Reptiles 1 Flashcards
reptiles taxonomy, number of species
- what are the 4 orders
- 4 orders:
- Squamata – snakes and lizards
- Testudines (chelonians) – turtles
- Crocodylia
- Rhynchocephalia – tuatara
<><> - > 11,000 species
<><><><> - Reptiles are the animals in the class Reptilia, a paraphyletic grouping comprising all sauropsid (“lizard faces”) amniotes except Aves (birds). Living reptiles comprise squamates (snakes and lizards), turtles, crocodilians, and rhynchocephalians (Sphenodontia, tuatara).
- Toxicofera = “those who bear toxins“; it encompasses all venomous reptile species, as well as numerous related non-venomous species.
- As of October 2023, the Reptile Database includes about 92 families, 1253 genera, and 12,060 species.
common types of lizards we may see
- Agamids (f) – bearded dragon, Chinese water dragon, Uromastyx
- Chameleons (f)
- Iguanas(f)
- Geckos (sf)
- Skinks(sf)
- Tegus(sf)
- Varanids (monitors)(f)
f= family
common types of snakes we may see
- Pythons (sf)
- Boas (sf)
- Colubrids (sf)
- Elapids (sf)
- Vipers (f)
sf = subfamily
f = family
<><><><>
* Pythons – non-venomous, oviparous
* Boas – non-venomous, ovo-viviparous, vestigial pelvic girdle (spurs)
* Colubrids – generally non-venomous, can be rear-fanged
* Elapids – venomous, permanently erect fangs
* Viperids – venomous, hinged fangs
what are testudines
- Hidden neck (so)
> Tortoises
> Turtles - Side neck (so)
<><> - so = suborder
reptile metabolism
- speed
- anaerobic vs aerobic
- Slow metabolism:
- 1/5-1/7 mammalian metabolism
- Vary with species and metabolic state
<><><> - Anaerobic metabolism:
- Switch to anaerobiosis with vigorous activities
- Increased lactate production
what does it mean that reptiles are Ectothermic and poikilothermic
- pros and cons
- Pros: do not waste energy for thermogenesis
- Cons: all activities are limited by ambient temperature, limited aerobic capacity, brumation
- Preferred optimum temperature zone (POTZ)
<><><><> - Ectotherm (vs. endotherm) = an animal that is dependent on external sources of body heat.
- Poikilotherm (vs. homeotherm) = an animal that cannot regulate its body temperature except by behavioral means such as basking or burrowing.
- Brumation = a lethargic state that some ectothermic animals, such as many reptiles, assume during cold conditions. Partly analogous to hibernation, but physiological differences include that brumation does not depend on stored fat, but rather on reduced metabolic activity.
reptile integument
- what type
- shedding
- some lizards and crocodiles are…
- chelonians?
- chromatophores?
- Most reptiles have scales
<><> - Shed periodically = ecdysis
> Snakes: periodically in one piece
> Lizards: periodically in pieces
> Turtles and crocodilians: continuously in small pieces
<><> - Osteoderms in some lizards and crocodilians
<><> - Chelonian shell:
- Fused ribs, vertebrae, and some osteoderms
> Carapace, plastron, bridges - Covered by epidermal scutes
<><> - Chromatophores: colour change in some
reptiles musculoskeletal
- snake skull type?
- pectoral?
- regeneration?
- growth?
- Prokinetic skull
- Highly kinetic skull in snakes
- Pectoral girdle is different
- Autotomy and tail regenerationin
lizards - Some species keep growing all their life
<><><><> - Autotomy = “self-amputation”. Often, loss of the tail as a defensive strategy. It is created by a vertical fracture plane, containing no bone, passing through the body and part of the neural arch of each caudal vertebra. It occurs in many lizards, such as the iguana, skink, and gecko species, where the tail is not essential for survival. Species like chameleons and monitors, which rely on their tails for climbing and defense, do not shed their tails. Similarly, the marine iguana, which relies on its large rudder tail for swimming in the sea, lacks fracture planes.
