Herp Theriogenology & Neonatology Flashcards
1
Q
Describe the anatomy of reptile testes.
Where are they located in the coelom?
How do they change seasonally?
What are they supported by? What organ lives in that structure?
How are they supplied by the vasculature?
A
Male repro anatomy
- Testes
- Paired
- Consists primarily of seminiferous tubules and interstitium (interstitial cells, fibroblasts, blood vessels, lymphatics)
- Seminiferous tubules have lining of epithelium containing Sertoli cells and germ cells in different stages of development
- 3 organized layers of germinal cells
- Immature, along basement layer (spermatogonia)
- Developing, middle layer (spermatocytes)
- Mature, in center (spermatids and free spermatozoa)
- Embryonically derived from medullary region of germinal ridge
- Located dorsally in mid to caudal coelom adjacent to adrenal glands and near cranial portion of kidneys chelonians, crocodilians, tuatara, and most lizard species
- Testes considerably more cranial to kidneys in lizards with intrapelvic oriented kidneys
- Snakes and many lizard species the right testis cranial to left snakes and many lizards
- Right testis located just caudal to gall bladder in cranial portion of lower 1/3 of body snakes
- Right and left testes found 65% to 82% of total snout-to-vent length depending on taxa, with right testis cranial to left with a high degree of overlap
- Elongated
- Testes black in old world chameleons
- Size of the testes varies seasonally and correlates with reproductive activity
- Active spermatogenesis results in testicular enlargement, reduction in size associated with spermatogenic quiescence
- Mesorchium supports and attaches testis, surrounded by tunica albuginea, to dorsal coelom
- Adrenal glands contained within mesorchium in squamates
- Dorsal aorta gives rise to testicular arteries, which extend to ductus deferens
- Testicular vein empties into renal vein, which drains into post cava
2
Q
Describe the anatomy of the reptile epididymis and the vas deferens.
Where are they located?
What taxa lacks the epididymis?
Where does the vas run and empty into?
Describe the flow of sperm from the testes to the cloaca.
A
- Epididymis/Vas Deferens
- Genital ducts arise from mesonephric Wolffian ducts and paramesonephric Mullerian ducts
- Wolffian duct develops and persists with Mullerian ducts regressing under influence of testosterone in males
- Epididymis - flat tubular structure lateral to each testis and makes up anterior portion of ductus deferens
- Not typically present in snakes
- Ductuli efferentia from testis passes through mesorchium into epididymis
- Vas deferens courses caudally, along ventral portion of kidney, empties into urodeum at genital papillae
- Some species - vas deferens and ureters join to form common urinogenital papillae in urodeum
- Sperm: seminiferous tubules ductuli efferentia ductus epididymis ductus deferens urodeum
- Genital ducts arise from mesonephric Wolffian ducts and paramesonephric Mullerian ducts
3
Q
Describe the anatomy and physiology of the renal sexual segment in reptiles.
What does it produce?
What is the function of those secretions?
What taxa lack the renal sexual segment?
What secondary sex organ is it correlated with in mammals?
A
- Renal sexual segment
- Kidney of male squamates possesses enlarged (when active) sexual segment
- Hypertrophies, secretory cells fill with numerous granular inclusions
- Produce secretion that varies from holocrine to merocrine and contains proteins, amino acids, and phospholipids role unknown
- Production of copulatory plugs in some snakes remains in female’s cloaca and prevents rival males from copulating with same female
- Activate sperm - source of energy, help with survival of sperm in oviduct
- Composed of hypertrophied distal and collecting tubules
- Absent in crocodilians and chelonians
- Seasonal activity can dramatically change gross renal appearance (to a white-yellow color change)
- Lizards have more seasonal change than snakes
- Correlates with mammalian seminal vesicle
- Kidney of male squamates possesses enlarged (when active) sexual segment
4
Q
What are the copulatory organs of reptiles?
How does it vary by taxa?
Where are they located within the cloaca?
What taxa does not have a copulatory organ?
Does the urethra run within these organs? Why does this matter clinically?
A
- Copulatory organ
-
Chelonians and crocodilians - single median phallus
- Originates from floor of urodeum
- Resides in ventral aspect of proctodeum of cloaca
- Does not invert, tissue becomes engorged and pair of spongy longitudinal ridges on dorsal surface form seminal groove that directs semen toward vent
- Longitudinal ridges formed from coelomic canals and corpus cavernosa
-
Chelonians and crocodilians - single median phallus
Corpus cavernosa become engorged with blood from internal iliac vessels resulting in dorsal and medial curling of seminal ridges forming tube-like seminal groove to direct sperm down phallus
- Chelonian phallus - spade-shaped glans at distal end w/ 3 folds (plica externa, plica media, plica interna) direct sperm and help maintain phallus in cloaca
-
Squamates - hemipenes
- Paired
- Located laterally in ventral tail base and held there by retractor muscles
- Sulcus spermaticus - seminal groove located on everted surface
- Functions to direct sperm into cloaca
- Eversion occurs for copulation and no actual erectile tissue present
- Tuatara - no specialized copulatory organ
- Do not contain urethra and no direct connection with ductus deferens
5
Q
Describe the ovarian anatomy of reptiles.
Where are they located wtihin the coelom?
What structure are they supported by? What organ is contained within that structure?
How do the ovaries change as they mature?
How are the ovaries supplied by the vasculature?
What are the two phases of follicular development?
