Reptiles Reptiles n n n First truly terrestrial

Reptiles

Reptiles n n n First truly terrestrial vertebrates ~7000 species worldwide ~300 species in U. S. and Canada

Reptiles n n n Probably best remembered for what they once were, rather than what they are now Mesozoic era - age of reptiles Dominant group for >150 millions years

Reptiles n n 12 or so principal groups of reptiles evolved Only 4 groups remain today

Order Squamata n n n Snakes and lizards >5800 species Most successful group

Order Crocodilia n n Crocodiles, alligators, caiman ~25 species Have survived for 200 million years Today: concerns that humans may drive them to extinction

Order Chelonia (Testudines) n n n Turtles ~330 species Ancient group that survived, remained mostly unchanged from early ancestors

Order Rhynchocephalia n n n Snout head or tuatara Only 1 species From New Zealand sole surviving species of ancestral stock

Reptilian Characteristics n n Tough, dry scaly skin Protection against desiccation, physical injury Thin epidermis shed periodically Much thicker dermis with chromatophores

Reptilian Characteristics n n n Dermis converted into snakeskin, alligator leather for shoes, purses, and so on Scales of keratin (epidermal) Not homologous to bony, dermal fish scales

Reptilian Characteristics n n Crocodilian scales remain throughout life Grow gradually to replace wear

Reptilian Characteristics n n In snakes and lizards, new scales grow beneath old Old scales shed with old skin

Reptilian Characteristics n Turtles add new layers of keratin under old layers of the platelike scutes (modified scales)

Shedding n Snakes turn old skin (scales, epidermis) inside out when shedding

Shedding n Lizards split skin and leave it right side out, or slough it off in pieces

Amniotic Egg Chorioallantoic membrane

Amniotic Egg n n Reptiles are able to lay their eggs in sheltered locations on land Young hatch as lungbreathing juveniles, not aquatic larvae

Amniotic Egg n n Amniotic egg widened division between amphibians and reptiles Probably greatly contributed to decline of amphibians and rise of reptiles

Reptile Jaws n n n Reptile jaws designed for crushing prey Fish, amphibian jaws designed for quick closure, but little force after Reptile jaw muscles larger, longer, arranged for better mechanical advantage

Reptile Copulatory Organ n Copulatory organ permitting internal fertilization Internal fertilization required for a shelled egg Copulatory organ formed from an evagination of cloaca

Reptile Circulation n More efficient circulatory system, higher blood pressure All reptiles have at least an incomplete separation of the ventricles Flow patterns prevent mixing

Reptile Circulation n n Crocodilians have two completely separated ventricles All reptiles have two functionally separate circulations

Reptile Lungs n n n Improved lungs Depend almost exclusively on lungs for gas exchange Supplemented by pharyngeal membrane respiration in some aquatic turtles

Reptile Lungs n n Lungs have larger respiratory surface than in amphibians Air sucked into lungs rather then forced in by mouth muscles Negative pressure Skin breathing completely abandoned

Reptile Kidney n n Kidneys more advanced (metanephric) Very efficient at conserving water Excretes uric acid (rather than urea, ammonia) A semisolid paste

Better Body Support n n n Limbs better design for walking on land More ventral, less lateral Many dinosaurs walked on only hindlimbs

Nervous System n n Much more advanced - relatively larger cerebrum CNS connections more advanced - permit complex behaviors not found in amphibians

Nervous System n Sense organs generally well-developed

Order Chelonia n n n Turtles Very ancient group Little change in morphology since Triassic period

Order Chelonia n n n Body enclosed in shell Dorsal carapace Ventral plastron

Order Chelonia n n n Thoracic vertebrae and ribs built into shell Shell of two layers Inner of bone Outer of keratin New keratin deposited under old as turtle grows, ages

Order Chelonia n n Jaws lack teeth Equipped with tough, horny plates for gripping, chewing food

Order Chelonia n n n Respiration poses a problem Shell prevents expansion of chest for breathing Adapted to use certain abdominal, pectoral muscles as a “diaphragm”

