Asexual Reproduction in Animal - Budding

Budding:

• In budding, the parent body produces one or more buds and each bud grows into a young one. The buds separate from the parent to lead a normal life.
• In budding, a new individual is formed by mitosis. 
• Exogenous or external budding and Endogenous or internal budding are two types of budding.

A) Exogenous or external budding:

When buds are formed on the outer surface of the parent body, it is known as exogenous budding. e.g. Leucosolenia (Sponge), Hydra, etc. In sponges, the buds constrict and detach from the parent body and the bud develops into a new sponge. 

In Hydra, when food is plenty, the ectoderm cells increase and form a small elevation on the body surface. Ectoderm and endoderm are pushed out to form the bud. The bud contains an interior lumen in continuation with the parent’s gastro-vascular cavity. The bud enlarges and develops a mouth and a circle of tentacles at its free end. When fully grown, the bud constricts at the base and finally separates from the parent body and leads an independent life.

B) Endogenous or internal budding: 

When buds are formed within the body of the parent. This is called endogenous budding. In Noctiluca, hundreds of buds are formed inside the cytoplasm and many remain within the body of the parent. In freshwater sponges and in some marine sponges a regular and peculiar mode of asexual reproduction occurs by internal buds called gemmules is seen. A completely grown gemmule is a hard ball, consisting of an internal mass of food-laden archaeocytes. During unfavourable conditions, the sponge disintegrates but the gemmule can withstand adverse conditions. When conditions become favourable, the gemmules begin to hatch.