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MEPS prepress abstract   -  DOI:

Host-switching among crabs: species introduction results in a new target host for native parasites

A. M. H. Blakeslee*, R. B. Barnard, K. Matheson, C. H. McKenzie

*Corresponding author:

ABSTRACT: Introduced species can be highly influential to community interactions, and there is increasing awareness of the impact invaders may have on symbiotic relationships, such as those involving parasites. Invasive species may introduce parasites into novel regions and/or acquire new parasites in introduced ranges. The resulting host-switching of native and non-native parasites could enhance or dilute parasite transmission and spread among host species utilized in parasite life cycles. We investigated the effect of host invasion on trematode parasitism in two nearby Newfoundland bays: one bay invaded by the European green crab Carcinus maenas and one bay not yet invaded. To determine the influence of the non-native crab C. maenas on host–parasite relationships in invaded versus uninvaded populations, we assessed trematode prevalence in three native Newfoundland hosts: two periwinkle snails (Littorina obtusata and L. saxatilis) serving as first-intermediate hosts for microphallid trematodes, and the Atlantic rock crab Cancer irroratus serving as a second-intermediate host. We additionally measured cyst abundance in both the native and non-native crabs. DNA barcoding was used to assess trematode identity in the native and non-native host species and to look for indications of host-switching. We found no difference in trematode prevalence between the bays among the four host species. However, cyst abundance was significantly higher in C. maenas versus C. irroratus in the bay where the crab distributions overlap, while it was lower in C. irroratus in the invaded versus uninvaded bay, suggesting a dilution of infection in the native host. Sequencing data of microphallid trematodes detected four genetically divergent lineages: a cosmopolitan lineage found in all host species; two lineages dominant in C. irroratus, suggesting a native origin for the trematodes that now utilize C. maenas as an additional host; and the final lineage represented just in C. maenas in Europe. Our study is the first to demonstrate the magnitude of trematode infection in crab hosts in Newfoundland, including the commercially-valuable native crab, C. irroratus. Moreover, our results demonstrate the influence that species introductions can have on parasite life cycles in native systems under recent host invasion.