Phylum: Chordata Class: Amphibia

1. Phylum: ChordataClass: Amphibia • Order Gymnophiona • Order Anura • Order Caudata

2. Class Amphibia • Derives from Greek: • The Greek prefix amphi- means "both" or "double" • The Greek word bios means "life.“ • Amphibian = “double life”

3. Class: Amphibia – means • Subclass Labyrithodontia (extinct) • Order Anthracosauria (extinct) • Subclass Lepospondyli (extinct) • Subclass Lissamphibia (living amphibians) • Order Gymnophiona (aka Apoda, Caecilians) • Infraclass Batrachia • Order Anura (frogs and toads) • Order Urodela (Caudata) (salamanders, newts, sirens, etc.) From Romer From Linzey 2001 From Conant and Collins

4. Class: Amphibia • Most have 4 limbs, except Caecilians (limbless) and Sirens (forelimbs only) • Many have webbed feet • Typically the glandular skin is smooth, moist, and lacks scales • Caecilians have concealed dermal scales Lesser Siren Caecillian Red-eyed Tree frog

7. Rough Spotted Newt

8. Wood frog

9. Caecilians

10. Movement onto Land • Life began in the water, animals are made of mostly water, and all cellular functions occur in water. • Invasion onto land required modification of almost every system in the vertebrate body. The Amphibian is an example of this terrestrial transition.

11. Amphibian Origins • Though actual origins are uncertain, it is clear that there was plenty of selective pressure for amphibians to emerge onto land • the Devonian was a period of tremendous climatic fluctuation • Wet and dry spells – dry spells would have set up intense competition in aquatic habitats • Would favor an ability to move from one pond to another • Oxygen poor waters would favor air-breathing

12. Amphibian Origins • Also, at this time, there was a tremendous radiation of arthropods into the terrestrial environment • Centipedes, millipedes, spiders, insects, etc. = food! • This would create an open niche in a relatively low-competition terrestrial environment

13. Accommodations to be considered when moving to land • Oxygen content • Oxygen diffuses more readily in air then water • Development of lungs • Support • Provides little support against gravity • Requires the development of strong skeleton and limbs to get around

14. Accommodations to be considered when moving to land • Development of limbs required only a few minor modifications • elongation of proximal elements into long-bones of limbs • Proliferation of more distal elements into bones of feet • Elaboration of pectoral and pelvic girdles (for anchoring the limbs)

17. Accommodations to be considered when moving to land • Temperature regulation • Air fluctuates in temperature more then water • Requires behavioral and physiological strategies to protect themselves from thermal extremes • Homeothermy—regulated constant body temperature • birds and mammals • Habitat diversity • Diverse biomes to live in and adjust to

18. Characteristics of Class: Amphibia—on both sides • 4,200 species • Require a metamorphosis from water to land during development • Skin is thin and requires moisture • Ectothermic—body temperature varies with outside changing temperature (cold blooded)

19. Body Plan • Bilateral symmetry • Skeleton mostly bony • Small teeth • Segmentation-head normally distinct from body • Four limbs (except caecilians) • Webbed feet • no nails or claws, 4-5 digits

20. Skin • Made of Keratin, a tough protein that protects against abrasions and water loss • Moist • Two layers—epidermis and dermis • With many glands • Serous glands secrete poison; effectiveness varies from species to species • Mucous glands waterproof the skin • Pigment cells—Chromatophores

22. Respiration • Air is forced into the lungs with mouth muscles [positive pressure] • Air can be diffused through skin and the inside of the mouth • The majority of carbon dioxide is released through the skin • Sound is created by forcing air over vocal cords and a large pair of sacs in the floor of the mouth

23. Respiration • Gas exchange occurs through lungs, gills, and/or the skin • Some salamanders have no lungs (secondarily lost) Eastern Red-backed Salamander – no lungs Larval tiger salamander showing gills Adult mudpuppy showing gills

25. Circulation • Closed system • Origin of the Systemic and Pulmonary Circuits • 3 chambered heart • 2 atria • 1 ventricle • Spiral valve helps separate the flows of oxygenated vs unoxygenated blood

27. Nutrition • Carnivores feeding on insects, spiders, worms slugs, snails, millipedes • Protrusive tongue is attached at the front of the mouth

28. Digestion • Complete digestion with both intracellular and extra-cellular digestion

29. Excretion • Pair of mesonephric kidneys • Urea main nitrogenous waste

30. Nervous System • Ten pair of cranial nerves • Senses • Smell—olfactory epithelium • Hearing--ear

31. Hearing • One advance associated with a more terrestrial existence is the refinement of the ear • the amphibian ear, unlike that of fishes, consists of three components • Inner ear, middle ear, outer ear • There is increased sensitivity to accommodate airborne sounds

33. Reproduction • Sexual with both “internal” and external fertilization • In the spring, males vocally attract females to mate with • Eggs are laid in large masses and can be anchored to vegetation, simply float in water, or laid under logs in moist ground • Packet of sperm may be left on vegetation and then inserted by the female herself • Male may force eggs to be evacuated from the female as he discharges his sperm over the eggs —amplexus

34. Reproduction Amphibian eggs are very vulnerable to desiccation. Hence, amphibians are reproductively constrained to exist in moist environments. Salamander eggs Toad eggs Frog eggs Spermatophores

35. Development • Eggs hatch into aquatic larva having external gills and tail • Metamorphosis

36. Reproduction • Australian Marsupial frog (A) • (use pouch on dorsum) • Surinam Frog Surinam (B) • (babies in skin on dorsum) • Poison Dart frog (C) • (carries tadpoles from forest floor to canopy) • Darwin’s frog (D) • (babies mature in vocal pouch) • Gastric Brooding frog • (keeps young in stomach!)

42. Environmental Interaction • Require a somewhat cool environment • Most amphibians hibernate during winter months in soft mud of the bottoms of pools and streams • Some can tolerate freezing temperatures by making a type of antifreeze by accumulating glucose and glycerol in body fluids

43. Environmental Interaction • Are both predators and prey to others, for protection amphibians have developed • Poison glands • Urinate on predator • Strong legs for leaping away • Biting at predators • Inflate lungs to avoid being swallowed • Camouflage

47. Importance of Amphibians • To Ecosystem – Pest control, food for other animals • To humans – Food, genetic research • They are “nature’s indicator”

48. Yikes • Worldwide, populations of frogs have been decreasing and experiencing mutations. No one knows the cause for sure!!!! • Pollution, acid rain, ozone depletion, pesticides/chemicals, introduction of non-native predators are just a few ideas

50. Order Gymnophiona -caecilians (aka Apoda) • Limbless (“naked snake”) • 160 species • Tropical forests of South America, Africa, and South East Asia • Most species totally blind • Burrow or aquatic • Carnivores