RYPIEN, K.L.*; ANDRAS, J.P.; SMITH, G.W.; HARVELL, C.D.; Cornell University, Ithaca, NY; Cornell University, Ithaca, NY; University of South Carolina, Aiken; Cornell University, Ithaca, NY: Fungal disease in Caribbean gorgonian corals: Pathogen popluation genetics

An epizootic of aspergillosis caused by the terrestrial fungus Aspergillus sydowii is currently affecting gorgonian corals in the Caribbean. Prevalence of aspergillosis is as high as 90% in some areas, with a recent study in the Florida Keys documenting a uniform prevalence of 43%. I am currently investigating the origins and geographic variation in virulence of A. sydowii. To determine if there are geographically distinct pathogen isolates that induce differential host responses, clonal replicates of Gorgonia ventalina (common sea fan) were infected in the laboratory with eight strains of A. sydowii isolated from diseased sea fans throughout the Caribbean, one genetically modified strain, and one non-pathogenic strain. Several aspects of sea fan response to infection were quantified, including the change in proportion of purple sclerites (calcium carbonate structures in the coenenchyme), and the antifungal properties of crude extracts. The results of this experiment demonstrate that there is variation in the host response induced by different pathogen isolates, and emphasize that this is a general stress response. Autosomal microsatellite markers were developed for A. sydowii to identify whether genetically distinct strains of the pathogen exist, and to see if these strains exhibit any patterns with regard to geography or magnitude of host response induced. An examination of allele distribution among sites in the Florida Keys and the Mesoamerican barrier reef system will reveal whether there are multiple pathogen strains in the environment, and may identify the origin of A. sydowii in coral reef ecosystems.