Fig 1. Map of all sites visited in BC, with orange dots indicating the presence of Peltogaster sp., purple diamonds indicating the presence of E. giardi, green triangles indicating the presence of Peltogasterella sp., and gray dots indicating no parasites detected.
Panel A depicts the survey sites on east central Vancouver Island and the sunshine coast. Panel B depicts the sites in Burrard inlet and Howe Sound. Panel C depicts the sites on Calvert Island. Panel D depicts the sites in the Barkley Sound. Panel E depicts the sites on south Vancouver Island, the gulf islands, and boundary bay. Maps were created using shapefiles obtained from Stats Canada and the US Census Bureau.
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Abstract
Parasites are common throughout the biosphere and can play significant ecological roles. However, most parasites are understudied, particularly with regards to how their prevalence and impacts vary with environmental conditions. As a result, there remains an incomplete understanding of how both parasites and their hosts may be impacted by climate change. We conducted field surveys to better understand the parasite distributions of the intertidal hermit crab Pagurus hirsutiusculus in British Columbia. We found three genera of externally visible parasites (Eremitione giardi, Peltogasterella sp., and Peltogaster sp.), and one hyperparasite (Liriopsis pygmaea), which were present throughout the surveyed region. The prevalence of E. giardi was related to salinity while Peltogaster sp. was related to host size. At some locations, we observed a decline in prevalence in the parasite Peltogaster sp. following the 2021 Pacific Northwest heat wave event. In the lab, we compared the metabolic rate across a temperature range and survivorship post heat stress in individuals infected with Peltogaster sp. and uninfected individuals. We did not find a difference in metabolism based on infection status but found that uninfected individuals had significantly higher survivorship following heat stress. This study highlights the pervasiveness of parasitic interactions and demonstrates the need to study them in combination with environmental factors to better understand the effects of climate change on populations.