A
Female Repro Anatomy
- Ovaries
- Paired
- Embryonically derived from cortex region of germinal ridge
- Intrafollicular stroma with associated hierarchy of follicles at different stages of development and atresia
- Located dorsally
- Located in mid to caudal coelom adjacent to adrenal glands near cranial portion of kidneys chelonians, crocodilians, tuatara, most lizards
- Lizards with intrapelvic-oriented kidneys - ovaries more cranial to kidneys and right ovary just caudal to tip of right liver lobe
-
Supported by mesovarium attached to dorsal coelom
- Squamates - adrenal glands contained within mesovarium
- Crocodilians and chelonians - adrenals retroperitoneal, dorsal to gonads, closely related to kidney
- Chelonians, crocodilians, tuatara - ovaries symmetrical
- Squamates - right ovary cranial to left
- Snakes - cranial pole of right ovary located just caudal to gall bladder in cranial portion of lower 1/3 of body
- Right and left ovaries found between 58% to 80% of total SVL length
- Right ovary cranial to left with high degree of overlap
- Vary in color depending on maturity and seasonal activity
- Immature ovaries - flat and granular in appearance
-
Mature ovaries - different stages of maturing follicles results in variable appearance
- Previtellogenic follicles - small and clear to white, no yolk
- Vitellogenic follicles - larger and yellow to orange as they develop yolk
- Dorsal aorta gives rise to ovarian arteries
- Ovarian vein - empties into renal vein, drains into post cava
-
Ovarian follicular development 2 distinct phases influenced by season:
- Previtellogenesis
- Vitellogenesis - movement of yolk into maturing ovarian follicle
- Liver hormonally influenced to produce yolk precursors to support vitellogenesis
- Vitellogenic follicles either ovulate, regress, or rarely become static and potentially inspissated (follicular stasis)
- Once ovulation occurs, corpora lutea develops producing progesterone and remaining active through gravid cycle
- After oviposition or birth corpora lutea regresses, becoming corpora albicans, which can remain for years
- Vitellogenic follicles that do not ovulate begin cycle of regression (atresia)
6
Q
Describe the anatomy and physiology of the reptile oviduct.
How many ociducts do these animals have?
What structure supports the oviduct?
What are the five regions of the oviduct? Do all species have these divisions?
A
- Oviduct
- Flattened tubular structures positioned adjacent to each ovary
- Arise from mesonephric Wolffian duct and paramesonephric Mullerian ducts
- Right and left oviduct
- 2 genera of snakes (Typhlops and Leptotyphlops) missing left oviduct
- Immature - thin bands of tissue
- Adults with previous repro activity - more distinct, “concertina” or “accordion” appearance demonstrating contraction from previous enlargement/stretching
- Mesosalpinx - supportive mesentery of oviduct, may contain prominent oviductal ligament
- Presence of ligament helps determine sex of some immature reptiles endoscopically – not present in male
- Infundibulum - opening of oviduct located on dorsal body wall just craniad to each ovary, oviducts then course caudally, pass ventromedial to kidneys, terminate individually in dorsal wall of urodeum at genital papillae
-
5 regions of oviduct (from cranial to caudal) recognized histologically: infundibulum uterine tube isthmus (a-glandular portion) uterus (glandular) vagina (thick muscular portion)
- Not all species have each oviduct division
- No true uterus exists
- Fertilization takes place in infundibulum and occurs before deposition of egg envelopes by oviduct glands
- Copulation occurs before ovulation - sperm must be stored by female
- Seminal receptacles in posterior uterine tube, isthmus, and anterior vagina of many reptiles to store sperm
- Ciliated and nonciliated mucous cells line oviduct with glands below epithelial lining
- Glands have both albumen-secreting and calcareous-secreting (shell and shell membranes) function
- No glandular structures in vagina
- Albumen layer provides both physical support to embryo and assists with water storage
- Also secretes antimicrobial peptides that may protect embryo from infection
- Oviparous - mucosal glands produce calcium and fibrous portions of shell membrane and egg shell, mineral for bone is primarily derived from the shell and shell membranes
- Viviparous - glands few or absent, calcium minerals derived from yolk material
7
Q
Discuss the role of the cloacal scent glands in snakes.
Are they larger in males or females?
What species can use them as a defensive spray?
What do they secrete?
What is their function?
A
Cloacal scent glands in snakes
- Specialized exocrine glands produce thick semiliquid material containing pheromones (intraspecific) and/or semiochemicals (interspecific) used to mark object/substrate/organism
- Paired
- Located within tail base just dorsal to and attached to hemipenes in males and in corresponding position in females
- Unique to snakes
- Present in both males and females but larger in females
- Some species have unique liquid gland material with ability to void as defensive spray
- Copperheads
- Duct at anterior portion of gland curves laterally and opens adjacent to opening of \ hemipenis/hemiclitoris
- Muscular sphincter associated with duct itself, gland surrounded by muscular sheath
- Holocrine - material consists of mostly (90%) free fatty acids (source of musk odor), primarily palmitic, oleic, and linoleic acids with mucopolysaccharides and mucoproteins
- Lipids can be unique to species and even between sexes
- Role variable – behavioral sex attractant, defensive/repellant, aggregation cues, alarm/alert, and territorial marking
8
Q
Describe the reproductive seasonality of reptiles.
What are the two modes of spermatogenic seasonality?
How is the vitellogenic cycle controlled hormonally?
What are the effect of estrogen, progesterone, and testosterone during the vitellogenic cycle?
