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Seagrasses, which form extensive meadows in coastal estuarine environments, are parasitized by species of the marine slime mold Labyrinthula. Zostera marina (eelgrass) is threatened by a recurrence of wasting disease, which we have demonstrated to be caused by L. zosterae (figure 1). Ongoing research is aimed at determining the world wide distribution and host range understanding of the genetic variability of the pathogen. The tropical seagrass, Thalassia testudinum (turtle grass) is parasitized by a different species of Labyrinthula. This undescribed parasite causes necrosis of turtle grass leaves and is probably in part responsible for a massive die-off of Thalassia in Florida Bay. We are describing the host-parasite interaction of this system.
Very little is known about the true biological nature of endolithic fungi and fungal-like structures that have been described as present in calcareous marine shells and shell fragments. We have recovered heterotrophic endoliths from planted, uninvaded shell fragments and identified their biological characteristics from TEM observations of reembedded and sectioned resin casts of these planted shell fragments (figure 2). Organisms consider the criteria for defining and identifying species of Labyrinthula. A combination of morphological and molecular characteristics are being used in this study. DNA sequence analysis is being used to help understand the phylogenetic position of Labyrinthula and related thraustochytrids. Initial analysis suggests a basal branch from the heterokont protists.
Porter, D. 1986. Mycoses of maine organisms: an overview of pathogenic fungi. In: ST Moss (ed.) Biology of Marine Fungi. Cambridge Univ. Press
Porter, D. and P. W. Kirk, Jr. 1987. Marine Fungi: Taxonomic and ecological considerations II. Lower fungi. Ch 12 in: KG Mukherji and VP Singh (eds.) Frontiers in Applied Microbiology. p 235-256.
Muehlstein, L.K., D. Porter and F.T. Short. 1988. A marine slime mold, Labyrinthula, produces the symptoms of wasting disease in eelgrass, Zostera marina. Mar. Biol. 99:465-472.
Porter D., S.Y. Newell and W.L. Lingle. 1989. Tunneling bacteria in decaying leaves of a seagrass. Aquat. Bot. 35:394-401.
Porter, D. 1990. Labyrinthulomycota. In: L Margulis, JO Corliss, M Melkonian and D Chapman (eds.) Handbook of Protoctisa. Jones and Bartlett, Boston
Muehlstein, L.K., D. Porter and F.T. Short. 1991. Observations of Labyrinthula zosterae sp. nov., the causative agent of wasting disease of eelgrass, Zostera marina. Mycologia 83:180-191.
Robblee, M.B., T Barber, P Carlson, M Durako, J Fourqurean, L Muehlstein, D Porter, L Yarbro, R Zieman and J Zieman. 1991. Mass mortality of the tropical seagrass Thalassia testudinum in Florida Bay (USA). Mar. Ecol. Prog. Ser. 71:297-299.
Lingle, W.L., D. Porter and D.J. O Kane. 1992. Preliminary genetic analysis of bioluminescence in the basidiomycete, Panellus stypticus. Mycologia 84:94-104.
Porter, D. and W.L. Lingle. 1992. Endolithic thraustochytrid marine fungi from planted shell fragments. Mycologia 84:289-299.