepam – Irritability, rapid swimming, unrestrained biting.
- Combos: Xylazine/ketamine, medetomidine/ketamine. Erratic.
- Doxapram causes dramatic arousal in anesthetized elasmobranchs.
- Concentrated midazolam solutions have been used in large elasmos i.e. mantas and whale sharks.
- Immersion – Disadvantage is drug volume needed. Not usually practical.
What are common sites of venipuncture in elasmobranchs?
Describe the techniques?
What anticoagulants can be used with elasmobranch blood?
How quickly does hemocytometer count need to be performed? If it can’t be performed quickly, how can cell morphology be preserved?
- Diagnostics
-
Venipuncture sites – Dorsal sinus, ventral coccygeal vein most common.
- Ventral coccygeal vein preferred because blood in the dorsal sinus pools rather than actively circulates.
- Ventral coccygeal vein – Insert needle at 90 deg angle directly on midline, may have to advance through cartilage before reaching the vessel; spinal needles may be used.
- Dorsal sinus – Insert needle on midline at 45 degree angle.
- Sampling – For sharks, heparin or EDTA can be used. ONLY heparin for stingray spp (EDTA causes rapid hemolysis in stingray spp). EDTA may also lower the concentration of calcium and other divalent ions.
-
Hemocytometer count should be performed immediately after collection to prevent thrombocyte and WBC aggregation. Otherwise, preserve in 10% formalin for later evaluation.
- Formalin can maintain cell morphology and prevent thrombocyte aggregation.
-
Venipuncture sites – Dorsal sinus, ventral coccygeal vein most common.
Describe typical clinicopathologic findings in elasmobranchs.
What are normal BUN ranges? What are differentials for decreased BUN?
What is a typical differential count for healthy elasmobranch hematology?
How do whale sharks differ in their biochemistry in managed care?
- Important clin path info:
- Marine elasmobranchs retain and reabsorb urea and other solutes so that plasma remains hyperosmotic to sea water.
-
Normal BUN should range from 1000-1300 mg/dL.
- Low values may indicate loss form renal dz or decreased production due to hepatic disease.
- Salt excretion occurs in kidney and rectal gland, compensates for influx of Na and Cl from the environment.
- Na and Cl tend to be higher than in mammals.
-
Normal BUN should range from 1000-1300 mg/dL.
- Differential counts generally should be 50-75% lymphocytes, 10-30% heterophils, 0-10% eos, 0-1% basos, 0-3% monos.
- Whale sharks – In captivity have higher cholesterol and triglycerides vs wild conspecifics. EHM2.
- Marine elasmobranchs retain and reabsorb urea and other solutes so that plasma remains hyperosmotic to sea water.
Describe the body conditioning of elasmobranchs.
What findings on examination, ultrasonography, and clinical pathology are used to make these evaluations?
- Body condition assessment –
- Epaxial muscles and muscles over pelvic girdle should be rounded and firm
- Coelomic contours should be flat to slightly convex.
- US can be used to evaluate liver size and echogenicity. Should be large, lipid-laden. Can calculate a liver-to-coelom ratio.
- Urea and total proteins decrease with inappetance in some studies.
- Glucose and electrolytes are generally well regulated during prolonged fasting.
Describe the development of goiter in elasmobranchs.
What life support elements or water quality parameters may interfere with iodine uptake?
Describe the gross and histologic findings of goiter.
- Iodine deficiency captive and free ranging animals
- Causes: ozone (converts iodide to iodate), high nitrates can inhibit uptake by thyroid, spitting out oral supplements
- Ozone reduces the amount of environmental iodine available, which is critical for thyroid hormone synthesis.
- Thyroid enlargement - may appear as mass ventral midline caudal to mouth, grossly thickened or rounded, pale orange
- Histo: diffuse hyperplastic goiter, diffuse colloid goiter, multinodular colloid goiter
- Note not all deficient animals will show gross or histologic evidence deficiency
- Thyroid iodine content is reliable indicator of thyroid status and can be used to assess efficacy of iodine supplementation
- Oversupplementation can cause iodine toxicity and gland enlargement; retinal necrosis
- Causes: ozone (converts iodide to iodate), high nitrates can inhibit uptake by thyroid, spitting out oral supplements
Describe soft tissue mineralization in cownose rays.
What are some potential etiologies?
What are the gross and histologic features of this condition?
- Soft tissue mineralization - common in captive cownose rays
- Progressive -> weight loss, death
- May be related to inappropriate calcium supplementation in water or prey
- Renal disease
- Lesions (domed or flat and ulcerated) - skin (distal pectoral fins, ventral torso), dorsal midline, tail; may have chalky white deposits on skin and internally in various organs
- Histo: basophilic mineral deposits in connective tissue, smooth muscle, myocardium, basement membrane; surrounded by granulomatous inflammation and fibroplasia (von Kossa stain can confirm presence of mineral)
What are some findings on necropsy that may indicate hypoxia in elasmobranchs?
How do species differ in their susceptibility?
- Hypoxia
- Causes: low DO secondary to equipment failure or high bioload or chronic gill damage
- Species variation with susceptibility - epaulette sharks and sleeper sharks can survive in hypoxic environments
- Buccal pumping: compensate with decreased activity and increased resp rate
- Obligate ram ventilators (lamnid sharks): increase swim speed and mouth gape
- Acute hypoxia: good condition, no gross lesions or nonspecific congestion, histologic lesions may include acute necrosis in viscera (gill lamellae, renal tubules)
Describe some of the metabolic consequences of restraint in elasmobranchs?
Are there certain species that are more suceptible?
Are there any obvious lesions on necropsy?
- Stress (metabolic consequences) associated with capture and handling
- Catecholamine release and inhibition of respiration
- Decreased pH and increased lactate of blood (metabolic acidosis); some sharks - concurrent respiratory acidosis, hyperglycemia
- No gross or histo lesions
- May also develop exertional rhabdomyolysis in skeletal and cardiac muscle
- Dogfish and tiger sharks less susceptible vs Atlantic sharpnose and blacktip sharks more susceptible
Describe the lesions associated with the following toxins in elasmobranchs:
Ozone
Heavy Metal Toxicity (what metals?)
Fenbendazole
Paint Fumes
Algal Toxins
Toxic
- Ozone toxicosis
- Oxidizing agent - toxic to gill epithelium and erythrocytes -> membrane peroxidation -> formation of methemoglobin -> death by hypoxia
- No specific gross lesions, congestion
- Histo: gill epithelium may show acute necrosis +/- gill congestion and lamellar atrophy
- Gas bubble disease
- Heavy metal toxicity (copper, tin)
- Sublethal copper exposure - decreased erythrocytes and HCT, decreased plasma urea, increased lactate and acidosis in dogfish
- Tin (tributyltin oxide in marine paint) - gill epithelial necrosis from peroxidation in yellow stingrays
-
Fenbendazole toxicity
- Lethargy, inappetence, increased respiratory rate, leukopenia, anemia
- Gross: ventral erythema and necrotic tips of tail or pectoral fins
- Histo: necrosis of hematopoietic tissues - epigonal organ, gi mucosa basal cells
- Die from sepsis from necrotic gi mucosa
- Volatile organic chemicals - paint fumes
- Acute mortality in sand tiger sharks (southern stingrays survived)
- Gross: gill congestion
- Histo: acute gill necrosis with thrombosis, laminar collapse and congestion
- Red tide (Karenia brevis)
- Mortality in blacktip sharks and Atlantic sharpnose sharks reported with bloom in FL
- High brevetoxin concentration in liver, gill and skeletal muscle
- Naturally bioaccumulate toxin, so diagnosis can be difficult
- Sharks appear to be resistant to domoic acid toxicity
What cardiac lesions are common in elasmobranchs?