Order Chelonia n n Air drawn in by contracting limb flank muscles to make body cavity larger Exhalation also active - shoulder muscles contracted, viscera compressed, air forced out of lungs

Order Chelonia n n Deformable plastron in snappers allows some elastic recovery during exhalation Compressive force of water against body also can force air out

Order Chelonia n n Many water turtles acquire enough O 2 when inactive by pumping water in and out of mouth Pharyngeal breathing Can stay submerged for extended periods Must lung breathe more frequently when active

Order Chelonia n n Nervous system - tiny brain Typical of most reptiles Never exceeding 1% of body weight, but cerebrum larger than in amphibians Turtle can learn, as quickly as a rat, to run a maze

Order Chelonia n n n Have both middle & inner ear, but sound perception is poor Turtles are virtually mute Tortoises may grunt or roar

Order Chelonia n Poor hearing compensated for by: n n n Good sense of smell Acute vision Color perception as good as that of humans

Order Chelonia n n n Mating & reproduction Many varieties of courtship Males of aquatic species may swim around looking for proper leg stripe pattern Pheromones also Males use claws

Order Chelonia n n Terrestrial species may vocalize Males may track females (pheromones) for days

Order Chelonia n n Males may mark territory with fecal pellets Courtship involves rubbing limbs against scent glands (underside of jaw) and sniffing

Order Chelonia n n Biting, ramming, hooking are directed at other males Biting - head & limbs Ramming - rearing up, smacking shells Hooking - bulldozing under plastron to flip or hurry

Order Chelonia n n n Turtles are oviparous Fertilization is internal, and all species bury eggs in ground in nests 4 to >100 eggs

Order Chelonia n n Exercise care in constructing nest Deposit eggs and abandon them Incubation 1 -14 months 40 -60 days most typical

Order Chelonia n n n Movements to nesting areas very faithful Terrestrial species use familiarity with area, sun Marine species use variety of mechanisms to traverse large distances

Order Chelonia n n n Earth’s magnetic field Polarized light Sun & stars Low frequency sounds Green sea turtles find Ascension Island (20 km) in mid-Atlantic from coastal Brazil - 2200 km

Order Chelonia n n Size - marine turtles largest Buoyed by aquatic environment May reach 2 m in length, 725 kg in weight Biggest species is leatherback

Order Chelonia n n Green sea turtle may exceed 360 kg Economically valuable - heavily exploited rarely gets to large size

Order Chelonia n n n Land tortoises generally not as large as aquatic forms Some may weigh several hundred kg Giant tortoises of Galapagos Islands among world’s largest terrestrial turtles

Order Chelonia n n n Lifespan - turtles are most long-lived vertebrates Individuals of at least 5 species known to live 100 years or longer Some believed to have lived more than 150 years

Order Chelonia n n n Longevity attributed to slow rate of metabolism Galapagos tortoise top speed: 300 m/hr Reports of box turtle caught in U. S. with “ 1850” carved into plastron n Skepticism!

Order Chelonia n n n Protective shell Head, appendages can be drawn in for protection Box turtles especially good because of hinged plastron

Order Chelonia n n Shell not as protective in many species Soft, leather-like in softshell turtles

Order Chelonia n n n Shell too small for protection in other species, e. g. , snappers Other means of defense - ferocious, short-tempered “Tigers of the pond”

Order Chelonia n n n Entirely carnivorous fish, frogs, ducks, whatever they can catch Alligator snapper hides on bottom and waves worm-like tongue to attract fish Wholly aquatic - come ashore only to lay eggs

Turtle Conservation n n Slow growth, long time to maturity predispose many species to risk of extinction Changing conditions may increase adult mortality, juvenile recruitment

Turtle Conservation n Problem severe for large tortoises, sea turtles Largest, slowestgrowing Human and animal invasion of beaches, isolated island habitats

Turtle Conservation n n Herbivores compete with tortoises for limited vegetation Eggs, young fall prey to dogs, cats, rats

Turtle Conservation n n Protection of land tortoises simpler than protection of sea turtles Limited range (single island) defines limits where protection is needed

Turtle Conservation n Sea turtles range over international, national borders Limited number of breeding sites Problems with exploitation controlled or outright ban?

