Midterm Flashcards
Herpetology
The study of reptiles and amphibians. Herpo is Greek for creeping thing.
Twofold Roots of Herpetology
Taxonomy and systematics
Taxonomy
Classification in an ordered system indicating natural relationships
Systematics
Evolutionary and genetic relationships, phenotypic similarities and differences
2 modern approaches to herpetology
Functional and levels of organization
Functional approach to herpetology
Genetics, physiology, ecology, behaviour
Levels of organization approach to herpetology
Molecular, cellular, organismal, population level, community level
John Ray
English botanist and naturalist that grouped reptiles and amphibians based on their heart structure and introduced the morphological species concept
Morphological species concept
Grouping animals together based on similarities in appearance
Carolus Linnaeus
Swedish naturalist that produced the modern taxonomy system, but he hated herps
What did Linnaeus say about reptiles?
Foul and loathsome, heart with a single ventricle and a single auricle, doubtful lungs, double penis
What did Linnaeus say about amphibians?
Abhorrent, cold body, pale colour, cartilaginous skeleton, filthy skin fierce aspect, calculating eye, offensive smell, harsh voice, squalid habitation, terrible venom, creator purposely didn’t make many
Georges de Buffon
French naturalist/physical scientist that published the journal “Natural History”, in which 8/44 volumes pertained to reptiles
Bernard Lacépède
Studied under de Buffon and edited Natural History
Number of amphibian species
8000
Number of reptile species
10 000
What is included in reptiles?
Turtles, lepidosaurs (snakes, lizards, tuatara), and archosaurs (crocs & birds)
What is included in Lissamphibia (amphibians)?
Anura (frogs & toads), caudata (salamanders), and gymnophiona (caecilians)
What is included in Diapsida?
Lepidosauromorpha (testudines (turtles)) and Archosauromorpha (crocodyla)
What is included in Lepidosauria?
Rynchocephalia (tuatara) and Squamata (snakes & lizards)
Synapomorphy
Shared traits from a common ancestor
What is similar about reptiles and amphibians?
Vertebrate tetrapods
What is different about reptiles and amphibians?
Egg structure, skin, land vs water
Anamniotic Egg
Fish and amphibian eggs. Yolk sac (endoderm, mesoderm, and ectoderm), embryo, and jelly matrix inside the egg membrane. Must be wet, either in water or in a very damp and moist environment.
Amniotic Egg
Reptile, bird, and mammal eggs. Calcified shell that prevents desiccation. There are some live births in which there is still an amniotic sac.
Rhipidistian Fish
Historical ancestor of reptiles and amphibians. The skull bone pattern closely matches that of early amphibians. Lobed fins.
Skull Bone Pattern of Rhipidistian Fish
Parietal bones with an opening for pineal gland (light sensing organ/3rd eye) and two movable joints - jaw and roof of mouth (to swallow large prey)
Lobed Fins of Rhipidistian Fish
Two pairs of fleshy projections with rayed fin at ends that they could kind of walk/move along on
Ichthyostega
First tetrapod that best combined fish (ichthy) and amphibian traits. First true amphibian with 4 limbs, 5 toes, and scales.
Pros of Terrestrial Life
Oxygen is more abundant and diffuses more rapidly in air, adaptive radiation in terrestrial habitats leads to diversity in body forms
Cons of Terrestrial Life
Air is less dense and provides less buoyancy than water so the skeleton must support more weight, air temperature fluctuates more rapidly that water temperature affecting hibernation
Early Tetrapods and Terrestrial Life
Amphibians were the first tetrapods to spend a substantial portion of time on land. Early tetrapods had relatively sturdy skeleton-supported legs instead of paired fins, and lived in shallow aquatic habitats.
Greerpeton
Last branch before amphibians. Almost entirely aquatic. Lateral line. Used limbs for steering and tail for propulsion.
Plants in the Devonian Period
Trees and other large vegetation allowed the transformation of terrestrial ecosystems. Plants at the edges of ponds and swamps deposited organic material into aquatic habitats from terrestrial, allowing new food and living conditions.
Fish in the Devonian Period
Resembled modern lobe-finned fishes and lungfishes. Used buccal pumping to breathe air.
Buccal Pumping
Used be Devonian fish and modern day frogs. Come to surface, drop floor of mouth to draw in air, raise floor to close mouth and force air into lungs.