What age groups are most commonly affected?
What are the gross and histologic lesions?
- Coronary arteriosclerosis (captive and free-ranging)
- Correlates with larger size and may be age-related
- Histo: loss of internal elastic lamina and proliferation of connective tissue and smooth muscle of the intima, reduction of vascular lumen; more common at branch points
- Arteriosclerosis also seen in meningeal and ocular choroidal vessels
- Histo: dense collagenous connective tissue within and around vessels
- Cardiac valvular proliferative lesions and myocardial fibrosis
- Geriatric animals may contribute to stress and mortality
- Gross: white fronds around valve leaflets of conus arteriosus
- Histo: papillary projections are mildly hyperplastic endothelium over collagenous or mucinous stroma. Fibrosis occurs specifically at the junction of the inner and outer myocardium of the ventricle
Trauma is a common presentation of elasmobranchs.
Describe the most common types of presenting trauma.
-
Trauma
- Male aggression, mating aggression - blunt force trauma during pursuit by male may cause hepatic rupture and hemocoelom in females with abundant lipid storage
- Self trauma common - poor exhibit design
- Ulceration of ventral pectoral girdle - excessive bottom resting that may indicate underlying disease - ischemic necrosis, ulcers, secondary infections
- Gastric eversion (mostly in sharks) is normal for voiding and cleaning, but can be fatal if stomach is not swallowed and replaced, prolapses through gill slits or entrapped in oropharyngeal cavity
- Spiral valve eversion - conspecific bite wounds may result in sepsis and death
Curvature of the pelvic fins is common in what two genera of sharks?
What is the suspected cause? What is an important sequelae?
What is found histologically in these cases?
- Curvature of pelvic fins in captive large Carcharias and Carcharhinus genus sharks
- Unknown cause, but may be associated with redundant swimming pattern
- The ram ventilators are not able to swim/ventilate as efficiently and may die from hypoxia
- Fins curved ventrally and medially, thickened at curved portions, traumatic erosions/ulcers may be on dorsal aspects
- Histo: increased mucinous and collagenous connective tissue between the dermis and curved ceratotrichia; fractured ceratotrichia in severe cases
Egg retention is common in sand tiger sharks.
What is the scientific name of the sand tiger shark?
Describe the pathogenesis of this condition.
What are the CS? How is this diagnosed? How is this treated?
What bacteria are commonly cultured?
-
Egg retention in sand tiger sharks (Carcharias Taurus).
- Wild C. Taurus females mature at 9-10 yrs age.
- No pregnancies have been recorded for C. Taurus on display in the US excluding animals gravid prior to capture.
- Continuously produce non-fertilized eggs, often released into tank.
- Can be retained and lead to lethal consequences.
- Eggs retained in one or both uterine horns eventually become necrotic, serving as a nidus for bacterial metritis and leading to septicemia and death.
- CS – Depression, anorexia, diffuse dermal abscesses or draining fistulas.
- Dx – Radiology, ultrasonography, endoscopy, nannulation and uterine lavage.
- Abx along generally not effective.
- Tx – Flushing out eggs with uterine lavage with antibiotic saline solution followed by parenteral antibiotics.
- Common bacteria cultured from necrotic eggs – Pseudomonas, Enterococcus.
- Two cervical openings which may be open or closed. Can manually dilate for egg removal.
- Gastric air can be lost during this procedure, may need to manually reinflate
Cystic ovaries and mucometra are common in southern stingrays.
What is the scientific name of the southern stingray?
Descrbie the reproductive physiology of this species and the pathogenesis of this disease.
How do these animals present?
How can this be managed?
Describe the approach to ovariectomy to prevent this.
-
Cystic ovaries and mucometra in southern stingrays (Dasyatis Americana).
- Can produce 2-10 pups annually.
- Impregnated within hours to days of parturition, consider any female to be pregnant.
- Uterus never involutes and villus trophonemata do not atrophy, continue to produce thick mucoid histotroph and uterus remains dilated.
- Induced ovulators – Copulation must occur to stimulate hormonal signals for ovulation.
- If mature follicles are not ovulated they will remain on the ovary.
- Many aquaria resort to single-sex exhibits; females will still produce large amounts of histotroph. Leads to marked mucometra.
- CS – Distention with no pups on US. May develop pressure sores from resting on the bottom. Coelomic wall can rupture leading to salt water intrusion and death.
- Tx – Temporary relief via cannulation of cervix and evacuation of uterus, will recur within months.
- Left ovary continues to produce follicles despite absence of pregnancy.
- Ovary will become cystic and get very large, can tear and result in hemorrhage and death.
- Surgical ovariectomy in juvenile D. Americana can be employed to avoid this.
- Size is critical to success of procedure.
- Ideal size candidate is ~60 cm disc width.
- Ovarian size should be evaluated pre-operatively with US.
- Left paralumbar surgical approach –EHM2 has full procedure.
What are some reproductive consequences of housing female elasmobranchs without males?
What lesions may result grossly and histologicallys?
Are any species particularly affected?
-
Southern stingrays (and other female elasmos) housed without males
- Coelomic distention, large left ovary (numerous mature follicles +/- cystic and inflamed follicles) and uterus with prominent trophonemata and histotroph accumulation, oviducts may contain mucosal cysts and fluid accumulation
- Chronically affected - poor nutrition condition
- Histo: ovarian tissue unremarkable, and stromal hyperplasia may occur, granulocytic inflammation and mural necrosis within cystic follicles, trophonemata elongated; affected rays have coelomic mesothelial hyperplasia
What are some common sequelae of uterine impaction in elasmobranchs?
- Uterine impactions - multiple egg cases
- May cause coelomic distention and rupture of dorsal hepatic lobe
- Infection may be present as well (caseous exudate) - do not survive long
- Not impaction: captive female sand tigers that do not breed - numerous follicles in uteri with marked distension (no abnormalities of uteri, unknown impact)
What are the effects of Aeromonas infections in blacktip reef sharks?
What are the effects of Flavobacterium infections in bonnethead sharks?
What are the lesions associated with Carnobacterium maltaromaticum? What sharks is this organism commonly isolated in?
What are the lesions associated with epitheliocystis in elasmobranchs? What shark is this commonly isolated in?
Bacterial infections of what anatomical structure result in sharks having the upper dental arcade permanently dropped in the pre-bite posture making it difficult to close their mouths?
- Aeromonas salmonicida – Hemorrhagic septicemia in blacktip reef sharks.
- Flavobacterium spp – Neurologic dz in bonnethead sharks.
-
Carnobacterium maltaromaticum-like bacteria (gram positive bacilli)
- Meningoencephalitis in stranded juvenile salmon sharks (homeotherms!) in California
- Thick red meninges, liver - pinpoint white/yellow foci, abscess formation in ventricles
- Histo: meninges - infiltrates of mononuclear cells and proteinaceous edema, congestion, hemorrhage and necrotic debris, bacteria, inflammation; hepatic - mononuclear cell infiltrates
-
Branchial epitheliocystis (order Chlamydiales); Leopard shark.
- Gram negative, infect gills
- Gills - pale, mottled
- Secondary lamellae epithelial cells enlarged by intracellular cysts (10-200 um) with granular light basophilic material surrounded by eosinophilic membrane +/- mixed inflammatory infiltrates, fusion of lamellae
- Can be incidental finding
- Mycobacteriosis
- Infection rarely reported, but most common infection is M. chelonae (single report of M. avium in epaulette shark)
- C. Taurus drop jaw syndrome – Shark loses ability to close mouth and upper dental arcade is dropped into pre-bite posture. Localized infections of the base of the ligamentum levator palatoquarati. Unknown cause but has happened in many aquaria – EHM2.