Coelomic Cavities of chelonians
- Pleural cavity and peritoneal cavity
- Separated by post-pulmonary septum
Coelomic Cavities of squamates
- Single pleuroperitoneal cavity in most, except:
- Monitors have a post-pulmonary septum
- Tegus have a post-hepatic septum
Coelomic Cavities of crocodilians
- Like birds (without the air sacs)
Generalities on Internal Anatomy
- fat
No subcutaneous fat
* Fat bodies in caudal coelom
* Fat stored in tail of leopard gecko
organ placement in snakes, generally
- are right or left more cranial
Elongated anatomy in snakes
* Right organs are more cranial than left
categories of reptile dental anatomy
- Acrodont
- Pleurodont
- Thecodont
- Beak
- Snakes have 6 rows of teeth
what is acrodont? who has this? prone to what?
- Agamids, chameleons
- Teeth are not replaced
- Direct attachment to jaw bones
- More prone to periodontal disease
what is pleurodont? who has this?
- Iguanids and snakes
- Teeth replaced
- Direct attachment to jaw bones on one side
who is thecodont?
- Crocodilians and some snakes
> more like what we are used to in ourselves
what reptiles have a beak?
chelonians
snake teeth orientation? venomous ones have what?
Snakes have 6 rows of teeth
* Venomous snakes have venom-delivering teeth (fangs)
* (Proteroglyphous vs opisthoglyphous vs solenoglyphous)
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* In most snakes, teeth are located on the dentary of the lower jaw, the maxilla, the palatine bone, and the lateral pterygoid plate. The latter form an “inner row” of teeth that can move separately from the rest of the jaws and are used to help “walk” the jaws over prey. Several snake lineages have evolved venom which is typically delivered by specialized teeth called fangs located on the maxilla.
* Most snakes can be placed into one of four groups, based on their teeth, which correlate strongly with venom and lineage:
* Aglyphous snakes (“lacking grooves”) have no specialized teeth. Most aglyphous snakes are non-venomous. All snakes have aglyphous teeth, i.e., teeth that aren’t considered fangs.
* Opisthoglyphous (“rearward grooves”) snakes possess venom injected by a pair of enlarged teeth at the back of the maxillae, which normally angle backward and are grooved to channel venom into the puncture. Called “rear-fanged”. Example = colubrids.
* Proteroglyphous snakes (“forward grooved”) have shortened maxillae bearing few teeth except for a substantially enlarged fang pointing downwards and completely folded around the venom channel, forming a hollow needle. Because the fangs are only a fraction of an inch long in even the largest species these snakes must hang on, at least momentarily, as they inject their venom. Example = elapids.
* Solenoglyphous snakes (“pipe grooved”) have the most advanced venom delivery method of any snake. Each maxilla is reduced to a nub supporting a single hollow fang tooth. The fangs, which can be as long as half the length of the head, are folded against the roof of the mouth, pointing posteriorly. The skull has a series of interacting elements that ensure that the fangs rotate into a biting position when the jaws open. Solenoglyphous snakes open their mouths almost 180 degrees, and the fangs swing into a position to allow them to penetrate deep into the prey. While solenoglyph venom is typically less toxic than that of proteroglyphs, this system allows them to deeply inject large quantities of venom. Unique to vipers.
Gastrointestinal System for reptiles depends on…
- how do they differ?
Depends on the diet:
* Herbivores: long GIT, 1 cecum, large colon
> Iguana, terrestrial chelonians
* Carnivores: Short GIT
> Varanids, snakes (very distensible stomach)
venomous gland are where in
- Viperids, elapids
- Colubrids
- Helodermatid lizards, e.g., Gila monster
Venomous glands
* Viperids, elapids: temporal region
* Colubrids: Duvernoy’s gland
* Helodermatid lizards, e.g., Gila monster: along the lower jaw
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* Duvernoy’s gland is a gland found in some groups of colubrid snakes. It is positioned posterior to the eye, encased in a thin cover of connective tissue, and consists mostly of serous cells. A single, short duct extends anteromedially from the lumen of the gland to the base of the posterior fangs. Function?
reptile tongue types
- Forked in snakes and some lizards
- Projectile and prehensile in chameleon
reptile butt is similar to what other animals
- Cloaca similar to birds
how does metabolism of digesting snake change?
