Amphibians

1. Amphibians

2. Diversity • Ex: Frogs, salamanders, newts, and caecilians • Amphibians are born without legs, and they grow legs as they develop (part of life cycle) • Differ greatly in size • 1 cm to 6 feet. • Diet: • Carnivorous (eat only meat/other animals) or • Insectivorous - eat other organisms, especially insects.

3. Diversity, cont. • About 5700 living speciesof amphibians. • The ancient amphibians were: • Typically larger in size • Contained massive teeth • Some had scaled skin • Modern amphibians are: • Much smaller in stature/size • Have evolved a number of adaptations that are fit for whatever environment they live in

5. General Characteristics • Ectothermal (cold-blooded) • Life requirements: • Require both land and water for survival • This is true for many amphibian species • However, others may be fully terrestrial, even being born on land (viviparity). • Others may only need a moist environment, not necessarily a pond or pool, while others may be completely aquatic (born in water, live in water)

6. General Characteristics • Metamorphosis • Go through life cycle changing event (from tadpole to adult) • All amphibians have a tadpole stage • Most are biphasic • This means they go through an aquatic stage, and a terrestrial stage at some point

7. General Characteristics • Metamorphosis • The transition from aquatic to terrestrial must have many physical changes • Include: • absorption of the gills and tail • modified eyesight to see on land • thicker skin to cope with atmospheric environments • stronger limbs to support the weight of the body • a more cylindrical tail • new ways to catch food

8. General Characteristics • Reproduction: • Separate sexes • Fertilization internal in salamanders/caecilians • Fertilization mostly external in frogs/toads • Mostly oviparous • Most produce shell-less (amniotic) eggs that are deposited in the water • These eggs rely on moisture from their surrounding water source, • Enclosed in protective, gelatin envelope • Nourished for very short time by mother

9. General Characteristics • Reproduction, cont.: • A typical biphasic species will return to the water a few years later (after it has matured and sexual maturity has been reached), • Then, it will begin the lifecycle all over again with its own offspring.

10. General Characteristics • Respiration: • Can use lungs, skin and gills (either separately or in combo with one another) • Salamander larvae possess external gills • Frogs and toad larvae possess internal gills • Usually two lungs (few exceptions) • Often need moist surroundings to help breathe

11. General Characteristics • Appendages/Limbs: • Most amphibians are tetrapods (four-legged) vertebrates • Some are legless • Webbed feet often present • No true nails or claws • Forelimb usually has four digits (sometimes five)

12. General Characteristics • Skin: • Amphibian skin is naked, lacking hair, feathers, or "true" scales • Smooth and moist • Highly glandular with mucous glands • Some glands can be poisonous • May contain chromatophores (pigment cells)

13. General Characteristics • Digestion: • Mouth usually large with small teeth (in both upper/lower jaws) • Two nostrils open into mouth cavity • Contain: stomach, small/large intestine, spleen, liver (two lobes), gallbladder, pancreas, cloaca and cloacal opening

14. General Characteristics • Circulation: • Three-chambered heart • Contains two atria, one ventricle • Double circulation through heart • Skin is always supplied with blood vessels/oxygen

15. General Characteristics • Excretion: • Cloaca—holding cell for the waste products • Paired mesonephric kidneys, bladder also present • Urea is main waste product • Skeleton: • Most bony with varying numbers of vertebrae • Ribs present in most • Exoskeleton is absent • Vertebrates: have a backbone and many bones

16. General Characteristics • Body forms: • Vary greatly: • Options: • elongated trunk with a distinct head • compact, depressed body with fused head • Ex: salamander vs frog vs caecilian

17. General Characteristics • Habitat: • The most abundant frogs are the 260 species of Rana found throughout temperate and tropical regions of the world • Frog species are often restricted to certain localities • Usually found near water • Amphibian populations are falling in most parts of the world • Winter: most amphibians will hibernate in soft mud in pools/streams

18. General Characteristics • Biodiversity: • VERY good bioindicators of pollution, pH levels, oxygen levels and humidity • Can observe multiple mutations in frogs/salamanders • This helps to indicate high pollution/radiation levels

19. Classification • The class Amphibia is comprised of three orders, Anura, Caudata, and Gymnophiona. • Anuran Biology – • Ex: Frogs and Toads • About 30 families and more than 4,500 species • Range in size from a few millimeters to a couple feet in length

20. Classification • Anuran Biology, cont. – • Found in nearly every niche on Earth (very diverse group) • Presence of four limbs • hind limbs are typically larger and modified for leaping or climbing • Capable of vocalizing, and produce an array of sounds from squeaks to barking noises. • Most are external fertilizers. 

21. Classification • Caudate Biology (Order Urodela) – • Ex: Salamanders, Newts, Sirens, Amphiuma, Waterdogs, and Mudpuppies • Commonly referred to as the "tailed amphibians", a feature lacking in frogs and often overlooked in caecilians. • 10 recognized salamander families, with a just more than 500 species. • Typical have four limbs of similar size that are used for terrestrial walking.

22. Classification • Caudate Biology, cont. (Order Urodela) – • Typical have four limbs of similar size • Used for terrestrial walking. • Some possess reduced limbs or lack limbs • Incapable of vocalization • Found in mostly temperate lands (although they have evolved to live elsewhere) • Vary size a great deal, and include the largest amphibian in the world which can reach nearly 6 feet long. 

23. Classification • Caecilian Biology – (Order Apoda) • Ex: Caecilians • Long, segmented, worm-like amphibians, • Very distinguishable because of body type/shape • Some species are aquatic, and some are terrestrial • The least studied amphibians, and definitely the most alien form.

24. Classification • Caecilian Biology, cont. – (Order Apoda) • Live underground and in aquatic habitats. • Most species are found in tropical and subtropical environments in South America, Asia, and Africa. • Lack appendages • Have powerful heads and skulls for burrowing • The only amphibians to possess dermal scales.