Necessary Adaptations for Living on Land
More capillaries and arterial blood from last aortic arch to improve air-filled cavity. Double circulation formed by oxygenated blood returning directly to heart by pulmonary vein. Bony elements of fins of lobe-finned fishes resemble limbs of amphibians.
Fossils of Acanthostega
Bony support of gills, basic skeletal elements as walking legs
The Age of Amphibians
The Carboniferous period when the earliest terrestrial tetrapods/amphibians benefitted from abundant food and relatively little competition. But the amphibians did begin to decline in number and diversity during the late Carboniferous period.
Maintenance of Adaptations for Life in Water During Carboniferous Period
Flattened bodies for moving in aquatic medium, weaker legs and a well developed tail (early salamanders), webbing on hind limbs for better swimming (anurans)
Permian Period
Amniotes became dominant land animals. Gymnosperms took over. Climate change resulted in the loss of 75% of species. Most surviving lineages of amphibians resembled modern species.
Causes of Mass Extinction at End of Permian Period
Loss of continental shelf habitat, volcanism (Siberian Traps), climate change
What went extinct at the end of the Permian period?
75% of terrestrial vertebrate species (considered to be the Earth’s most severe extinction event), 21 (63%) of terrestrial tetrapod species, 7 orders of insects (only extinction known to include insects), many marine taxa (especially benthic communities)
Extinct Groups of Ambhibians
Temnospondyls and Lepospondyls
Temnospondyls
Extinct amphibians, 5 m long, lived in polar rift valleys where it was too cold for primary predators (crocodiles), basically looked like a salamander-frog-crocodile
Lepospondyls
Extinct amphibians, boomerang shaped skull was hydrofoil for lift to move through water, theory that they had to tilt their heads back because it was too big for them to open their jaws, got too dry for them to survive
General Life Cycle of Amphibians
Small eggs need wet conditions, not much yolk so they need to feed themselves and grow (larval stage), amazing metamorphosis from gills to lungs
Order Caudata
Salamanders, tailed ones
Order Caudata
Salamanders, tailed ones. 2 or 4 legs, smooth skin.
Order Anura
Frogs and toads, tailless ones. Short tailless bodies, long hindlegs to launch and forelimbs for landing, sticky tongues to catch prey.
Traditional Phylogeny of Amphibians
Morphological characters, 2 groups are Anura/Caudata and Gymnophiona. Usually 4 limbs, opercular apparatus in middle ear, absence of scales, and green rods in Anura and Caudata. Highly reduced skull in Gymnophiona.
Recent Phylogeny of Amphibians
Morphological and molecular characters, 2 groups are Anura and Caudata/Gymnophiona. Absence of limbs in gymnophionans is secondary, absence of limbs precludes operculum, reduced development of eyes and fossorial lifestyle preclude need for green rods.
Recent Phylogeny of Amphibians
Morphological and molecular characters, 2 groups are Anura and Caudata/Gymnophiona. Absence of limbs in gymnophionans is secondary, absence of limbs precludes operculum, reduced development of eyes and fossorial lifestyle preclude need for green rods.
Families in Order Gymnophiona
Caecilidae, Ichthyophiidae, Typhlonectidae
Caecilians
Order Gymnophiona. Legless and nearly blind, small heads, adapted for burrowing as they live underground in moist soils near water. Terrestrial, semi, and aquatic species. Resemble earth worms with grooves.
Family Caecilidae
Caecilians. No true tails, burrowers, ossified skulls adapted for burrowing
Family Ichthyophiidae
Caecilians. Asian, tailed, ovaparous, maternal care
Family Typhlonectidae
Water caecilians. Large, viviparous, lateral compression that gives fishy shape
Variation in Life History of Order Caudata
Either entirely aquatic, aquatic eggs/larvae and terrestrial adults, or entirely terrestrial
Body and Movement of Salamanders on Land
Distinct heads with well developed tails and legs. Legs are small for the body (indicative of older species), so they kind of swagger with a side to side bending of the body, like early terrestrial tetrapods.
Families in Order Caudata
Sirenidae, Proteidae, Amphiumidae, Cryptobranchidae, Ambystomidae, Salamandridae, Plethodontidae
Family Sirenidae
No metamorphosis, external gills, small forelimbs and no hindlimbs. Very long and skinny. Look juvenile for whole life.
Family Proteidae
Totally aquatic, retain external gills, large body size, robust forelimbs and hindlimbs. Some are cave dwellers and live in deep waters so they have depigmented skin and degenerate eyes.
