GENETIC-STUDY OF THE EXTENT AND CONSEQUENCES OF SEXUAL AND ASEXUAL REPRODUCTION IN THE DEEP-SEA EPIZOIC ANEMONES AMPHIANTHUS-INORNATA AND KADOSACTIS-COMMENSALIS (CNIDARIA, ANTHOZOA)

The anemone Amphianthus inornata is found at bathyal depths living on colonies of the gorgonian Acanella arbuscula. Previous studies of the morphology and reproductive stage of this anemone, during different ti mes of the year, have indicated that it reproduces sexually on a seaso nal basis. A small proportion of the study population were also report ed to be undergoing asexual reproduction by fission. The anemone Kados actis commensalis is also bathyal, but lives mainly on the holothurian Paroriza prouhoi. Previous morphological studies have indicated that K. commensalis is a protandrous hermaphrodite that exhibits non-season al sexual reproduction only. In the present study, allozyme electropho resis was used to examine the prevalence and genetic consequences of a sexual reproduction in a population of Amphianthus inornata from 2200 m in the Rockall Trough, North Atlantic Ocean. Genetic evidence, from five randomly selected polymorphic enzyme loci, for asexual reproducti on in this species was weak. Exact tests indicated that genotype frequ encies did not differ significantly from those expected under Hardy-We inberg equilibrium. F-IS (correlation of homologous alleles with refer ence to local population, assuming random mating) values also did not differ significantly from zero, and observed heterozygosity (H-o = 0.4 46) and genotypic diversity (G(o) = 17.0387) were very similar to Hard y-Weinberg expected frequencies (H, = 0.446; C-e = 17.0010). Evidence suggests that the contribution of asexual reproduction to recruitment in the study population of A. inornata is low. For a single populatio n of K. commensalis from 4850 m on the Porcupine Abyssal Plain, North Atlantic Ocean, the hypothesis that inbreeding due to reduced occurren ce of outcrossing between anemones on a single holothurian host was ex amined by electrophoresis of ten randomly selected enzyme loci. Single -locus genotypic frequencies were significantly different from expecte d frequencies for one locus [P less than or equal to 0.05, hexokinase- 1 (Hex-(1))]. F-IS values were significantly different from zero for t wo enzyme loci (Hex-1 and Hex-2, P less than or equal to 0.01 and P le ss than or equal to 0.05, respectively), and the overall observed hete rozygosity was lower than the expected heterozygosity (H-o = 0.125, H- e = 0.140). The hypothesis of inbreeding could not be rejected by the present study, although sample size was small (N = 55), leading to pos sible bias in tests of significance. Genetic variation in A. inornata was higher than that recorded for most eukaryotes, although interlocus sampling error for only five loci is high. High genetic variability h as been found in other sea anemones, and has been related to high long evity and mixed reproductive modes. Genetic variation in K. commensali s was in the higher range of that found in other eukaryotes, and is no t unusual for anemones.