Transcript What*s an Amphibian?

What’s an
Amphibian?
OVERVIEW
Basic Characteristics of Amphibians

Being tetrapods (4 limbs) that facilitate moving about on
land - these limbs evolved from the pectoral and pelvic
fins
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Skin is thin, soft, glandular (lack scales except in the
caecilians) - skin of caecilians with scales similar to those
of fish.
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Ectothermic
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Both gill and lung breathers - usually gills in the larval
stage, replaced by lungs in the adult; cutaneous
respiration in many
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Three-chambered heart with two atria and one ventricle
Vocabulary

Ectothermic: Any so-called cold-blooded
animal; that is, any animal whose regulation of
body temperature depends on external sources,
such as sunlight or a heated rock surface.
Reproduction
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fertilization may be internal or external
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egg-layers (oviparous) but may have modifications
associated with development
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egg anamniotic – doesn’t have a shell but covered with
a series of gelatinous layers and are laid in water.
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hatchling in aquatic larval form which breath by gills
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most larvae herbivorous, some omnivorous to
carnivorous
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larval stage may last from 10 days to 20+ years
Amphibians
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unable to regulate body temperature
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skin types limit distribution to warm, moist climates (i.e.
tropics, subtropics, and temperate zones)
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most US species in the south; not found in dry areas
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generally limited to freshwater lakes, streams, ponds none are true marine forms
Represented by three sub classes
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Subclass Labrinthodontia - looked like a salamander
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represented by genus Ichthyostega (fish with feet or
legs)
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identified by specific labronthodont tooth
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Subclass Lepospondyli
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named for vertebral type with three fused parts
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Subclass Lissamphibia - contains all living specimens
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where living amphibians evolved is not clear - modern
(living) amphibians appeared in Triassic Period
Three primary orders of Amphibia
within the Subclass Lissamphibia
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Caudata (Urodela) - Salamanders
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Anura (Salientia) - Frogs and toads
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Apoda (Gymnophiona) - Caecilians
Order Caudata - Salamanders

"bearing a tail"