Family Amphiumidae
Totally aquatic, no gills, 4 tiny limbs, up to 1 m long
Family Cryptobranchidae
Giant salamanders & hell-benders. Flat heads, big enough to eat baby deer, males guard eggs and fight for them. Need fast-flowing, clear, crisp water to breathe.
Family Ambystomatidae
Mole salamanders. Stout with small heads, large parotid glands, facultative metamorphosis. Spend most of adult life underground.
Family Salamandridae
Newts & old world salamanders. Adults have no gills but are usually highly aquatic. Lack costal grooves, may be slender or robust.
Salamandridae Reproduction
Male deposits spermatophore and female walks over and picks it up with cloaca. Vivaparous, internal reproduction without sex.
Family Plethodontidae
Lungless. Eggs can be terrestrial, larvae in streams or sphagnum bogs. May be totally aquatic.
Anura Adaptations to Avoid Predation
Camouflage, distasteful or poisonous mucous secreted from skin glands, bright aposematic colours
Suborders of Anura
Archeobatrachia, Mesobatrachia, Neobatrachia (advanced frogs & toads)
Families of Suborder Archobatrachia
Ascaphidae, Bombinatoridae, Discoglossidae
Family Ascaphidae
Internal fertilization by intermittent organ (“tail”). Vertical pupils (weird for frogs), no tympana, clawed forefeet and webbed hindfeet, sucker to help hold onto rocks. Ancient. Live in turbulent streams and indicate mountain stream health.
Family Bombinatoridae
Fire-bellied toads. Behavioural defence called unken reflex (back blends in but they flip over and show their bright bellies).
Family Discoglossidae
Burrow. Male carries fertilized eggs on his back and deposits larvae into water.
Families of Suborder Mesobatrachia
Megophryidae, Rhinophrynidae, Pipidae
Family Megophryidae
Asian toad frogs. Mimic dead leaves
Family Rhinophrynidae
Burrowing toad. One fossorial species that only comes to the surface for breeding. Spade-like edge of foot for digging, thick skin, dorsal stripe, use tongue differently to catch termites (termite specialists)
Family Pipidae
Highly aquatic, no tongue (no use for a tongue in water), lateral line, polyploid, widely used in research
Families of Suborder Neobatrachia
Leptodactylidae, Centrolenidae, Ranidae, Bufonidae, Hylidae, Dendrobatidae
Leptodactylidae
Pacman frogs and big head frogs. Big mouth, fang-like upper teeth, capture and consume large prey (lizards, other frogs, small mammals), big heads and little bodies.
Centrolenidae
Glass frogs. Breed on leaves. Threatened by parasitoidism by flies. Parental care by males (lay eggs on leaves above water, male stays with them until they hatch, they drop into water below.
Ranidae
True frogs. Forelimbs and thumb bases become enlarged during breeding season.
Bufonidae
True toads. More terrestrial than frogs. Prominent parotid glands, no teeth, bidder’s organ (gonadal tissue in males that looks like testes but turns into ovaries if something happens to the testes), poison glands that ooze white goo (not warts)
Hylidae
Treefrogs. Sticky toe pads to hold onto trees.
Subfamilies of Family Hylidae
Hemiphractinae (marsupial frogs that hold their eggs inside their skin) and Phyllomedusinae (leaf frogs, poster child of the tree frogs)
Dendrobatidae
Poisonous (most poisonous get alkaloid poison from ant diets). Complex paternal care (male carries tadpoles from hatching place to permanent water).
Early Amniotes
Small, slender, lizard-like, 20 cm long. Skull and tooth morphology suggest insectivorous diet. Oldest are Hylonomus and Paleothyris.
Who are amniotes?
Mammals, birds, and reptiles
Characteristics of Amniotes
Waterproof skin, increased use of rib cage to ventilate lungs, amniotic egg
Oldest Amniote vs Oldest Amniotic Egg
90 million year difference because the eggs weren’t mineralized enough to fossilize
Amniotic Egg Extraembryonic Membranes
Gas exchange, waste storage, transfer of stored nutrients to embryo, fluid shock-absorber. Develop from tissue layers that grow out from embryo.
Adaptations of Animals Inside Amniotic Egg
Egg tooth/horny caruncle to break out. Yolk provides nutrients and allows the animal to skip the larval stage.
Mesozoic Radiation of Amniotes
Were more widespread/numerous/diverse than today, dominated terrestrial vertebrates for 200+ MY (10-15 m, bigger than T rex)
Two Great Waves of Amniote Radiation
Early Permian period (3 evolutionary branches based on skull fenestration) and late Triassic Period (dinosaurs on land and flying pterosaurs)
Sarcosuchus
Giant prehistoric (112 MYA) reptile. One of the largest (11-12 m) crocodile-like reptiles that ever lived.
