Parachordeumium amphiurae: a cuckoo copepod?

The impact of the endoparasitic copepod Parachordeumium amphiurae (=Amphiurophilus amphiurae of Goudey-Perrière, 1979) on a host population of the brooding, hermaphroditic ophiuroid Amphipholis squamata in intertidal rock pools in South Devon, UK was assessed. In August 1986 the parasite prevalence was 20.6% and the mean population intensity of infection 0.286 parasites per brittlestar. Female parasites inhabited the genital bursae of hosts and most were found in hosts that were potentially reproductively active. In such hosts brooding capacity was reduced by copepod parasitism. Infected brittlestars showed a reduction in numbers of brooded developmental stages when compared with uninfected hosts of similar size (but the mean size of brooded development stages was not affected). For the population sampled, the overall reduction in brooding capacity was about 44%. The association between Amphipholis and Parachordeumium was compared with normal brood parasitism.