MEPS 214:111-119 (2001)  -  doi:10.3354/meps214111

ABSTRACT: The crown-of-thorns starfish Acanthaster planci (L.) is well adapted to feed on a wide range of different corals, but often exhibits striking preference for a small suite of available prey species. Numerous theories have been forwarded to explain its feeding preferences, but many of these theories have not been tested. In this study, I test whether coral symbionts significantly affect the feeding preferences of crown-of-thorns starfish by removing symbionts from replicate colonies of 6 different coral species. Crown-of-thorns starfish had a clearly defined hierarchy of preference for the 6 different corals when these contained symbionts (Acropora gemmifera > A. nasuta = A. loripes > Seriatopora hystrix > Pocillopora damicornis > Stylophora pistillata). However, when coral symbionts were removed, then the starfish readily consumed all 6 corals and did not exhibit any significant selectivity. Further manipulation of symbiont assemblages showed that the trapeziid crabs (Tetralia and Trapezia species) were the most effective of the various coral symbionts in deterring starfish from feeding on their host colony. Moreover, those corals that were least preferred by crown-of-thorns starfish contained the largest and most powerful species of Trapezia (T. cymodoce), whereas the most preferred corals contained only very small Tetralia spp. crabs. Further experimentation is required to assess the generality of these results, but for the 6 coral species tested, it is clear that coral symbionts (and particularly trapeziid crabs) do have a marked influence on the feeding preferences of the crown-of-thorns starfish.

KEY WORDS: Acropora · Host defence · Pocilloporidae · Prey selection · Symbiosis · Trapeziidae