Amniote Skull Fenestration
Holes in the skull, probably for jaw muscles. Synapsids, anapsids, and diapsids.
Synapsids
Only lower hole in skull. Mammal-like reptiles and therapsids from which mammals evolved.
Anapsids
No skull holes. Probably extinct but debate on position of turtles.
Diapsids
Upper and lower hole in skull. If turtles are included, all modern reptiles and some extinct swimming, flying, and land reptiles.
Euryapsids
Only upper hole in skull. Extinct water reptiles.
Turtle Skull Fenestration
Anapsid, but not always. A secondary loss back to anapsid from first change to dyapsid. The oldest skull bone configuration is different from the original anapsid ancestor.
Evolutionary Branches of Diapsids
Archosauromorpha (crocs, birds, and their extinct relatives) and Lepidosauromorpha (lizards, snakes, Sphenodon, and their extinct relatives)
Archosauria
Crocs, birds, and their extinct relatives. Most diverse in the warm Mesozoic era.
Dinosaurs
Extremely diverse group (varying shapes, sizes, and habitats), agile, fast-moving, good parents, social in some species
Groups of Dinosaurs
Ornithischians (mostly herbivorous) and Saurischians (long-necked herbivores and carnivores, including the ancestor of birds)
Parental Care in Dinosaurs
Nested, protected eggs, and protected children (like crocs)
Are dinosaurs ectotherms or endotherms?
Anatomy suggests endotherms but the mesozoic climate and surface area to volume ratio suggest ectotherms
Dinosaur Extinction
End of the Cretaceous period but some species may have survived into the early Cenozoic era. Asteroid, climate change, other theories.
Orders of Class Reptilia
Crocodilia, Testudines, Rhynchocephalia, Squamata
Order Crocodilia
Crocodiles and alligators. Among the largest living reptiles. Closer to birds and mammals than to other reptiles. Spend most time in water and breathe air through upturned nostrils. Confined to tropics and subtropics. Functionally successful because they haven’t really evolved further.
Order Testudines
Turtles and tortoises
Order Testudines
Turtles and tortoises. Evolved in Mesozoic era and have changed little. Few synapomorphies with other animals. Hard shell protects against predators. Returned to water during their evolution but still crawl ashore to lay eggs. Mostly omnivorous but some specialists.
Order Squamata
Lizards, snakes, and amphisbaenians. Monophyletic with lots (50) synapomorphies. Specialized wrist and ankle joints, fused premaxillary, no vomerine teeth, vomeronasal organ hemipenes in males and femoral and prenatal glands in females.
How Reptilian Heritage Differs from Amphibians
Scales containing keratin to waterproof the skin and prevent desiccation in dry air. Respiration only with lungs, not through skin. Lay amniotic shells on land.
How does turtle breathing differ from other reptiles?
They use moist vascularized surfaces of the cloaca for gas exchange
Crocodilia Eggs and Parental Care
Oviparous with internal fertilization. Lay eggs in a mound of vegetation (like an island) and stays to guard them. Mama may help open shells to free babies and carries them to the water. Mama knows her babies’ calls (like birds).
Families of Order Crocodilia
Crocodylidae Alligatoridae, Gavialidae
Family Crocodylidae
Largest confirmed reptiles. Temperature-dependent sex determination. Freshwater, tropics (some saltwater species).
Family Alligatoridae
Alligatorinae and Caimaninae.
Crocodiles vs Alligators
Alligators are smaller and cuter. Croc teeth stick out while mouth is closed but alligator teeth don’t.
Family Gavialidae
1 species. True Gharial. Ghara (pot) on tip of male’s snout. One of the largest croc species. Critically threatened. Males guard females.
Tomistoma
Potentially part of family Gavialidae but more research is needed, controversy over taxonomy. False Gharial. Freshwater. No nest guarding or parental care.
Tuatara
Slow metabolism. 100+ or maybe even 200 year longevity, mature at 10-15 years, female needs 2-3 years to develop a clutch of eggs and the eggs need a year (longest gestation of all reptiles and maybe even mammals), egg incubation. No penis. Pineal eye. Dino dentition. Cold tolerance (different hemoglobin enzymes work at lower temperatures). No external ear holes so not a lizard.
