OCCURRENCES OF THE ISOPODA FLABELLIFERA GNORIMO-SPHAEROMA RAYI HOESTLANDT ON THE COASTS OF JAPAN, EASTERN SIBERIA AND HAWAII, WITH A BRIEF NOTE ON ITS GENETIC POLYCHROMATISM

Abstract

Along the coasts of Japan, Eastern Siberia and Hawaii, the Sphaeromatid (Isopoda Flabellifera) Gnorimosphaeroma rayi is widely spread; it is an Isopoda previously discovered in California (Tomales Bay) where it had very likely been imported accidentally together with Japanese oysters. G. rayi is very similar to the other two American Pacific species, G. oregonense and G. luteum; the differences between those three species are described. In the inventoried localities (8 in Japan, 1 in Eastern Siberia and 1 in Hawaii) there are two types morphologically distinct (chaetotaxy of the peraeopod I), among which one is more northern than the other. The validity of G. salebrosa and G. lata is proved, too. The polychromatism of G. rayi in Japan is more variable than that of G. rayi in California. The three closely related species G. oregonense, G. luteum and G. rayi may have had a common origin in a comparatively recent past in more northern regions which were once temperate in climate.