Lecture 4 - Reptile and Amphibian Anatomy and Physiology Flashcards
What class do reptiles belong to?
Reptilia
Describe the 4 main orders of reptiles
1) Crocodilia: alligators and crocodiles
2) Squamata: snakes and lizards
3) Chelonian: turtles and tortoises
4) Rhynchocephalia: tuataras
What class do amphibians belong to?
Amphibia
Describe the 3 main orders of amphibians
1) Gymnophiona: caecilians
2) Anura: frogs and toads
3) Caudata: salamanders and newts
Describe what it means for reptiles and amphibians (herptiles) to be cold blooded
They are ectothermic
Unable to generate large amounts of heat internally, so their body temp depends on the environmental temperature
Some reptiles can markedly raise body temperature by___?
Muscular contractions
Leatherback sea turtle - swimming
Pythons - shiver when incubating eggs
Describe herptiles
Mainly regulate body temperature via behavior
Ex. sunbathing, changing skin colour. coiling or uncoiling
True or false:
Thermoregulation is less important in hot environments
True
It is more important in cold environments
Describe in ectothermy in reptiles and amphibians
Related to energy conservation
These animals metabolism depends on body temperature
This allows many herptiles to survive on very small amounts of food (most being able to maintain body temp)
Temperature of herptiles depends on access to temperatures within the POTZ. What is this?
Preferred optimal temperature zone (changes with species)
This is the range of temperature in which the animal can perform all necessary metabolic functions
Why is it critical that sick patients environment is at POTZ when administering medications? What could happen if it is not at POTZ?
This allows proper absorption, metabolism and excretion of the medications
If not, can lead to no response to treatment, lack of healing, overdose, or death
Heat sources such as heat rocks and red light bulbs are not acceptable in the herptiles world. What is the best source of heat?
Non-light providing sources ex. ceramic bulbs or heat mats that go under the enclosure
What is something that is often unknown about UVB or UVA bulb?
Lose the ability to provide nutrients before they stop lighting up
Recommended they be changed every 6 months
Why is it difficult to give subcutaneous injections to reptiles/
Very little subcue space
Describe the dermis of reptiles
Dense connective tissue
Contain blood and lymph vessels, nerves and chromatophores (pigment containing cells)
Contain osteoderms: bony plates within the dermis of some lizards and crocodilians
Describe the epidermis of reptiles
Scales and scutes of reptiles are formed by epidermal folds in most reptiles, vary in size and shape
Is keratinized
What are some other epidermal structures that mat be present on reptiles?
Crests Tubercles Spines Dewlaps Keels Horns Barbules
Describe the integument of turtles/tortoises
Scales and scutes are thick epidermal plates
Nomenclature aids in species ID and medical recording
Cervical scute: first scute at base of neck area
Vertebral scutes: run down center of the shell (numbered)
Pleural scutes: lay right over the lungs (numbered and labeled L or R)
Marginal scutes: the border of the shell (numbered and labeled L or R)
Describe ecdysis
Shedding of the skin
Occurs with growth and in response to injury
Shed in pieces or in one large piece
Skin does not grow with the animal, so body outgrows it and sheds
Exuvia
the skin that has been shed
Describe dysecdysis
Abnormal or difficulty shedding
Usually due to poor husbandry: low humidity, no objects to rub on, malnutrition, dehydration
Can be from skin wounds, disease, dermatitis, parasites
If not corrected can lead to dyspnea, dermatitis, future shed issues, loss of toes or tail tip
What can be done to help dysecdysis
Correcting underlying problems
2 hours warm water baths - soften shed and can pull it off
What is different about amphibian integument? What are drink patches?
Extremely permeable: absorb water directly from environment
Drink patches: areas of increased permeability on ventral surfaces
Describe the epidermis of amphibians
Single or few layers of keratinized cells - very thin
Aquatic amphibians do not have keratinized cells
Amphibians regularly shed layers of epidermis and usually eat exuvia
Describe the dermis of amphibians
Contain chromatophores and glands
Glands produce secretions which help to protect the animal’s skin
Very little space in salamanders and caecilians
Anurans have looser attachments of dermis
May have toxic secretions produced by some glands within the dermis and epidermis
What do the reptilian and amphibian nervous system depend on?
Spinal segmental reflexes and locomotor centers for control of movement
Describe the nervous system of reptilians, what reflexes are present?
