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Amphibians
Amphibians live both on land and in water, breathing through lungs, skin, and mouth. They are cold-blooded, soft-skinned, and most give live birth to larvae that live in water before transforming into land-dwelling adults. The three orders of amphibians are Caudata (salamanders), Gymnophiona (caecilians), and Anura (frogs and toads). Salamanders have tails and internal fertilization, while frogs and toads lack tails and have external fertilization through aquatic eggs and larvae. Caecilians are worm-like and mostly blind, living underground.
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Amphibians
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- 2. GENERAL CHARACTERISTICS Amphi-double; bios- life; living on land and breeding in water Respiration by lungs, skin and buccopharynx Larval forms with lateral line system Exclusively fresh-water; no marine forms Poikilothermic(cold-blooded) Exoskeleton absent Soft, moist and glandular skin without scales Homodont teeth Skull is dicondylic Protrusible tongue Cloaca present 3-chambered heart(2atrium+1ventricle)
- 3. GENERAL CHARACTERISTICS R.B.C.large oval and nucleated Mesonephric kidneys Amphibians are ureotelic Middle ear with single rod like bone collumella auris Cranial nerves 10 pairs Sexual dimorphism found Oviparous and external fertilization Indirect development through tadpole larva mostly Anamniotes(extra-embryonic membrane amnion absent) Batrachology-study of amphibian Evolved from crossopterygian fishes
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- 5. ORDER CAUDATA 115-350described species of salamendars Mostly terristrial, few lives in moist forest floor and have aquatic larva Posses tail throughout their life Their size varies from few centimeters to 1.5m Members of the family Salamandridea are commonly called newts Most salamanders have internal fertilization
- 6. ORDER CAUDATA Maleproduce gelatinous spermatophores that is caped with sperm and deposited on the substrate. Female pick up the sperm with cloaca and store the sperm in spermatheca Eggs are fertilized as they pass through the cloaca and are usually deposited singly, in clumps or in strings. Larva posses external gills, a tail fins, larval denitition and rudimentary tongue
- 7. ORDER CAUDATA Theaquatic larval stage usually metamorphoses in to terrestrial adult Other show incomplete metmorphosis and are paedomorphc that is they became sexually mature while still showing larval characteristics
- 8. ORDER GYMNOPHIONA Memberare caecilians 160 described species They are worm like burrowers Feed on worms and other invertebrates in the soil Body segmented because of folds in the skin that overlie separations between muscles bundles
- 9. ORDER GYMNOPHIONA Retractiletentacles between their eyes and nostrils may transport chemicals from environment to the olfactory cells in the roof of the mouth Skin covers the eyes so caecilians are probably nearly blind Fertilization is internal Larval stages are often passed in the oviduct, other lay egg that develop either into aquatic larvae or embryo that develop on land
- 10. ORDER ANURA Include3500 species Frogs and toads Lives in moist environment Few may occur in dry dessert Adult lack tail Vertebrae fuse into a rodlike structure called urostyle
- 11. ORDER ANURA Hindlimbare long and muscular and end in webbed feet Fertilizartion is external Eggs and larva are typically aquatic Tadpole have well developed tail larva are herbivores and posses proteinaceous beaklike structures used in feeding
- 12. ORDER ANURA Theyundergo metaamorphosis Toad usually refers to anurans with relatively dry and warty skin that are more terresitrial than other members