Class Amphibia Chapter 25

Accommodations to land 1.Oxygen content: oxygen is 20x more abundant in air and diffuses more rapidly through air than water 2.Air density: provides little support against gravity-had to develop strong limbs and remodeled skeleton 3.Temperature regulation: air fluctuates more than water does and therefore experience more harsh and unpredictable conditions 4.Habitat diversity: variety of habitats provides safe shelter for protection of young

Tetrapods Group of vertebrates that includes amphibians, reptiles, birds and mammals

Characteristics of modern amphibians 1.Usually 4 limbs (tetrapod) 2.Skin smooth and moist with many glands 3.3 chambered heart (2 atria and one ventricle) 4.Ectothermal 5.Sexes separate 6.Moderately yolky eggs with jellylike membrane coverings

3 Orders Comprise more than 5400 species 1.Caecilians: Order Gymnophiona 1.Contains approximately 160 species of elongate, limbless, burrowing creatures commonly called caecilians 2.Occur in tropical forests of S. America, Africa, and SE Asia 3.Posses a long slender body, small scales in the skin of some, many vertibrae, long ribs, no limbs, and a terminal anus 4.Eyes are small, and most species are totally blind as adults 5.Special sensory tentacles on the snout

Caecilians Food consists mostly of worms and small invertebrates Fertilization is internal and males have a protrusible copulatory organ Eggs are usually deposited in moist ground near water Larvae may be aquatic or complete larval development may occur in the egg In some species eggs are carefully guarded during their development in folds of the body

Salamanders: Order Urodela Consists of tailed amphibians, approximately 500 species Occur in almost all northern temperate regions of the work Most have limbs set at right angles to their body, with forelimbs and hindlimbs of approximately equal size Carnivorous both as larvae and adult, preying on worms and small arthropods or mollusks Most eat only animals that are moving Ectothermic (cold blooded)

Salamander breeding Fertilized internally (a female recovers in her cloaca a packet of sperm-spermatophore- deposited by a male on a leaf or stick

Red spotted newt Aquatic larve metamorphose into a brightly colored red eft stage, which remains on land from 1-3 years before transforming into a secondarily aquatic adult

Dusky salamander Female dusky salamander attending eggs, which includes rotating eggs and protecting them from fungal infections and predation by various arthropods and other salamanders

Salamander respiration General amphibian condition of having the ability to exchange oxygen and carbon dioxide across their skin Longtail salamander

Frogs and Toads: Order Anura More than 4840 species of frogs and toads A.Bullfrog, largest American frog and the mainstay of the frog-leg market B.Green tree frog, inhabitant of the swamps in SE USA

Frogs and Toads Smallest measures less than 1cm in length-can be covered by a dime Live in Cuba and Brazilian rainforest Largest is the West African Conraua goliath, more than 30 cm long from tip of nose to anus Eats rats and ducks

Frogs and Toads Toads Have short legs Stout bodies Thick skins Usually prominent warts American toad feasts on insects, snails, and earthworms The rough skin contains numerous glands that produce a milky fluid, providing excellent protection from a variety of potential predators

African clawed frog Frog has been introduced to California, where it is considered a serious pest

Eat or be eaten Snakes, aquatic birds, turtles, raccoons, and humans prey on frogs Fish prey on tadpoles Frogs & toads in tropics are aggressive, jump and bite at predators Most can inflate lungs so they are difficult to swallow When held, they will leap violently, voiding its urine Some have poison glands in their skin

Frog skin Frogs have 2 layers: Epidermis and dermis Epidermis contains ketatin, a protein that provides protection against abrasion and loss of water Epidermis contains mucous glands secrete a protective mucous waterproofing the skin surface Serous glands produce a whitish watery poison highly irritating to predators All amphibians produce a skin poison, but its effects vary from species to species and with different predators

Gray Tree frog Cryptic coloration: so good that the presence of this frog usually is disclosed only at night by its resonant flutelike call

Respiration Use 3 respiratory surfaces for gas exchange in air Skin (cutaneous breathing) Mouth (buccal breathing) Lungs Frogs and toads are more dependent on lung breathing than salamanders Skin is important for gas exchange during hibernation

Frogs are positive-pressure breathers that fill their lungs by forcing air into them A.Floor of mouth is lowered, drawing air in through nostrils B.With nostrils closed and glottis opened, the frog forces air into its lungs by elevating floor of mouth C.Mouth cavity rhythmically ventilates for a period D.Lungs are emptied by contraction of body wall musculature and by elastic recoil of lungs

Vocalization Both male and female frogs have vocal cords, but those of males are much better developed Frog produces sound by passing air back and forth over the vocal cords between the lungs and a large pair of sacs (vocal pouches) in the floor of the mouth Vocal pouches also serve as effective resonators in males, which are used to attract mates

Reproduction

Male green tree frog clasps a larger female during breeding season. Clasping is maintained until the female deposits her eggs. Like most tree frogs, these are capable of rapid and marked color changes. Male is usually green and has darkened during mating

Reproduction Female S American pygmy marsupial frog carries developing larvae in a dorsal pouch

Reproduction Female Surinam frog carries eggs embedded in specialized brooding pouches on the dorsum; froglets emerge and swim away when development is complete

Reproduction Male poison arrow frogs carry tadpoles adhering to its back

Reproduction Tadpoles of a male Darwins frog develop into froglets in its vocal pouch. When ready to emerge, a froglet crawls into the parents mouth, which the parent opens to allow the froglets to escape