What is a gemmule? Explain its importance in the life of sponges.
Answers
Gemmules are internal buds found in sponges and are involved in asexual reproduction. It is an asexually reproduced mass of cells, that is capable of developing into a new organism i.e., an adult sponge
Explanation:
An asexually produced mass of cells, which are capable of developing into a new organism or into an adult freshwater sponge is termed as a Gemmule. They are small bud-like cells, which are formed by sponges to withstand unfavourable environmental conditions. A freshwater sponge reproduces both by sexually and asexually.
Asexual reproduction is mainly carried out by budding and also by gemmulation. The internal buds, which are formed by the freshwater sponges are called gemmules. These gemmules are tough and coated with a dormant cluster of embryonic cells. Freshwater sponges are multicellular, marine living species of a Kingdom Phylum – Porifera. The species of this kingdom includes sponges, Ficulina ficus, sea sponges and much more. All the species related to the same kingdom and carry the same characteristic features.
The internal buds, gemmules are resistant to dehydration, freezing and can survive even without an oxygen supply. The outer layer of the gemmule is enclosed and protected with the endospore that is surrounded by a layer of spicules, which helps the gemmule from all other unfavourable environmental conditions and also helps gemmules in growing into an adult freshwater sponge.Gemmules are usually found in a round or a ball-like structure, along with a central mass of amoeboid cells and a thick peripheral layer of a small siliceous spicule.
The structure of Gemmules includes Micropyle, Spicule, Inner layer, Archaeocytes and an Outer pneumatic layer. The micropyle is an outer coat of a cell with a minute opening and the peripheral layer is made up of a thick pneumatic layer and air chambers, which helps gemmules to float in water bodies. The Archaeocytes are reproductive cells and the spicule is the sharp-pointed structure, which is involved in protecting the gemmules from predators and also provide structural support to the gemmules.