Tuatara
Slow metabolism. 100+ or maybe even 200 year longevity, mature at 10-15 years, female needs 2-3 years to develop a clutch of eggs and the eggs need a year (longest gestation of all reptiles and maybe even mammals), egg incubation. No penis. Pineal eye. Dino dentition. Cold tolerance (different hemoglobin enzymes work at lower temperatures). No external ear holes so not a lizard.
Evolution of the Turtle Shell
Plastron (lower shell) and carapace (upper shell). Oldest turtle fossil had a fully developed shell but early carapaces were not ossified enough to be fossilized. Shell is an expanding of the ribs to form wide plates.
Turtle Necks
2 clades based on neck movement/retraction - side to side (slide head in side) or pull the head back into the shell. Neck is extremely flexible
Cryptodira
Hidden neck/pull head in turtles. More common.
Pleurodira
Side-neck turtles. Less common.
Pleurodira Families
Chelidae, Pelomedusidae & Podocnemidae
Family Chelidae
Side-neck turtles. Highly aquatic, aestivation during dry periods (dormancy during drought or high summer temp).
Families Pelomedusidae & Podocnemidae
River turtles with streamlined shells. Bottom walkers in slow moving water. Feed on benthics and aquatic plants.
Cryptodira Families
Cheloniidae & Dermochelyidae, Chelydridae & Platysternidae, Carettochelidae, Trionychidae, Kinosternidae, Emydidae, Testunidae,
Families Cheloniidae & Dermochelyidae
Sea turtles. Flippers, streamlined shells, front limbs stronger than back limbs. Specialist feeders on jellyfish and sponges. Among oldest turtles evolutionarily. Spend years in water and then lay many eggs on land.
Families Chelydridae & Platysternidae
Snapping turtles and big headed turtles. Long tails (longest of all turtles). Opportunistic omnivores. Use tongues as a fishing lure to catch prey. Bioaccumulate toxins and change the environment. Hunted for food and persecuted.
Persecution of Snapping Turtles
Eaten. Nailed to trees to die slowly. Run over. Eggs are killed. Extra bad to lose adults in long-living species. Now a species of concern but used to be allowed to hunt with a fishing licence.
Family Carettochelidae
Only freshwater turtle with paddle-like limbs. 1 species, the pig nose turtle (a v cute boy).
Family Trionychidae
Softshell turtles. Reduced and “naked” carapace and plastron. Flattened pancake turtle with leathery skin covering. Long necks. Snorkel-like noses to breathe while in mud underwater.
Family Kinosternidae
Mud turtles and musk turtles. Forage and mate underwater, some species hibernate on land, some babies even dig down and hibernate underground in their first winter.
Family Emydidae
Pond turtles, cooters, sliders, American box turtles. Sexual dimorphism, female may be 10x bigger than male.
Family Testunidae
Tortoises. High-domed shell, elephantine limbs. Terrestrial in semi-arid habitats. Herbivorous. Live a couple hundred years with 18 month gestation. A lot of morphological differences as present on many different islands of the Galapagos.
Lizards
Most numerous and diverse reptiles. Many legless forms (limblessness has evolved 60 times). Mostly relatively small. Insectivorous. Nest in crevices and decrease activity during cold periods, enabling survival through the Cretaceous crunch.
Lizard Groups
Iguanidae, subfamily Phrynosomatinae, Chamaeleonidae, Gekkonidae, (suborder) Amphisbaenia, Lacertidae & Teiidae, Scincidae, Varanidae
Family Iguanidae
Dry adapted lizards. Mostly terrestrial and mostly herbivorous.
Subfamily Phrynosomatinae
Fence lizards. Xeric (dry & arid) habitat. Social. Rock Paper Scissors reproductive strategy that maintains colour morphology.
Family Chamaeleonidae
Chameleons. Zygodactylous feet (mitten hands) to hold on, independently mobile eyes, prehensile tails (basically 5th leg), laterally compressed bodies, crest for head and neck protection, projectile tongue.
Family Gekkonidae
Geckos. Millions of microscopic hairs (setae) on bottom of feet that function as a dry adhesive (electrostatic sticky) and can even stick to glass), caudal anatomy, well developed limbs, tiny scales that make them feel soft, very different toes. Nocturnal, arboreal and pantropic, insectivorous (big ones sometimes eat smaller ones).
