ENTOCLADIA ENDOZOICA SP. NOV., A PATHOGENIC CHLOROPHYTE: STRUCTURE, LIFE HISTORY, PHYSIOLOGY, AND EFFECT ON ITS CORAL HOST

¹ Department of Biological Sciences, Florida International University, Miami, Florida 33199

A new species of the marine microalgal genus Entocladia (Ulvellacea, Chlorophyta) is described from cultured material and from its natural habitat, the skeleton of a gorgonian coral (Pseudoplexaura spp.). Host tissues react to the presence of this filamentous chlorophyte by producing a capsule composed primarily of scleroprotein skeleton, and secondarily of calcareous spicules. The skeletal capsule separates the algae from contact with host tissue but in doing so the skeleton loses more than 60% of its tensile strength and over 90% of its elasticity. The coral colony readily breaks apart at the site of the weakened skeleton, exposing the contained algal filaments to relatively high light fields and sea water, an amino acid-depleted environment. These conditions lead to rapid cytological changes that convert the alga to a reproductive state. Regeneration of damaged host tissue re-seals the capsule and causes resumption of the vegetative condition typical of enclosed algae. Experiments with native and cultured material suggest that host-derived amino acids, especially tyrosine or cystine, play a key role in regulating the reproductive condition of Entocladia filaments.