Question

Asexual reproduction in sponges takes place with the help of
A. Multiple fission
B. Binary fission
C. Gemmule formation
D. Gemmae

Answer 1

Hint: Sponges are pore bearing animals and belong to phylum porifera. They have cellular organization, cell aggregate plan and mostly asymmetrical.

Complete answer:
The sponges body wall is formed by two layers-outer dermal layer or pinacoderm of flat pinacocytes and inner gastral layer or choanoderm of flagellated collar cells or choanocytes whose flagella beat and maintain a water current.
Porifera contains endoskeleton which is siliceous spicules or of sponging fibres. They are divided into classes based on the endoskeletal elements:
-Class Calcarea
-Class Hyalospongiae
-Class Demospongiae

They have basically two types of pores: numerous and smaller ostia and one or few larger osculates which acts as inlets and outlets of water currents. They have a peculiar canal system whose central cavity is called spongocoel.
Most sponges are bisexual or hermaphrodite. Fertilization is internal and development is indirect and involves the formation of a free swimming parenchymella larvae. Asexual reproduction occurs by the external budding or gemmules.
Gemmule is an internal bud of the Spongilla which is a freshwater sponge. It is composed of bulk of archaeocytes shielded by a coat of amphi disk spicules which promotes in perennation. These gemmules have characteristics like their resistance to dry environment or dehydration and they are also resistant to freezing and absence of oxygen such as anoxia for long duration. These gemmules are generally similar to bacterial endospores and are composed of amoebocytes which are surrounded by a layer of Spicules where they also survive the conditions which can kill adult sponges and this gemmule starts growing or resumes growing when the environment reverts to favour. These are the spores of sponges and their formation is known as gemmation. Gemmules are also found in some aquatic sponges like Ficulina, Tethya etc.

Hence, the correct answer is option (C).

Note: Sponges are diploblastic animals and there are about 5000 living species of them. They are mostly marine but about 150 sponge species inhabit fresh water like Spongilla.