Turtle Conservation n Ocean plastics pollution - bags look like natural jellyfish prey Not enough known about biology do devise protective management program Tag a turtle? 2000 X

Order Squamata n n “characterized by scales” Lizards, snakes, worm lizards Most recent products of reptile evolution Most successful 95% of known living species of reptiles

Order Squamata n n n Lizards began diversifying at time when dinosaurs were near end of their dominance Were successful because of adaptability Adopt various body forms, occupy various habitats

Order Squamata n Snakes likely arose from group of lizards whose descendents include monitor lizards, but fossil record poor

Order Squamata n n Legless character apparently evolved as adaptation to burrowing lifestyle Snakes since have radiated into terrestrial, aquatic, arboreal niches

Order Squamata n n n Two adaptations characterize snakes: Extreme body elongation displacement, rearrangement of organs Highly mobile jaws swallow prey larger than own diameter

Order Squamata n Two suborders: n Sauria - lizards n “lizard” n Serpentes - snakes n “to creep”

Lizards n n n Very diversified group (3300 species) Terrestrial, burrowing, aquatic, arboreal, aerial Many familiar groups:

Lizards n Geckos n Mostly small, nocturnal, with adhesive toe pads (walk anywhere)

Lizards n Iguanas n Often bright-colored New World lizards n Marine iguana - only marine lizard in world

Lizards n Skinks n Elongate bodies, reduced limbs

Lizards n Chameleons n Arboreal n Tongue flicked to greater distance than body length Prehensile tail Zygodactylous feet n n

Lizards n Independently moveable eyes elevated on cones good eyesight - gauge distance accurately

Lizards n n n Lizard body form not as distinctive as other reptiles Many functional, behavioral modifications e. g. , degenerate or absent limbs - no good in dense grass

Lizards n Differ from snakes: n Halves of lower jaw firmly united at mandibular symphysis n Teeth, but not developed into fangs

Lizards n Moveable eyelids (snake eyes covered with permanent, transparent cap) n Keen daylight vision

Lizards n Size - 3 cm to 3 m n Hawaiian gecko n n Komodo dragon 75 kg n Fossils: 5. 5 m, >1000 kg

Lizards n n n 80% of lizards are <20 g in weight Generally insectivorous (opportunistic), although some specialists N. Amer. horned lizards eat only ants

Lizards n n Most large lizards are herbivores Trees in tropics, ground vegetation on oceanic islands, seaweed in ocean

Lizards n n n Monitor lizards are exception to vegetarians Food of vertebrates (birds, mammals), invertebrates Komodo - ambush predator on large mammals (deer, goats, water buffalo)

Lizards n Foraging strategies: n Sit and wait (insects come to them) n Active foragers (move to encounter prey)

Lizards n n n Foraging modes alternate at successive levels of food chain Moving insect -> sitand-wait lizard -> active predator Sitting insect -> active lizard -> sit-and-wait predator

Lizards n n n May use territorial and courtship behaviors Male anoles have gular fan (dewlap) for conspicuous displays Skin distended by hyoid apparatus

Lizards n Behaviors include: n Extending, contracting fan Pushups Bobbing head n n

Lizards n n n Territories defended by males for access to females (bite & chase, but no fighting) Females have nonoverlapping home ranges for feeding Male territory includes several females mates with all

Lizards n n n Mate by pressing cloacal regions together Males grip female’s neck, shoulders Males have paired copulatory organs hemipenes - to aid sperm transfer

Lizards n Range of reproductive modes from oviparity to viviparity n Skinks - eggs retained in oviducts, receive nutrients across a “placenta”

Lizards n n n All-female (parthenogenetic) species occur in at least 6 families Especially common among racerunners (Teiidae) Diploids and triploids known

