Ostreobium quekettii (Ostreobiaceae: Chlorophyceae) invading the barnacle Acasta sp. (Pendunculata: Acastinae), endozoic in the octocoral Rumphella suffruticosa (Alcyonacea: Gorgoniidae) from Fiji, South Pacific

Abstract

The eukaryotic alga Ostreobium quekettii (Ostreobiaceae: Chlorophyceae) is reported from Fiji for the first time. It is found creeping over the calcareous plates of dead specimens of species of a barnacle genus Acasta (Pendunculata: Acastinae), which was endozoic in the gorgonian Rumphella suffruticosa. The barnacles are lodged in cavities in the coenenchyme of the gorgonian, mostly in the vicinity of colonial branching points. There is little external evidence of the location of the barnacles where the gorgonian tissue is thick, but where it is thin, prominent galls are visible. There is no evidence that the barnacle or algal association causes stress to the host, which was otherwise healthy in appearance. The presence of the algae would appear to be associated with the occurrence of the barnacles.