What are some other fungal infections seeen in elasmobranchs (besides Fusarium)?
How do these elasmobranch fungal pathogens differ histologically?
- Other fungi in captive sp - Exophiala, Paecilomyces
- Paecilomyces lilacinus – fungal infection in a hammerhead shark with systemic and terminal disease.
- Skin and/or gill necrosis, erosion, ulceration, or systemic infection
- Systemic infections may be present without apparent skin lesions
- Coinfection with Exophiala pisciphila and Mucor circinelloides in a zebra shark also fatal.
- Exophilia detected in a swell shark that displayed abnormal circular swimming patterns and mineralization of the cartilage of the skull and cervical vertebrae.
Monogeneans are a common source of morbidity and mortality for elasmobranchs.
What monogenean commonly affects stingrays?
What about lemon sharks?
What about blacktip reef sharks?
Are any elasmobranch species particularly sensitive to monogenean infestation?
Describe the life cycle of monogeneans and why they are difficult to eradicate.
What are the lesions typically associated with infestation?
What treatments are available?
-
Monogeneans - many species specific, may have wider host range in aquarium settings.
-
Common monogeneans
- Monocotylidae i.e. Dendromonocotyle spp
- Capsalidae i.e. Benedeniella spp, Entobdella spp, Neoentobdella spp.
- Microbothriidae i.e. Dermophthirius spp and Neodermophthirius spp.
- Hexabothriidae i.e. Erpocotyle spp and Heterocotyle spp.
- Tx usually praziquantel immersion, organophosphate immersion, or temp or salinity changes. Take into account eggs, host range, and host sensitivity to tx.
- Dermophthirius nigrelli – Wild lemon sharks.
- Dionchus penneri – Chronic skin lesions in blacktip reef sharks.
- Skin, gills, nasal, urogenital, gallbladder, coelom
- Usually incidental in free-ranging
-
Direct life cycle can cause problems in human care- warmer water
- Lay eggs that are negatively buoyant and sink to form egg bank in substrate.
- Ciliated larva (onchomiracidium) actively seeks a host. LC est 3-5 wks at 24C.
- Spotted eagle rays, bonnethead sharks predisposed to fatalities
- Skin: multifocal thick gray to white lesions, erosion and ulceration may develop (rubbing, flashing)
- Thickened gill filaments with chronic gill parasitism and occasional yellow exudate, fusion of secondary lamellae, gill hyperplasia, mucoid and alarm cell metaplasia, partial collapse of gill tips, nodular metaplasia in primary filaments
- Adult monogeneans - large haptor organ, thick eosinophilic cuticle
-
Capsalidae:
- Characterized by a posterior holdfast organ for attachment (haptor) and hooks.
- Eat mucus and skin.
- Clear to milky white in color.
- R. bonasus – Benedeniella posterocolpa.
- May be detectable on the cornea with a light source.
- Can be seen falling off during FW or praziquantel tx.
- Benedeniella distinguished from other capsalids by presence of a long vagina that opens on the left body.
-
Common monogeneans
Describe the effects of digenean trematode infestation in elasmobranchs.
Describe the effects of cestode infestation in elasmobranchs.
Where does nematode infestation typically occur in elasmobranchs?
Describe the lesions associated with Huffmanela. How is this parasite diagnosed and treated?
What are the effects of spirurid larvae in elasmobranchs?
- Digenean trematodes uncommon, but severe infections of rectal gland may disrupt osmoregulation and have been associated with vascular necrosis and hemorrhage in the brain
- Cestodes common in free-ranging, species specific, most in spiral valve; can be encysted in mesentery or viscera as well. Typically considered incidental.
- Paraorygmatobothrium spp in lemon sharks, Pedibothrium spp in nurse sharks, Crossobothrium spp in wild seven gill sharks, Tetraphyllidean spp in spadenose shark, Calliobothrium schneiderae in smooth-hound sharks.
- Nematodes
- Common in spiral valve
-
Huffmanela ova (larvated, bipolar plugs) in skin and oral cavity of sharks - affected animals have black serpiginous tracks or discrete black foci
- Adult migrates through the dermis and leaves behind a serial chain of heavily-tanned eggs visible through the epidermis.
- Dx with skin scrape. Tx – Levamisole, may be self limiting.
- Spirurid larvae - meningoencephalitis in free ranging nurse sharks, also incidental
- Spirurida and Dracunculoidea have been linked to vasculitis, bronchitis, pancreatitis, meningoencephalitis, oophoritis, metritis. Decisions to treat not always straight forward.
- Myxozoans (generally incidental, biliary tract) and acanthocephalans reported.
- Cestodes (GI, spiral valve), myxozoa (biliary), microsporidia (anywhere) in quarantine generally considered incidental.
What is the most significant protozoal pathogen of elasmobranchs?
What species are particulary susceptible?
How is this disease diagnosed?
WHat lesions does it produce?
Are there any treatments?
-
Coccidia - Eimeria (E. southwelli)
- Most are small intestine and spiral valve parasites, only disease causing with heavy infections - spiral valve epithelial necrosis, sloughing and hemorrhage
-
Eimeria southwelli - coelomic epithelium of cownose rays and associated with high mortality in captive animals (unknown affect in free-ranging population). All myliobatid rays should be considered susceptible.
- Coelomic distention (turbid effusion), weight loss, prominent cutaneous blood vessels, mesothelial hypertrophy and hyperplasia
- Mesothelial cells - sporulated or unsporulated oocysts and meronts
- Also reported in testes and within tubules of the kidney.
- ID in coelomic fluid from coelomic pore flushes
- Serosa of organs may appear roughened on necropsy.
- Tx – Sulfadimethoxine, clindamycin, toltrazuril or ponazuril. Elimination of parasite is difficult. Manage rather than elimate.
Describe teh lesions associated with scuticociliate infestation in elasmobranchs.
- Fatal systemic scuticociliate infection reported
- One case - ID was Philasterides dicentrarchi
- Multifocal necrohemorrhagic hepatitis, cutaneous ecchymoses, turbid intracranial and coelomic fluid, and/or necrotizing pancreatitis
- Histo: necrotizing vasculitis and intravascular fibrin thrombi associated with necrosis
- Organisms: 20x50 um diameter, single hyperchromatic round macronucleus and cytoplasmic eosinophilic globules
- Invasive Scuticociliatida-like (Uronema-like) ciliates have been associated with morbidity and mortality – Skin, gills, brain, liver of skates and demersal sharks.
A recent paper described the mesopterygial vein as a reliable venipuncture site in batoids.
Describe the venous drainage of the wings of batoids to the heart.
Describe the technique for collecting blood from this site.
What are some advantages of this site from others?
Westmoreland, L. S., Archibald, K. E., Christiansen, E. F., Broadhurst, H. J., & Stoskopf, M. K. (2019). The mesopterygial vein: a reliable venipuncture site for intravascular access in batoids. Journal of Zoo and Wildlife Medicine, 50(2), 369-374.