~340 species worldwide, 9 Nearctic
families(geographical division comprising temperate
Greenland and arctic North America), 6 in US - most
Holarctic (N. hemisphere)
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have four limbs usually of equal size, a tail, and
elongated body
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skin is smooth and glandular with mucus and poison
glands
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found primarily under leaf litter, in soils, or may be fully
aquatic
Salamanders
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most have internal fertilization by way of a
spematophore (packet of sperm deposited by the male
which is picked up by the female following courtship;
gelatinous coating dissolves to release sperm
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all predaceous - none herbivorous: feed on insects,
worms, etc.
In southern US reproduction occurs
primarily in the winter
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come out of burrows, mate, and return to burrows
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eggs develop in ponds
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increased rainfall seems to stimulate breeding
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most species breed annually although some breed
every two years
Sexual dimorphism is limited
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Sexual dimorphism: little differences between males and
females
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cloacal glands enlarge during reproductive activity to
contribute mucus layers to spermatophore
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male skin slightly rougher and caudal fins become longer
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hedonic glands(any of several glands of various
salamanders and reptiles that produce a secretion
believed to function in sexual attraction and stimulation)
in male
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90% of all salamanders utilize spermatophores for internal
fertilization
5 Pathways for Egg and Larva
Development
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1. Both egg and larval stages are aquatic
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Necturidae, Amphiumidae, most Ambystomatidae
permanently aquatic
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2. Eggs terrestrial, larvae aquatic
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Ambystoma opacum (marbled salamander) lay eggs in
depressions which fill with rainfall; eggs hatch as aquatic
larvae
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3. eggs terrestrial, larvae terrestrial
Egg and Larva Development
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Plethodontid Desmognathus aeneus - larval form does
not feed before developing into adult
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4. eggs terrestrial with direct development
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Plethodontids which develop from egg directly through
larval stage to adult
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5. eggs retained in the oviduct and fully develop,
followed by live birth
Reproductive strategies based on
site of oviposition
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Oviposition :to deposit or lay eggs, especially by means
of an ovipositor.
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in open static water (lentic systems) - sirens and
salamandrids
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in running water (lotic systems) - some plethodontids
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terrestrial sites - Plethodontids
Family Cryptobranchidae hellbenders
Hellbenders
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"hidden gill"
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contain the largest living salamanders
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distributed in eastern US, Japan, one species in China to
9’
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Cryptobranchis alleganiensis found in Appalachians of
Kentucky/Tennessee
Family Ambystomatidae - mole
salamanders
Mole Salamanders
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restricted to US and Canada
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represented by marbled, tiger, and small-mouthed
salamanders
Family Amphiumidae - congo eels
Species of Congo Eels
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only three species in the world
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all are carnivorous
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named for the number of toes
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All are found in the United States
Two-toed amphiuma
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The two-toed amphiuma (Amphiuma means) is a snakelike salamander found chiefly in the southeastern United
States. It is commonly, but incorrectly, called "congo
snake", "conger eel" or the "blind eel".
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One of the largest extant species of amphibians in the
world, they can grow from 39 to 1,042 g (1.4 to 36.8 oz) in
mass and from 34.8 to 116 cm (13.7 to 45.7 in) in length.
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They have four vestigial legs that end in two or three toes
which are virtually useless, and eyes with lids.
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They are blue-black in color.
A.means
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They feed on small fish, crawfish, insect larvae, and even
small snakes; they are harmless to humans when left
alone, but when disturbed, they can deliver a tough
bite, which may lead to a severe infection.
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Unlike other salamanders, which are mute, A. means
gives a clear whistle when disturbed.
Amphiuma pholeter
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The one-toed amphiuma is considered aquatic, and
ranges in coloration from gray-black to purplish-brown.
Unlike the other two Amphiuma species which have
distinctively lighter undersides, one-toed amphiumas are
the same color on both the dorsum (back) and the
venter (belly).
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It can also be distinguished by its cone-shaped head
and toe number -- one-toed amphiumas have one toe
on each foot as opposed to the two or three exhibited
by other Amphiuma species.
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It is the smallest species in the genus Amphiuma with the
average adult size being 8.5 inches (220 mm).
One-toed A. means
Amphiuma tridactylum
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The three-toed amphiuma looks rather eel-like, with an
elongate, dark grey-black, or brown colored body, and
tiny vestigial legs. They are capable of growing to
lengths of 41 inches (1 m). They have small, lidless eyes,
and gill slits. They have four tiny legs each with three toes
and an average of 62 costal grooves.
Family Plethodontidae - lungless
salamanders
Lungless Salamanders
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breath entirely through the skin and floor of the mouth
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many New World species which may breed on land
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any of more than 370 species of lungless amphibians
dependent largely on cutaneous respiration (gas
exchange through moistened skin).
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Plethodontidae is the largest group of salamanders, and
its members occur predominantly in the Americas from
southern Canada to the Amazon basin in Brazil.
Family Necturidae (Proteidae) mudpuppies
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Their popular name derives from the mistaken belief that they
are able to bark.
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They are found in lakes, rivers, and swamps of eastern North
America. Species inhabiting the southern United States are
commonly called water dogs.
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Adults range from approximately 20 to 40 cm (8 to 16 inches)
in total length. The body is gray or brown and usually has a
scattering of blurry blue-black spots. The external gills,
retained throughout life, are bright red. The tail is flattened
and exhibits dorsal and ventral fins; it is the major locomotor
appendage. The legs are short and moderately robust.
Mudpuppies
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Mud puppies prefer clear, silt-free water and usually hide
during the day under stones or debris. They eat small
animals such as crayfish or mollusks and the eggs of
other aquatic animals. Fertilization is internal, and the
female lays eggs.
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represented by five species in the US all in the genus
Necturus
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permanently aquatic salamanders which retain
functional gills as adults
Mud puppy
Family Salamandridae - newts
Newts
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US and European distribution
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rough-skinned with no costal grooves
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Newts have the ability to regenerate limbs, eyes, spinal cords,
hearts, intestines, and upper and lower jaws!
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Many newts produce toxins in their skin secretions as a
