The Effects Of An Invasive Crayfish (Faxonius Cristavarius) On Native Symbiont Communities In The New River In North Carolina

A few species of branchiobdellidan worms engage in a mutualism with native crayfish hosts. Faxonius cristavarius, an invasive crayfish, is a noncompetent host of branchiobdellidans and will remove any worms that colonize it. The distributions of three native crayfish overlap with F. cristavarius in the North and South Forks of the New River in northwestern North Carolina. If F. cristavarius acts as a sink for these worms, this could reduce the fitness of native crayfish. In a field survey, branchiobdellidan abundance and richness on native Cambarus crayfish declined significantly in response to an increasing relative abundance of F. cristavarius. I also tested whether F. cristavarius caused changes in the abundance of symbiont worms on native Cambarus robustus after subjecting individuals to one of two treatments: 1) a control treatment consisting of a single C. robustus stocked with 5 worms placed with an unstocked C. robustus and 2) an experimental treatment consisting of a single, stocked C. robustus placed with an unstocked F. cristavarius. Significantly fewer worms remained on native crayfish in the presence of F. cristavarius. This research contributes to a greater understanding of potential impacts on populations and communities of native symbionts caused by the introduction of invasive hosts.