Amphibians and reptilian anatomy and physiology Flashcards
Class reptillia- four orders
Crocodylia
Squamata
Chelonian
Rhyncocephalia
Class Amphibia - three orders:
Gymnophiona
Anura
Caudata
Metabolism of ectothermic animals
Reptiles and Amphibians (Herptiles) are ectothermic or “cold- blooded”
Ectothermic animals are unable to generate large amounts of body heat internally.
Body temperature depends on environmental temperature
Some large reptiles can markedly raise body temperatures by muscular contractions
Leatherback Sea Turtle (swimming)
Pythons (shiver when incubating eggs)
Environmental thermoregulation for amphibian and reptiles
Herptiles – mainly regulate body temperatures via behavior
Sunbathing, changing skin colour, coiling or uncoiling
Thermoregulation less important if living in hot environments
Ectothermy is
Related to energy conservation
Animals metabolism depends on body temperature
Allows many herptiles to survive on very small amounts of food
Depends on access to temperatures within the preferred optimal temperature zone (POTZ)
POTZ is
Range of temperature in which the animal can perform all necessary metabolic functions
Critical that an ill patient’s environment is at POTZ as well as when administering medications.
Providing a heat source is very important if keeping herps as pets, especially in a colder climate like Saskatchewan
Why is POTZ important for administering
This allows proper absorption, metabolism and excretion of the medications
If not, can lead to no response to treatment, lack of healing, overdose or even death
Size of SQ space for reptiles
Limited SQ space so it is difficult to administer SQ injections
Dermis of reptiles
dense connective tissue
Blood and lymph vessels, nerves, and chromatophores (pigment-containing cells)
Chromatophores allow some lizards to change skin color and pattern
Osteoderms: bony plates within dermis of some lizards and crocodilians
Epidermis on reptiles
Epidermis- scales and scutes of reptiles are formed by epidermal folds in most reptiles. They vary in size and shape. The epidermis is keratinized
Other epidermal structures may be present
Crests, tubercles, spines, and dewlaps, keels, horns, barbles
Scale and scute (thick epidermal plates e tortoise) nomenclatures- aids in species identification and medical recording
Ecdysis for reptiles is
Shedding of the skin
Occurs with growth and in response to skin injury
Shed in pieces or in one large piece
Exuvia means
shed skin of reptiles
Ecdysis is controled by
Controlled by the thyroid gland
Cells replicate new epidermis
Enzyme containing lymph secreted between old and new epidermal layers
Skin colour dulls: spectacle opacifies
Lymph- reabsorbed prior to ecdysis
Mechanical rubbing on objects aids in shedding
Dysecdysis is and caused by
Abnormal shedding
Usually from poor husbandry
Low humidity, no objects in environment to rub against, malnutrition and dehydration
Can also be due to skin wounds, illness, dermatitis, and parasites
Fix by correcting problem and a 2 hour warm water bath
If not corrected can lead to dyspnea, dermatitis, future shed issues, and loss of toes or tail tips
Amphibian Integument is
Extremely permeable
Absorb water directly from environment
“Drink patches”: areas of increased permeability on ventral surfaces
Epidermis of amphibians
Single or few layers of keratinized cells
Aquatic amphibians - no keratinized cells
Amphibians regularly shed outer layers of epidermis and usually eat the exuvia
Dermis of amphibians
chromatophores and glands
Glands produce secretions which help protect the amphibian’s skin
little subcutaneous space in salamanders and caecilians
Anurans: looser attachments of dermis (more subcutaneous space)
Toxic secretions are produced where by amphibians
produced by some glands within dermis and epidermis
Defense mechanisms
Reptile nervous system
Depend on spinal segmental reflexes and locomotor centers for control of movement (same in amphibians)
Tongue withdrawal, jaw, pedal and tail reflexes are all present.
When monitoring depth of anesthesia in reptiles other than snakes, you can use corneal and palpebral reflexes.
In snakes, the tongue withdrawal reflex will be maintained at the surgical plane of anesthesia.