Abstract: Intravascular access in batoid species is commonly achieved using the ventral coccygeal or radial wing vessels. However, these approaches can be difficult because of the presence of cartilage, lack of specific landmarks, species variation, and small vessel size in many species. This study used postmortem contrast radiography and gross dissection to develop landmarks for a new, dependable vascular access in three Myliobatiform species commonly maintained in captivity: Atlantic stingray (Hypanus sabinus), cownose ray (Rhinoptera bonasus), and smooth butterfly ray (Gymnura micrura). The mesopterygial vein provides quick vascular access and is suitable for administration of large fluid volumes and intravascular drugs. It is located immediately ventrolateral to the metapterygium cartilage, which sits adjacent to the coelomic cavity and supports the caudal half of the pectoral fin. Using the pectoral girdle and cranial third of the metapterygium cartilage as landmarks, vascular access can be achieved by directing a needle medially at approximately a 30 (adult cownose rays) or 45 angle (Atlantic stingrays, juvenile cownose rays, smooth butterfly rays) toward the metapterygium cartilage. Differences in the degree of needle direction are due to species and age-specific shapes of the metapterygium cartilage. The mesopterygial vein is an alternate site of quick and reliable venous access in batoid species.
BACKGROUND INFO:
- Cartilaginous skeleton supports pectoral fins, propterygium cranially, mesopterygium and then caudal metapterygium which are anchored via pectoral girdle
- Radial wing veins drain blood medial to large propterygial vein cranially and mesopterygial vein caudally.
- Metapterygial vein drains between the pectoral fin and body wall
- All 3 of these go to brachial and subclavian veins to heart
KEY POINTS: Mesopterygial vein located just ventrolateral to metapterygium cartilage in all 3 species
- Ventral approach favorable with less tissue damage
- Largest cranial 1/3, then decreased moving caudally
- Technique: dorsal recumbency, palpate pectoral girdle centrally then palpate lateral margin of metapterygial cartilage in proximal pectoral fin (cranial 1/3). 45 degree angle for some species (30 for cownose). 22G 1inch needle/20g 2inch for adult cownose.
- Clinically applicable, may induce tonic immobility in some species
- Less muscle in ventral approach than dorsal approach, less chance for tissue damage
- Very large vessel, away from barb
- Separation of artery and vein in this site, less mixing of A-V blood
- Helpful to use a spinal needle with stylet in larger species with thick connective sheath
- Cranial 1/3 avoids more prominent lip found caudally
TAKE HOME: Mesopterygial vein reliable for IV access in multiple species of batoidsC
A recent study described an epizootic of leopard sharks in San Francisco Bay in 2017.
How many sharks were affected? What were their clinical signs? Has this occurred before?
What is a typical approach to studying epizootics? What was unique about this study?
What was the pathogen identified?
What were the lesions seen on necropsy?
What makes the San Francisco bay a likely place for these epizootics to occur?
Retallack, H., Okihiro, M. S., Britton, E., Sommeran, S. V., & DeRisi, J. L. (2019). Metagenomic next-generation sequencing reveals Miamiensis avidus (Ciliophora: Scuticociliatida) in the 2017 epizootic of leopard sharks (Triakis semifasciata) in San Francisco Bay, California, USA. Journal of wildlife diseases, 55(2), 375-386.
Abstract:
During March to August of 2017, hundreds of leopard sharks (Triakis semifasciata) stranded and died on the shores of San Francisco Bay, California, US. Similar mass stranding events occurred in 1967 and 2011, but analysis of those epizootics was incomplete, and no etiology was confirmed. Our investigation of the 2017 epizootic revealed severe meningoencephalitis in stranded sharks, raising suspicion for infection. We pursued a strategy for unbiased pathogen detection using metagenomic next-generation sequencing followed by orthogonal validation and further screening. We showed that the ciliated protozoan pathogen, Miamiensis avidus, was present in the central nervous system of leopard (n¼12) and other shark species (n¼2) that stranded in San Francisco Bay but was absent in leopard sharks caught elsewhere. This ciliated protozoan has been implicated in devastating outbreaks in teleost marine fish but not in wild elasmobranchs. Our results highlight the benefits of adopting unbiased metagenomic sequencing in the study of wildlife health and disease.
- Leopard sharks in San Francisco Bay, CA
- Die-offs over past 50 years:
- 1967 -1,000 dead sharks, mainly leopard sharks, w/in 1 mo.
- 2006
- 2011 (hundreds of leopard sharks)
- Moribund sharks -described as confused and disoriented, with erratic behaviors and swimming patterns
- 2017 1,000 estimated L sharks dead (sometimes as many as 30 daily)
- Close to shore, disoriented and neuro behavior
- Die-offs over past 50 years:
- Conventional approaches to epizootic investigation: environmental assessment, observation of animal behavior, and necropsy with cytology, histology, microbiological and chemical analyses
- Molecular techniques like PCR have enabled rapid and specific pathogen identification
- Limited to genetic information available
- Metagenomic next-generation sequencing (mNGS): Analysis of all nucleotides in a sample
- Scuticociliates are free-living opportunistic marine protozoa that belong to the subclass Scuticociliatida of the phylum Ciliophora
- Inflammatory meningitis
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Meningoencephalitis: characterized by hemorrhage, cloudy CSF, and thickened meninges lesions
-
Prominent lesions at olfactory bulbs and lobes
- Olfactory lamellae: often markedly hemorrhagic and inflamed
-
Prominent lesions at olfactory bulbs and lobes
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Meningoencephalitis: characterized by hemorrhage, cloudy CSF, and thickened meninges lesions
- Ciliated protozoan parasites (consistent with M. avidus): observed in the brains of 5 affected sharks, and in olfactory lamellae of 1 shark
- Data does not exclude the possibility that M. avidus was not the primary or sole driver of disease and mortality.
- Water temperature, salinity, toxins, or other pathogens could increase susceptibility to an opportunistic infection by M. avidus
- In SF Bay, leopard sharks aggregate in large numbers in the warm shallow waters of bays and estuaries, with greater exposure to runoff that may contain toxins or decreased salinity.
Takeaway: Miamiensis avidus = Inflammatory meiningoencephalitis, leopard sharks, SF Bay CA.
A recent study evaluated the reproductive hormones of cownose rays in conjunction with ultrasonography to determine stages in reproductive cycles.
Describe the reproductive cycles of the cownose ray - gestation time, litter size, repro strategy.
How did the hormones vary in males?
How did the hormones vary in females?
Describe the stages of pregnancy in cownose rays as assessed on ultrasonography.
Sheldon, J. D., Allender, M. C., George, R. H., Bulman, F., & Abney, K. (2018). Reproductive hormone patterns in male and female cownose rays (Rhinoptera bonasus) in an aquarium setting and correlation to ultrasonographic staging. Journal of Zoo and Wildlife Medicine, 49(3), 638-647.
Abstract: Reproductive management of cownose rays (Rhinoptera bonasus) under professional care plays an important role in conservation of the species, but hormone and ultrasonographic analyses of their 12-mo reproductive cycle have not been documented previously. Plasma reproductive hormone concentrations (17Bestradiol, progesterone, testosterone, and androstenedione) were measured monthly via radioimmunoassay for 1 yr in an aquarium-managed population of adult females (n ¼ 15) and males (n ¼ 5). Ultrasounds of the uterus were performed each month at the time of sample collection to identify gestation stage (0–5) based on a previously developed in-house staging system. Stages were correlated to hormone concentrations to track progression through pregnancy. Thirteen females were reproductively active, and each produced one pup in March–June, similar to timing for free-ranging populations. Female estradiol increased steadily throughout gestation from stages 0 to 5, while progesterone, testosterone, and androstenedione were increased only in early gestation (stages 1 and 2). Unlike month of year, gestation stage strongly predicted hormone concentration, but specific values to predict parturition date were not identified. Male testosterone and progesterone were higher in March–June (mating season) than July–January, while estradiol and androstenedione did not exhibit a seasonal pattern. Aquarium-managed cownose rays have similar reproductive patterns to what is reported in wild populations. Ultrasonographic monitoring with serial hormone analysis and accurate mating records will provide the most useful information for managing a reproductive population of cownose rays in an aquarium setting.
