1. Amphibians show variations in temperature sensitivity and shed their skin periodically. They are found throughout the world except Antarctica and Greenland. 2. They have four limbs, loosely attached skin with warts, eyes with lids, tympani behind eyes, and morphology varies by species. 3. Their skin has mucus glands and is permeable. They are cold-blooded, detect low sounds, and communicate using signals. Some camouflage or use bright colors. 4. They have indirect development with larvae and metamorphosis to adults. Reproduction involves eggs laid in water with gel coats that swell. Fertilization varies between internal and external.

1. CLASSIFICATIONAND
FEATURESOF
AMPHIBIA
NEHA KATARIA
M.SC ZOOLOGY

3. General Characteristics
•Amphibians show great variations in temperature sensitivity.
Some species are active only in higher temperature whereas,
others can survive lower temperatures also without
hibernating.
•Amphibians generally shed their skin periodically. Unlike
birds and mammals who shed their skin in flakes, amphibians
shed theirs in single piece. They generally feed on exuviated
skin.
•Amphibians are distributed in water and land throughout the
world, except in Antarctica and Greenland where there are no
amphibians.
•Amphibians hibernate for long time. These hibernations may
even last for several months.

5. Morphological Characteristics
•Amphibians have 4 limbs.
•They have a loosely attached skin which is characterized by local
thickenings (warts). These warts are commonly found in many
species.
•Their eyes have lids and associated glands which aid the protection
of eyes.
•Amphibians do not have external ear (pinna). They have external
tympani (eardrums) which are positioned just behind the eyes.
•The morphology of amphibians vary according to the species;
salamanders look like lizards whereas caecilians resemble snakes
i.e., both these groups resemble reptiles. The morphology of frogs
and toads is entirely different from both these two groups.

7. Anatomical Characteristics
•Amphibian skin has several mucus glands which keep it moist. Their permeable skin allows
water to pass through. Some species have poison glands on their skin which are used for
defense.
•Amphibians are cold blooded animals. Their body temperature is lesser than their
surroundings.
•They have a special patch of ‘papilla amphiborum’ cells, which enables them to detect low
frequency sounds.
•Amphibians can communicate using airborne and seismic signals. They normally
communicate with each other using these signals, rather than sounds. This is possible
because of a unique structure, called collumella-opercular complex, present in their auditory
capsule.
•Some amphibians use camouflage mechanisms to hide from their predators. They also use
bright colors to warn their enemies.
•Amphibians have vocal sac which resonates and amplifies the vibrations from the vocal
cord.

9. •Many amphibians are nocturnal; they become active during night
and this helps them stay away from diurnal predators.
•Amphibian dentition consists of an upper crown and lower base
(pedicle). However, teeth are generally not used for chewing, but for
holding the prey firmly.
•The nervous system of amphibians consists of brain, spinal cord
and nerves that run throughout the body.
•Their stomach is generally voluminous to accommodate food.

11. Physiological Characteristics
•Gas exchange in amphibians takes place through gills in juveniles and
through lungs in adults. Certain level of gas exchange takes place through
skin as well (cutaneous reparation).
•Amphibians generally swallow their prey as a whole. However, some
species may also chew their food.
•Lungs are the primary respiratory organs in amphibians. They respire
through buccal pumping, a respiratory method in which the animals moves
its buccal floor (floor of mouth) rhythmically, taking in the respiratory gas.

13. Reproductive Characteristics
•Amphibians generally reproduce in fresh water. However, some species
reproduce in brackish water in mangrove swamps.
•Most amphibian eggs have a gelatinous coat that swells up when it comes
in contact with water.
•Most of the amphibians have indirect development; their eggs hatch into
larval forms which are quite dissimilar from the adult form. These larvae
undergo metamorphosis and become miniature adults. Once this stage is
reached, the growth process happens and the young animal grows to
adulthood.
•In some amphibians, like the male salamanders, a jagged crest along their
back is developed during the breeding season.

15. •The resonating sound of frog that you hear is actually breeding call and is
species specific.
•The type of fertilization varies according to the species. Some species have
internal fertilization where the eggs get fertilized inside the body of the female.
Some species, like frogs, follow external fertilization method where the females
lay unfertilized eggs in water and males deposit their sperms over the egg and
fertilize them.
•Some amphibians brood their eggs while some species carry the eggs along
with them (on their back or legs or sometimes even in their vocal sac).
•Amphibians are distinct animals owing to their double life which is unique to
this class. The characteristics mentioned above are generic to the class.

18. General Characteristics of Class
Amphibians:
Some of the general characters
of class amphibian are listed
below:
1. They are the first cold blooded
vertebrates from evolution point of
view which came to the land. Class
Amphibian includes about 3,000
species.

19. 2. They are amphibious in nature, viz. they can
live on land as well as in water. They are mostly
found in warm countries. They are ectothermic
(cold blooded).
3. Body is divisible into head and trunk. Tail may
be present in some amphibians.
4. The skin is smooth or rough having glands
which keep it moist.

20. 5. They are usually without scales, but if
present they are hidden beneath the skin
(e.g caecilians).
6. Paired fins are absent. Unpaired fins may
be present. Two pairs of limbs are used for
locomotion except caecilions.
7. The gills are present at least in the larval
stage; some adult forms also carry external
gills in addition to lungs (e.g., Necturus,
Proteus).

21. 8. Skull is dicondylic, i.e., with two occipital condyles for articulation with
vertebral column.
9. The respiratory organs are lungs, buccopharyngeal cavity, skin and gills.
10. The heart is three chambered, having two auricles and one ventricle.
 In the heart, there are present sinus venosus and truncus arteriosus.
 Both hepatic portal and renal portal systems are well developed.
 RBCs are biconvex, oval and nucleated.

22. 11. Kidneys are mesonephric. Urinary
bladder is present in frog. Larvae and tailed
amphibians (e.g., salamanders) are
ammonotelic.
Frogs and toads are ureotelic.
12. Alimentary canal, urinary and
reproductive tracts open into a common
chamber called cloaca which opens outside
through cloacal aperture.

23. 13. Ear consists of internal and middle ear. Tympanum (outer
membrane) covers the middle ear. The eyes have eyelids. Nictitating
membrane is well developed.
14. Ten pairs of cranial nerves are present.

24. 15. Lateral line system is found during their
development.
16. Fertilisation is external. However in
Salamander and Ichthyophis (blind worm)
fertilisation is internal.
They are mostly oviparous; however,
Salamandra is viviparous. Development is
mostly indirect.

25. Living Amphibians are divided into three orders:

26. Apoda (Gymnophiona or Caecilia)
•Apoda means “without legs”.These are limbless organisms
with scales on their body.
•They are also known as “blind-worms” because their eyes are
covered by skin or bone.
•The tentacles on their head are the chemosensory organs that
help them to detect the underground prey. Eg., Caecilians
•They possess venom glands.
•They secrete mucus to reduce water loss.

28. Urodela (Caudata)
•These are the organisms with a tail.
•The body is elongated with four equally sized limbs.
•The skin is smooth with poison glands.
•Fertilization is internal.
•They feed on insects and worms. Eg., Salamanders
•They are found under leaf litter, in the soil, or in water.
•In the southern US, they reproduce primarily in winters.
•Very little differences between male and female.
•Spermatophores are utilized for internal fertilization.
•They possess hidden gills.

29. Anura (Salientia)
•There are around 3400 species of Anura in the
world.
•They have four limbs. The front limbs are elongated
and modified to jump.
•The head and trunk are fused together.
•The tail is present only in the larval stage and is lost
in the adults.
•Fertilization is external and the eggs are laid in
water. Eg., frogs and toads.