(Suborder) Amphisbaenia
Worm lizards. Poorly understood. Scales in rings, usually legless (some have forelimbs), caudal anatomy, right lung reduced, many are pinkish colour, small (15 cm), look like primitive snakes. Burrowers (not common among lizards) with variable head morphology for differential burrowing, but head is stout like tail end and can move backwards and forwards. Some live births.
Families Lacertidae & Teiidae
Wall and rock lizards and whiptail lizards (ecological equivalents)
Family Scincidae
Skinks. Worldwide distribution.
Family Varanidae
Monitor lizards. Active predators. Tropics. Long, robust, muscular, long head, some small and some huge, very strong, fast, poisonous/venomous (lunge bacteria in saliva).
Caudal Anatomy
Can drop tail (it still wiggles for a bit) and it grows back, but never as perfectly as the original
Snakes
Descendants of lizards adapted for burrowing through loss of limbs (no pectoral girdle but some primitive ones have vestigial pelvic girdle). Everywhere except Antarctica, more aquatic than lizards so on more islands.
Snake Fangs
No fangs, rear fangs, fixed front fang, movable front fang (folds back in when mouth closes)
Evolutionary History of Snakes
Living sister group appears to be Varanids because of the forked tongues. Extinct Mosasaurs may be the closest relatives to modern snakes because they swam sideways like snakes (not up and down like whales).
Snake Suborders and Families
Scolecophidians (Anomalepididae). Alethinophidians (Boidae, Pythonidae, Colubridae, Viperidae, Elapidae). There was a deep split early on but there is a lot of debate over these 2 groups.
Family Anomalepididae
Blind snakes. Recessed and reduced eyes. Vestigial pelvis, absence of large ventral scales and no annelid (ring) pattern. Fossorial specialists (live under forest floor and in termite mounds and ant hills, poisonous too then).
Family Boidae
Boas. Constrictors. Infrared receptors in pits, cloacal spurs. Viviparous. Heaviest snake.
Family Pythonidae
Pythons. Constrictors. Infrared receptors. Oviparous. Cloacal spurs. Arboreal or aquatic.
Family Colubridae
Colubridae, Homalopsinae, Xenodontinae. Highly diverse group with confusing evolutionary relationships
Family Viperidae
Vipers and pit-vipers. Most advanced snakes with thermoreception (heat-seeking pits) and rotating fangs (like a hypodermic syringe). Bites, poisons, lets go, tracks dead.
Family Elapidae
All venomous with fixed fangs (holds prey), petroglyphous (primitive) without infrared receptors.
Biggest Snake Ever
Titanoboa. 58-60 MYA in South America. 13 m long and over 1100 kg. Ectotherm this big needed a consistent 33 degree climate for metabolism.
Groups of Elapidae
Elapinae and Hydrophiinae
Elapinae
Predominantly terrestrial and semi-fossorial or litter foragers, mostly oviparous
Hydrophiinae
Sea snakes. Most toxic snakes. Eat fish. So highly adapted to water that they can’t move on land so viviparous (can’t come to land to lay eggs). Laterally compressed and tail fans out like fin. Smaller scales.
Gametogenesis & Fertilization
The production of gametes. Internal fertilization, in the oviduct in reptiles and in the cloaca in amphibians. Ultimately controlled by the environment.
When is the shell produced in reptiles?
The last step before oviposit because the sperm has to get in.
When is the shell produced in amphibians?
Enveloped get deposited around the egg in layers throughout the entire process and the number of capsules depends on species.
Aquatic vs Terrestrial Eggs
Aquatic amphibian eggs are an amniotic because they lack extraembryonic membranes. Terrestrial reptile eggs are amniotic with 4 extraembryonic membranes.
Extraembryonic Membranes
Allantois (fluid), amnion (shock absorber), chorion (selective membrane), yolk sac (food)
Egg Shell
Ovum is coated with albumin and several layers of protein fibers. Fiber layer is impregnated with calcite crystals in crocs and squamates and with aragonite crystals in turtles. These fibres make the hard shell structure.
Fertilization
When a spermatozoon and and ovum unite to form a diploid zygote. Only one sperm fertilizes the egg and then there’s a separation to prevent more from getting through.
Polyspermatic Fertilization
In salamanders. More than one sperm gets through o the egg but only one merges with the nucleus of the egg.
Courtship in Anurans
Each species has a different song
Courtship in Lizards
Colours and dances, puff up body
Courtship in Sand Lizards
Head rubbing
Amplexus
Male lines up his cloaca with female’s and fertilizes the eggs as they come out. Most frogs and hellbenders.
