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 Characteristics
Ectothermal (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 Characteristics
 Metamorphosis
◦ 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 Characteristics
 Metamorphosis
◦ 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 Characteristics
 Reproduction:
• 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 Characteristics
 Reproduction, 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 Characteristics

Respiration:
◦ 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 Characteristics

Appendages/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.