Amphibians

Modern AmphibiansSkeleton 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 bodyLimbs usually four (tetrapod)

Some are limblesssome have forelimbs much smaller than hindlimbs Some have limbs small and vestigial

Webbed feet often presentno true nails or clawsforelimb usually with four digits but sometimes

five and sometimes fewer

Modern AmphibiansSkin usually smooth and moist with many glands

some of which may be poison glandspigment cells (chromatophores) common, or

considerable varietyno scales - except concealed dermal ones in some

Mouth usually large with small teeth in upper or both jawstwo nostrils open into anterior part of mouth cavity

Respiration by lungs (absent in some salamanders), skin, and gills in someeither separately or on combinationexternal gills in the larval form and may persist

throughout life in some

Modern AmphibiansHeart

sinus venous, two atria one ventricle, a conus arteriosus,

double circulation through the heart

skin abundantly supplied with blood vessels

EctothermsExcretory system

paired mesonephric or opisthonephric kidneys

urea main nitrogenous waste

Ten pairs of cranial nerves

Modern AmphibiansMany amphibian species make use of both

aquatic and terrestrial habitatseither 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 AmphibiansAll 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 AmphibiansThree living amphibian orders comprise more

than 5400 speciesOrder Gymnophiona (Apoda)

caeciliansOrder Urodela (Caudata)

SalamandersOrder Anura (Salientia)

Frogs & toads

Order Gymnophiona160 speciesElongate, limbless, burrowing

creaturesFound in tropical forests of

South America, Africa, Southeast Asia

Long, slender body, small scalesDiet consists of worms & small

invertebratesInternal fertilization; eggs

deposited in moist ground near water

Caecilians – legless amphibians

Order UrodelaOura – tail; delos – evident

Tailed amphibians~500 species of salamanders

Found in almost all northern temperate regionsMost abundant & divers in North AmericaAlso found in tropical areas of Central America

& South AmericaMost are less than 15 cm long

Japanese giant salamander exceeds 1.5 m

Order UrodelaBreeding behavior

Internal fertilizationFemale recovers in her vent a packet of sperm

(spermatophore) Deposited by a male

on a leaf or stickAquatic lay eggs in

waterTerrestrial lay eggs in

soft moist earth

Order AnuraAn – without; orua - tail

Frogs & Toads – more than 4840 speciesOccupy a variety of habitats

Aquatic mode of reproduction & water-permeable skin prevents them from wandering too far from water

Ectothermsfour limbs usually of unequal size

hind limbs are elongated and modified for jumpinghead and trunk fused, tail in larval form lost as adultvocalizations are restricted primarily to the male for

courtship, establishing territoriesmost 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 AnuraHabitats & Distribution

Temperate & tropical regions Except New Zealand

Oceanic islands & southern South AmericaLive near water

Some in damp forestPatchy in distribution

Restricted to certain localities (specific stream or pool)

Order AnuraReproduction

External fertilization Eggs begin to develop immediately

Tadpoles develop within a few days