Metabolism of digesting snakes may increase by 7-10 times
reptiles resp system - trachea
- chelonians and crocodilians
- squamates
- intubation, bifurcation
- Complete tracheal rings in chelonians
and crocodilians - Incomplete in squamates (snakes and lizards)
- Tracheal bifurcation very cranial in chelonians
> Risk unilateral intubation if too deep
reptiles larynx similar to?
- what property in snakes?
Larynx is similar to birds
* Very mobile in snakes
types of resp systems, who has them
- Unicameral
> Snakes, some lizards, e.g.,
geckos, skinks
<><> - Paucicameral
> Iguanas, chameleons,
agamids (bearded dragon)
<><> - Multicameral
> Monitor lizards, chelonians, crocodilians
<><> - Reptiles form an interesting intermediate between birds and mammals in terms of lung structure.
- Reptilian lung types can be divided into single-chambered (unicameral), few-chambered (paucicameral), and more complex many-chambered (multicameral) lungs.
- Reptiles typically have much lower metabolic rates (~10-fold) compared with birds and mammals of the same size, but they show wide variability in O2 demand, and their lung structure has evolved accordingly.
- For example, the varanid (monitor) lizards, which are known for their relatively high metabolic scopes and active behavior patterns in the wild, have relatively complex multicameral lungs. By contrast, the tegu lizard has lower O2 demands, and its unicameral lung has a large central lumen lined with gas-exchanging falveoli resembling a layer of honeycomb.
reptiles resp system gas exchange surface??
Gas exchange surface
* Ediculae (wide) or faveolae (deep)
* 100x larger than alveolae
squamate lungs
- cranial and caudal parts
- what animals
- chamelions have what?
Squamates:
* Cranial part: respiratory
* Caudal part: avascular, air sac like
> Mainly in snakes and skinks
> Large diverticulae in chameleons
snakes use what lung? except which
- Only right lung functional (vestigial left lung)
- Except Pythonidae and Boidae
chelonians breathing aided by what? some use what other strat?
- Breathing aided with leg movement
- Some utilize cloacal respiration (diving)
reptile lung morphology?
- The lung morphology of reptiles is distinct from the alveolar lungs of mammals. The reptile lung is analogous to a single, oversized mammalian alveolus.
- Vascularized septae penetrate centrally from the lung’s perimeter and subdivide the pulmonary lumen into a series of spatial units termed ediculae or faveoli. The respiratory exchange takes place principally on the septae.
- As in the mammalian lung, airflow during lung ventilation in reptiles is bidirectional and bellows-like. However, unlike mammalian alveoli, ediculae or faveoli are relatively passive participants and contribute little to the movement of air during inhalation and exhalation. In partial compensation, a large part of the lung volume in reptiles is maintained as an essentially non-vascularized region whose primary function is to assist in the ventilation of vascularized portions of the lung.
- Additionally, in comparison to mammalian alveoli, reptilian septae are invariably less well vascularized.
- The result is that the reptile lung exhibits a reduced pulmonary anatomical diffusion factor and is probably unalterably constrained from supporting respiratory exchange that is consistent with the aerobic metabolic rates typical of active endotherms.
- The left lung of snakes is vestigial or absent, except in pythons and boas, where two lungs in boids are almost equal in length. The left lung is never greater than 85% of the right lung size.
reptiles CV system chambers
- Squamates, turtles, and tuatara
- 3 chambers
- Left, right atrium
- Cavum arteriosum, cavum venosum, cavum pulmonale
- Inter-ventricular canal – mixing of deO2 and O2 blood
- Lymphatic hearts
<><><><> - Crocodilians
- 4 chambers
reptile kidneys
- structure, functions
Only loopless “reptilian” nephrons
* Does not concentrate water
* Post-renal handling of urine
kidney locations
- snake sexual segment?