A
Repro cycle
- Seasonal changes in temperature, photoperiod, and rainfall (food availability) affect endogenous control of repro cycles by influencing hypothalamic-pituitary-gonadotropin endocrine system
- Spermatogenic cycle
- 3 most important environmental factors that influence endogenous control of spermatogenesis temperature, rainfall, and photoperiod
-
“Prenuptial” and “postnuptial” spermiogenesis
- Prenuptial – testicular recrudescence occurs in spring after emerging from hibernation and ends in late spring/summer before mating
- Postnuptial - testicular recrudescence begins in spring but continues through summer, with spermiogenesis occurring at end of summer
- Spermatozoa often stored overwinter in vasa deferentia for use in following spring
- Vitellogenic cycle
- Dependence on adequate amounts of energy required for folliculogenesis compared with spermiogenesis
- Major step in maturation of ovarian follicle accumulation of yolk (vitellogenesis)
- Energy for vitellogenesis comes primarily from fat stores of female but in some species can also be derived from calories taken in during vitellogenesis
- Cycle controlled by pituitary gonadotropins
- Hypothalamic-pituitary-gonadotropin endocrine system influenced by environmental cues as mentioned for males but also with greater dependence on energy reserves in females
- Squamates - FSH–like pituitary gonadotropin identified, similar function as mammals
-
Crocodilians and chelonians - FSH and LH–like pituitary gonadotropins identified, similar function as mammals
- Increase in LH, progesterone, and testosterone levels have been documented with ovulation in many chelonian species
-
Estrogen, progesterone, and testosterone (androgens) important in repro cycle of female reptiles
-
Female veiled chameleons - fecal hormone values utilized to evaluate sex steroid hormonal patterns associated with nonovulatory and ovulatory phases
- Estrogen increased during vitellogenesis, peaked in late vitellogenesis
- Progesterone increased during late vitellogenic cycle, peaked at midgravidity, and fell to baseline values at oviposition
- Testosterone varied during previtellogenic and vitellogenic phases, but peaked during ovulation and gravidity
- Ovulation found to occur with decreasing estrogen/progesterone ratio
-
Estrogen and progesterone - role in vitellogenesis and stimulating liver to convert lipid from fat stores to vitellogenin
- Liver enlarges dramatically and takes on a yellow color - physiological increase in intrahepatic fat, not pathological hepatic lipidosis)
- Vitellogenin (yolk protein) - selectively absorbed from bloodstream by ovarian follicles
- After egg deposition, concentrations of estrogen, progesterone, and testosterone decrease in many chelonian species
-
Female veiled chameleons - fecal hormone values utilized to evaluate sex steroid hormonal patterns associated with nonovulatory and ovulatory phases
- Calcium predominantly supplied to embryo via yolk, plasma calcium levels elevated during vitellogenesis
- Thyroid activity also influences reproduction
- Estrus period usually corresponds with active vitellogenesis
- Occurs early in vitellogenic cycle in snakes and later stages in lizards
- Vitellogenic cycles do not necessarily coincide with active spermatogenesis, stored sperm often used for breeding
- Tropical and subtropical species have more frequent repro cycles, often polyestrous, may have second breeding season, or breed throughout year
9
Q
What are the three basic ovulation strategies of reptiles? Give taxa examples of each.
Where does fertilization occur?
Does fertilization occur before or after ovulation?
A
Fecundity and clutch dynamics
- 3 basic ovulation strategies
- Polyautochronic ovulation - simultaneous ovulation of many ova from both ovaries
- Many squamata and chelonian species (iguanids, bearded dragons, boids, colubrid snakes, red-eared sliders, many box turtles and tortoises)
- Monoautochronic ovulation - single ovum simultaneously from each ovary
- Common in Gekkonidae
- Monoallochronic ovulation - one ovum from either right or left ovary ovulates, and ovaries alternate between each single egg clutch
- Anolis spp.
- Polyautochronic ovulation - simultaneous ovulation of many ova from both ovaries
- Inverse relationship between offspring size and clutch size
- Ablating some developing follicles during early vitellogenesis reduces clutch size and allows for greater allocation of energy to remaining ova
- FSH at onset of repro cycle will increase clutch size while decreasing offspring size
Courtship
- Intermale rivalry with visual displays (of colors and/or head and leg movements), vocalizations, physical fighting, and chemical cues (pheromones) used
Copulation
- Copulatory behavior in males does not necessarily coincide with peak spermatogenesis and testicular development due to stored sperm
- Tuatara copulates by pressing vent lips together for sperm transfer (no copulatory organs)
- Copulation time - short in many lizards (seconds) or longer (hours to days) in chelonians, snakes
- Aquatic turtles breed in water, box turtles and tortoises on land
- Male box turtles utilize rear feet by placing them between plastron and carapace to keep female from closing plastron on phallus
- Females more likely to receive trauma during courtship
Fertilization
- All fertilization occurs internally
- Occurs at cranial end of the oviduct (infundibulum) before any deposition of egg envelopes
- Copulation occurs before ovulation and sperm stored in seminal receptacles
- Can store sperm up to 6 years but fertility highest when copulation occurs with female’s repro cycle
- Multiple male paternity possible due to sperm storage
- Exact gestation length difficult to determine
10
Q
Describe the reproductive strategies of reptiles.
Which species are oviparous?
How much embryonic development occurs by the time of ovpiosition?
How does shell calcification vary?
What species are viviporous?
How are embryos supported nutritionally?
Parthenogenesis has been documented in which species?
Which species provide parental care?
