MATING SYSTEMS IN THE SEA-ANEMONE GENUS EPIACTIS

Four morphologically similar species in the sea anemone genus Epiactis exhibit overlapping distributions on the Pacific coast of North Ameri ca; E. prolifera, E. lisbethae, E. ritteri and E. fernaldi. All brood their offspring up to the juvenile stage, but each has a different com bination of internal versus external brooding and hermaphroditism vers us gonochory (separate sexes). Specimens were collected from sites ran ging from British Columbia to southern California between December 198 8 and July 1992. Mating systems were inferred from genetic comparisons of mothers and offspring, histological analyses of sex expression and observations on brooding and spawning behavior. Allozyme and multiloc us DNA fingerprint analyses of the gynodioecious hermaphrodite E. prol ifera showed that offspring were all identical to their mothers, a res ult consistent with either asexual reproduction, self-fertilization or extreme biparental inbreeding. In the gonochore E. lisbethae, mothers and offspring were also electrophoretically identical, but variation in DNA fingerprints indicated cross-fertilization. Similar DNA fingerp rint differences between mother and offspring in the gonochore E. ritt eri implied that cross-fertilization also occurs in this species. No m other-offspring comparisons were performed on E. fernaldi, as this spe cies was not observed brooding offspring during this study. Although i ncomplete, the results of this study increase our knowledge of the ver y unusual combination of reproductive modes in the genus Epiactis, and argue for further investigations of the evolution and genetic consequ ences of mating systems in these species.