Abstract

The porcellanid crab Allopetrolisthes spinifrons, a symbiont of the sea anemone Phymactis papillosa, shows a suspension-feeding behavior related to flow oscillations (repetitive changes of flow direction). Individual crabs oriented their filter appendages (third maxillipeds) to maintain a concave face upstream, showing a higher frequency of maxilliped movements (flexion) at the start of inverted flow. The crab is primarily a suspension feeder that can ingest host mucus and feces. Contrary to free-living porcellanids, the symbiotic life-style offers access to exposed sites in the intertidal and subtidal environments that are favorable for passive suspension-feeding activities and consequently, an alternative feeding mechanism is not necessary.