Spongilla is a genus of freshwater sponges. They are found attached to rocks, sticks and plants. To withstand adverse weather conditions, they have a dormant stage known as gemmules. These sponges have a thin dermal layer and have a soft texture. Spicules present on the dermal layer provide skeletal framework and protection.
Spongilla Classification and Examples
Spongilla is classified under phylum Porifera. They belong to the class Demospongiae, characterized by the skeleton of spongin fibres, siliceous spicules or both.
The common species of Spongilla is Spongilla lacustris.
Spongilla Structure and Characteristics
- Spongilla are found in freshwater, lakes and slow streams. They get attached to submerged plants, logs and sticks
- They may be branched or unbranched and have numerous Ostia present all over the surface
- The colour varies from light yellow to green. It depends on the amount of zoochlorella, a green alga (symbiotic association)
- The outer surface is soft textured and supported by a skeleton of spicules, spongin fibres or both. Spicules may be simple, siliceous or tetraxial
- The canal system is leuconoid type. It is a complex system of interconnected canals, which lead to irregular symmetry to Spongilla. In the larval form, rhagon type of primitive canal system is found
- Water goes inside through Ostia and to incurrent canals. Incurrent canals open into flagellated chambers, which are lined by choanocytes. Flagellated chambers open into the excurrent canal and then water flows outside from osculum
- Excurrent canals are formed by extensive division and shrinkage of spongocoel
- Gaseous exchange and excretion is by diffusion
- They feed on small organic particles. Many insects feed on them
- They reproduce sexually as well as asexually
- Asexual reproduction is by budding or forming gemmules. Gemmules are formed during adverse conditions, which on the return of favourable conditions, germinate
- Spongilla are hermaphrodite. Each sponge produces both egg and sperm. Sperm of one sponge reaches to the Ostia of another sponge and after developing inside the cavity, free-swimming larvae are born
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