Amphibians Modern Amphibians Skeleton mostly bony varying numbers

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) �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

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

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

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. �

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.

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

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

Caecilians – legless amphibians

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

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

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

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)

Order Anura �Reproduction �External fertilization � Eggs begin to develop immediately �Tadpoles develop within a few days