Question

Describe the structure and life cycle of polystomnela

Answer 1

1. It is a marine protozoan common on sea shores.
2. Body enclosed in a many chambered shell and each chamber is perforated with numerous pores.

3. Chambers are arranged in a spiral fashion.

4. Ectoplasm gives rise to numerous thread like extensions-the reticulopodia, which project out of the pores.

5. Adults exhibit dimorphism and alternation of generation between a microspheric and a megalospheric 6. Microspheric form has small central chamber – the proloculum and many scattered nuclei. It reproduces only asexually i.e., through multiple fission.

7. The megalospheric form has large central chamber and only one nucleus. It reproduces only sexually i.e., through gametogamy and conjugation.

8. Nutrition holozoic.

Answer 2

The fusion of similar gametes is known as isogamy). The zygotes, thus, formed develop into microspheric forms. However, the life cycle of Elphidium may be summarised in the following way, that the microspheric forms produce amoebulae by asexual fission which develop into megalospheric forms.