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Date of Award


Document Type

Restricted Thesis: Campus only access

Degree Name

Bachelor of Science



First Advisor

Dr. Brad Goodner

Second Advisor

Dr. Lisa Muehlstein


In the 1930's, a wasting disease caused massive destruction of the eelgrass Zostera marina L. in the North Atlantic region (Muehlstein, 1989). Eelgrass provides a nursery bed for shellfish and other organisms, so destruction of eelgrass beds destroyed many ecosystems. Only after several decades did the eelgrass beds recover (Porter, 1990).

Recently, Muehlstein and Porter (1991) positively identified a pathogenic species of Labyrinthula zosterae as the causative agent of this wasting disease. L. zosterae is a heterotrophic marine protist, often referred to as a slime net (Leipe et al., 1994), or a marine slime mold (Muehlstein and Porter, 1991). There is an ongoing dispute over the proper taxonomic classification of this organism. Some mycologists treat L. zosterae as a fungi, Porter (1990) placed it in a new phylum called Labyrinthulomycota, and researchers studying the 18s rRNA of this organism have placed it in the kingdom Chromista, in the phylum Heterokonta (Cavalier-Smith, 1994).

L. zosterae is characterized by its wall-less ectoplasmic networks, which are produced at the cell surface by specialized structures called sagenogens or bothrosomes. These ectoplasmic networks absorb nutrients and provide for cell attachment to surfaces. The network allows for gliding motility, and may be involved in the pathogenicity of L. zosterae to eelgrass. The ectoplasmic network enables the cells to decompose microorganisms, such as yeast. In laboratory cultures, Labyrinthula has been observed to penetrate vascular plant cell walls and decompose the cell contents, and the ectoplasmic network may be responsible for this ability (Porter, 1990).