- Cownose ray reproduction
- 11-12 month gestation, 1 pup
- Aplacental viviparity – single embryo, left uterus - histotrophy
- Annual synchronous reproductive cycles (ovulation & parturition mostly around April-May)
- Males
- Higher progesterone, testosterone, androstendione than females
- Lower testosterone in winter months than in spring/summer months
- Higher testosterone in those months correlates to increased spermatogenesis in wild males
- Females
- Estradiol rose through each stage of pregnancy
- Progesterone, testosterone, and androstendione peaked in stages 1-2
- Higher testosterone in may through august reflects peak fertile periods, similar to Atlantic stingrays
- Increasing estradiol throughout pregnancy seen in bonnetheads, Atlantic stingrays, spiny dogfish – may play a role in pregnancy maintenance & lecithotrophy, yolk sac, matrotrophy, and histotroph production
- Progesterone rises postovulation in bonnetheads, early-midgestation in dogfish, and prior to ovulation & parturition in Atlantic stingrays
Take home: Estradiol increases throughout pregnancy. Males have higher testosterone and progesterone during mating season, and females have peaks in progesterone, testosterone, and androstendione during stages 1-2 (early preg).
A recent study described the reproductive pathology and hormone profiles of southern stingrays in managed care.
Describe the normal reproductive patterns of this species.
Describe the typical hormone profiles of elasmobranchs (they can differ from what you would expect).
How did hormone levels correlate with reproductive disease?
How was disease severity assessed?
Mylniczenko, N. D., Sumigama, S., Wyffels, J. T., Wheaton, C. J., Guttridge, T. L., DiRocco, S., & Penfold, L. M. (2019).
Ultrasonographic and hormonal characterization of reproductive health and disease in wild, semiwild, and aquarium-housed southern stingrays (Hypanus americanus).
American journal of veterinary research, 80(10), 931-942.
Objective: To characterize physical examination, plasma biochemical, and ultrasonographic findings in aquarium-housed, managed semiwild, and wild southern stingrays (Hypanus americanus) with and without reproductive disease.
Animals: Southern stingrays from aquarium (n = 48), lagoon (managed semiwild; 34), and wild (12) habitats.
Procedures: Limited, opportunistic prosections were performed of presumed anatomically normal wild southern stingrays and compared with findings for aquarium-housed stingrays with reproductive disease. Ultrasonographic video data from both groups were used to assign a score (1 to 5) indicating increasing severity of ovarian and uterine reproductive disease. Plasma total 17β-estradiol (E2), estrone (E1), progesterone (P4), and testosterone (T5) concentrations were measured with enzyme immunoassays validated for use in southern stingrays.
Results: Ultrasonographic ovarian scores were significantly correlated with uterine scores. No reproductive disease was detected in semiwild or wild stingrays, but 65% (31/48) of aquarium-housed stingrays had developing or advanced reproductive disease (ie, ultrasonographic ovarian or uterine score of 4 or 5). Significant correlations were identified between ovarian and uterine disease status and plasma concentrations of all steroid hormones except testosterone.
Conclusions and Clinical Relevance: Findings suggested that ultrasonography and plasma hormone concentrations may be useful in the identification of reproductive disease and determination of disease severity in southern stingrays.
Background:
- Southern stingrays – Slow to mature, produce low numbers of offspring. Aquariums developing sustainable breeding populations important for education, etc.
- Mating can occur immediately after parturition. Females likely gravid for most of life span.
- In aquaria, can reproduce biannually and are often housed in single-sex groups to prevent this.
- Nonreproductive states for extended periods.
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Elasmobranchs produce P2, P4, T5, do not always regulate reproduction as expected.
- P does not increase during early or midgestation.
- Free P and T concentration peaks prior to parturition in Atl stingrays.
- No P detectable in granulosa tissue throughout gestation in dogfish.
- Other P4 metabolites and E metabolites may be important.
- E2 prime regulatory steroid, and E1 also strong role in repro.
- Collected blood samples for plasma hormones, US data over 1 year.
- Ultrasound scoring system on a 5 pt scale on basis of width of ovary, number of follicular layers, presence of cysts, overlap with uterus.
- General opportunistic postmortem exams on 10 wild stingray cadavers. All gravid. Ovary against left lateral surface of epigonal organ. EO always overlapped uterus on the left side. Width of ovary did not exceed 4 cm. Individual ova rarely exceeded 2 cm. No cysts. Ovary did not overlap with uterus. Right oviduct visibly attenuated with no ova present. Oviduct assoc with epigonal tissue more caudal and smaller than contralateral epigonal tissue.
- Right and left ostia originated ventral and lateral to esophagus, led dorsal then lateral into oviducts. Supported by a ligament connected to each oviduct. Right oviduct widened into vestigial right uterus.
- Left oviduct expanded into nidamental gland aka oviducal or shell gland at cranial uterus. No obvious isthmus. Uterus on left attached to kidney, terminated into urogenital sinus analogous to mammalian cervix, lateral to single urogenital pore and into cloaca.
US Scores:
- 2 – Single layer of uniform follicles and occasional small follicles in periphery of ovary.
- 3 – ovary appeared wider, multiple layers, various sizes of follicles and cysts.
- 4, 5, - greater numbers of different-sized follicles with heterogeneous echogenicity (varying stages of vitellogenesis) and degeneration, cystic structures.
- Semiwild or wild stingrays, only one in category 3, none in 4, 5.
Hormones:
- Plasma E1, E2, P4 increased with increasing ovarian scores.
- E1 also increased with ovarian disease. Some exceptions.
- No differences in T among ovarian scores.
Severity of repro dz positively correlated with plasma total E2, E1, P4.
17β-estradiol (E2), estrone (E1), progesterone (P4)
- Plasma total T5 high in stingrays assigned highest uterine score.
- Regular pregnancy cycles with normal hormone fluctuations presumed to prevent accumulation of ova in southern stingrays, unbred females higher risk of disease.
- Ova produce estrogens in elasmobranchs, increase in number of ova may create estrogen rich environment.
- E2 secretion increases dramatically in Atl stingrays during period when histotroph is produced. E2 in this study only high for highest uterine score, E1 increased with increasing uterine score.
- Plasma conc of total E1 was higher than total E2, may be a more consistent steroid signal to monitor for indication of ovarian and uterine disease. E2 low regardless of disease in some individuals. Examining both probably best.
- Repro disease correlated with disk width, may be due to age and reproductive activity being related.
A recent study described the utility of coelomic fluid analysis in elasmobranchs.
How is this fluid collected?
What may be seen on cytology in normal samples? What about abnormal samples?
How does the clinical chemistry change in abnormal samples?
Donnelly, K. A., Stacy, N. I., Guttridge, T. L., Burns, C., & Mylniczenko, N. (2019). Evaluation of Comprehensive Coelomic Fluid Analysis through Coelomic Pore Sampling as a Novel Diagnostic Tool in Elasmobranchs. Journal of aquatic animal health, 31(2), 173-185.
