Coralliophila from Grand Cayman: Specialized coral predator or parasite?

Abstract

Species of Coralliophila are well-knowncnidarian associates. Coralliophilaclathrata, an obligate symbiont of thecolonial zoanthid sea anemone Palythoa,feeds on nematocysts and zooxanthellaesloughed off in the host mucus (Robert-son 1980). Coralliophila abbreviata rap-idly consumes coral tissues causingsubstantial colony mortality. Corallio-philaviolacearemainssedentaryandtapsinto coral energy reserves, a ‘‘prudent’’sessile feeding strategy that allows thesnails to feed without moving over longperiods, maximizing energy exploitationwhile minimizing coral damage andmortality (Oren et al. 1998).We found numerous specimens ofCoralliophila caribbea (Fig. 1a–c) onMontastrea cavernosa (only coral ob-served)atGrandCaymanIsland.Thissnailfeeds by introducing its proboscis throughthepolyp’soralopening(Fig. 1d,e)or,lessfrequently, through the coral epidermis(Fig. 1f), as previously observed for C.abbreviata (Miller 1972). Also a ‘‘pru-dent’’ strategy, this would allow sessilefeeding for extended periods. Together with the presence of zooxanthellae in the digestive tract (Miller 1972), it suggests utilization of coraltissuesandenergyreserves,notkleptoparasitism(i.e.,st ealingfoodfrompolyps).Inturn,thelackoffeedingscarson M.cavernosa suggestsafeeding strategy that is closer to parasitism than to specialized predation.A similar behavior was observed in an undescribed species of autolytine polychaete (Proceraea sp.). It appears to live in thesubstrate surrounding the coral and feeds by inserting its head through the oral opening of the polyps (Fig. 1g, h). With two unrelatedspecies apparently exploiting the same resources, we argue that energy reserves may be present in many other corals and exploitedby Coralliophila and perhaps other scleractinian associates.