A
Repro strategies
- Oviparity
- Chelonians, crocodilians, tuatara, most squamates
- Once ovulation occurs, little transfer of nutrients between female and ova
- Embryos have often completed 25% to 30% of development at oviposition in squamates
- Health of offspring dependent on environmental conditions during (external) egg incubation and (viviparous species) on conditions of female post-ovulation and prior to oviposition
- Degree of shell calcification varies among species
- Minimal, pliable eggs - snakes, most lizards, some turtles)
- Pronounced, rigid eggs - crocodilians, tortoises, and many geckos
- Ultrasonography can distinguish stages of gonadal inactivity, early previtellogenic follicle growth, vitellogenesis, ovulation, and either shelling or fetal development
- May suspend feeding during latter stages of egg development but length of time shorter than viviparous species (weeks vs months)
- Viviparity
- Many species of lizards and snakes
- Subdivided into ovoviviparous and viviparous
- Nutrients provided to embryos by lecithotrophy (via yolk during follicular development) or matrotrophy (during embryonic development such as across placenta)
- Limited to single clutch per year
- Females usually reduce intake or cease feeding during latter stages of gestation due to space occupation effecting GIT
- Parthenogenesis
- Asexual reproduction
- Some lizards and snakes whiptails, Komodo dragons
- All blind snakes are triploid females
- Some snakes can switch between asexual and sexual reproduction
- Garter snakes, rattlesnakes, copperheads, cottonmouths, file snakes, Burmese pythons
- Parental care
- Most show no parental care of eggs or offspring beyond choosing appropriate nesting site and concealing eggs
- Exceptions – some pythons, crocodilians, Burmese mountain tortoise, skinks, glass lizards, cobras, rattlesnakes
- Most show no parental care of eggs or offspring beyond choosing appropriate nesting site and concealing eggs
11
Q
When do reptiles become sexually mature?
How does it vary by taxa?
A
Sexual maturity
- Determined primarily by size, age less significant
- Snakes raised under optimal conditions usually mature in 2-3 years
- Small lizards – 1-2 years
- Large lizards – 3-4 years
- Chelonians take longer to mature - usually 5- 7 years
12
Q
Describe the various methods of sexing reptiles.
What species have mineralized hemipenes?
What species have temperature dependent sex determination?
What are the chromosomal variations among reptiles?
A
Sex identification
- No external genitalia
- Other than differences in maximal body size, secondary sexual characteristics rare in snakes and crocodilians
- Probing
- Some lubricant spermicidal, use saline in breeders
- Common species in which female hemiclitores well developed and misidentification of sex likely - short-tailed (blood) pythons and monitor lizards
- Does not work as well in lizards as in snakes, many lizards have increased musculature in this area and contraction hinders probe advancement
- Manual hemipene eversion
- Should not be used in species that perform tail autotomy
- More difficult in heavy-bodied juvenile snakes, including many boas and pythons and some colubrids, risks trauma
- Hydrostatic eversion of hemipenes
- Eversion by saline injection
- More invasive and uncomfortable
- Increased risk for injury
- Useful for neonatal snakes where manual eversion ineffective and for many lizards
- Digital palpation of cloaca
- Preferred method for sex identification of crocodilians
- Palpate for presence of phallus
- Plasma sex hormone evaluation
- Can measure plasma testosterone levels and fecal hormone levels
- Radiography
- Many mature monitor species - mineralized hemibacula within hemipenes
- Pelvic measurements taken from rads in Gila monsters useful to differentiate sexes
- Contrast studies have also been used – inject contrast around hemipenes/hemiclitoris
- Contrast radiography and contrast CT considered effective, noninvasive, but more costly, techniques for gender identification in lizards
- US
- Limited to identifying females with ovarian follicles (spherical anechoic to hypoechoic structures based on cycle)
- Immature females, acyclic females, and all males often undistinguishable
- CT/MRI
- CT – poor accuracy without contrast
- Surgical or endoscopic sex determination
- Visualization of gonads via surgery or coelomic endoscopy is definitive method for determining sex of reptiles
- Endoscopy not useful in snakes
- Endoscopic evaluation of gonads through transparent bladder wall of juvenile tortoises has been performed
- Less invasive
- Does not provide the same degree of visual acuity as direct coelomic examination
- Unsafe in juvenile sliders
- Temperature-dependent sex determination
- All crocodilians, most chelonians, few species of lizards (bearded dragon, leopard gecko, crested gecko)
- Species dependent - warmer temperatures produce males in some, and in others, warmer temperatures produce females
- Some even bimodal - one sex produced at moderate temperatures and other produced at high and low temperatures
- Genotyping (DNA/Molecular Sexing)
- Heterogametic sex varies among species
- With chromosomal determination some genera have XY sex chromosome, some genera have ZW sex chromosome, some genera have no recognizable sex chromosome, some may show all 3 variations
- Limited to threatened or endangered species as this test is species specific
13
Q
Describe the breeding of managed reptiles.
What species have seasonally cooling?
How long do these animals need to be fasted before going through brumation or hibernation?
How are animals determined to be gravid?
What is a pre-lay shed? Why does it happen?
A
Captive breeding
- Seasonal cooling - period of cooler temperature necessary for most species to initiate reproductive behavior
- Brumation, hibernation, or cycling
- Don’t cool unhealthy animals
- Fast prior to cooling
- Snakes - at least 2 weeks before extended cooling
- Lizards and chelonians - several days to a week
- Cooling duration commonly range from 4 to 12 weeks
- Water ad lib but beware high humidity (can cause resp infections)
- Other repro stimuli - increased cage humidity, artificial raining, increased feeding, repeated introduction to multiple potential mates, adding shed skins from conspecifics, and male-male combat
- Pregnancy determination
- Midbody swelling apparent in gravid snakes and lizards (also in obese animals)
- Eggs seen through semitransparent skin over ventrum in some geckos
- R more cranial than L – ovaries
- Fat bodies – symmetrical
- Classic behaviors of gravid reptiles - increase in basking time (increase in selected body temperature), partial or complete anorexia, change in body positioning
- Snakes - looser coiling and lying in semilateral or dorsal recumbency
- Coelomic palpation – snakes and sometimes lizards, sometimes shelled eggs palpable in vertically tilted chelonians
- Radiography and ultrasonography – best method
- Rads better in chelonians due to hard calcium rich eggshell
- Lizards and snakes – rads more challenging, lower amount/lack of calcium in eggshell, US preferred
- US
- Vitellogenesis in squamates - follicles becoming larger and progressively more echogenic but remaining clustered (lizards)
- Vitellogenesis in chelonians - similar but follicles are not as clustered
- Ovulated follicles and eggs are linearly arranged, occupying caudal half of reptile
- Gestation and oviposition
- Low-grade infections often fulminate during gravidity – negative energy balance
- True gestation time hard to determine
- Temporal separation between copulation and ovulation
- Prevalence of multiple copulations
- Temperature-dependent effect - warmer temps may decrease gestation time
- Gestation lengths for viviparous species range from 1.5 to 6 months
- Most snakes undergo ecdysis before oviposition (associated with concurrent thyroid hormonal activity) “prelay shed” relatively reliable predictor of oviposition for snakes
- US study performed in ball pythons to describe entire follicular cycle and gestation period published
- Nesting and oviposition
- Not providing an appropriate nesting site can lead to dystocia
- Common in green iguanas, monitors, old world chameleons
- Not providing an appropriate nesting site can lead to dystocia
14
Q
Describe artificial insemination of reptiles.