Abstract: The objectives of this study were to describe a minimally invasive coelomic fluid sampling technique in elasmobranchs, to characterize the coelomic fluid composition in clinically normal and abnormal animals, and to compare findings from wild and managed populations. Fluid was collected via the coelomic pore in 89 individuals from 16 species spanning clinically normal and abnormal patients within a managed population (n = 54), a semi‐managed open‐lagoon population (n = 18), and a wild population (n = 17). Biochemical and cytological fluid analyses were performed on all samples, and bacterial and fungal culture, protein electrophoresis, and cholesterol electrophoresis were performed on a subset of samples. The presence of a variable volume of colorless to white and clear to slightly turbid coelomic fluid was consistent with a normal finding; however, the cytological and chemical makeup of coelomic fluid was found to provide additional clinically relevant information. The coelomic fluid from some of the abnormal samples (n = 37) contained white blood cells (n = 15) and concurrent bacteria (n = 7), the latter suggestive of bacterial coelomitis. Yolk was identified in both clinically normal and abnormal females. Of the biochemical parameters tested, calcium, chloride, cholesterol, osmolality, phosphorus, salinity, sodium, specific gravity, total protein, and urea nitrogen have clinical utility. Abnormal samples were mostly associated with reproductive disease, but to a lesser extent with coelomitis and hemocoelom. The wild and semi‐managed groups had biochemical differences presumably reflective of the higher salinity of ocean water compared with that in the managed habitat. Aerobic bacteria were identified in normal (n = 7) and abnormal (n = 11) animals. Positive bacterial culture without inflammation may be normal. This study contributes to a further understanding of elasmobranch coelomic fluid analysis and its use as a diagnostic modality for the evaluation of elasmobranch health.
- Gross description variable – clear to white to slightly cloudy. Some green, blue, red.
- Presence of yolk identified in all sample colors.
- No association between sample color and fluid calcium.
- Cytology – Salt crystals, mesothelial cells, RBC may be normal. Also yolk.
- Abnormal population – RBC, WBC, mesothelial cells, yolk material, bacteria, salt crystals.
- WBC should be considered abnormal.
- Abnormal population – RBC, WBC, mesothelial cells, yolk material, bacteria, salt crystals.
- Clinical chemistry – Significant differences between normal and abnormal animals.
- Osmolality and UN significantly higher in abnormal animals.
- Significantly higher TS in abnormal animals.
- Abnormal samples had higher Ca, chol, P, SG, and TS when comparing normal managed and abnormal managed animals.
- Across the four populations of southern stingrays (normal managed, abnormal managed, semi managed, and wild), significant differences in Ca, Cl, Na, osmolality, P, salinity, and UN.
- Abnormal managed had significantly higher P than all other groups.
- Salinity in managed normal group significantly lower vs semi-managed group.
- Both managed populations significantly lower osmolality vs semi managed and wild.
- Normal managed and semi managed groups had higher Ca.
- Protein and CHOL electrophoresis.
- NSF between normal and abnormal samples. Neither protein nor CHOL electrophoresis are recommended for evaluation of elasmobranch coelomic fluid.
- Microbiology – Aerobic bacterial and fungal organisms isolated from normal and abnormal managed animals.
- Urine dipstick – Findings generally supportive of cytology (WBCs, RBCs, etc). No nitrites, ketones, or glucose in any sample. Dipsticks not recommended for acquiring additional information.
- Changes in color when used in conjunction in cytology, can be helpful in monitoring individual patients.
- Coelomic pores are considered excretory, and coelomic walls an active part of the excretory system of these animals.
- Sampling coelomic fluid via coelomic pore catheterization is a safe and effective technique.
- Variable amounts of fluid is normal.
- Microfauna without inflammatory cells may be considered normal vs WBC with bacteria supportive of coelomitis.
A recent study described the treatment of argulus infestation in freshwater stingrays.
Argulus are what type of parasite? They are thought to be mechanical vectors of what diseases? How can they be identified?
What is the mechanism of action of milbemycin?
What is the mechanism of action of lufenuron?
Is toxicity a concern with these drugs?
Was this treatment effective in these rays?
Tang, K. N., O’Connor, M. R., Landolfi, J., & Van Bonn, W. (2019). Safety and efficacy of milbemycin oxime and lufenuron to treat argulus spp. infestation in smooth back river stingrays (potamotrygon orbignyi) and magdalena river stingrays (potamotrygon magdalenae). Journal of Zoo and Wildlife Medicine, 50(2), 383-388.
Abstract: Fish lice, ectoparasites of the genus Argulus, are branchurian crustaceans that can significantly impact fish health by causing mechanical damage to cutaneous barriers and increasing susceptibility to other infections. While many treatments have been reported in teleosts and invertebrates, there are no published treatments for elasmobranchs. This study evaluated the safety and efficacy of a commercial formulation of milbemycin oxime and lufenuron in freshwater stingrays for treatment of Argulus spp. Seven juvenile Magdalena river stingrays (Potamotrygon magdalenae) and 10 juvenile smooth back river stingrays (Potamotrygon orbignyi) had severe infestations of Argulus spp. that were identified visually and microscopically. Animals were treated with milbemycin oxime and lufenuron (at 0.015 mg/L and 0.30 mg/L, respectively) in a 6-hr immersion once weekly for two treatments. They were visually examined for skin lesions as well as behavior and appetite daily by animal care staff. A subset of animals was euthanized and necropsied on days 8, 9, 43, and 78 after treatment initiation. There were no Argulus spp. detected at the time of the second treatment. Complete gross and histologic evaluations were completed for all animals. At all time points, no gross abnormalities were detected with the exception of thin body condition in some animals; no Argulus spp. were noted. Histologic lesions were all attributed to poor nutritional state at the time of acquisition. No histologic evidence of acute or chronic toxicosis was detected. The commercial formulation of milbemycin oxime and lufenuron, applied at the dose and for the exposure time used in this study, effectively eradicated Argulus spp. in a population of juvenile P. magdalenae and P. orbignyi, and did not cause mortality or clinical gross or histologic evidence of acute or chronic toxicity.
Fish lice (Argulus sp.): branchurian crustaceans
- Esp affect trout and carp species, but wide host range
- Mechanical vectors (virus & bacteria = spring viremia of carp, Flavobacterium columnare)
- Life cycle takes approx. 2 months. Peak abundance in summer and fall
- Attach to back using suckers and hooks, compress epithelial, in a ring shape, vacuum effect, loss of cohesion, irritation, discomfort, hemorrhage. Can cause edema and anemia in severe infections
- Dx by morphological ID: compound eyes, 2 large suckers that resemble eyes, shell-like carapace, 4 thoracic legs, jointed appendages, flattened saucer shape, 5-20 mm in size, visible to the naked eye
Milbemycin:
- Macrocyclic lactone effective on arthropods and nematodes (ineffective w/ cestodes and Platyhelminthes)
- Binds to glutamate-gate Cl channels in neurons and myocytes in invertebrates -> paralysis and death
- Lethal doses have been described in fish + limited efficacy when given PO against nematodes
Lufenuron:
- Benzoyl urea pesticide
- Inhibits chitin synthesis -> prevents exoskeleton formation
- Lethal doses have been described in fish
Results/Discussion: Was effective after the first tx (day 8). No adverse effects
Take-home:
- Immersion bath w/ lufenuron and milbemycin oxide in stingrays effective and safe against Argulus
- Lufenuron inhibits chitin synthesis, milbemycine oxide binds to Cl channels in neurons
A recent study described squamous cell carcinoma in a whitespotted bamboo shark.
What are the most commonly reported neoplasms in sharks?
What histologic features were seen in this case?
