Impact of the acanthocephalan parasite Profilicollis altmani on the fecundity of its crustacean intermediate host, the Pacific mole crab, Emerita analoga

Parasites may influence their hosts in multiple ways, ranging from physiological changes and behavioral modifications, to altering life history traits. One fitness component that is often considered in relation to parasitism is host fecundity. The larval acanthocephalan parasite, Profilicollis altmani, commonly infects the Pacific mole crab, Emerita analoga; yet this parasite's effect on the crab's fecundity is unknown. Consequently, we examined the effects of acanthocephalan parasitism on the fecundity of this mole crab species. Crabs were collected from the swash intertidal zone in Monterey Bay, CA, and the following parameters were quantified: crab body size (carapace length) and weight, egg-bearing status (nongravid and gravid), egg number and diameter, total volume and weight of egg mass, and their developmental stages (from newly laid eggs to recognizable zoea larval stage). Parasite prevalence, intensity of infection, and body size of larval cystacanths (measured as volume) were assessed. Host fecundity was positively correlated with both body size and body weight. No differences in egg weight were found between uninfected and infected crabs. Similarly, no difference in crab body weight at various embryonic developmental phases was documented between uninfected and infected crabs. Cystacanth volumes in infected nongravid and infected gravid crabs were not significantly different. Our study suggests that the parasite P. altmani does not have any appreciable effect on the fecundity of E. analoga and that female mole crabs undergo normal reproduction and maintain robust population sizes in their natural environments. Our findings thus appear to moderate the pervasive notion of a major impact of parasitism on host reproduction.