Lizards n n High reproductive potential - every individual capable of producing offspring Can repopulate habitat faster than bisexual species after flood, other disaster

Lizards n Parental care n Many lizards remain with eggs or nest site n Little if any care given after young hatch or are born

Suborder Serpentes - Snakes n n n 2300 species 10 cm long up to 10 m long Highly specialized body form

Suborder Serpentes - Snakes n n Entirely limbless Lack pectoral, pelvic girdles (except vestige of latter in pythons, boas) Short, wide vertebrae for quick lateral undulations Ribs improve rigidity

Suborder Serpentes - Snakes n n n Rearranged internal anatomy Left lung reduced or absent Gall bladder posterior to liver Right kidney anterior to left Gonads similarly displaced

Suborder Serpentes - Snakes n n n Little modification for various lifestyles: Elongate for arboreal Shorten for burrowing Broaden for swallowing big prey Compress laterally for swimming

Snake Sense Organs n n n Snake, lizard eyes different: focusing, retina morphology Re-evolved from burrowing ancestors Permanent transparent covering - non-blinking stare Lack of eyeball mobility Poor vision - except binocular in arboreal snakes

Snake Sense Organs n n Hearing - no obvious external ear No obvious response to aerial sounds Not deaf - have internal ears - hearing similar to lizards Sensitive to vibrations carried in ground

Snake Sense Organs n n n Olfaction important, but not in nostrils Jacobson’s organs (vomeronasal organs) Tongue carries scent particles to organ

Snake Feeding n n n Skull, jaws highly specialized for feeding Eat prey several times their own diameter Non-joined mandibles Loose skull bones Tracheal opening far forward between mandibles

Snake Feeding n n n Prey swallowed head first Pulled in by teeth, jaws, alternating sideto-side Contractions of neck muscles force prey down digestive tract

Snake Feeding n Two ways to subdue prey: n Constricting - grab prey in mouth and suffocate by looping body coils and tightening

Snake Feeding n n n Venom - toxic concentrations in saliva Neurotoxic blindness, paralysis Hemolytic - ruptures blood vessels, cells

Snake Feeding n n n Poisonous snakes in 4 families Viperidae - viper, pit vipers (heat sensitive) Elapidae - coral snakes (inject venom by chewing) Hydrophiidae - sea snakes Colubridae - rear-fanged venom to calm, not kill

Snake Feeding n Sea snakes have most deadly venom n King cobra most dangerous, largest (5. 5 m) - kill 9, 000 people per year

Snake Locomotion n n 4 basic types: Lateral undulation - Sshaped path, pressure against surface irregularities

Snake Locomotion n n Concertina movement - movement upward or along narrow passages Extend forward while bracing S-shaped loops

Snake Locomotion n Rectilinear movement - slow, straight-line movement

Snake Locomotion n Sidewinding - sandy surfaces, body thrown forward in loops, body at 60° angle to line of travel, 1 or 2 parts of body in contact with ground at once

Snake Reproduction n n Most oviparous - lay eggs in protected areas Most of remainder are ovoviviparous (including rattlesnakes) Very few viviparous Females store sperm from single mating, can lay several clutches over long interval

Order Crocodilia n n Unchanged for 160 million years Crocodiles larger, more dangerous than alligators Prey drowned, ripped into pieces by rapid rolling No natural enemies

Order Crocodilia n n n Oviparous - lay eggs in mass of vegetation Guarded by mother Incubation temperature determines sex of alligator hatchlings Low - females High - males 5: 1 (M: F) in some areas

Order Crocodilia n n Vocalizations by hatchlings cause mother to open next, allow hatchlings to escape Some adults carry young to water

Order Crocodilia n Mothers may guard young in pools for period of time to protect them from predators (fish, mammals)

Order Sphenodonta n n Tuatara - single species in New Zealand Lizard-like, <66 cm Lives in burrows Slow-growing, longlived (77 years)

Order Sphenodonta n n n Living fossil - primitive features identical to fossilized forms Primitive skull structure Well-developed parietal eye with retina, lens on top of head (non-functional)