ELLIPTOCHLORIS MARINASP. NOV. (TREBOUXIOPHYCEAE, CHLOROPHYTA), SYMBIOTIC GREEN ALGA OF THE TEMPERATE PACIFIC SEA ANEMONESANTHOPLEURA XANTHOGRAMMICAANDA. ELEGANTISSIMA(ANTHOZOA, CNIDARIA)

Symbiotic green algae from two species of intertidal Pacific sea anemones, Anthopleura elegantissima and Anthopleura xanthogrammica, were collected from the northeastern Pacific coast of North America across the known range of the symbiont. Freshly isolated Anthopleura symbionts were used for both morphological and molecular analyses because Anthopleura symbiont cultures were not available. Light and transmission electron microscopy supported previous morphological studies, showing the symbionts consist of spherical unicells from 5 to 10 μm in diameter, with numerous vesicles, and a single bilobed chloroplast. Pyrenoids were not seen in LM, but a thylakoid-free area was observed in TEM, consistent with previous findings. Many algal cells extracted from fresh anemone tissue were observed in the process of division, producing two autospores within a maternal cell wall. The morphology of the green symbionts matches that of Elliptochloris Tscherm.-Woess. Molecular phylogenetic analyses of the nuclear SSU rDNA and the plastid encoded gene for the large subunit of RUBISCO (rbcL) support the monophyly of these green algal symbionts, regardless of host species and geographic origin. Phylogenetically, sequences of the Anthopleura symbionts are nested within the genus Elliptochloris and are distinct from sequences of all other Elliptochloris spp. examined. Given the ecological and phylogenetic distinctions among the green algal symbionts in Anthopleura spp. and the named species of Elliptochloris, we designate the green algal symbionts as a new species, Elliptochloris marina (Trebouxiophyceae, Chlorophyta).