How is semen collected?
How is the ejaculate evaluated?
How is it preserved?
What insemination techniques are commonly used?
A
Artificial insemination
- Semen collection
- Manual collection
- Recommended for crocodilians
- Successful in many boids, colubrids, and vipers
- Skinks
- Electroejaculation – has been used in crocodilians and chelonians, some snakes, green iguana, chameleon
- Vibrator – chelonians
- Highest frequency, move along carapace in a linear or circular motion
- Manual collection
- Sperm analysis
- Evaluated for 3 major parameters: concentration, motility, and morphology
- Ejaculates collected either manually or by EEJ are comparatively much lower in volume than those produced by mammals and must be diluted for accurate counts
- More correct to quantify sperm per ejaculate (spermatozoa/ejaculate) because of small volumes reptiles produce
- Sperm storage and cryopreservation
- Generally difficult to preserve
- Extenders or media for short-term storage that have been utilized include Hamm’s F-10, egg yolk buffer, lactated ringers solution, phosphate-buffered saline, and TCG-Tris-citrate-glucose
- Extenders have only been evaluated in crocodilians
- Storage temperature has been evaluated in snakes, lizards, chelonians
- Cooled short-term semen storage successful in crocodilians for up to 2 days
- Shorter duration in snakes
- Chelonian semen fragile and does not store well
- Cooled short-term semen storage successful in crocodilians for up to 2 days
- Cryopreservation does not work well in reptiles
- AI procedures and techniques
- Fresh semen and short-term cooled semen successfully used in American alligators
- AI successful in saltwater crocodile with oviductal catheterization
- Catheterization of oviduct using cloacoscopy has been performed in turtles, snakes
- Endoscopic deposition into oviduct has also been attempted
15
Q
Describe the imaging modalities used to evaluate the reptile reproductive tract.
How do follicles change ultraonsographically? What changes suggest surgery is indicated?
A
Repro Imaging
- Rads
- Useful for differentiating between preovulatory follicles and postovulatory eggs
- Preovulatory follicles (rarely seen in chelonians) - more spherical with no mineralized shell, clustered, and more dorsally positioned
- Useful to determine normal gravidity and to identify obstructive or pathological conditions
- Identify mineralized eggs (squamate egg shells are generally much less calcified than chelonian eggs) and confirm egg numbers, abnormalities (shell thickening, breaks), ectopic eggs, comparative egg size, and pelvic diameter versus egg size
- Identify underlying nutritional secondary hyperparathyroidism or concurrent coelomic pathology, such as cystic calculi, obstipation, or organomegaly
- Viviparous squamates - useful but not until late in gestation when skeletal structures become mineralized
- Useful for differentiating between preovulatory follicles and postovulatory eggs
- US
- Imaging modality of choice to evaluate reproductive tract in squamates
- Chelonians - useful for preovulatory conditions, otherwise rads preferred
- Evaluation of ovarian follicular activity (previtellogenic and vitellogenesis) and oviductal egg/fetus development
- Identify reproductive disease and disorders such as follicular stasis and dystocia
- Follicle size as indicator for ovulation reported in ball python, short-tailed python, boa constrictor, the viviparous lizard Barisia, American alligator, and many chelonian species
- Viviparous species
- Can determine if fetus alive or dead later in gestation
- Birth predicted with monitoring of loss of yolk -birth usually occurs about a week after yolk is no longer detectable
- Diagnose follicular stasis
- With resorption follicles continue to reduce in size; with stasis and degenerative change they appear to coalesce, and anechoic fluid often surrounds them
- If echogenic free-floating debris noted within anechoic fluid, follicles are likely degenerate and inflamed, and surgical intervention indicated
- Postovulatory disease such as dystocia or salpingitis - normally smooth wall of egg may become irregular with notable heterogenous echogenicity change and increase in free fluid within oviduct and/or coelom
- Imaging modality of choice to evaluate reproductive tract in squamates
- CT/MRI
- Very useful for chelonian repro disease
- Ability to evaluate each ovarian follicle and oviductal egg individually
- Useful to identify advanced changes in follicular stasis distinct horizontal leveling of contents of static ovarian follicles noted once degeneration started
- Horizontal leveling also evident in retained oviductal eggs, and with more chronic retention a gas cap often formed within, and gas pockets around, egg
- Endoscopy
- Coelomic evaluation of repro tract more challenging in snakes and crocodilians except via cloacoscopy for evaluation of urodeum and oviducts
- Due to unique anatomy, intimacy of coelomic organs, multiple membranes/compartments restricting movement
- Coelomic evaluation of repro tract more challenging in snakes and crocodilians except via cloacoscopy for evaluation of urodeum and oviducts
19
Q
Describe the management of dystocia in reptiles.