defense mechanism against predators.
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Newts metamorphose through three distinct developmental
life stages: aquatic larva, terrestrial juvenile (called an eft),
and adult.
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Adult newts have lizard-like bodies and may be either fully
aquatic, living permanently in the water, or semiaquatic, living
terrestrially, but returning to the water every year to breed.
Family Sirenidae - sirens
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There are only three species of sirens. This species ranges
from Virginia south along the Atlantic coast through
Florida and into the gulf coast of Alabama.
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This fully aquatic siren is found in a greater variety of
habitats than the other sirens, including ditches, streams,
rivers, swamps, lakes, ponds, and some bays. They spend
most of their time buried in mud or sand.
Siren Reproduction
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Siren reproduction is a mystery because mating has
never been observed. The males lack the gland that
secretes spermatophores and the females lack a
receptacle in which the sperm is stored.
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This suggests that they practice external fertilization,
however, the female lays eggs singly on widely dispersed
aquatic plants. This suggests that the eggs were fertilized
before they were laid
Siren
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Either sirens have internal fertilization unlike that
seen in any other salamander or the male
follows the female around during egg-laying,
fertilizing each individual egg.
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Scientists do know that the eggs are laid in either
late winter or early spring and the larvae hatch
about two months later.
Sirens
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Sirens are generally regarded as the most
primitive of living salamanders although their
ecology and natural history are poorly known.
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They lack hind limbs and are completely aquatic
throughout their lives, as evidenced by their
external gills.
Sirens
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This salamander can aestivate to survive. If the siren’s
body of water dries up it can burrow in the mud bottom
and secrete a cocoon of mucus and shed skin that
covers its body to prevent water loss. All body functions
slow down, some by 70 percent, and it can live for more
than a year, until the pond refills with water.
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When grasped, they commonly emit a yelping sound.
Order Anura - frogs and toads
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~3,400 species
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have four limbs usually of unequal size - hind limbs are
elongated and modified for jumping
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head and trunk fused, tail in larval form lost as adult
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more widespread than the salamanders
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vocalizations are restricted primarily to the male for
courtship, establishing territories - may be resonated by a
vocal pouch
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most have external fertilization where eggs and sperm
are shed directly into the water - general reproduction
patterns follow that of salamanders
Generalized reproductive pattern
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males vocalize to attract females
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amplexus (clasping of the female by the male for
mating) brings the cloacas of the male and female
together
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external fertilization of eggs by sperm; both deposited in
the water
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tadpoles develop - length of development depends on
the species
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metamorphosis
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adults predaceous - insectivorous/carnivorous
Two primary reproductive positions
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Axillary - male grasps the female just behind the
forelimbs
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Inguinal - male grasps the female around the
waist just in front of the hind limbs remain in
position until eggs and sperm are released for
fertilization
Primary skeletal modifications in
Anurans
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a general reduction in skull and girdle elements
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pelvic girdle attackes to a single sacral vertebra
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single cervical vertebra (atlas) articulates with two
occipital condyles - no second differentiated axis
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no differentiation in the thoracic and lumbar vertebrae
anterior to the urostyle followed by a single sacral
vertebra
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ribs if present never articulate with the sternum
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distal limb bones fused - tibiofibula and radio-ulna
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increased joints in pelvic limbs to increase jumping ability
Family Ascaphidae - tailed frog
Tailed Frog
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represented only by Ascaphus truei in mountainous
Pacific NW
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male retains its tail as an intromittent organ(An
intromittent organ is a general term for an external organ
of a male organism that is specialized to deliver sperm
during copulation) as an adaptation for mating in fastflowing streams - copulation may last for 24-30 hours,
sperm viable for up to 2 years
Tailed Frog
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A flat, toadlike frog with fairly rough skin.
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The pupil is vertical.
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The fingertips are hardened like claws to help the frog
crawl among rocks on stream bottoms.
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Lungs are reduced in size to decrease buoyancy, and
respiration takes place through the skin.
Family Bufonidae - true toads
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~350 species worldwide - all 17 US species in the genus
Bufo
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skins very warty with partid glands behind the eyes secretes bad tasting poisonous substance as a
protection against predators
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shorter legs designed for hopping rather than leaping
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typically burrow at night
Family Bufonidae
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Bufonids are unique among anurans in having a Bidder's
organ, a rudimentary ovary that develops at the anterior
end of the larval testes of males.
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Its persistence in adult males is considered by many to
be paedomorphic(the retention of juvenile
characteristics by an adult).
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Toads are further diagnosed by an absence of teeth
which, though known in some other frogs, appears to
have evolved separately in those lineages.
Cane Toads
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toads have glands behind their eyes that can secrete a burning
milky toxin
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cane toads, which can grow as large as a dinner plate, prefer to
eat native frogs, small marsupials and snakes.
Cane Taod
Family Ranidae - true frogs
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small to large frogs with long legs and slim waist
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large, distinct eardrum
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broadly webbed hind feet and usually with a prominent
ridge down each side of the back
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aquatic to terrestrial with aquatic larvae
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represented by the genus Rana
Characteristics that True Frogs
share
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characteristics include horizontal eye pupils, bony breast
bones, teeth on the upper jaw, webbed hind feet, and
an excellent jumping ability.
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Other characteristics include a slender waist,
dorsolateral folds along their backs, long legs with
pointed toes, and a strictly carnivorous diet.
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Frogs belonging to the Ranidae family are also found in a huge
range of sizes. The largest true frog is called the Goliath frog
(Conraua goliath) which can measure 12.5 inches long from nose
tip to rump and up 24 inches long or more when its legs are
stretched out. Goliath frogs can weigh up to 7 pounds and easily
dwarf the largest Bullfrog.
The goliath frog is the largest living frog
on Earth. Specimens can grow up to 32
cm in length from snout to vent, and
weigh up to 3.25 kg. This species has a
relatively small habitat range in
Cameroon and Equatorial Guinea.
Microbatrachella capensis

