Protection of host anemones by snapping shrimps: a case for symbiotic mutualism?

Abstract

The sea anemone Bartholomea annulata is an ecologically important member of Caribbean coral reefs which host a variety of symbiotic crustacean associates. Crustacean exosymbionts typically gain protection from predation by dwelling with anemones. Concurrently, some symbionts may provide protection to their host by defending against anemone predators such as the predatory fireworm, Hermodice carunculata, which can severely damage or completely devour prey anemones. Herein we show through both field and laboratory studies that anemones hosting the symbiotic alpheid shrimp Alpheus armatus are significantly less likely to sustain damage by H. carunculata than anemones without this shrimp. Our results suggest that the association between A. armatus and B. annulata, although complex because of the numerous symbionts involved, may be closer to mutualism on the symbiotic continuum.