Widespread Occurrence of a Rarely Known Association between the Hydrocorals Stylaster roseus and Millepora alcicornis at Bonaire, Southern Caribbean

Among symbiotic associations, cases of pseudo-auto-epizoism, in which a species uses a resembling but not directly related species as substrate, are poorly documented in coral reef ecosystems. In the present study, we assessed the distribution of an association between the hydrocorals Stylaster roseus  and Millepora alcicornis  on about 50% of coral reef sites studied in Bonaire, southern Caribbean. Although previously thought to be uncommon, associations between the lace coral S. roseus and the fire coral M. alcicornis  were observed at both the windward and leeward sides of Bonaire, mainly between 15 and 25 m depth, reaching a maximum occupation of 47 S. roseus  colonies on a single M. alcicornis  colony. Both species’ tissues did not show any signs of injuries, while an in-depth inspection of the contact points of their skeletons revealed that both partners can partially overgrow each other. How it is possible that S. roseus  is able to settle on the stinging tissue of Millepora  as well as how, by contrast, the latter may facilitate the lace coral by o ering a certain degree of protection are questions that deserve further investigations