Meeting Abstract
The recent massive sea star die-off event, linked to sea star wasting disease (SSWD), provides researchers with an opportunity to examine how parasite prevalence and abundance responds to changes in host populations. Information on the nature of host-parasite relationships is essential to address the reproductive capability of Pisaster ochraceus as they attempt to recover from the recent die-off. This study determined if North American populations of the ochre star, Pisaster ochraceus, host a facultative ciliate parasite, Orchitophyra stellarum, and if this host-parasite relationship has shifted in the wake of sea star wasting disease. We surveyed 16 sites in three regions: Washington State, Oregon State, and Northern California, sampling from the epidermis of P. ochraceus as well as removing gonads in search for O. stellarum. We found no evidence of parasitism in the gonads of P. ochraceus, but did find that 51% of sea stars were associated with the ciliate on their epidermis. We compared current percent prevalence of epidermal association with O. stellarum with data from Stickle and Kozloff 2001, 2007 and 2008. We found that, at the three sites they surveyed, percent prevalence is currently higher. We found no significant relationship between host population size and O. stellarum percent prevalence, or between percent male hosts and percent prevalence. There lack of a decrease in ciliate prevalence as host populations shrink suggests that facultative parasites are more resilient to changes in host populations. Previous research has found that male:female ratios were low in populations infected with O. stellarum; this doesn’t seem to be the case when sea stars are associated with the ciliate. Increase in association in previously studied sites suggests that either ciliates are increasing in abundance due to warmer ocean temperatures or there is a higher parasite:host ratio.
