Some aspects of the biology of the amphipods Ischyrocerus anguipes associated with the red king crab, Paralithodes camtschaticus, in the Barents Sea

This paper describes size composition, morphometric, and reproductive parameters of the summer generation of the amphipod Ischyrocerus anguipes (KrCyer, 1838) associated with the red king crab Paralithodes camtschaticus (Tilesius, 1815) in Dalnezelenetskaya Bay (southern Barents Sea, Russia). In summer 2004-2007, prevalence and mean number of I. anguipes per host were 15.0% and 6.9 +/- A 1.1 specimens, respectively. The majority of amphipods were found on the host carapace (47.4%) and the limbs (43.9%). High infestation indices and absence of negative impacts for the host indicate that I. anguipes is a facultative commensal of the red king crab. The amphipods sex ratio was significantly biased toward females (F:M = 2:1). Females had a greater size than males. The size at 50% maturity of I. anguipes females was estimated to be 3.37 mm. The number of eggs laid is linearly correlated with the size of a female. Some differences in biological features of symbiotic and free-living amphipods (data obtained in 1940-1950) may be explained by climatic changes in the Barents Sea or advantages of living on the crab.