Amphibians Urodela (salamanders, newts) Terrestrial, aquatic: ~550 species
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Transcript of Amphibians Urodela (salamanders, newts) Terrestrial, aquatic: ~550 species
I. Amphibians
A. Urodela (salamanders, newts)• Terrestrial, aquatic: ~550 species• Retain tails as adults (paedomorphic character)• Fertilization usually internal
B. Anura (frogs, toads)• Terrestrial, aquatic: ~5400 species• Possess tails as juveniles; not in adults• Fertilization usually external
C. Apoda (caecilians)• Terrestrial (mostly), aquatic: ~170 species• Legless (secondary)• Fertilization internal
II. Reptiles
• Keratin scales• Amniotic eggA. Testudines/Chelonii (turtles, tortoises)
• Terrestrial, aquatic: ~325 species (7 marine)
B. Rhynchocephalia (tuataras)• Terrestrial; 2 species (New Zealand)• Least specialized reptile (similarities to Amphibia)• Caudal autotomy (similar to Squamata)
C. Squamata (snakes, lizards)• Terrestrial, aquatic; ~9000 species (62+1 marine)• Sister group to Rhynchocephalia
D. Crocodilia (alligators, crocodiles, caimans, gavials)• Semi-aquatic; 24 species (1 marine)• More closely related to birds than to other reptiles
Fig. 11-2
Amniotic Egg
II. Reptiles
• Secondarily marine• Ectotherms and poikilothermsA. Sea Turtles
• Unable to retract head or legs into shell (keratin + bone)
• Shell: dorsal carapace + ventral plastron• Subcutaneous fat deposits; light spongy bones
(buoyancy)
• Legs modified as flippers for swimming, steering (rear)
• Seven species – Mainly warm water• Some migrate or may appear in temperate waters
• Can be submerged up to 3 hours
Fig. 11-4
Video
III. Marine Reptiles
A. Sea Turtles• Mate offshore; sperm storage up to 2-3 years• Lay eggs on land at night
• Dig hole in sand and lay 80-150 eggs• Incubation period ~ two months
• Gender of hatchlings determined by incubation temperature (environmental sex determination)
• Warm (>30 oC) Females• Cool (<30 oC) Males
• Females return to same beach to spawn every 1-3 years; may migrate >2000 km
• DNA evidence that site fidelity spans generations
• Require 10+ years to reach sexual maturity
Fig. 11-6
Fig. 11-7
III. Marine Reptiles
B. Marine Iguana• One species – Galápagos Islands
• Males colored more brightly than females• Different populations (different coloration) on various islands• Dark colors may aid rapid heat absorption after leaving water
• Herbivores: Feed on algae• Can dive to 15+ m video• Can hold breath for 30-60 minutes• Eliminate salt with salt glands near nostrils; nasal spraying
• Good swimmers• Long, laterally flattened tail
• Territorial• Males fight to establish territories• Males maintain small harems• Females dig nests in sand for eggs
Fig. 11-9
III. Marine Reptiles
C. Sea Snakes• 65 species – Mainly tropical (Indian, Pacific)
• Coral reefs, open ocean• Adaptations to aquatic lifestyle
• Scales reduced or absent• Nostrils higher on head vs. terrestrial snakes; specialized valves that
seal nostrils when submerged• Bodies flattened laterally (3-4 feet long at maturity)
• Paddle-shaped tail video• Huge lung (extends into tail); gas exchange across trachea & skin
• Can dive to 150 m (typically ~5 m); hold breath 2+ hours• Eliminate salt via salt gland under tongue
• Ovoviviparous• Gestation 4-11 months• Few species lay eggs on shore
• Venomous• Closely related to cobras• Venom typically used to kill small prey (fishes, squids)• May hunt in schools• Some actively trap prey; others lie in wait
• Few natural predators (seabirds, sharks, saltwater crocodiles)