JZWM 2017 48(3) 902-905
SQUAMOUS CELL CARCINOMA OF THE ROSTRAL MAXILLA IN AN ADULT CAPTIVE WHITESPOTTED BAMBOO SHARK (CHILOSCYLLIUM PLAGIOSUM)
Betsy E. Culp, D.V.M., Martin Haulena, D.V.M., Dipl. A.C.Z.M., M.Sc., Kelly Britt, D.V.M., Hannah Evans, B.A., and Stephen Raverty, D.V.M., Dipl. A.C.V.P., Ph.D., M.Sc.
Abstract: An approximately 10-yr-old adult female whitespotted bamboo shark (Chiloscyllium plagiosum) presented with a smooth, white, irregular, ulcerated, and expansile lesion on the left lateral aspect of the maxillary rostrum. The lesion had short periods of abrupt and rapid proliferation and then remained static for several months. Cytology and culture were nonspecific and did not reveal any discernible etiologic agents or cellular atypia. The lesion was nonresponsive to parenteral antibiotics. One year after the initial onset of the lesion, the ulcer was 10 cm in diameter, a percentage increase in size of 455%. Due to a protracted clinical course and lack of response to medication and supportive care, coupled with an acute onset of neurologic signs and self-inflicted trauma, the shark was euthanized. Histopathology of the mass disclosed a locally invasive squamous cell carcinoma with no evidence of metastasis.
Key points:
- Mesenchymal tumors more commonly reported
- Polygonal cells arranged as cords, broad fronds, trabeculae, and tightly packed pearls with moderate amounts of intervening stroma and mitotic figures
Take home: First SCC in Orectolobiformes ‘‘carpet shark’’ order
A recent study described monogenean associated branchitis in a southern stingray.
Describe the life cycles of monogeneans, clinical signs of affected animals, and the difficulties in managing these cases.
Compare monopisthocotylean and polyopisthocotylean monogeneans in terms of morphology and the associated pathology they cause.
What monogenean parasite was described in this case of branchitis?
Molter, Christine M., and Laura J. Baseler. “Clinical challenge: Diagnosis of Loimopapillosum sp. Branchitis in a southern stingray (Dasyatis Americana).” Journal of Zoo and Wildlife Medicine 48.4 (2017): 1267-1269.
- Adult F southern stingray found dead
- Necropsy findings
- skin around gill slits erythematous, petechiae on cutaneous ventrum, ectoparasites attached to irregularly thickened gills, blood in oral cavity
- chronic, severe, proliferative branchitis with lamellar fusion caused by Loimopapillosum sp. and a secondary mixed bacterial infection
- Monogeneans
- common parasites of skin and gills of freshwater and marine bony and cartilaginous fish
- direct life cycle with unknown duration of each lifecycle stage
- rapid reproduction rate
- some species have eggs resistant to available treatments
- poor water quality and overcrowding exacerbate infection
- signs - dyspnea, hyperpnea, pruritus, lethargy, anorexia, behavioral changes, flashing, death
- two subclasses à Monopisthocotylea and Polyopisthocotylea
- Monopisthocotylea
- simple haptor
- feed on skin and gill epithelium and mucus
- lesions - increased mucus on gills and skin, cutaneous hemorrhages, and hyperpigmentation and fraying of fins
- gill histo - epithelial hyperplasia and necrosis, lamellar fusion, hemorrhage, increased mucus production, inflammatory cell infiltration
- skin lesions - increased mucus production, dermatitis, epidermal hyperplasia
- diagnosis - rigid endoscopy and gill biopsy
- tx - freshwater and praziquantel baths
- Polyopisthocotylea
- complex haptor
- feed on blood
- can cause anemia
A recent study evaluated the biochemistry and hematology of spotted eagle rays.
Describe the unique morphology of elasmobranch granulocytes.
What is the predominant leukocyte for elasmobranchs?
Greene, W., Brookshire, G., & Delaune, A. J. (2018). Hematologic and biochemical summary statistics in aquarium-housed spotted eagle rays (aetobatus narinari). Journal of Zoo and Wildlife Medicine, 49(4), 912-924.
Abstract: During this retrospective study, 18 plasma blood chemistry and 17 complete blood count (CBC) samples were analyzed from clinically healthy spotted eagle rays (Aetobatus narinari) at Georgia Aquarium in order to generate hematological ranges for complete blood count (CBC) and biochemical profiles. Summary statistics were generated according to the American Society for Veterinary Clinical Pathology guidelines for the determination of reference intervals in veterinary species.4 The mean packed cell volume (PCV) was 28.09% with a range of 23–35%. Mean total solids were 5.72 g/dl with a range of 5–7.0 g/dl. Lymphocytes were the dominant leukocyte observed on differential (67.35%), followed by fine eosinophilic granulocytes (FEGs) (15.41%), coarse eosinophilic granulocytes (CEGs) (10.24%), monocytes (1.88%), and basophils (1.24%). Chemistry samples were analyzed at two diagnostic laboratories, Michigan State University (MSU) and University of Miami (UMiami), and the results were compared. Both labs have the capacity to run blood chemistries on zoo and aquatic species, but utilize different methods to obtain chemistry analyte values. UMiami uses a thin-film dry-slide technology, whereas MSU uses an ion-selective electrode (ISE) and Beckman Coulter AU 640 analyzer. There is poor agreement between the analyzers used by the two laboratories for both alkaline phosphatase and BUN, because of proportional error. Establishing hematological ranges in spotted eagle rays and in elasmobranchs in general may enhance the understanding of the species and their health. This information may aid clinicians in deciding when and how to treat elasmobranchs.
- Key Points:
- Elasmobranch WBCs are unique in that they have both fine eosinophilic granulocytes (FEGs) and coarse eosinophilic granulocytes (CEGs) vs heterophils.
- Lymphocytes dominant leukocyte on differential (~67%), similar to other elasmobranchs.
- Elasmobranch WBCs are unique in that they have both fine eosinophilic granulocytes (FEGs) and coarse eosinophilic granulocytes (CEGs) vs heterophils.
- Takeaway: Spotted eagle rays similar to other elasmos in regards to CBC/chem values. Monitoring trends within individual recommended; laboratories can vary in results for chem analysis.
A recent study described the gastrointestinal emptying times in cownose rays and whitespotted bamboo sharks.
How much barium did they give them?
How much metoclopramide did they give them?
What are the four distinct phases of gastrointestinal transit in elasmobranchs?
How do the two species differ?
Does metoclopramide appear to be effective in elasmobranchs?
RADIOGRAPHIC DETERMINATION OF GASTRIC EMPTYING AND GASTROINTESTINAL TRANSIT TIME IN COWNOSE RAYS (RHINOPTERA BONASUS) AND WHITESPOTTED BAMBOO SHARKS (CHILOSCYLLIUM PLAGIOSUM) AND THE EFFECT OF METOCLOPRAMIDE ON GASTROINTESTINAL MOTILITY
Journal of Zoo and Wildlife Medicine 51(2): 326–333, 2020
Abstract: Gastrointestinal (GI) pathology is common in elasmobranchs; however, information regarding normal GI transit time and the effect of therapeutics on GI motility is lacking. The objective of this study was to determine baseline gastric emptying and GI transit times in cownose rays (Rhinoptera bonasus) and whitespotted bamboo sharks (Chiloscyllium plagiosum) via radiographic barium sulfate contrast studies. Additionally, a pilot study was undertaken to determine the effect of metoclopramide on GI transit time in whitespotted bamboo sharks. Eight cownose rays and eight whitespotted bamboo sharks were administered a 98% w/w barium sulfate suspension at 8 ml/kg via orogastric tube. Post-contrast radiographs were obtained at 2 min, 3, 6, 12, and 23 hr for rays; and 2 min, 3, 6, 9, 12, 16, 25, 30, 36, and every 12 hr until complete gastric emptying occurred for sharks. In cownose rays, the mean and standard error were established for time of initial spiral colon filling (3.4 6 0.4 hr), complete spiral colon opacification (12 6 0 hr), initial spiral colon emptying (21.6 6 1.4 hr), and complete gastric emptying (23 6 0 hr). In bamboo sharks, the mean and standard error were established for time of initial spiral colon filling (5.3 6 0.5 hr), complete spiral colon opacification (12.4 6 1.3 hr), initial spiral colon emptying (22.5 6 2.7 hr), and complete gastric emptying (39.9 6 3.3 hr). Cownose rays had a significantly shorter time to spiral colon filling and complete gastric emptying compared with bamboo sharks (P , 0.05). Whitespotted bamboo sharks (n ¼ 8) were administered metoclopramide (0.4 mg/kg orally once daily for 10 days) and the barium series was repeated. Complete gastric emptying time was significantly shorter in treated sharks compared with control (P , 0.05), suggesting that metoclopramide may be a useful therapeutic for GI motility disorders in elasmobranchs.
