Interactions between the life histories of a parasitic copepod, Parachordeumium amphiurae, and its brittle-star host, Amphipholis squamata

Abstract

A rock pool population of the brittle star Amphipholis squamata parasitized by a copepod, Parachordeumium amphiurae, has been followed through one year. Data from field collections made within the habitat on the English Atlantic coast are presented. The host population has continuous brooding and pulsed breeding and recruitment with the highest number of newly released juveniles occurring in the summer months. The size of the brittle star has significant effect on embryo production and development of juvenile brittle stars is inhibited in parasitized specimens. The degree of inhibition is correlated with the size of the parasite. Brittle stars were found with parasites throughout the year, but a peak of infestation was recorded during late summer, timed with the appearance of the new brittle-star cohort. Overall prevalence and variance mean ratio were 14.1% and 1.80, respectively. Information presented indicates that development from the youngest parasitic stage to the adult female takes about 3 months at summer temperatures. An artificial infestation was set up, but failed to reveal more about the timing of the development of the parasites.