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Amphibians

Amphibians. Modern Amphibians. Skeleton mostly bony varying numbers of vertebrae; ribs present in some, absent or fused to vertebrae in others Body forms vary greatly elongated trunk with distinct head, neck, and tail to a compact, depressed body Limbs usually four (tetrapod )

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Amphibians

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  1. Amphibians

  2. Modern Amphibians • Skeleton mostly bony • varying numbers of vertebrae; ribs present in some, absent or fused to vertebrae in others • Body forms vary greatly • elongated trunk with distinct head, neck, and tail to a compact, depressed body • Limbs usually four (tetrapod) • Some are limbless • some have forelimbs much smaller than hindlimbs • Some have limbs small and vestigial • Webbed feet often present • no true nails or claws • forelimb usually with four digits but sometimes five and sometimes fewer

  3. Modern Amphibians • Skin usually smooth and moist with many glands • some of which may be poison glands • pigment cells (chromatophores) common, or considerable variety • no scales - except concealed dermal ones in some • Mouth usually large with small teeth in upper or both jaws • two nostrils open into anterior part of mouth cavity • Respiration by lungs (absent in some salamanders), skin, and gills in some • either separately or on combination • external gills in the larval form and may persist throughout life in some

  4. Modern Amphibians • Heart • sinus venous, two atria one ventricle, a conus arteriosus, • double circulation through the heart • skin abundantly supplied with blood vessels • Ectotherms • Excretory system • paired mesonephric or opisthonephric kidneys • urea main nitrogenous waste • Ten pairs of cranial nerves

  5. Modern Amphibians • Many amphibian species make use of both aquatic and terrestrial habitats • either simultaneously or sequentially during different life stages. • A typical life cycle involves semiterrestrial adults that breed and lay eggs in water. • Eggs then develop into aquatic larvae. • the larvae undergo metamorphosis, or transformation, and become semiterrestrial adults. • Metamorphosis is triggered by changes in concentrations of circulating hormones • metamorphosis is most extreme among frogs, where there is a striking difference between the larva (the tadpole) and the adult.

  6. Modern Amphibians • All amphibians are carnivorous, • exception of larval frogs (tad-poles), • which are primarily herbivorous. • Most amphibians are generalists, and will eat anything they can capture and ingest. • Frogs and salamanders capture prey with their tongues, which are highly developed. • Certain salamander species have specialized projectile tongues that they fire with impressive accuracy to capture prey.

  7. Modern Amphibians • Three living amphibian orders comprise more than 5400 species • Order Gymnophiona (Apoda) • caecilians • Order Urodela (Caudata) • Salamanders • Order Anura (Salientia) • Frogs & toads

  8. Order Gymnophiona • 160 species • Elongate, limbless, burrowing creatures • Found in tropical forests of South America, Africa, Southeast Asia • Long, slender body, small scales • Diet consists of worms & small invertebrates • Internal fertilization; eggs deposited in moist ground near water

  9. Caecilians – legless amphibians

  10. Order Urodela • Oura – tail; delos – evident • Tailed amphibians • ~500 species of salamanders • Found in almost all northern temperate regions • Most abundant & divers in North America • Also found in tropical areas of Central America & South America • Most are less than 15 cm long • Japanese giant salamander exceeds 1.5 m

  11. Order Urodela • Breeding behavior • Internal fertilization • Female recovers in her vent a packet of sperm (spermatophore) • Deposited by a male on a leaf or stick • Aquatic lay eggs in water • Terrestrial lay eggs in soft moist earth

  12. Order Anura • An – without; orua - tail • Frogs & Toads – more than 4840 species • Occupy a variety of habitats • Aquatic mode of reproduction & water-permeable skin prevents them from wandering too far from water • Ectotherms • four limbs usually of unequal size • hind limbs are elongated and modified for jumping • head and trunk fused, tail in larval form lost as adult • vocalizations are restricted primarily to the male for courtship, establishing territories • most have external fertilization • where eggs and sperm are shed directly into the water • Generalized reproductive pattern males vocalize to attract females • adults predaceous - insectivorous/carnivorous

  13. Order Anura • Habitats & Distribution • Temperate & tropical regions • Except New Zealand • Oceanic islands & southern South America • Live near water • Some in damp forest • Patchy in distribution • Restricted to certain localities (specific stream or pool)

  14. Order Anura • Reproduction • External fertilization • Eggs begin to develop immediately • Tadpoles develop within a few days

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