Slime Molds in the Laboratory

Abstract

The plasmodial slime molds, or Myxomycetes, are a small (about 450 known species), rather insignificant, but widely distributed group of organisms having characteristics of both plants and animals. They produce fruiting bodies and spores similar to those of many fungi. However, the free-living, multinucleate, assimilative stage (the plasmodium) in the slime mold life cycle is totally unlike anything produced by fungi or plants (Martin and Alexopoulos 1969). The use of slime molds in the laboratory is usually limited to living cultures of the plasmodium of a single species, Physarum polycephalum, obtainable from most biological supply houses. However, slime mold fruiting bodies collected in Nature also have considerable potential value in laboratory studies, especially those involving taxonomy or classification. Because of their small size and the types of situations in which they occur, slime molds are usually overlooked in Nature. However, during the warmer months of the year, especially after a period of rainy weather, the fruiting bodies of a surprising number of species can be collected in virtually any region of the country -if one knows where to look for them! Fruiting bodies are most abundant in moist, forested areas, where they occur on the decaying wood of logs and stumps, leaf litter, and other similar substrates. Since most fruiting bodies are quite small, most measuring only a few millimeters in height, suitable substrates must be carefully examined in order to locate any specimens which may be present. One decaying log will often yield several different species. Few if any students will be familiar with the group, but on the initial collecting foray, after gaining firsthand evidence of their relative abundance, many will probably express amazement at never having noticed them before. The careful searching required to successfully locate slime mold fruiting bodies will undoubtedly have a much desired side effect: it will invariably direct the students' attention to representatives of various groups of organisms-the true fungi, lichens, and mosseswhich occur in similar situations. As a result, students are given an opportunity to become more aware of a number of other less conspicuous inhabitants of the natural world. Collecting slime molds requires very little in the way of special equip ment, although a sheath or pocket knife is useful for removing portions of the substrate bearing fruiting bodies. Because of their fragile nature, specimens should be placed directly into small cardboard boxes or metal cans. Particularly delicate specimens can be loosely wrapped in tissue paper to protect them from damage while being transported back to the laboratory. Upon returning from the field, the containers should