Question

Give an account of somatic structure and life cycle of an acellular slime mould that you have studied.

Answer 1

The somatic structure of acellular slime mould is called as Plasmodium. It is diploid in nature. It consists of multinucleate protoplasm. It has many diploid nuclei in the protoplasm which keeps on dividing by mitosis. It does not have the definite shape. The movement is with the help of finger-like projection called as pseudopodia. It also contains moving strands called as phaneroplasmodium for the locomotion. It is saprophytic in nature. It depends on the dead and decaying matter of growth and nourishment. It also ingests bacteria, protozoa, etc for nutrition.

Plasmodium attains certain size before entering the reproductive phase. During this phase, the slime dries. The diploid protoplasm concentrates at a few points forming a cushion-like mass. This mould like structure grows into a stalked sporangium. The diploid protoplasm divides into many young spores, each containing the diploid nucleus. The diploid nucleus of spore undergoes meiosis to form meiospore. After maturation, the meiospore is released and dispersed by wind. It falls on a suitable substratum. Under the favourable condition of moisture, temperature and pH, then it germinates to release swarm cells. These behave like gametes and fuse in pairs to form the zygote. Here, the diploid condition is re-established. The zygote remains naked and feeds on bacteria. Upon repeated mitotic division, it forms into multinucleate plasmodium.