Infections by the trematode Microphallus nicolli and the acanthocephalan Profilicollis altmani in relation to the reproductive condition of their intermediate host, the Pacific mole crab Emerita analoga

Parasites can dramatically influence fecundity of their hosts, so for any host species it is important to establish whether parasite infections affect host reproduction. The Pacific mole crab, Emerita analoga, commonly harbors metacercarial cysts of the trematode Microphallus nicolli and cystacanths of the acanthocephalan Profilicollis altmani. Although these helminths are known to infect primarily larger female mole crabs, they may do so disproportionately when tied to their host’s reproductive condition. This study was undertaken to examine differences in parasite prevalence and abundance between non-ovigerous and ovigerous hosts. Crabs from Del Monte Beach, Monterey, California were collected, carapace length measured, sexed, examined for parasites, and had their reproductive state noted. The vast majority of the crabs sampled were infected with at least one parasite, and over half of the crabs had both M. nicolli and P. altmani. Ovigerous females were significantly larger than non-ovigerous crabs. Prevalence of both trematode metacercarial cysts and acanthocephalan cystacanths was significantly higher in ovigerous females than in non-ovigerous ones. Egg-bearing females were also more heavily infected by both parasites than non-egg-bearing individuals. These results suggest that larger ovigerous crabs may provide greater resources and thus are able to support higher levels of infections. This study shows that neither parasite prevalence nor abundance seemed to affect egg production in E. analoga.