Spermatophore Fertilization in Cloaca
Male produces spermatophore with stalk, base, and pile of sperm. H leaves it on the substrate in water and attracts the female to come pick it up with her cloaca. Salamanders other than hellbenders.
Oviparous
Egg-laying. All embryo nutrition comes from yolk of egg.
Viviparous
Live birth. Embryo nutrition provided entirely by yolk, by oviductal secretions, or by a complex placenta.
Why do amphibians have a larval stage?
For more nutrition because there is not much in the yolk.
Vivaparous Modes of Reproduction
Lecithotrphy, Matrotrophy, Patrotrophy
Lecithotrphy
Provision of all nutrients necessary for hatching/birth from yolk of egg
Matrotrophy
Provision of at least some nutrients by mother. Some babies chew on the inners of mom.
Patrotrophy
Provision of at least some nutrients by father
Amphibian Reproduction
External fertilization, oviparity
Caecilians Reproduction
All internal fertilization, more than half viviparous (in oviduct), maternal nutrition, oviparous lay on land and may redirect development or larval stage in water
Maternal Nutrition of Caecilians
Fuelled by yolk but fetus switches to the oviducal lining on the wall of the mother’s oviduct. They have special teeth to scrape it off.
Salamander Reproduction
Hellbenders and giant salamanders have external fertilization, but all others have internal by spermatophore. None have intromittent organs. Most are oviparous but there are 4 viviparous species.
Anuran Reproduction
Mode of reproduction categorized by placement of eggs for development. Eggs may be deposited in aquatic habitats, in arboreal or terrestrial habitats, or retained in or on the body.
Maternal Care in Anurans
May guard eggs (may be in or on body) or lay them high up in trees to prevent predation, oophagy, gastric brooding
Oophagy of Anurans
Some Hylid frog mamas come back and lay unfertilized eggs for her larvae to eat
Gastric Brooding in Anurans
Female deposits aquatic eggs and then swallows them after fertilization so they develop in her stomach, and then baby frogs come out of her mouth. Only about half of the eggs survive, so the first half could be what triggers inhibition of acid.
Foam Nests
Leptodactylid frogs construct foam nests to create a 100% humidity environment for the eggs. If it dries up, the tadpoles can rub on each other to create more foam.
Anuran Egg Guarding (not on body)
Male guards eggs until they hatch, puts the baby tadpoles on his back, and hops them over to the water.
Anuran Egg Guarding (on body)
Pipa Pipa male presses eggs from female’s cloaca onto her back and she embeds them into her skin. The tadpoles later come out of her back. Marsupial frog females guard the eggs and the male comes back after they hatch and pushes them into his back and he keeps living his life with them on his back until little frogs hop out.
How do tadpoles get to the water when Anurans lay on land?
Parental transport, foam nests, or lay on leaves above water and they drop to the water below when they hatch. Some have direct development so there is no larval stage in need of water.
Reptile Reproduction
Only about 20% of lizards and snakes are viviparous and rest of reptiles are oviparous.
Pros of Reptiles Evolving Viviparity
Temperature control and predation control
Cons of Reptiles Evolving Viviparity
Mom’s mobility is limited by the extra weight and bulk making her more susceptible to predation. If she gets eaten, all the babies are gone too.
Viviparity in Reptiles vs Amphibians
Rarer in amphibians as they do not require high developmental temperatures so there is no thermal advantage. Direct development and egg attendance in amphibians are equally successful as squamate viviparity.
Evolution of Viviparity in Squamates
Primary reason is for temperature regulation. Females can maintain body temperature to maintain egg temperature. Development is more rapid at higher temperatures and neonate survival is higher.
How do pythons keep eggs warm?
Wrap around eggs and twitch/shiver
Why is sex costly?
Only half the genes are transferred in meiosis, not every individual can reproduce (males vs asexual females), time and energy put into mating and defending
Benefits of Sex
Purge mutations from the lineage, break up bad combinations, put good combinations back together
Sexual Reproduction
Male and female contribute genetic material to offspring
Types of Unisexual Reproduction
Hybridogenesis, gynogenesis, kleptogenesis, parthenogenesis
Hybridogenesis
Hybridization between two closely related species. Female mates with male of parental species and only female offspring are produced, all containing genome of mother, and male genome is not included.
Gynogenesis
Egg begins development after penetration by sperm but no fusion of genetic material
Gynogenesis Hybrids
Blue spotted salamander (Ambystoma laterale) and Jefferson’s salamander (A. jeffersonianum) hybridize, resulting in triploid females JJL (A. platineum) or JLL (A. tremblayi). These females then go back and mate with the parent species again, not the triploids.