Reptile iris look like
iris made up of skeletal muscle under voluntary control
Pupillary light reflex: consensual reflexes usually not seen
What does lower eyelids doe for reptile
Lower lid usually more mobile than upper
What is unique about some lizards eyelids
Some species of lizards have thin, transparent lower lids
Allows for a degree of vision even when lids are closed
Nictitans are
well-developed, mobile in many reptiles
What do snake eyelids look like
Snakes, some lizards - no true eyelids
Clear, fused scale (spectacle)
Caecilians eyes are
eyes covered with skin
Eyelids absent in some aquatic species
Reptilian extraocular muscles
poorly developed extraocular muscles
Exception - chameleons; eyes move freely and independently of one another
Tear film for reptiles and amphibains
between cornea and spectacle in sub- spectacular space
Tears drain into mouth through nasolacrimal duct system
Chelonians eye ducts
no nasolacrimal ducts; tears spill over the lid margin
Lacrimal and harderian glands
present in most reptiles and amphibians
Produce secretions that combine to form the tear film
Amphibian eyes
often protrude ventrally into the oral cavity when animal swallowing
Ossicles are
Ossicles: scleral bones present in most reptiles (except snakes and crocodilians)
Lens of reptilian eyes
Lens: more fluid in reptiles than mammals (more rigid in snakes)
Vision accomidations in some species
Chelonians - lens is squeezed through the pupil
Snakes - lens moves back and forth due to pressure changes within the aqueous and vitreous humors
Parietal (rudimentary) eye in some reptiles
Hypovitaminosis A is casued by and treatment
One of the most common diseases affecting turtles and tortoises
Usually from deficient diet
Treated with vitamin A (injectable or dietary supplements)
Also need to treat any secondary bacterial infections, etc.
Some possible signs of Hypovitaminosis A:
Swollen eyelids
Loss of appetite and weight
Raw skin with secondary bacterial infections
Nasal discharge (runny nose)
Abnormal development of the eyes in embryos
Ears of reptiles and amphibians
Ears - both sides of head, usually caudal to eyes
Ears of snakes
no external ears; columella articulates with quadrate bone
Allows snakes to be very sensitive to ground vibrations transmitted through the mandibles
Snakes also able to hear aerial sounds
Aural Abscess
Middle ear infections are common in chelonians
Can be secondary to hypovitaminosis A
Cardiovascular system location of heart
Location of the heart varies
Chelonians - on midline just caudal to thoracic girdle, ventral to the lungs
Most lizards - within thoracic girdle
Crocodilians and some lizards - farther back in the coelomic cavity
Snakes - usually at junction of the first and second third of the body length
Fairly mobile within the coelomic cavity
Shape of heart for reptiles
Most reptiles and amphibians have a three-chambered heart with two atria and one ventricle
Crocodilians have a four-chambered heart, but it is not like the mammalian or avian heart.
No mixing of oxygenated and deoxygenated blood
Heart rate of reptiels
It is difficult to auscultate reptilian hearts. You may be able to see cardiac movement through the skin.
Rate depends on species, size, temperature, activity level, and metabolic function
Lizards - vasovagal reflex induces drop in heart rate, blood pressure, and a catatonic state
Triggered by applying gentle pressure to both eyeballs through closed lids
Lizard recovers with cessation of pressure or mild stimulation
Respiratoy system of reptiles
Reptiles capable of surviving long periods without breathing
Respiration driven by oxygen levels in blood
Lizards tend to experience severe respiratory depression while under anesthetics, so it is important to administer positive pressure ventilation (two to four respirations per minute)
What does the glottis look like in reptiels
Glottis of most amphibians and reptiles: rostral portion of oral cavity
Glottis very mobile in snakes; protrudes from mouth to allow respiration during ingestion of prey
Paired arytenoid cartilages: border glottal opening; open during respiration
The visible glottis makes it easy to pass an endotracheal tube for anesthesia and to avoid the trachea when passing a stomach tube for force feeding.
Vocalization of reptiles
No vocal cords
Only vocalizations possible are hissing, grunting, bellowing
Frogs and toads - vocal sacs arise from trachea
Glottal keel present in some species of snakes
Increases volume of vocalizations (makes intubation difficult)
How do reptiles breath
No true diaphragms
Action of intercostal muscles and parts of axial musculature used for respiration
So do not restrain them too tightly!
