AMPHIBIANS

Diversity◦Ex: Frogs, salamanders, newts, and caecilians◦Amphibians are born without legs, and they grow legs as they develop (part of life cycle)◦Differ greatly in size

1 cm to 6 feet.◦Diet:

Carnivorous (eat only meat/other animals) or Insectivorous -eat other organisms, especially

insects.

Diversity, cont. ◦About 5700 living species of amphibians.◦The ancient amphibians were:

Typically larger in size Contained massive teeth Some had scaled skin

◦Modern amphibians are: Much smaller in stature/size Have evolved a number of adaptations that are fit

for whatever environment they live in

General CharacteristicsEctothermal (cold-blooded)Life requirements:◦Require both land and water for survival

This is true for many amphibian species However, others may be fully terrestrial, even

being born on land (viviparity). Others may only need a moist environment, not

necessarily a pond or pool, while others may be completely aquatic (born in water, live in water)

General CharacteristicsMetamorphosis◦Go through life cycle changing event

(from tadpole to adult) All amphibians have a tadpole stage

◦Most are biphasic This means they go through an aquatic

stage, and a terrestrial stage at some point

General CharacteristicsMetamorphosis◦The transition from aquatic to terrestrial

must have many physical changes Include:

absorption of the gills and tail modified eyesight to see on land thicker skin to cope with atmospheric

environments stronger limbs to support the weight of the body a more cylindrical tail new ways to catch food

General CharacteristicsReproduction:• Separate sexes • Fertilization internal in salamanders/caecilians • Fertilization mostly external in frogs/toads• Mostly oviparous Most produce shell-less (amniotic) eggs that are

deposited in the water These eggs rely on moisture from their surrounding

water source, Enclosed in protective, gelatin envelope Nourished for very short time by mother

General CharacteristicsReproduction, cont.:◦A typical biphasic species will return to

the water a few years later (after it has matured and sexual maturity has been reached), ◦Then, it will begin the lifecycle all over

again with its own offspring.

General CharacteristicsRespiration:◦Can use lungs, skin and gills (either separately

or in combo with one another)• Salamander larvae possess external gills • Frogs and toad larvae possess internal gills

◦Usually two lungs (few exceptions)◦Often need moist surroundings to help

breathe

General CharacteristicsAppendages/Limbs:

Most amphibians are tetrapods (four-legged) vertebrates

Some are legless Webbed feet often present No true nails or claws Forelimb usually has four digits (sometimes

five)

General Characteristics Skin:

Amphibian skin is naked, lacking hair, feathers, or "true" scales• Smooth and moist

Highly glandular with mucous glands Some glands can be poisonous May contain chromatophores (pigment cells)

General Characteristics◦Digestion: Mouth usually large with small

teeth (in both upper/lower jaws)

Two nostrils open into mouth cavity

Contain: stomach, small/large intestine, spleen, liver (two lobes), gallbladder, pancreas, cloaca and cloacal opening

General Characteristics◦Circulation: Three-chambered heart Contains two atria, one ventricle Double circulation through heart Skin is always supplied with blood

vessels/oxygen

General Characteristics◦Excretion: Cloaca—holding cell for the waste products Paired mesonephric kidneys, bladder also

present Urea is main waste product

◦Skeleton: Most bony with varying numbers of vertebrae Ribs present in most Exoskeleton is absent Vertebrates: have a backbone and many bones

General Characteristics

◦Body forms: Vary greatly:

Options: elongated trunk with a distinct head compact, depressed body with fused head

Ex: salamander vs frog vs caecilian

General Characteristics◦Habitat: The most abundant frogs are the 260 species

of Rana found throughout temperate and tropical regions of the world

Frog species are often restricted to certain localities Usually found near water

Amphibian populations are falling in most parts of the world

Winter: most amphibians will hibernate in soft mud in pools/streams

General Characteristics◦Biodiversity: VERY good bioindicators of pollution, pH

levels, oxygen levels and humidity Can observe multiple mutations in

frogs/salamanders This helps to indicate high pollution/radiation

levels

Classification ◦The class Amphibia is comprised of

three orders, Anura, Caudata, and Gymnophiona. Anuran Biology –

Ex: Frogs and Toads About 30 families and more than 4,500 species Range in size from a few millimeters to a couple

feet in length

Classification ◦Anuran Biology, cont. – Found in nearly every niche on Earth (very

diverse group) Presence of four limbs

hind limbs are typically larger and modified for leaping or climbing

Capable of vocalizing, and produce an array of sounds from squeaks to barking noises.

Most are external fertilizers.

Classification Caudate Biology (Order Urodela) – ◦Ex: Salamanders, Newts, Sirens, Amphiuma,

Waterdogs, and Mudpuppies ◦Commonly referred to as the "tailed

amphibians", a feature lacking in frogs and often overlooked in caecilians.

◦10 recognized salamander families, with a just more than 500 species.

◦Typical have four limbs of similar size that are used for terrestrial walking.

Classification Caudate Biology, cont. (Order Urodela) – ◦Typical have four limbs of similar size

Used for terrestrial walking. ◦Some possess reduced limbs or lack limbs ◦ Incapable of vocalization◦Found in mostly temperate lands (although

they have evolved to live elsewhere)◦Vary size a great deal, and include the largest

amphibian in the world which can reach nearly 6 feet long.

Classification Caecilian Biology – (Order Apoda)◦Ex: Caecilians ◦Long, segmented, worm-like amphibians, ◦Very distinguishable because of body

type/shape◦Some species are aquatic, and some are

terrestrial◦The least studied amphibians, and definitely

the most alien form.

Classification Caecilian Biology, cont. – (Order Apoda)◦ Live underground and in aquatic habitats. ◦Most species are found in tropical and

subtropical environments in South America, Asia, and Africa.

◦ Lack appendages◦Have powerful heads and skulls for

burrowing◦The only amphibians to possess dermal

scales.