Submitted to: Society for Invertebrate Pathology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/8/2005
Publication Date: 8/8/2005
Citation: Slothouber-Galbreath, J., Smith, J.E., Terry, R.S., Becnel, J.J., Dunn, A.M. 2005. The diversity of microsporidia in freshwater amphipods: host-parasite interaction during invasions. Society for Invertebrate Pathology Annual Meeting. Interpretive Summary: N/A.
Technical Abstract: Parasitism may moderate invasion success. The 'enemy release' theory predicts that the prevalence and diversity of parasites may be reduced during invasion events. Successful invasive amphipods and their microsporidia provide an informative model to examine host-parasite interactions during invasion events. Fibrillanosema crangonycis (describers and year) is a vertically transmitted, sex ratio distorting microsporidium described from invasive European populations of the North American freshwater amphipod Crangonyx pseudogracilis. Vertically transmitted microsporidia may have little direct impact on host fitness but they may utilize sex ratio distortion by feminization to increase transmission success. We predict that vertically transmitted microsporidia will not be lost by invading hosts and may be selectively retained. Additionally, by increasing host population growth rate, feminizing microsporidia may increase host establishment success. Over 17 species of horizontally and vertically transmitted microspordia have been attributed to at least 14 species of European amphipod hosts but only one other microsporidium had been characterized from North America hosts. , We have undertaken a study to examine archived specimens and re-sample source populations to establish the diversity of and characterize microsporidia in North American amphipods. In addition, we surveyed candidate sites in North America and Europe to determine the origin and spread of the invasive C. pseudogracilis and F. crangonycisWe demonstrate that F. crangonycis is present across northern Europe and that both the host and parasite exhibit low genetic diversity. This may indicate the occurrence of a single host/parasite invasion event or low genetic diversity in the source population(s). During this survey, no additional invasive microsporidia were found. This implies that the vertically transmitted F. crangonycis may have been selectively retained and that sex ratio distortion by the parasite may have increased establishment of the host and parasite. We summarize data on the diversity of microsporidia present in North American amphipod populations and show that the occurrence and prevalence of these microsporidia and their hosts have changed significantly over the previous 30 years. This may be due to land use change and a recent seven-year drought in the study areas. We discuss how these factors may impact parasite prevalence and diversity in a manner similar to invasion events.