Amphibians are a class of vertebrate animals that are noted for their unique features—living both in water and on land. These amazing animals have a lot of interesting characteristics.

Characteristics Of Amphibians

Frogs are a classic example of amphibians but, they are not the sole members of this class. There are other members too but some of them, like the salamanders, may be misapprehended as reptiles because of their close resemblance with reptilians like lizards! The class Amphibia consists of faunae like frogs, toads, newts, salamanders, and caecilians. They are cold-blooded animals, characterized by a unique feature, as their name suggests, i.e. survival both in water and on land. Most amphibians lay eggs in aquatic mediums, which hatch into larvae. These larvae usually look entirely different from their adult form. They undergo metamorphosis to become miniature adult and then grow into adulthood. However, some species, like the Common Coquí frog, are characterized by direct development, which lacks the larval forms. Larval forms use gills for respiration whereas adults use lungs and skin. There are about 7000 different species of amphibians. The major orders of this class are Anura (frogs and toads), Caudata (salamanders and newts) and Gymnophiona (caecilians, limbless amphibians). Learn more about the characteristics of amphibians from the following section. 

General Characteristics Of Amphibians

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. 
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. 
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.
  • 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. 
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. 
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.
  • 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.

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