Introduction to Frog

Classification:

Kingdom: Animalia

Phylum: Chordata

Group: Craniata

Sub phylum: Vertebrata

Division: Gnathostomata

Super class: Tetrapoda

Class: Amphibia

Genus: Rana

Species: tigrina

Common name: Indian bull frog

Habit/Habitat:

They are cosmopolitan found in fresh water or live in or near water like ponds, pools, stream, lake etc or damp places.Water is required for respiration.They required water for respiration, protection, to complete lifecycle.They are carnivorous.Sometimes they eat their own species.Their main foods are insects, worms, spider, molluscans, crustaceous.They are a cold-blooded animal.

In hibernation, the frog buried in the damp mud and cease all the activities like feeding etc.The mouth and nostril are closed, respiration is only by cutaneous.Heart beat rate slows down.They utilize facts and glycogen stored in their body.

In extreme hot temperature i.e. at 40-degree celsius, they are affected, inactive and may also die.So, to save their life they bury in soil.In may and June, they go for aestivation.

Male frog during rainy season produces croaking sound with the help of vocal sacs in a throat.The croaking sound is a mating call.The male frog is well developed than the female.

External features of frog:

External features include shape, size, coloration which is visible. It is also the outer appearance.

Shape:

They are bilaterally symmetrical, streamlined body i.e pointed at anterior and posterior region and the middle part is broad. They are dorsoventrally flattened. Streamlined body help for leaping in the land, swimming in the water, walking.

Size:

It is variable in size.Generally, its size varies from 12-18 cm long, and width 5-8 cm.

Colour:

The frogs are protectively coloured and cause camouflage. The dorsal side is green in colour with a yellow mid-dorsal line which extends from the tip of snout to vent. The dorsal side is with black and brown. The ventral side is pale yellow in colour. So, they are protected in their environment.Colour is due to chromatophores.

Divison of body:

The body is divided into head and trunk.

Head:

The head is triangular, flattened with short narrow blunt interior end called snout. The posterior region of the head is bold which is directly attached to the trunk. A pair of nostril lies dorsally at the tip of the snout. It bears mouth, nostrils, eyes, brow spot and tympanum on the upper side and throat on the lower side.

spot and tympanum on the upper side and throat on the lower side.

Mouth:

The mouth lies on the snout which is wide transverse slit-like aperture which extends from one side of the tympanum to other. It is very large as it preys on larger food materials.

Nostril:

A pair of nostril lies dorsally at the tip of the snout.Through it fresh air enter inside the body.

Eye:
Two large spherical bulged eye lies on the top of head laterally.The large eye compensates the absence of neck. It has immovable upper eyelid and movable lower eyelid. The nictitating membrane arises from the lower eyelid which is transparent, thin membrane and covered the eyes completely while they are in the water. So, it is protective.In land, it clears the dust particle and keeps the eye moist.

Tympanum:

Below and behind the eyes a circular depressed patch of skin which is dark in the colour called tympanum is present.It plays a role in receiving sounds.

Brow spot:

It is a light patch of skin dorsally and median, in front of the eye. It is also known as the third eye.It is a vestigial organ and below it lies the pineal gland.

Vocal sacs:

A pair of a bluish patch of skin which lies on either side of a throat of male frog which acts as a resonator to make sound louder.

Trunk:

A trunk is dorsoventrally flattened, broad and the back side of which is raised to form a hump due to the connection between pelvic girdle and vertebra. Dorsally, it has a fold of skin called elica and the trunk bear an opening called cloacal aperture through which gametes, urine and faeces comes out.It contains forelimbs and hind limbs.

Limbs:

Two pair of limbs arises laterally from the trunk. The forelimb is short which absorb external shock while landing whereas hind limb is very long and muscularized for jumping and swimming.Forelimb consists of the brachium, antebrachium wrist and hand with four digits.