Evidence of an original scale development during the settlement phase of a coral reef fish (Acanthurus triostegus)

As the majority of coral reef fishes, the Convict Surgeonfish Acanthurus triostegus (Acanthuridae) has a complex life cycle that involves an ontogenetic change in morphology, physiology and behaviour as its pelagic larval stage colonizes the benthic habitat. Few studies are devoted to the changes in skeleton during the settlement phase of coral reef fishes. In the present study, we highlighted an unexpected scales development in A. trisostegus just after the reef settlement. At settlement (t0), A. triostegus showed calcified and very thin vertical plates, lying in the dermis on the whole body. During the first 9 days after settlement, thin vertical plates regressed and adult scales began to appear simultaneously. At 12 days post-settlement, the whole body was covered with small scales. Overall, such a rapid skeletal transformation is an example of morphological changes dealing with metamorphosis of coral reef fishes.