Amphibian respiratory system
Simple saclike lungs
Some salamanders have no lungs
Cutaneous respiration
Pulmonary ventilation results from pumping of buccal cavity and pharynx
Gas exchange can also occur across mucous membranes of buccal cavity, pharynx, and cloaca
Gills may also be present, particularly in young amphibians
Feeding strategies for reptiles
Reptiles can be carnivorous, omnivorous or herbivorous
Snakes, crocodilians, and adult amphibians are strict carnivores
Some diets are very specialized
Oral cavity of snakes and lizards
deeply forked tongues
Function as particle delivery system for vomeronasal (Jacobson’s) organ (accessory olfactory organ)
Allow for detection of particle gradients
Oral cavity of chameleons
specialized projectile tongues designed for capturing prey from long distances
Sticky end which the prey items stick to
Oral cavity of turtles and tortises
typically thick, fleshy, relatively immobile tongues
Oral cavity of crocodilians
mmobile tongue attached to intermandibular space
Muscular flaps from base of tongue and dorsal pharynx allow for opening of mouth while submerged without ingesting or inhaling water
Amphibian oral cavity
Tongue used to capture prey (most amphibians)
Anurans, most terrestrial
salamanders: tongue is flipped to prehend food (lingual flipping)
Salivary galnds of reptiles
Numerous salivary glands
Venom glands (some snakes, lizards) - modified salivary gland
Dentition of turtles and tortoises
Turtles and tortoises
No teeth
Tomia (keratinized beaks)
Dentition of snakes
Snakes have 6 rows of teeth: two mandibular, two maxillary, two on palantine/pterygoid bones
Snakes without venomous fangs are called Aglyphous snakes
Caecilians and salamanders dentition
both maxillary and mandibular teeth
Palatal teeth in some species
Dentition of amphibians
most have teeth
Odontoid process:
cutting plates on rostral mandibles of some frogs
Esophagus of reptiles
thin and distensible
Unique morphology reflects type of prey
Esophagus of amphibians
Amphibian esophagus very short and wide, especially in anurans
Reptile stomach
- variable size and shape
Snakes - highly distensible
Crocodilians - thick muscle comparable to avian gizzard
Amphibian stomach
anurans capable of prolapsing stomach through the mouth
Used for emptying the stomach if they ingest something undesirable
Gastric prolapse is a terminal event in dying animals
Can be seen with some methods of anesthesia
Foreign bodies with amphibians and reptiles
Just like dogs and cats, reptiles and amphibians are known to consume objects that they shouldn’t. Foreign body consumption and the associated gastrointestinal upsets are just as common in these animals as in our warm-blooded patients.
Reptilian Intestinal Tract
Varies according to diet
Herbivores - longer intestinal tracts than carnivores
Snakes - relatively straight intestinal tracts
Colon - large and complex in herbivores
Hindgut fermentation for digestion
Cecae - site of hindgut fermentation in herbivorous lizards and chelonians
Liver - usually large and bi-lobed
Cloaca is
Common outflow tract for GI and urogenital tracts (all reptiles and amphibians)
Reptile Kidney
Reptiles, like birds, have a renal portal system arising from the veins of the pelvic limbs and tail.
Avoid administering injections in the caudal half of the reptile.
Amphibian Kidney
Some amphibians excrete ammonia as a nitrogenous waste product; others excrete urea, some excrete uric acid
No ability to concentrate urine
Urinary bladders and cloacal anatomy similar to reptiles
Reptile Reproductive System of males
Males have internal testes located in dorsal coelomic cavity
Ductus deferens leads from testes to dorsal wall of the urodeum
They possess a copulatory organ such as a phallus or paired hemipenes.
