Habit and Habitat of Rana tigrina (Indian Bull Frog)
Frogs in general are found in water or near water and in damp places on land. The common Indian bullfrog, Rana tigrina lives in water or, near freshwater lakes, bonds and stream. They live in the water most of the time. They live in water mainly because of the two reasons: first, To keep skin moist to carry on cutaneous respiration and Secondly, to immediately jump or slip into water to escape from enemies.
Frogs are non-poisonous, harmless and silent amphibian. The presence of frog is difficult to detect unless it is disturbed. It is very agile and an excellent jumper.
Locomotion in frog is performed in two ways, by leaping on land and by swimming in water. Their exoskeletal systems are specialized to do so.
- Leaping- A frog rests on land with their short fore limbs upright and long and powerful hind Limbs or legs Flexed Or folded in the manner or ‘Z’. During resting position front part is inclined upwards and is called squatting posture. They jump or leap by suddenly extending the hind limbs which act like spring is throwing the body up into the air. A frog may leap a distance of 1.5 to 2 metres in a single jump. On landing back the forelimbs act like shock absorbers. The forelimbs also manipulate and adjust the direction of the jump.
- Swimming- The frog swims in water by powerful backwards thrust of its hind limbs which act like During their backward strokes, the toes are spread apart and the broad webs push against water, moving the body forward. Forelimbs usually take no part in swimming. However, the right and left forelimbs are moved alternatively when the frog is paddling around leisurely. Forelimbs Basically perform two functions, they help in propelling the animal to some extent and in guiding the direction of movement. When frog comes to surface to breathe, or simply to float, only the tip of snout carrying nostrils is exposed, with fore an hind limbs extended in water. When disturbed in this position, they immediately dives under water.
Frogs are Carnivorous and food consist mainly of living insects, worms, molluscs and tadpoles, which are caught by a sudden flip of their large protrusible sticky tongue attached at the front end and free behind. Any motionless object or food is simply ignored. The food is not chewed but swallowed as whole.
The Characteristic sound or noise made by frogs is known as croaking. it is commonly heard in breeding season during rains and is a mating call. It is produced by forcing air from lungs over vocal cords into mouth cavity and back again. Frogs can croak under water as well as on land. Croaking is louder in males due to the presence of a pair of distensible balloon like loose skin folds on throat, called as vocal sacs. These act as resonators.
Hiberation and Aestivation:
Since frogs are cold-blooded or poikilothermus animals, The body temperature of frog fluctuates with that of the environment. during adverse environmental conditions in cold winter or dry hot summer days, frogs burry in the soft damn bottom mud for protection. , They become metabolically inactive and stop feeding, living only on the glycogen and fact stored in their bodies. Lung respiration is suspended and cutaneous respiration through damp skin alone is sufficient. this state of dormancy or suspended animation is called hibernation or ‘winter sleep’ during winter and aestivation or ‘summer sleep’ in summer. With the end of cold winter or hot summer season, the frogs come out to lead a normal active life once again. Although some zoologist believe that, frogs do not undergo aestivation.
Frogs have the capability to change their skin colour and match with that of the surrounding. This capability or protective coloration is known as camouflage. It helps frog in their protection from enemy and frogs are not easily noticeable by their enemies. Changes in color are possible by dispersion or concentration of special amoeboid pigment cells in their skin.
With The onset of rainy season, frogs emerge out of aestivation and immediately start breeding which lasts from the month of July to September. Meals gather in appropriate shallow water and start croaking to attract females for mating or copulation. The male mounts upon the back of the female and grasp firmly around her thorax by their forelegs. The roughened nuptial pads on the bases of inner fingers of male are fully developed during breeding season and help him in holding the slippery female. This sexual embrace called amplexus, may continue for several days until The female deposits several hundred ova or eggs through her cloaca into water. The male also discharges milt or seminal fluid containing spermatozoa over eggs to fertilize them. Thus, fertilization is external. The male now releases His grip and leaves the female. Mass of eggs called frog’s spawn, is embedded in a gelatinous material which on contact with water swells into a protective transparent jelly. Within two weeks fertilized eggs or zygotes develop into free swimming aquatic larvae, called tadpoles, which undergoes metamorphosis to become adult terrestrial frogs.
The chief enemies of frogs are snakes, turtle, mongooses, racoons, crows, vultures, aquatic birds, fishes, other amphibians and man. Several natural enemies eat adult frogs and tadpoles thus reducing their numbers. Frogs also serve as hosts for different kinds of parasites, such as protozoans (Opalina, Nyctotherus, Balantidium, Trichomonas, Entamoeba), Lung flukes (Haematoloechus, Pneumobites) and nematodes (Rhadias).
Economic Importance of Frogs
From is used for laboratory study more often than any other animal as a vertebrate type. It is also used for researchers in Physiology, pharmacology and human pregnancy tests and as a fish-bait. Frog is a good friend of farmers as it feeds on insects harmful to crops. The muscular handlimbs of frogs are used as food by men. they are even reared at farms in some parts of the world.
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