Kleptogenesis
All unisexual populations share the same mtDNA and local unisexuals steal nuclear genomes from sexual males of 4 species. The females breed in ponds with male sperm donors and pick up the spermatophore.
Results of Kleptogenesis
Egg development is triggered and male genome kicked out (gynogenesis), male genome added to offspring & all female genomes retained (ploidy increase), male genome added & one of female genomes kicked out (genome replacement), or some combo of these
Parthenogenesis
Females reproduce without males at all. Clonal, all female offspring genetically identical to mother.
How is ovulation triggered in parthogenesis?
Pseudocopulation. A postovulatory females acts like a male and attempts to mate with the preovulatory female. The act of mating triggers a hormonal response that produces the egg.
Parental Care
Any form of post-ovipositional parental behaviour that increases survival of offspring at some expense of the parent. Most herps do not show any parental care beyond nest construction.
Categories of Parental Care in Herps
Nest/ egg attendance, nest/egg guarding, egg/larval/hatchling transport, egg brooding, feeding of young, guarding/attending young
Nest/Egg Attendance in Amphibians
Aquatic egg aeration, terrestrial egg hydration, protection from pathogens and predators, manipulation to prevent developmental adhesions. No actual defence.
Nest/Egg Attendance in Reptiles
Hydration of eggs, prevent drowning of eggs, deter fungal infection, aid in keeping eggs hidden. No actual defence.
Nest/Egg Guarding
Active defense
Egg Brooding
Retaining eggs or babies for a longer period than just transport
Trophic Eggs
Feeding eggs for oophage
Parental Care in Amphibians vs Reptiles
More terrestrial = bigger offspring = more parental care in amphibians (bigger offspring = less offspring = need to protect young). Parental care in reptiles is associated with egg protection from predators or fungi and keeps egg warm.
Parental Care Cost to Parent
Decrease future survival or reduced feeding time and decreased investment into more offspring, but benefits outweigh the costs.
Life History
Traits associated with fitness and survival. Including clutch size and frequency, size of young at birth/hatch, age and size at maturity and death, modes of reproduction.
Early Reproduction
Fast growth rate, early maturity, reduced survival because all of energy is going to growth, limited potential for further reproduction. No parental care. r species
Late Reproduction
Slower growth rate, later maturity but could die before reproduction, increased survival, decreasing fecundity after each reproductive event. Parental care. K species
K Strategists/K-Selected Species
Slow life history. Constant environments allow populations to grow to carrying capacity. Results in high competitive abilities. Reptiles.
r Strategists/r-Selected Species
Fast life history. Unpredictable adult mortality in unpredictable environments, so populations rarely grow to carrying capacity. Rapid reproduction. Amphibians.
Bet-hedging Species
Predictable environments for adults but unpredictable for eggs/babies so adults invest a little bit of energy into babies every year in hopes that one will pay off. Turtles.
Phenotypic Plasticity
Different life history responses to different situations. Individual can alter physiology, morphology, and behaviour in response to a change in environmental conditions.
Reaction Norms & Plasticity
Small slope = insensitive/not very plastic. Steep slope = sensitive/very plastic
K/r Strategists & Seasonality
Seasonal/temperate areas are unpredictable so these species are usually r. Tropical areas with little change are predictable so these species are usually K.
Croc Life History
Late maturation, extended fertile period, long-lived. Clutch size varies from 6-60 eggs.
Turtle Life History
Late maturation, extended fertile period, long-lived. Clutch size varies from 1-100 eggs.
Anuran Life HIstory
Males sing to attract females but also attract predators, so they have more males to tackle this loss in the population
3 Patterns of TSD
Cool chicks, hot mamas, and high/low females & intermediate males
Pivotal/Threshold Temperature
Incubation temp when equal number of males and females
Mechanism of TSD
Aromatase for females and 5a-reductase for males. Genes that code for these are turned on or off depending on temperature.
Implications of TSD
Saving turtle eggs and made all females without knowing about TSD. Dino TSD could have caused demise.
Reproductive Effort
Total energy spent on 1 reproductive episode. Energy invested by female (parental care and getting her body ready) and energy put into producing the offspring.
Clutch Size vs Offspring Size
More babies = smaller babies. Less babies = bigger babies. Bigger body = bigger babies. Optimal fixed clutch size that evens out size and number of kids with the costs.