The smallest member of the Ranidae family is the Micro
frog (Microbatrachella capensis) which is found in the
moist woodlands of South Africa.
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The size of an adult Micro frog ranges from 0.4 to 0.7
inches from nose tip to rump.

This tiny frog is on the critically endangered list as its
environment is shrinking due to human encroachment
and the introduction of non-native species of plants that
use up the water that the Micro frog depends on for
breeding.
Micro Frog Adult and Baby
Micro Frog
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The frog has been named after the species of pitcher
plant that it needs to breed called Nepenthes
ampullaria, one of many pitcher plant species in Borneo.
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The frogs attach their eggs to the sides of the pitcher,
and the tadpoles grow in the watery liquid inside the
plant.
Order Apoda (Gymnophiona) Caecilians
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name means “without legs” - a worm-like animal
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subterranean diggers
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~160 species restricted to tropics and subtropics
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eyes may be covered by skin or even bone
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tentacle of head may serve as a chemosensory organ to
detect underground prey
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vivipary common - young 30-60% of female’s body size
when born
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initial growth of fetus supported by yolk sac, embryos
feed on uterine milk secreted from the epithelial wall of
oviduct
Caecilians
Caecilians

Caecilians (pronounced ‘seh-SILL-yuns’) are limbless
amphibians that on the surface resemble a worm or a
snake.

The smaller species measure less than three inches, but
the largest one (Caecilia thompsoni from Colombia)
grows to almost five feet long.
Caecilians
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1) Some have protrusible eyes, others lack them entirely.
The word caecilian comes from the Latin “caecus,”
which means blind. Some caecilian species are eyeless,
while others have small eyes hidden under their skin.

2) Caecilians are the only tentacled amphibians. They
have short, sensory tentacles located between their
eyes and nostrils that help them probe their environment
and find prey.
Caecilians

3. Caecilian mouths are filled with dozens of needle-like
teeth. They tend to eat soil-dwelling invertebrates such
as worms and termites, but some species may also grab
small snakes, frogs, and lizards. No matter what the meal
is, it is swallowed whole.

4. Most caecilians have two sets of muscles for closing
the jaw, as opposed to the single pair most animals
possess. These come in handy for burrowing, where they
help keep the skull and jaw rigid
Caecilians

5.Caecilians are the only amphibians to exclusively use
internal insemination. Males have a penis-like
appendage called a phallodeum, which they insert into
the female’s cloaca for mating sessions that can last
several hours.

6. ) They can give birth to live young. About 25% of
caecilian species lay eggs, but the other 75% give birth
to already-developed offspring. Before birth, baby
caecilians use their special scraping teeth to feed on the
lining of their mother’s oviduct.

Caecilian mothers have a special way of providing for
their young. Some baby caecilians have very odd teeth:
short, blunt ones built for scraping and long, curved
ones, like hooks.

It turns out these teeth serve a unique purpose early in
life. For several weeks after birth, the young caecilians
stay with their mother. During this time, she grows a thick
outer layer of skin that is rich in fat and other nutrients.

Her babies use their modified teeth to peel her skin off
and eat it. This unusual parental care behavior is known
as dermatotrophy and seems to be unique to caecilians