How- -o -Do-It

Slime Molds in the Laboratory

Steven L. Stephenson

FairmontState College Downloaded from http://online.ucpress.edu/abt/article-pdf/44/2/119/39769/4447422.pdf by guest on 02 October 2021 Fairmont,West Virginia 26554

The plasmodial slime molds, or most fruiting bodies are quite small, true fungi, lichens, and mosses- Myxomycetes, are a small (about most measuring only a few milli- which occur in similar situations. As 450 known species), rather insignifi- meters in height, suitable substrates a result, students are given an oppor- cant, but widely distributed group of must be carefully examined in order tunity to become more aware of a organisms having characteristics of to locate any specimens which may number of other less conspicuous both plants and animals. They pro- be present. One decaying log will inhabitantsof the natural world. duce fruiting bodies and spores often yield several differentspecies. Collecting slime molds requires similarto those of many fungi. How- Few if any students will be familiar very little in the way of special equip - ever, the free-living, multinucleate, with the group, but on the initial ment, although a sheath or pocket assimilative stage (the plasmodium) collecting foray, after gaining first- knife is useful for removing portions in the slime mold life cycle is totally hand evidence of their relative of the substrate bearing fruiting unlike anything produced by fungi abundance, many will probably ex- bodies. Because of their fragile or plants (Martin and Alexopoulos press amazement at never having nature, specimens should be placed 1969). The use of slime molds in noticed them before. The careful directly into small cardboard boxes the laboratory is usually limited to searching required to successfully or metal cans. Particularly delicate living cultures of the plasmodium of locate slime mold fruiting bodies will specimens can be loosely wrapped a single species, Physarum poly- undoubtedly have a much desired in tissue paper to protect them from cephalum, obtainable from most side effect: it will invariablydirect the damage while being transported back biological supply houses. However, students' attention to representatives to the laboratory. Upon returning slime mold fruiting bodies collected of various groups of organisms-the from the field, the containers should 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 over- looked 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 virtuallyany region of the country -if one knows where to look ,,6 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~4 for them! Fruiting bodies are most abundant in moist, forested areas, where they occur on the decaying wood of logs and stumps, leaf litter, FIGURE 1. The egg-shaped fruitingbodies of Trichiafavoginea occur in closely packed clusters and other similar substrates. Since on well-decayed wood. (Magnificationx 10)

HOW-TO-DO-IT 119 be opened and the specimens set aside to dry at room temperature. Most collectors then glue the speci- men to the inside-on either the bot- tom or the lid-of a small cardboard box for permanent storage. I have found that small trays approximately 1-1/2" x 3" x 3/4" work just as well. The relatively small size of the stor- age containers permits a considerable number of specimens to be stored in limited space. A single drawer will probably accommodate all but the largest collections. Fortunately, slime mold fruiting bodies are quite resist- Downloaded from http://online.ucpress.edu/abt/article-pdf/44/2/119/39769/4447422.pdf by guest on 02 October 2021 ant to most insects and other pests which often plague collections of preserved plant specimens. Although the small size of some FIGURE 2. The slender, cylindricalfruiting bodies of Stemonitis axifera may sometimes reach a slime mold fruiting bodies can pro- height of 20 millimeters. (Magnificationx 5) vide real challenges, their intricate beauty may very well suggest pos- sible projects for students interested in photography. Additionally, rela- tively few biologists have studied the slime molds to any real extent, and distributional data are rather limited for some regions of the coun- try. Consequently, students so in- clined could make real contributions to science with some diligent collect- ing. Identification of slime molds is based upon such features as the gross structure of the fruiting body, spore color in mass, nature of the capilli- tium, and the presence or absence of lime deposits. The capillitium, a net- work of threadlike elements found FIGUJRE3. The fruiting bodies of Metatrichia vesparium, an extremely common species look within the spore mass of many like miniaturewasps' nests. (Magnificationx 7.5) species, is a structure of remarkable beauty in such genera as Trichia (fig. 1) and Hemitrichia. Although Taxonomic concepts are well having the students construct their some important diagnostic features illustrated in this group, as all of the own keys to slime molds. can be observed with a hand lens or orders, most families, and most The only non-technical, yet fairly magnifying glass, many others are genera (and in some instances, even comprehensive, guide to the slime evident only through examination species) are relatively easy to recog- molds currently available is Farr's with a microscope. Practically all of nize. Some of the genera commonly How to Know the True Slime Molds these features are readily discernible encountered, in addition to the two (1981), although a few taxa are con- with the magnification possible using mentioned above, include Lycogala, sidered in How to Know the Protozoa the standard laboratory microscope Arcyria, Fuligo, Physarum, Stemon- (Jahn and Jahn 1979). The most available in most high schools and itis (fig. 2), Comatricha, and Meta- comprehensive taxonomic treatment colleges, although having an instru- trichia (fig. 3). After a majorityof the is The Myxomycetes by Martin and ment equipped with an ocular micro- specimens collected in the field have Alexopoulos (1969). The Mycetozoa meter and an oil immersion objective been at least tentatively identified, of North America (Hagelstein 1944) is a prerequisite for the accurate they can then serve as the basis for is also quite useful. determination of some features. a laboratory exercise which involves (Continued on p. 127)

120 THE AMERICAN BIOLOGYTEACHER, VOLUME44, NO. 2, FEBRUARY 1982 CROCKER, D.W., and BARR, D.W. HOBBS, H.R., Jr. 1972. Crayfishes HUXLEY, T.H. 1880. The crayfish. 1968. Handbook of the crayfishes of (Astacidae) of North and Middle New York: Macmillan Publishing Co., Ontario. Toronto: University of To- America. Environmental Protection Inc. ronto Press. Agency Biota of Freshwater Ecosys- MEREDITH, W.G., and SCHWARTZ. EDMONDS, W.T. 1976. Collecting and tem Identification Manual No. 9. F.J. 1960. Marylandcrayfishes. Educa- preserving Kansas invertebrates. Tech- Washington, D.C.: Environmental tional Series No. 46. Solomon, Md.: nical Publication No. 3. Lawrence, Protection Agency. Maryland Department of Research Kan.: State Biological Survey of . 1974. A checklist of North and and Education. Kansas. Middle American crayfishes (Deca- PENNAK, R.W. 1978. Fresh-water in- pods: Astacidae and Cambaridae). vertebrates of the United States. New Smithsonian Contribution to Zoology York: John Wiley & Sons. No. 166. Washington.D.C.: Smith- sonian Institution.

Erratum Slime Molds Downloaded from http://online.ucpress.edu/abt/article-pdf/44/2/119/39769/4447422.pdf by guest on 02 October 2021 . . . from p.120 The following was inadvertently omitted from "Makingthe Most of Onion Root Tip Mitosis"(ABT 43 References (7): 386): FARR, M.L. 1981. How to know the true The author respectfully acknowl- slime molds. Dubuque. Iowa: William edges that the root elongation exer- C. Brown Company. cise described in this paper is based HAGELSTEIN,R. 1944. The mycetozoa of North America. Mineola. N.Y.: on an exercise originally devised by self-published. Professor Emeritus Ernst C. Abbe JAHN, T.L., and JAHN, F.F. 1979. How and used by him for many years in to know the protozoa. 2nd ed. Du- introductory botany and plant buque, Iowa: William C. Brown Com- anatomy courses at the University pany. MARTIN, G.W., of Minnesota. and ALEXOPOULOS, C.J. 1969. The myxomycetes. Iowa MarshallD. Sundberg City: Universityof Iowa Press. Universityof Wisconsin-EauClaire Eau Claire, Wisconsin 54701

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