Date of Award

7-1-1978

Document Type

Thesis

Degree Name

Master of Arts (MA)

Department

Biology

First Advisor

Dr. A. Thomas Weber

Abstract

Dictyostelium mucoroides was the first cellular slime mold reported (Brefeld, 1869) and it has since been found to have a worldwide distribution (Cavender, 1973)- Increasingly, the cellular slime molds have become the object of intensive developmental studies, in part because their life cycles exhibit distinct periods of growth and differentiation. In D. mucoroides, whose life cycle.is typical of these organisms, the growth phase begins upon germination of the spore which releases a single amoeba. The amoebae independently grow and divide until their food sources, bacteria and other microorganisms, become depleted. Then the individual amoebae aggregate into multicellular mounds, thereby initiating the differentiation phase of the life cycle. The amoebae in the aggregates form coneshaped mounds that continue to rise until the influx of cells ceases, whereupon these masses usually lie flat on the substrate and migrate as pseudoplasmodia, producing a stalk as they proceed. Three distinct cell types can be recognized at this stage: prespore, presumptive stalk and mature stalk cells. At the end of migration stalk cells within the pseudoplasmodium accumulate on top of the basal-most stalk cells on the substrate lifting the developing spores off the surface. In this manner, the spheroid sorus, the mature spore-bearing structure, comes to rest at the apex of the stalk, or sorophore. The whole, differentiated body is referred to as the sorocarp (Bonner, 1967).

Comments

A Thesis Presented to the Department of Biology and the Faculty of the Graduate College University of Nebraska at Omaha In Partial Fulfillment of the Requirements for the Degree Master of Arts. Copyright 1978 William H. Roccaforte.

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