INTERACTIONS BETWEEN THE LIFE-HISTORIES OF A PARASITIC COPEPOD, PARACHORDEUMIUM-AMPHIURAE, AND ITS BRITTLE-STAR HOST, AMPHIPHOLIS-SQUAMATA

A rock pool population of the brittle star Amphipholis squamata parasi tized by a copepod, Parachordeumium amphiurae, has been followed throu gh one year. Data:From held collections made within the habitat on the English Atlantic coast are presented. The host population has continu ous brooding and pulsed breeding and recruitment with the highest numb er of newly released juveniles occurring in the summer months. The siz e of the brittle star has significant effect on embryo production and development of juvenile brittle stars is inhibited in parasitized spec imens. The degree of inhibition is correlated with the size of the par asite. Brittle stars were found with parasites throughout the year, bu t a peak of infestation was recorded during late summer, timed with th e appearance of the new brittle-star cohort. Overall prevalence and va riance mean ratio were 14.1% and 1.80, respectively. Information prese nted indicates that development from the youngest parasitic stage to t he adult female takes about 3 months at summer temperatures. An artifi cial infestation was set up, but failed to reveal more about the timin g of the development of the parasites.