Numerous non-indigenous species (NIS) have successfully established in new locales, where they can have large impacts on community and ecosystem structure. A loss of natural enemies, such as parasites, is one mechanism proposed to contribute to that success. While several studies have shown NIS are initially less parasitized than native conspecifics, fewer studies have investigated whether parasite richness changes over time. Moreover, evaluating the role that parasites have in invaded communities requires not only an understanding of the parasite diversity of NIS but also the species with which they interact; yet parasite diversity in native species may be inadequately quantified. In our study, we examined parasite taxonomic richness, infection prevalence, and infection intensity in the invasive Asian shore crab Hemigrapsus sanguineus De Haan, 1835 and two native mud crabs (Panopeus herbstii Milne-Edwards, 1834 and Eurypanopeus depressus Smith, 1869) in estuarine and coastal communities along the east coast of the USA. We also examined reproductive tissue allocation (i.e., the proportion of gonad weight to total body weight) in all three crabs to explore possible differences in infected versus uninfected crabs. We found three parasite taxa infecting H. sanguineus and four taxa infecting mud crabs, including a rhizocephalan castrator (Loxothylacus panopaei) parasitizing E. depressus. Moreover, we documented a significant negative relationship between parasite escape and time for H. sanguineus, including a new 2015 record of a native microphallid trematode. Altogether, there was no significant difference in taxonomic richness among the crab species. Across parasite taxa, H. sanguineus demonstrated significantly lower infection prevalence compared to P. herbstii; yet a multivariate analysis of taxa-specific prevalence demonstrated no significant differences among crabs. Finally, infected P. herbstii had the highest proportion of gonad weight to total body weight. Our study finds some evidence for lower infection prevalence in the non-native versus the native hosts. However, we also demonstrate that parasite escape can lessen with time. Our work has implications for the understanding of the potential influence parasites may have on the future success of NIS in introduced regions.
