Toxic coral gobies reduce the feeding rate of a corallivorous butterflyfish onAcroporacorals.
The obligate coral-dwelling gobiid genusGobiodoninhabitsAcroporacorals and has developed various physiological, morphological and ethological adaptations towards this life habit. While the advantages of this coral-fish association are well documented forGobiodon, possible fitness-increasing factors for the host coral are unknown. This study examines the influence of coral-dwelling gobies on the feeding behaviour of obligate corallivorous butterflyfishes. In an aquarium experiment using video observation, the corallivorous butterflyfishChaetodon austriacusfed significantly less on corals inhabited by twoGobiodonspecies compared to unoccupied coral colonies of similar size. The more agonistic speciesG. histrio, which mostly displayed directed movements towards butterflyfishes, decreased butterflyfish bite rate by 62-98 % compared to uninhabited colonies. ForGobiodonsp. 3, which mostly displayed undirected movements in response to visits byC. austriacus, bite rate reduction was 64-68 %. The scale-less skin ofGobiodonspp. is covered by mucus that is toxic and multi-functional by reducing predation as well as affecting parasite attachment. A choice flume experiment suggests that the highly diluted skin mucus ofGobiodonspp. also functions as a corallivore repellent. This study demonstrates thatGobiodonspp. exhibit resource defence against coral-feeding butterflyfishes and also that coral colonies without residentGobiodonsuffer higher predation rates. Although the genusGobiodonis probably a facultative corallivore, this study shows that by reducing predation on inhabited colonies by other fishes, these obligate coral-dwellers either compensate for their own fitness-decreasing impact on host colonies or live in a mutualistic association with them.
Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria.
M
M
Dirnwoeber
Faculty of Life Sciences, Department of Integrative Zoology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria.
J
J
Herler
Chaetodon austriacus; Coral-fish association; Gobiodon; Red Sea; Resource defence; Selective corallivory