What are some of teh common causes of dystocia?
What are the two types of dystocia?
What medical management options exist?
What surgical management options exist?
A
- Dystocia
- Inability to successfully expel term eggs or fetuses from the lower reproductive tract
- Causes - abnormal (especially large or fused) eggs/fetuses, failure of distal repro tract to contract (especially metabolic causes), lack of suitable nesting/birthing sites, lack of viable embryos
- Dystocia in squamates and chelonians involving infertile ova is common
- More commonly in oviparous reptiles
- Usually a seasonal problem
- Obstructive dystocia
- Anatomical barrier that prevents passage of one or more eggs/fetuses through oviduct and cloaca
- Fetal or maternal abnormality possible
- Fetal - oversize, malformations, adhesions
- Maternal - misshapen pelvis, oviductal stricture, or coelomic pathology, including cystic or cloacal calculi, obstipation, organomegaly, abscesses, neoplasia
- May result from complications during oviposition - malpositioning of eggs or broken/damaged eggs
- Chronicity, salpingitis can cause fibrinous adherence of eggs to oviduct mucosa
- Non-obstructive dystocia
- Causes - improper nesting sites (common with lizards and chelonians), improper temperature, malnutrition, dehydration, poor physical condition of female, infectious disease
- Most common cause - calcium deficiency
- Diagnosis of true dystocia is difficult
- Chelonians may voluntarily retain oviductal eggs for up to 6 months
- Tenesmus without successful oviposition or parturition - clear sign of dystocia
- Radiographs - exclude obstruction, ID mineralized eggs, confirm egg numbers, shell abnormalities, ectopic eggs, comparative egg-to-pelvic dimensions, check for concurrent coelomic pathology
- US - useful to differentiate between follicular stasis and postovulatory eggs
- Tx
- Medical management
- Oxytocin - used in nonobstructive dystocia
- Small window of efficacy in squamates - within 48 to 72 hours of normal laying
- Fibrinous adherence prevent use in chronic cases
- Viviparous snakes - within a week of normal parturition
- Chelonians more responsive to oxytocin, even chronic cases
- Can repeat dosing up to 2-3 times
- Causes elevations in prostaglandins, maybe lysed CL
- Beta-blockers may potentiate effects
- Supportive care and calcium (before oxytocin)
- Monitor for days to weeks for progress or decline
- Oxytocin - used in nonobstructive dystocia
- External manipulation of eggs to vent
- can be done in snakes
- Only recommended in lizards and chelonians if egg visible within cloaca
- Medical management
- Cloacoscopy
- Manipulate retained eggs/fetuses out of cloaca if medical and/or less-invasive techniques have failed or not appropriate
- Useful in snakes and chelonians, less so in lizards
- Best utilized when only one or a few ova or fetuses retained
- Percutaneous ovocentesis
- Can be considered in snakes
- Risks - leakage of egg contents into coelom, iatrogenic trauma
- Last resort
- US guidance recommended
- Eggs retained more than several weeks not likely to aspirate as contents solidify
- Surgery
- Ovariosalpingectomy
- Salpingotomy (breeding animals)
23
Q
Describe surgery of the male reproductive tract in reptiles.
What approaches are used for orchiectomy or orchidectomy? Removal of which testicle is more likely to result in significant hemorrhage? Removal of which testicle is more likely to result in accidental removal of the adrenal gland?
Describe the procedures for hemipenal amputation.
Describe the procedure for phallectomy. In larger chelonians, what are the vessels that must be identified and ligated individually?
A
- Male repro surgery
- Orchiectomy/Orchidectomy
- Indications in lizards and chelonians - reduce aggression, population control, research, eliminate testicular pathology such as neoplasia or orchitis (abscess, granuloma)
- Indications in snakes and crocodilians - less common, primarily to manage pathological change
- Lizards
- Ventral (paramedian or midline) coeliotomy approach
- Exception – chameleons
- Lateral (flank) celiotomy approach
- Exception – chameleons
- Testes usually paired (right more cranial) and dorsally in mid to caudal coelom cranial to kidneys
- Testes surrounded by fibrous, mesorchium capsule – if ruptures, testes are friable
- Exteriorize teste (if possible), fenestrate mesorchium, and ligate vessels
- Mesorchium pigmented in bearded dragons
- Right testis is attached directly to vena cava with short vessels (1–2 mm)
- Right adrenal gland located on opposite side of vena cava
- Accidental damage or removal of right adrenal gland unlikely
- Left testis has distinct testicular artery and vein
- Left adrenal gland located adjacent to left testis utilizing same vessels
- Take care not to damage or remove
- Castration can be performed endoscopically as well
- Ventral (paramedian or midline) coeliotomy approach
- Chelonians
- Prefemoral coelomic approach preferred
- Less invasive than plastronotomy
- May require bilateral approach to get both testes if no endoscopic assisted
- Testes paired and found dorsally in caudal coelom cranial to kidneys
- Difficult to impossible to exteriorize testes
- Prefemoral coelomic approach preferred
- Testicular biopsy
- Indications – possible neoplasia, orchitis (abscess, granuloma), abnormal sperm production (infertility)
- Endoscopy preferred
- Phallectomy and hemipenal amputation
- Has been used to control reproduction in chelonians and green iguana
- Less invasive and safer than castration
- Allows normal (testosterone-driven) social behaviors without insemination of females
- Commonly performed when tissue prolapses
- Amputation does not affect urinary system - do not contain urethra
- Squamates - removal of one hemipenis allows copulation with other hemipenis
- Copulatory organs very vascular - transfixing sutures required
- Hemipenal amputation - hemipenis clamped close to base with hemostat, 1-2 absorbable monofilament transfixing sutures placed proximal to hemostat
-
Phallectomy - phallus retracted caudally, clamped at base with hemostat or tissue clamp, 2+ absorbable monofilament transfixing and encircling sutures placed each approximately halfway across phallus, remaining stump closed with simple continuous pattern using absorbable monofilament suture
- Larger chelonians - blood supply to each distinct longitudinal ridge (dividing phallus in half longitudinally) must be identified, each body (corpus cavernosa) and blood supply individually clamped and double ligated with absorbable monofilament sutures
- Has been used to control reproduction in chelonians and green iguana
- Orchiectomy/Orchidectomy
24
Q
Describe surgery of the female reproductive tract in lizards.