Intro
- GI pathology is common in elasmobranchs
- Little info on normal GI transit times
- The objective of this study was to establish baseline gastric emptying time and GI transit time of barium sulfate contrast in cownose rays and whitespotted bamboo sharks
- A pilot study was also undertaken to determine the effect of metoclopramide on gastric emptying and GI transit time in the whitespotted bamboo shark
M&M
- 8 cownose rays and 8 whitespotted bamboo sharks were given 8 ml/kg barium PO and then radiographed in series to measure gastric emptying
- 3 weeks after each bamboo shark was given metoclopramide 0.4 mg/kg PO SID x 10 days. On day 7 the barium series was repeated in the same manner
Results and discussion
- Results of this study reveal that transit time of barium through the elasmobranch GIT can be broken up into four distinct, easily identifiable time points including initial spiral colon filling, complete spiral colon opacification, initial spiral colon emptying, and complete gastric emptying.
- Cownose rays displayed a significantly shorter mean initial spiral colon filling time (3.4 hr) and mean gastric emptying time (23 hr) as compared to whitespotted bamboo sharks (5.3 hr and 39.9 hr, respectively)
- No differences when evaluated for sex or weight
- With metoclopramide, treated sharks displayed a statistically shorter time to complete gastric emptying (27.6 hr) compared with non-treated sharks (39.9 hr)
- Takeaway: GI transit time in cownose rays and whitespotted bamboo sharks consists of 4 distinct time points, GI transit time is shorter in cownose rays than bamboo sharks, and reglan orally may be useful in treating motility disorders in sharks
A recent study described the diagnosis and management of congestive heart failure in a Sand Tiger Shark.
What is the scientific name of this species?
Describe elasmobranch cardiac anatomy
- What are the chambers of the heart
- Describe the flow of blood through the heart
- How is cardiac output changed in elasmobranchs?
How did this case present?
- What was observed on sonography?
- How was teh case treated?
What are some differentials for cilated cardiomyopathy in elasmobranchs?
DIAGNOSIS AND MANAGEMENT OF SUSPECTED CONGESTIVE HEART FAILURE SECONDARY TO DILATED CARDIOMYOPATHY IN A SAND TIGER SHARK (CARCHARIAS TAURUS) WITH ESTABLISHMENT OF PRELIMINARY NORMAL ECHOCARDIOGRAPHIC INDICES
Michael W. Hyatt, DVM, DACZM, and Trevor J. Gerlach, DVM, DACVIM
Journal of Zoo and Wildlife Medicine 53(2): 363–372, 2022
Abstract: Elasmobranch cardiac anatomy and physiology has been well described; however, there is a dearth of information regarding cardiac disease. In support of a clinical case of suspected congestive heart failure in a 22-yrold male sand tiger shark (Carcharias taurus), a study was undertaken to identify feasible echocardiographic imaging planes and preliminary indices for this species. Eleven echocardiograms were performed on six apparently healthy sand tiger sharks. Echocardiographic parameters are presented using descriptive statistics, including mean, median, standard deviation (SD), minimum and maximum values. These data were utilized for the diagnosis and clinical management of the affected shark. The shark initially presented with increased respiratory effort, dependent, peripheral edema, and anemia. Echocardiography revealed atrial, ventricular, and sinus venosus dilation. As congestive heart failure secondary to dilated cardiomyopathy was strongly suspected, therapy was initiated with oral benazepril and torsemide, and later pimobendan. After a year of therapy, clinical signs resolved. Cardiac size and function improved on echocardiography with a reduction in sinus venosus dilation, maximum and minimum atrial and ventricular inner diameters, and an increase in atrial and ventricular fractional shortening. Cardiac disease in elasmobranchs may be underdiagnosed, so it may be necessary to develop standardized ultrasound techniques and cardiac measurements for each species of elasmobranch managed within zoos and aquaria.
Key Points:
- Elasmobranch heart – 2 chambers (atrium and ventricle) with accessory structures of sinus venosus located caudally and conus arteriosus cranially.
– Atrium and ventricle are cardiac muscle while sinus venosus and conus arteriosus are smooth muscle with cardiomyocytes.
– Contained within pericardium with variable amounts of pericardial fluid
- Blood returns from systemic circulation to the heart via hepatic and cardinal veins emptying into sinus venosus 🡪 sinoatrial valve into the atrium 🡪 AV valve into the ventricle 🡪 out conal calve and conus arteriosus 🡪 ventral aorta to gills 🡪 dorsal aorta to systemic circulation
- Heart rate stable during exercise – CO more heavily influenced by stroke volume in elasmobranchs
– Lack sympathetic innervation to heart 🡪 rely on parasympathetic innervation and circulating catecholamines
- Aim of study was to describe clinical case and the results of normal sand tiger shark echos
- Case report 🡪 sand tiger shark presented with increased respiratory effort (mouth gape and buccal pumping), dependent peripheral edema of claspers and base of pelvic fins
– Atrial, ventricular, and sinus venosus dilation with reduced atrial and ventricular contractility
– Hepatic veins emptying into sinus venosus dilated
– DCM with secondary congestive heart failure suspected
– No evidence of coelomic effusion, moderate anemia (11%)
- Treatment – benazepril (ACE inhibitor), torsemide (pyridine-sulfonylurea loop diuretic), iron.
– Pimobendan (inodilator) added after no echo changes and progressive edema were seen
– Progressive clinical and echo improvements seen – peripheral edema and dyspnea resolved by 9 months, and echo parameters normalized within 1 year
– Compared to healthy group, prior to treatment, shark had increased atrial and ventricular maximum and minimum inner diameters, an increased atrium:conus arteriosus (A:CA) ratio, reduced atrial and ventricular shortening fractions, and increased sinus venosus measurements prior to initiation of therapy.
– Another case of suspected DCM in leopard shark 🡪 anemia, increased ventricular maximum inner diameter, and reduced shortening fraction though also had coelomic effusion, wt loss, and poor appetite
– Ddx for DCM 🡪 toxic insult, nutritional deficiency, metabolic derangements, genetic disease, and myocarditis, or the cause may have been idiopathic toxic insult, nutritional deficiency, metabolic derangements, genetic disease, and myocarditis, or the cause may have been idiopathic
- In elasmobranch, cardiac output increases occur by increased stroke volume but indirectly regulate this through transfer of pericardial fluid into coelomic cavity
Take-Home Message:
- First case of clinical DCM with secondary CHF in a sand tiger shark. -
- Clinical signs of dependent peripheral edema were consistent with CHF.
- Study provides reference values for normal sand tiger sharks.
