Enzyme and colour variation in the hoplonemertean Tetrastemma nigrifrons from the Sea of Japan

Five sympatric colour varieties of the hoplonemertean Tetrastemma nigrifrons (var. pallidum, var. bicolor, var. purpureum, var. punctata, var. albino) were found in Vostok Bay (the Sea of Japan). The taxonomic status of the varieties, some of which have been known for almost a century, was uncertain. Starch gel electrophoresis was used to compare allele frequencies of these varieties at 19 isozyme loci. Neither fixed allelic differences nor statistically significant differences in allele frequencies between different colour varieties was revealed. It was concluded therefore that all the colour varieties studied are conspecific. As estimated from the electrophoretic screening of 24 isozyme loci, the species is highly variable at the molecular level. It has high mean values of observed and expected heterozygosity estimates, H_o =0.313 ± 0.049 and H_e =0.323 ± 0.050, and is one of the most variable species among invertebrates.