The microdistribution of the trichomycete Smittium culisetae in the hindgut of the black fly host Simulium vittatum

Abstract

We examined the distribution of hyphae of the trichomycete fungus Smittium culisetae (Harpellales: Legeriomycetaceae) in the hindgut of a larval black fly (Simulium vittatum, cytospecies IS-7) by analyzing its prevalence and relative abundance. Hyphal prevalence was highest in the posterior colon (93.1%) and rectum (86.3%), with low prevalence (12.0%) in the anterior colon. Relative abundance of hyphae was highest in the posterior colon, followed by the rectum; relative abundance of hyphae in the anterior colon was lower. Hyphae of S. culisetae were not observed in the pylorus. We used a novel method of quantifying the relative abundance of S. culisetae in the host hindgut. The hindgut was observed with an ocular grid, and abundance was expressed as the ratio of grids occupied by hyphae to the number of grids occupied by hindgut.

• aquatic insects
• habitat selection
• Simuliidae
• symbiosis
• Zygomycota

We wish to thank S. A. Axsmith, D. T. Ihle, A. F. McCreadie, M. P. Nelder and B. Reynolds for their assistance in the laboratory. We thank P. H. Adler for reviewing the manuscript and E. W. Gray for providing black fly eggs. Financial support for this study was obtained from NSF Grant DEB 0075269 awarded to the authors.