Kidneys are dorsal and caudal
* Extend within the tail base in lizards
* Male snakes and some lizards have a “sexual segment”
<><><>
* The sexual segment of the kidney (SSK) comprises a hypertrophied portion of the nephron found in males of Squamata. The secretions of SSK may maintain and activate sperm, provide pheromones, form copulatory plugs, or have functions associated with seminal fluid.
reptiles bladder
- do they have it
- Most lizards have one (can reabsorb water)
- NOT bearded dragons
- Chelonians do too (water reservoir in tortoises)
- Snakes and crocodilians do not
type of urine reptiles produce?
- Most are uricotelic
- Some excrete significant urea, e.g., chelonians and tuatara
reptiles repro system?
- who has a phallus
- hemipenes?
- eggs?
- Intracoelomic gonads like birds
<> - Chelonians and crocodilians
have a phallus
<> - Squamates have hemipenes
> Sockets caudal to the cloaca
> Can be “probed” to sex snakes
<> - Most reptiles lay eggs
> Some are (ovo) viviparous, e.g., boids, viperids, some chameleons
<><><><> - Interesting facts
- Some squamates can undergo parthenogenesis
- Sex ratios influenced by the temperature in some species
- Most reptiles do not incubate eggs
- parthogenesis?
- sex ratios?
- egg incubation?
- Some squamates can undergo parthenogenesis
- Sex ratios influenced by the temperature in some species
- Most reptiles do not incubate eggs
<><><> - Parthenogenesis is a natural form of asexual reproduction in which growth and development of embryos occur in a gamete (egg or sperm) without combining with another gamete (e.g., egg and sperm fusing).
- Sexual reproduction is ubiquitous in all vertebrates, and the formation and development of gonads, either testes or ovaries, is determined by the sequential action of members of the same genetic network. While the downstream actors of this network are well conserved, the elements triggering the process are surprisingly variable. In Environmental Sex Determination (ESD), the future sex of the gonad depends on environmental conditions. This environmental factor is generally the incubation temperature of the developing egg, and this peculiar case is known as Temperature Sex Determination (TSD). In Genetic Sex Determination (GSD), the bipotential gonad develops into either the testis or ovary based on the control of a master sex-determining (MSD) gene upstream of the whole network. This MSD gene is located on only one member of a special pair of non-identical chromosomes called sex chromosomes. The sex with an odd number of MSD is the heterogametic sex, and the other is the homogametic sex. By convention, when male is the heterogametic sex, the male-specific sex chromosome is named Y and the other X. When it is female, the female-specific sex chromosome is called W and the other Z. The MSD gene can act in two different ways, either as male or female dominant gene on the Y or W chromosome respectively, or in a dose-dependent manner as a male gene on the Z chromosome or a female gene on the X chromosome.
- In reptiles, there is a relative abundance of TSD and GSD species. All crocodilians are TSD species. In turtles, GSD is relatively rare (94 GSD species versus 262 TSD species), but it is now clear that GSD is the rule in Squamates and TSD rarer than previously thought. Currently, TSD is clearly documented in two groups only (Gekkota and Agamidae). Even in Gekkota, its occurrence is demonstrated in only a few genera. Temperature can overrule GSD in a few skinks or agamids, but it is rather rare. The general evolution trend is from TSD to GSD, and a return to TSD likely constitutes a rare event.
Reptile sexing for chelonians
- Concavity of plastron – male
- Length of toenails (males longer)
- More caudal vent on tails (males)
Reptile sexing for lizards
- Precloacal pores (gecko – males more
prominent) - Femoral pores (most lizards – males more prominent)
- Size and other attributes (e.g., iguana)
snake sexing strategy
Probing
