Physarum overview

Physarum plasmodium-tops of the sporangia cut

Originally, there were two subsections in the Protist (a/k/a Protoctista) kingdom: the Phylum_Protozoa (the animal-like protists) and the Division_Algae (the plant-like protists). Both groups were previously members of the animal and plant kingdoms, respectively. When you study zoology and botany, these groups will be included in the review of the animal and plant kingdoms. Since the early days of the Protist kingdom in the 1800’s a few more groups have been added to the kingdom, including the fungus-like (slime_molds and water_molds) protists.

Use pages 18-23 and 32-38 in the Photo Atlas as a reference for your review of the Protists. Recall that the authors of your Photo Atlas do not use the same exact method of classification as the authors of your textbook. Hence, the water molds and most algae are placed in the Protist group by your text authors, but not the Photo Atlas authors.

Physarum is an acellular plasmodial slime mold. Physarum is, basically, an enormous single cell that contains thousands of nuclei. It is, in other words, coenocytic. The plasmodium forms when individual flagellated cells swarm together. The plasmodium is the feeding stage of the organism and migrates across the available food source. Physarum feeds on bacteria and fungi as well as bits of decaying organic material.

During the reproductive phase, a fruiting_body forms. When the environment becomes inhospitable, the cytoplasm merges to create reproductive sporangia (sing: sporangium), which are supported on a sporangiophore.