How are some of them used?
Tongue withdrawal, jaw, pedal, and tail reflexes
When monitoring anesthesia in reptiles OTHER than snakes, use the corneal and palpebral reflexes (snakes do not blink)
In snakes: tongue withdrawal reflex will be maintained at the surgical plane of anesthesia
Describe the vision of reptiles
Iris made up of skeletal muscle under VOUNTARY control (PLR: consensual reflexes not seen)
Lower lid is usually more mobile than upper lid
Nictitans: well developed and mobile
Some species of lizards have thin transparent lower lids to allow for
Some vision when lids are closed
Describe the spectacle found in snakes and some lizards
A clear fused scale on the eye above the cornea (small space between containing tear film)
Tears drain into mouth through nasolacrimal system
No true eyelid
In caecilians, eyes are covered with skin
Eyelids are absent in some aquatic species
Most reptiles have poorly developed extraocular muscles (have to move entire head to look around) what is the exception to this?
Chameleons: their eyes move freely and independently of one another
Describe the lacrimal and harderian glands. What’s different about chelonians?
Present in most reptiles and amphibians: produce secretions that combine to form the tear film
Chelonians: no nasolacrimal ducts, tears spill over the lid margins
What happens in some amphibian eyes when swallowing?
Protrude ventrally into the oral cavity when swallowing
Describe the eyes in reptiles
Contain ossicles: sclera bones present in most reptiles (not snakes or crocodilians)
Lens: more fluid in reptiles than mammals (more rigid in snakes) allows for further accommodation
Parietal (rudimentary) eye in some reptiles (space - not an eye thought to be associated with light cycles)
Describe what’s different about accommodation abilities in chelonians and snakes
Accommodation:
1) chelonians: lens is squeezed through the pupil to adjust its size
2) snakes: lens move back and forth due to pressure changes within the aqueous and vitreous humors (doesn’t actually change shape)
Describe hypovitaminosis A
One of the most common diseases affecting turtles and tortoises
usually from a diet deficient in Vit A resulting in abnormal functioning of the skin
Signs: swollen eyelids, loss of appetite, weight loss, raw skin with secondary bacterial infections, nasal discharge, abnormal development of eyes in embryos
Treated with Vit A injectable or dietary supplements (may also need to treat secondary bacterial infections)
What is different about a snake’s ability to hear?
Snakes: no external ears, columella articulates with the quadrate bone of the jaw - allows snakes to be very sensitive to ground vibrations transmitted through the mandibles and converted to sounds
Snakes can hear aerial sounds but it is not as highly developed
Who are aural abscesses common in? What are they often secondary to?
Middle ear infection are common in chelonians
Can be secondary to hypovitaminosis A
Location of the heart varies in amphibians and reptiles.
Describe the location in some different species.
Chelonians: on midline just caudal to thoracic girdle, central to the lungs
Most lizards: within the thoracic girdle
Crocodilians and some lizards: farther back in coelomic cavity
Snakes: usually at the junction of the first and second third or the body length
Describe the heart of most reptiles and amphibians.
Describe the heart of crocodilians.
3 chambered with two atria and one ventricle
Crocodilians: 4 chambered heart unlike mammals or avians
How is there no mixing of oxygenated and deoxygenated blood in a 3 chambered heart? (only one ventricle)
Ventricle is divided (septum), it is just not considered 2 chambers
Why is it difficult to auscultate reptilian hearts? What can be done instead?
Usually can’t hear it, very slow, difficult to find, in turtles can’t hear past shell
Watch cardiac movement through skin
What does heart rate depend on?
Species Size Temperature Activity level Metabolic function
What is the vasovagal reflex in lizards?
Induces a drop in heart rate, blood pressure, and catatonic state
Triggered by applying gentle pressure to both eyeballs through closed eyelids (recover when pressure is release or with mild stimulation)
True or false:
Reptiles can’t survive long without breathing
False
Reptiles can survive long periods without breathing
Respiration is driven by?
Oxygen levels in the blood
Lizards tend to experience severe respiratory depression while under anesthesia, so it is important to provide _____?
Positive pressure ventilation (2-4 breaths per minute)
If they stop breathing on their own the anesthesia will wear off
Where is the glottis of most reptiles and amphibians located?
Describe the glottis in snakes.
Is there an epiglottis present?
