Floating corallites: a new ecophenotype in scleractinian corals

摘要

Over the last five years, while working with planulae of several coral species in the Caribbean (Montastraea faveolata, Montastraea cavernosa, Acropora palmata, Siderastrea radians, Agaricia humilis) and Hawaii (Montipora capitata), a previously undescribed floating life-stage of corals was observed in various aquarium settings (Fig. 1). A subset of planulae (3.5–7.0%) excreted a buoyant skeleton, causing the individual to float upside down on the water surface as tentacles developed pointing downward. Excreted skeletons were larger and flatter than those excreted by benthically settling planulae. Endosymbiontic algae (zooxanthellae) became abundant at the aboral side of the floating corallite, now facing the incoming light. The calcareous skeletons were extremely buoyant and floated back to the surface when submerged in a 0.5 m deep water basin.