First case of caprellid amphipod-hydrozoan mutualism

Abstract

The caprellid amphipod Paracaprella tenuis Mayer is in a mutualistic relationship with the hydrozoan Bougainvillia rugosa Clark. Adult male P tenuis aggressively displace Tenellia pallida (Alder and Hancock), a nudibranch predator of the hydroid. The aggressive displacement of the nudibranch occurs when the nudibranch crawls within a caprellid body-length of the amphipod. Hydrozoan polyps within the response area of the caprellid are protected from predation, and the rapid retreat by the nudibrancb precludes polyp predation immediately following the interaction. The caprellid receives a suitable substratum and food in the form of attached diatoms and entrapped detritus.