In the rostral portion of the oral cavity
Glottis is very mobile in snakes and protrudes from the mouth to allow respiration during ingestion of prey
Is often no epiglottis present, but paired arytenoid cartilages bordering the glottal opening
Is it east to pass an endotracheal tube in reptiles? Why or why not?
Yes
It is clearly visible and distinct from the esophagus
Describe the vocal ranges of reptiles
No vocal cords
Only possible vocalizations: hissing, grunting, or bellowing
Frogs and toads: vocal sacs arise from the trachea
Describe the glottal keel
Present in some species of snakes
Increases the volume of vocalizations
Found at the glottal opening so makes intubation diffcults
How do reptiles breathe without a diaphragm?
Action of the intercostal muscles, ribs, and parts of the axial musculature used for respiration
Do not restrain them too tightly
Describe the amphibian respiratory system
Simple sac like lungs
Some salamanders have no lungs (sub cue respiration - absorb through skin)
Pulmonary ventilation from pumping of the buccal cavity and pharynx (necks get bigger/smaller) gas exchange occurs through mucous membranes of the buccal cavity, pharynx, and cloaca
Gills may be present in young amphibians
Some reptiles can be carnivorous, omnivorous, or herbivorous
Snakes, crocodilians, and adult amphibians are strict ____?
Carnivores
What is the function of the deeply forked tongues of snakes and lizards?
Particle delivery system from the vomeronasal organ (accessory olfactory organ)
- smelling air by tasting it
Allow for detection of particle gradients
Describe the tongue of chameleons
Specialized projectile tongues for capturing prey from long distances
Describe the tongue of turtles and tortoises
Typically thick, fleshy, and relatively immobile
Describe the tongue of crocodilians, what structure of the oral cavity aids them when being under water?
Immobile and 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 (blocks off throat)
Describe the oral cavity of amphibians
Tongue used to capture prey (most amphibians)
Salamanders: tongue is flipped to prehend food (lingual flipping)
Has numerous salivary glands to provide stickiness
Some have venom glands (snakes and lizards) which is a modified salivary gland with a canal that runs down the tooth
Describe the dentition of tortoises and turtles
Do not have teeth, have tomia (keratinized beaks)
Describe dentition of teeth
Have 6 rows of teeth: two mandibular, two maxillary, two palatine/pterygoid bones
Snakes without venomous fangs are called
Aglyphous snakes
Describe venomous snakes
Specialized dentition for delivery
Venom teeth: hollow with an opening near end where venom is expelled
Fangs receive venom through a duct from a venom gland at its base
Contraction of muscles around venom gland forces venom out of the fang
True or false:
Snakes control the amount of venom delivered with each bite
False
Describe the dentition of most amphibians
Most have teeth
Caecilians and salamanders: both maxillary and mandibular dentition
Some have odontoid process: cutting plates on rostral mandibles of some frogs
Describe the esophagus in reptiles and amphibians
Reptiles: thin and distensible - unique morphology reflects type of prey
Amphibians: very short and wide (especially in anurans)
Describe the stomach of reptiles
Variable in size and shape
Snakes: highly distensible
Crocodilians: thick muscle comparable to avian gizzard
What are anurans capable of doing with their stomach?
Prolapsing the stomach through the mouth
Used for emptying the stomach if they ingest something undesirable
Gastric prolapse can be terminal event in dying animals
Can be seen with some methods of anesthesia
Describe the intestinal tract of reptiles
Varies according to diet
Herbivores: longer than carnivores
Snakes: relatively straight (not a lot of coiling)
Colon: large and complex in herbivores (hind gut fermentation)
Cecum: site of hind gut fermentation in herbivorous lizards and chelonians
Liver: bilobed and large
Describe the cloaca
Common outflow tract for GIT and urogenital tracts (all reptiles and amphibians)
Three chambers, similar to birds: coprodeum, urodeum, proctodeum
Describe the reptilian kidney
Have a renal portal system arising from the veins of the pelvic limbs and tail (avoid injection of meds in caudal half)
Describe the amphibian kidney
Some amphibians excrete ammonia as a nitrogenous waste product - others excrete urea or uric acid
Have no ability to concentrate their urine
Urinary bladders and cloacal anatomy similar to reptiles
Male reptiles have internal testes located in the ___?
Dorsal coelomic cavity
In male reptiles, the ductus deferens leads from the testes to the ____?
