Strobilation - Types of Asexual Reproduction
Strobilation is a type of asexual reproduction in which successive segments are separated off from the body one after other. It is well demonstrated in some jellyfishes (Scyphozoa) and in tapeworms. In the life-history of Aurelia, a scyphozoan, the planula larva develops into a hydra-like stage termed as hydra tuba or scyphistoma. From the stolon, the scyphistomae may generate new scyphistoma. After a certain period of life this scyphistoma undergoes transverse division producing buds of medusae. This provides it a kind of pattern of a pile of saucers arranged one above the other. In this pile, the youngest (smallest) saucer lies towards the base and the oldest and the largest one at the free end. This "pile of saucers" stage is called the strobila. The transverse discs or young medusae - buds separate one after other from the strobila, each resultant in a kind of larva (called ephyra) which gradually metamorphoses to turns the adult Aurelia. A situation somewhat identical to the above also occurs in the tapeworms. New segments (proglottides) are continuously demarcated off from the neck by a sort of transverse fission; here also, it is the oldest proglottid at the free end that breaks off and the process keeps on repeating.