Most also have a sexual portion to the kidney tubules
Develops in response to high levels of circulating sex hormones and provides secretions that contribute to the seminal fluid
Copulatory organs vary in structure
Crocodilians and chelonians - phallus of erectile tissue rising from floor of cloaca
Snakes and lizards - paired hemipenes everted from the tail base through the vent
Female reproduction system or reptiles
Females - paired ovaries in dorsal coelomic cavity
Paired oviducts lead to cloaca and end at genital papillae in dorsal wall of the urodeum
Reptile Reproductive Cycle
In viviparous species, fetuses are retained and nourished in uterine portion of oviduct
Oviposition - many reptiles dig nests to lay eggs
Without suitable nesting material, female may experience dystocia
Chelonians and lizard species may excavate deep holes to deposit eggs
What do reptiles do after birth
After oviposition or parturition, reptiles not involved with care of eggs or offspring
Exceptions - crocodilians protect their nests and young for a period of time following hatching
Pythons and cobras - protect their nests until hatching
Egg incubation of reptile eggs
Development and hatching requires proper temperature, humidity, and gas composition of nest
Incubation time and temperature varies
Reptile eggs should not be rotated during incubation
Sex Determination in Reptiles
Determined by genotype or temperature at which eggs are incubated
Sex chromosomes:
Females are heterozygous (ZW) and males are homozygous (ZZ)
Some species do not have sex chromosomes
Higher incubation temperatures produce males in crocodilians and lizards
Opposite occurs in chelonians
Temperature range within the nest allows for production of a mixed clutch of hatchlings
Secondary Sex Characteristics of reptiles
Snakes - no real sexual dimorphism
In some species, pelvic spurs can be larger in males
Pelvic spurs: remnants of pelvic limbs; provide tactile stimulation to females
Male chelonians may have concave plastron and more distally located vent
Allows closer apposition of the cloacas when the male mounts the female
Some lizards show obvious dimorphism
Example: the male Jackson’s chameleon has three well-developed horns on its face
Sexual dimorphism in some species of amphibaisn
Poison dart frog males have enlarged toe pads
Large tympanic membranes in some male anurans
Prominent cloacal glands in male salamanders
Amphibian Reproduction
Paired gonads in dorsocaudal coelomic cavity
Most caecilians (serpentine amphibians) are viviparous
Most anurans and salamanders are oviparous
Amplexus - Male frogs and toads fertilize eggs as they are laid while grasping the female
Spermatophores - packets of sperm deposited onto substrate by male salamanders
Picked up by the female salamander’s cloaca
Spermatotheca - pocket in cloaca of female salamanders where sperm can be stored
What do amphibains do after laying eggs
Eggs are usually deposited in or near water
Some parental care of eggs and/or young in anurans and most salamanders
Larval anurans (tadpoles) have completely aquatic lives prior to metamorphosis
Tadpole metamorphosis- usually complete within 90 days
Metamorphosis by thyroid hormones
Reptile Musculoskeletal System
Snake skulls -extremely mobile
Mandibular symphysis is connected by ligaments that allow jaws to move independently of each other
Tail anatomy or reptiles
Tail autonomy - defensive mechanism
Some lizards and salamanders
Discarded tail usually continues to wiggle and distract predator
The species capable of tail autonomy have “fracture planes” along which tails break
Little to no blood loss
Lost tail can regenerate; regenerated tail stiff and cartilaginous
Metabolic Bone Disease is
Caused by an imbalance of calcium, phosphorous and Vitamin D3
Proper diet, temperature and lighting will prevent MBD
Symptoms include swollen mandible, curvature of the tail and possibly the spine and decreased bone density on radiographs.
How to restrain a snake
control the head
Grasp just behind the head, then support the rest of the body with your other hand/arm; or allow body to rest on the same arm so one hand is free
Must support at least 2 points
How to restrain a lizard
depends on the type of lizard
Support the body and give something for feet to rest on
How to restrain a iguana
Iguanas – very large tails that can thrash (wear long sleeves); may bite; very fast
How to restrain a geckos
may lose their tail if handled roughly (avoid handling tail if possible)
Always warn owners of this possibility prior to handling/blood collection
How to restrain a chelonians
support the shell
May bite
Can use a block in front of face to keep their heads retracted into shell (ie. Tongue depressor)
Where to collect blood from a snake
Cardiocentesis (only if anesthetized)
Tail vein
Where to take a lizards blood
tail vein
Where to take chelonians blood
jugular vein
Reptile Radiographs goal
Goal is similar views as for mammals for most reptiles
At least one lateral and a VD/DV
Often easier said than done
Sometimes, you have to get creative
Very helpful to have a mobile X-ray tube
Can use dental x-ray for very small reptiles (tiny lizards, pediatrics, etc.)
Often, anesthesia (or at very least sedation) may be required
Radiograph for a snake
Can manually hold the section you want to X-ray
“Snake in a box” can give a nice whole-body DV view
How to xray a chelonian
Extra view required
“Craniocaudal view” as well as lateral and DV
From head to tail
Chambers of the cloaca
Three chambers: coprodeum, urodeum and proctodeum
What are crocodylia
aligators and crocodiles
What are squamata
Snakes and lizards
What are chelonians
Turtles and tortoises
What are Rhyncocephalia
tuataras
What are gymnophiona
Caecillians
Worm/snake like amphibian
What are anura
frog and toads
What are caudata
salamanders and newts
