THE ASSOCIATION BETWEEN THE CAPRELLID PARIAMBUS-TYPICUS KROYER (CRUSTACEA, AMPHIPODA) AND OPHIUROIDS

Caprellid amphipods are small marine crustaceans which usually live as epibionts on a variety of substrates. Apart from mostly sessile organ isms such as algae, hydroids and bryozoans, they also frequently use v agile fauna as substrates. Pariambus typicus (Kroyer, 1844) is a commo n associate of subtidal asteroids and echinoids in European seas, but has also been found free-living on the sea floor. In the German Eight, P. typicus has also been discovered regularly on ophiuroids (Ophiura albida Forbes and Ophiura ophiura (L.)), which had not been described before. Several aspects of the biology of both partners were investiga ted with major focus on their distribution and relation to different s ubstrates, behavioural and morphological adaptations to their habitat and their modes of nutrition. Various behavioural and morphological ad aptations enable Pariambus typicus to live on a variety of substrates, on which the amphipod settles after contact. The highly mobile ophiur oid hosts open up new habitats for the caprellid (phoresis). Extensive grooming behaviour and specialized mouthpart morphology enable P. typ icus to use detritus as an important food source, which contributes al so a great part to the ophiuroids' nutrition. The complex association between P. typicus and Ophiura is interpreted as a commensalism.