Novel aquatic silk genes Simulium (Psilozia) vittatum (Zett) Diptera: Simuliidae.

The silks of arthropods have an elementary role in the natural history of the organisms that spin them, yet they are coded by rapidly evolving genes leading some authors to speculate that silk proteins are non-homologous proteins co-opted multiple times independently for similar functions. However, some general structural patterns are emerging. In this work we identified three major silk gland proteins using a combined biochemical, proteomic, next-generation sequencing and bioinformatic approach. Biochemical characterization determined that they were phosphorylated with multiple isoforms and potentially differential phosphorylation. Structural characterization showed that their structure was more similar to silk proteins from distantly related aquatic Trichopteran species than more closely related terrestrial or aquatic Diptera. Overall, our approach is easily transferable to any non-model species and if used across a larger number of aquatic species, we will be able to better understand the processes involved in linking the secondary structure of silk proteins with their function between in an organisms and its habitat.

First report of a trichomycete fungus (Zygomycota: Trichomycetes) inhabiting larvae of Simulium ochraceum sensu lato Walker (Diptera: Simuliidae) from the Galapagos Islands.

A collection of the larval black fly Simulium ochraceum sensu lato Walker was made at six lotic habitats on San Cristobal Island, Galapagos Islands, Ecuador, during May 2003. Sixty-eight larvae were assayed for the presence of gut fungi (Zygomycota: Trichomycetes). A trichomycete, designated as Smittium sp. was found inhabiting the hindgut of 17.6% of S. ochraceum s.l. larvae. Implications of this finding with respect to both host and trichomycete biogeography are discussed.

Cytogenetics of laboratory colonies of simulium vittatum cytospecies IS-7 (Diptera: Simuliidae).

Laboratory colonies of the black fly Simulium vittatum Zetterstedt cytospecies IS-7 were analyzed cytogenetically and compared with the original New York population from which source material was collected 18 yr earlier. All sex chromosomes and major autosomal polymorphisms that were present in the source population were still represented in the laboratory colonies. However, the extent of sex linkage and the frequencies of four of the five major autosomal inversions changed significantly in at least one colony, perhaps because of bottlenecks experienced by the colony. A complete absence of males homozygous for the IS-7 inversion in both field and colony material is explained by postulating that the Y2 chromosome, representing the inverted condition for the IS-7 sequence, is absent from the population or acts as a rare reproductive lethal. This example possibly represents pseudo-partial sex linkage involving the X-linked sequences.