What approach is used for ovariectomy? Removal of which ovary is more closely associated with the vena cava? Removal of which ovary is more likely to accidentally remove the adrenal gland?
Describe the procedure for salpingectomy in lizards. When is it indicated? What procedure needs to be completed following a salpingectomy?
What is the procedure for salpinotomy in lizards?
A
- Female repro surgery
- Ovariectomy/Ovariosalpingectomy
- Lizards
- Ovariectomy
- Ventral coeliotomy (midline or paramedian) approach
- Chameleons – lateral (flank) coeliotomy
- Both ovary can be removed via same incision in most cases
- Chameleons – lateral (flank) coeliotomy
- Ovaries - paired (right ovary cranial to left) dorsal structures in mid to caudal coelom
- Oviducts filled with eggs or fetuses need to be exteriorized and removed first to see ovaries (in dystocia cases)
- Right ovary attached directly to vena cava with short vessels (1–2 mm)
- Right adrenal gland located on opposite side of vena cava
- Left ovary has own distinct ovarian artery and vein
- Left adrenal gland located adjacent to left ovary, using same vessels
- Ovary exteriorized, mesovarium fenestrated, vessels ligated
- Mesovarium pigmented in bearded dragon
- Right liver lobe closely associated with vasculature of right ovary in bearded dragons
- With preovulatory follicular stasis – large follicles may be fragile and may require larger incision due to size
- Ventral coeliotomy (midline or paramedian) approach
- Salpingectomy
- First procedure performed in cases of surgical dystocia
- Exteriorized and fimbria identified, clamped with hemostat, ligated with absorbable monofilament suture or vascular clips and transected
- Fimbria - thin and poorly vascular, may only require radiosurgical/laser dissection (without ligation)
- Mesosalpinx fenestrated and vessels ligated
- Distal oviduct clamped with hemostat at junction with urodeum, double-ligated with circumferential and transfixing absorbable monofilament sutures or vascular clips, and transected
- Perform ovariectomy after to prevent fatal yolk coelomitis
- Salpingotomy
- Used to maintain repro potential
- Incision longitudinal along antemesenteric border with scalpel to ensure primary intention healing
- Closed with simple continuous or inverting pattern using fine monofilament absorbable suture
- Ovariectomy
- Lizards
- Ovariectomy/Ovariosalpingectomy
25
Q
Describe reproductive surgery in female snakes.
What is the approach typically used?
Where are the ovaries located? What important anatomical structure may be in the surgical field during an ovariectomy?
After a salpingectomy, what secondary procedure needs to occur?
What are the indications for salpingotomy over salpingectomy?
A
- Snakes
- Ovariectomy
- Not considered a routine preventative procedure in snakes
- Ipsilateral ovary must be removed if oviduct removed
- Ventrolateral coeliotomy approach recommended
- Ovaries in most species in 60% to 80% snout-to-vent position
- US to find ovaries before sx helpful
- Single long incision or multiple smaller incisions required
- May be several fascial layers to breach to get to ovaries
- Staggered, overlapping ovaries (right cranial to left)
- Found dorsally
- Most cranial portion of right ovary starting just distal to the gallbladder
- Most caudal portion of left ovary ending just cranial to kidneys
- Saccular lung (air sac) often extends into repro surgical field
- Salpingectomy
- Ipsilateral ovary must also be removed to avoid ectopic follicles and yolk coelomitis
- Similar procedure to lizards
- Can do both sides through same incision
- Salpingotomy
- Maintain breeding potential
- Goal is to minimize trauma to oviduct
- Incision made in nonvascular area of oviduct with scalpel in a strategic location to remove as many egg/fetus as possible via single incision
- Closed with simple continuous or inverting pattern using fine monofilament absorbable suture
- Ovariectomy
26
Q
Describe surgery of the female chelonian reproductive tract.
What is the typical approach for an ovariectomy?
Where are the ovaries located?
When is a transplastron approach recommended?
A
- Chelonians
- Ovariectomy
- Prefemoral approach – least invasive
- Ovaries paired and found dorsally in mid to caudal coelom cranial to kidneys
- Interfollicular tissue grasped with atraumatic forceps and gently manipulated to prefemoral incision for visualization
- May need second incision on opposite side to get second ovary but sometimes possible to get both via same incision
- Endoscopic assisted preferred
- Salpingectomy
- See above
- Salpingotomy
- Less common
- Unobstructed dystocias often responsive to medical management with oxytocin
- Longitudinal incision along antemesenteric border with scalpel in strategic location
- Transplastron coeliotomy recommended with obstructive dystocia involving many eggs, yolk coelomitis, ectopic follicles/eggs, or if other concurrent coelomic issues
- Yolk Coelomitis and Ectopic Follicles/Eggs
- Sequela to reproductive disease in females
- Take samples and copiously and repeatedly lavage coelom with warm sterile saline to remove as much yolk material as possible
- Fibrinlike yolk material may be adhered to serosal surfaces in chronic cases – debride
- Ovariectomy
27
Q
Describe the various components of the reptile egg.
