Dictyosteliomycota

Figure 18.31 Common slime mold sporangia. A. Lamproderma, x 25. B. Lycogala, x 10. (B. courtesy L. L. Steimley)

sporangia (Fig. 18.31), each containing thousands of minute, one-celled spores. The sporangia often are globe shaped, but in some species, they develop as long or wide stationary bodies that may resemble a jumbled network of tubes, or they may resemble erect hairs or end up as a shapeless blob. The sporangia may or may not have slender stalks, depending on the species. Others exhibit combinations of body forms. The spores are often distributed throughout a jumbled mass of threads called a capillitium.

When a spore is formed, a single nucleus and a little cytoplasm become surrounded by a wall. Meiosis takes place in the spore, and three of the four resulting nuclei degenerate. When the spore germinates, one or more amoebalike cells called myxamoebae emerge. Sometimes, these have flagella, in which case they are called swarm cells. Either form may become like the other through the development or loss of flagella. At first, myxamoebae or swarm cells feed on bacteria and other food particles. Sooner or later, however, they function as gametes, fusing in pairs and

Chapter 18

Life Cycle Myxamoebae
Figure 18.32 Life cycle of a plasmodial slime mold. (After C.J. Alexopoulos, and C.W. Mims, 1979. Introductory Mycology. 3d ed. © John Wiley & Sons, Inc. New York. Redrawn by permission of John Wiley & Sons, Inc.)

forming zygotes. A new plasmodium usually develops from the zygote, although occasionally zygotes or small plas-modia may fuse and form larger plasmodia (Fig. 18.32).

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