Dorsal wall of the urodeum
Possess a copulatory organ such as phallus or paired hemipenes
Most male reptiles have a sexual portion to the kidney tubules, what does this do?
Develops in response to high levels of circulation sex hormones and provides secretions that contribute to seminal fluid
Describe how copulatory organs vary in structures in male reptiles
Crocodilians and chelonians: phallus or erectile tissue rising from floor of cloaca
Snakes and lizards: paired hemipenes everted from the tail base through the vent (caudal to the vent)
Describe the female reptilian anatomy
Paired ovaries in dorsal coelomic cavity
Paired oviducts lead to cloaca and end at the genital papillae on dorsal wall of the urodeum
Describe fetus development in viviparous species
Birth live young
Fetuses are retained and nourished in uterine portion of the oviduct
Describe the birth of young in oviparous species
Birth of young by laying eggs
Dig nests to lay eggs in
Without suitable nests many will not lay their eggs and experience dystocia
Chelonians and some lizards may dig deep holes to___?
Deposit their eggs into and leave after
After oviposition or parturition, reptiles are often not involved with the care of eggs or offspring. What are the exceptions to this?
Crocodilians: protect their nests and young for a period of time following hatching
Pythons and cobras: protect their nests until hatching
Describe incubation of eggs
Development and hatching requires proper temp, humidity, and gas composition of the nest
Incubation time and temp varies in species
Reptile eggs should NOT be rotated during incubation
Describe sex determination of reptiles with incubation
Sex can be determined by genotype or temperature at which the eggs are incubated
Females: heterozygous SW
Males: homozygous ZZ
In some species they do not have sex chromosomes, describe how sexes are made in incubation
Higher incubation temperatures produce males in crocodilians and lizards (opposite in chelonians)
Temperature range within the nest allows for production of mixed clutch of hatchlings
Artificially can determine sex of animals
True or false:
Snakes have no real sexual dimorphism
True
In some species, pelvic spurs are present and can be larger in males, What are these?
Remnants of pelvic limbs that provide tactile stimulation to females
Describe a male chelonian’s vent
May have concave plastron and more distally located vent than females
Allows closer apposition of the cloaca when the male mounts the female
What is an example of a species of lizards that show obvious sexual dimorphism?
Male Jackson’s chameleon has three well developed horns on its face
Describe the different sexual dimorphism in amphibians
Poison dart frog: males have enlarged toe pads
Anurans: males have large tympanic membranes
Salamanders: males have prominent cloacal glands
Most caecilians (serpentine amphibians) are ___?
Viviparous
Most anurans and salamanders are?
Oviparous
What are amplexus frogs and toads?
Fertilize eggs as they are laid while grasping the female
What are spermatophores in salamanders?
Packets of sperm deposited onto substrate by male salamanders
Picked up by females cloaca in spermatotheca (pocket in cloaca where sperm can be stored)
When amphibians lay eggs, they are often laid in or near
Water
There is some parental care of eggs/young in what amphibians
Anurans and most salamanders
Larval anurans (tadpoles) have completely aquatic lives prior to
Metamorphosis
Tadpole metamorphosis is usually complete within
90 days
What is tadpole metamorphosis stimulated by?
Thyroid hormones
What is the life cycle of a frog
Egg Embryo Tadpole Front legs break through Pulmonary breathing starts Tadpole frog Adult frog
Describe the snake skull
Extremely mobile
Mandibular symphysis is connected by ligaments that allow the jaws to move independently of each other
Allows mouth to open wide for ingesting large prey
Describe the shell of a turtle
Part of their skeleton - actually connected
Can grow and heal like bones
Have a backbone/spine connected to shell
Most of the space inside is occupied by lungs
What is tail autonomy
Defensive mechanism: species will drop their tail that will continue to move to distract predators
In some lizards and salamanders
Have a fracture plan on the tail where it is designed to break off from which results in very little blood loss
Lost tail can regenerate but is often stiff and cartilaginous
Describe metabolic bone disease
Caused by imbalance of calcium, phosphorus, and vitamin D3
Proper diet, temp, and light prevent this
Symptoms: swollen mandible, curvature of tail and sometimes spine, decreased bone density (will not appear as white on rads)
What are some common reptile/amphibian species native to Sk
Plains garter snake
Great short horned lizard
Prairie rattle snake
Tiger salamander
