Laboratory investigations of trichomycete prevalence, abundance and fecundity in a Smittium-simuliid model

Abstract

Smittium, the most speciose genus of the “gut fungi” (Zygomycota: Trichomycetes), is found attached to the hindgut cuticle of larval aquatic Diptera. Smittium spp. colonize several host families (e.g., Smittium culisetae in Chironomidae, Culicidae and Simuliidae), but some species appear to be specific to a single host family (e.g., Smittium morbosum Sweeney in Culicidae). The specificity of Smittium spp. within a host family has been difficult to resolve. This research presents evidence that certain Smittium spp. differentially colonize particular species of black fly (Diptera: Simuliidae) hosts as measured by differences in prevalence, abundance and fecundity. Reasons for this differential occurrence and fecundity in hosts are unclear but might include fungal responses to variations in host morphology, physiology, distribution or behavior. Variable fitness of Smittium spp., within a suite of available hosts, could be a factor in the diversity of this fungal group.

• axenic cultures
• colonization
• Harpellales
• Simuliidae
• symbiosis

The authors thank Peter H. Adler (Clemson University) for input on the experimental design of the project. Financial support for this research was provided by National Science Foundation grant DEB No. 0075269 awarded to Peter H. Adler, Charles E. Beard, John W. McCreadie and Thomas M. McInnis, University of South Alabama and Clemson University. The authors are indebted to Elmer W. Gray (University of Georgia, Athens, Georgia) for providing eggs of Simulium vittatum. The authors also thank Elizabeth Benton and Svjetlana Vojvodic for laboratory assistance.