Metamorphosis in Toad | Frog

The adult toad reproduces sexually. During courtship, the male makes a croaking sound which attracts the female which is usually swollen with eggs.

The male toad grasps the back of a receptive female with the help of nuptial pads associated with forelimbs and releases sperm. This stimulates the female to lay about 500 to 5000 eggs which the male fertilizes as they shed sperm over them.

The eggs are surrounded by strings of jelly. The jelly protects the eggs from mechanical injury and also, allows them to receive enough oxygen. Furthermore, it prevents them from drying up and infection from bacteria and fungi.

The Young Tadpole:

The young tadpole emerges from the jelly after 1-2 days and grows. It attaches itself to a water weed by a sticky substance secreted by the cement gland, a v-shaped structure at the underside of the head.

At this stage, it does not have a mouth but feeds on the egg yolk. Respiration is through the skin.

Developing eyes, ears, eyes and nostrils are seen as marked portions 

External Gill Stage:

The tadpole develops three pairs of external feathery gills at either side of the head for respiration. It feeds on water weeds with the aid of the horny jaws and it has a long and coiled intestine.

Internal Gill Stage:

The external gills disintegrate 6-10 days after hatching while the internal gills develop. The operculum grows and covers the gills while leaving an opening called the spout through which water flows out of the gill chamber. At this stage, the tadpole breathes like a fish.

The Limb Stage:

At this stage, the hindlimbs develop first followed by the forelimbs which appear through the opercula opening. Other changes that occur include shortening of the intestine leading to a change in their diet. The eyes become bigger and more prominent at this stage. The hindlimbs develop in about 39 days after the eggs are hatched.

The Young Toad Stage:

The mouth becomes widened and the lungs are fully developed. The tail is now reduced considerably by reabsorption into the body. The toad leaves the water and moves to the land where it feeds on worms and insects. The intestine becomes reduced as a result of a change in the diet

It takes about 60 days for a toad to develop from the egg to the adult. It attains sexual maturity in about three years.