Shell - what determines whether the egg is soft or leathery? What are the funcitons of the shell?
Albumen - where is it produced? What are its functions?
What are the three extra-embryonic membranes? What are their functions?
What is the function of the yolk?
What toxins and pathogens might be passed vertically?
A
- Egg components - eggshell, extraembryonic membranes, albumen (or whites), yolk
- shell
- hard vs leathery
- Depending on environment where incubation takes place
- Arid – hard shell
- Moist – soft shell
- Depending on environment where incubation takes place
- porous nature of shell allows for gas and water exchange
- Softer-shelled eggs - higher rate of oxygen exchange
- embryos derive 20-25% of their calcium from the eggshell
- hard vs leathery
- albumen
- derived from specialized oviductal glands
- high water content
- provides embryo with physical support and assists in water storage
- antimicrobial peptides secreted by oviduct into albumen layer - protects developing embryo from infection
- extra embryonic membranes - amnion, allantois, chorion
- amnion - membrane that directly surrounds embryo
- contraction of specialized amniotic smooth muscles at start of hatching causes retraction of amnion and responsible for internalization of yolk
- allantois
- originates at body stalk (paired with vitelline duct and associated vessels)
- continuation of urachus external to embryo
- allantoic cavity - major storage site for protein catabolism excretion products (urea and uric acid)
- chorion - outermost membrane that encloses embryo, amnion, allantois, yolk, and yolk sacs
- amnion - membrane that directly surrounds embryo
- yolk and yolk sac
- primary energy source for developing embryo and hatchling
- retinal (storage form of retinoids), hormones, fatty acids, proteins, and minerals such as calcium, phosphorus, and magnesium from yolk
- attached to developing embryo at body stalk via vitelline duct (omphalomesenteric duct)
- vitelline duct - continuous with embryonic intestines, direct transfer of nutrients from yolk
- yolk size decreases while embryo size increases
- corn snakes - yolk is solid for last third of incubation due to proliferation and invasion of endodermal cells and blood vessels from yolk sac
- maternal diet influences yolk fatty acid content and yolk size
- maternal transfer of toxins (heavy metals, selenium, persistent organic pollutants) and antibodies also possible
- possible vertical transmission of sunshine virus and Hepatozoon spp.
- primary energy source for developing embryo and hatchling
- shell
28
Q
Describe the incubation of reptile eggs.
What happens if the humidity is too high? Too low?
What happens if temperatures aren’t appropriate?
What is the relationship between temperature and incubation length?
What species have temperature-based sex determination?
What other factors may play a role in sex determination?
A
- Incubation
- species-specific incubation conditions
- humidity
- too dry - soft-shelled eggs will lose water mass, begin to crinkle or collapse, nonviability possible
- too wet - oxygen diffusion may stop, hypoxia, death
- temperature
- abnormal incubation temps lead to hatchling performance deficits, reduced growth and immunity, and latent effects on growth after hatching
- “failure to thrive syndrome” in hatchling crocodilians
- 2.5x more likely to occur in clutches that incubated at lower air temps
- inverse relationship exists between temperature and incubation length when within species specific temp range
- temperature-based sex determination in some species
- most chelonians
- except Chelidae (Pleurodira)
- crocodilian and sphenodontia
- some lizards – leopard geckos and bearded dragons
- most chelonians
- yolk size, presence of exogenous hormones, and water availability may also play a role in sex determination in some species
29
Q
Describe the diagnostics that can be performed on reptile eggs.
What changes in external appearance might be significant?
How can you tell an egg is viable?
A
- Diagnostics
- external appearance
- marked changes in color or texture, or growth of fuzzy mold usually indicates that embryo died or that egg was nonfertile
- viable crocodilian eggs have distinct band around pole of egg that increases in size with the growth of embryo
- candling
- viable - diffuse developing vascular pattern or presence of embryo
- nonviable - lack vascular pattern, homogenous diffuse yellow-white appearance
- noninvasive heart rate monitoring
- modified yolk biopsy technique
- necropsy - histopathologic, bacteriologic, and/or toxicologic exam
- external appearance
32
Q
Describe some of the common diseases of neonatal reptiles.
What are some of the risks of yolk sac disease? How can it be managed?
What are some common infectious disease?
How do husbandry deficiencies affect neonates?
What congenital diseases have been reported?
A
- Diseases
- Yolk sac disease
- if not internalized at emergence, at risk for yolk sac rupture and/or infection
- natural progression of internalization may progress on its own if neonate is closely monitored and maintained on a clean damp surface, such as a moistened paper towel
- ligate and transect yolk sac as proximal to neonate as possible if pendulous
- may need to close body wall
- infection can occur prior to envelopment into coelom, through an incompletely closed umbilicus and ascension from omphalitis, or it may become infected through ascension of intestinal bacteria from the vitelline duct
- infection can cause closure of vitelline duct cutting off nutritional sources to neonate or coelomitis
- internalized infected yolk sac may need surgical removal and antibiotics
- infectious disease
- common snake mite
- subclinical in adults but can exsanguinate neonates
- salmonellosis
- infection can be transovarially and from salmonella contaminated environments
- common snake mite
- husbandry associated disease
- higher morbidity and mortality when husbandry deficiencies present
- nutritional secondary hyperparathyroidism common
- sand/substrate impaction and predation by prey items and predation from cage mates due to inappropriate pairings or high stocking densities
- congenital disease
- may be genetic or related to inappropriate incubation
- reports:
- two ball pythons - bifid ventricles secondary to abnormally small-sized muscular ridge
- prehensile-tailed skink - patent urachus diagnosed in hatchling
- Yolk sac disease
