Food preferences of juvenile corallivorous crown-of-thorns (Acanthaster planci) sea stars

Population outbreaks of adult Acanthaster planci cause significant reductions in coral cover and reduce the resilience of coral reefs, but little is known about the behaviour and food preference of juvenile A. planci. In 2014, food preferences and feeding rates of recently settled (<1 year) juvenile A. planci were tested and determined at the National Sea Simulator facilities of the Australian Institute of Marine Science. Juveniles were offered eight species of coral (Acropora formosa, A. millepora, A. tenuis, Pavona cactus, Echinopora lamellosa, Pocillopora damicornis, Stylophora pistillata and Porites lutea), known to be either consumed or avoided by adult sea stars, in a multiple-choice and a no-choice experiment. In the multiple-choice experiment, a preference for A. tenuis was detected, while S. pistillata, E. lamellosa and P. lutea were avoided. The no-choice experiment showed that the avoidance of these species was not influenced by the presence of other coral species, the exception being E. lamellosa, which was only consumed when no other choice was offered. Interestingly, all juveniles consuming E. lamellosa died post-predation. The study suggests that as A. planci matures it feeds on a wider range of species, even those which would have been lethal to them if consumed as a juvenile.