Abstract
Japanese bitterlings in the Rhodeinae have been classified into five genera (Okada, 1960), four genera (Aoyagi, 1957;Nakamura, 1963) or a single genus (Miyadi et al., 1976) on the basis of morphological characters of adult fishes.Recently, Miyadi et al. (1976) and Arai (1978) made phylogenetic discussions of Japanese bitterlings on the basis of morphological and karyotypic results which had been obtained by many authors.Arai (1978) emphasized the validity of minute scaly tubercles on the surface of the yolksac of rhodeine fish in prolarval stages.In the paper, however, he did not mention about morphology of the tubercles.
The present authors microscopically confirmed that there are tubercles in all six species, which makes possible classification into two groups and/or four types by morphology of the tubercles.Although prolarvae of both Acheilognathus lancolata and A.limbata have been regarded to have a nearly smooth body surface, our observations showed that they have many tubercles (the major and the minor axises are about 20μm and 15μm, and the height 20-30μm).The former species tends to differ from the latter in having sharper and higher tubercles, but the tendency is not clearcut. Other species of Acheilognathus have very large ellipsoid tubercles of which the posterior part forms a ridge. A.cynaostigma and three subspecies (see Nakamura, 1963) of A.tabira have tubercles of an equal size (the lengths of both the major and the minor axises are 30-45um and 20-35 um, and the height is about 20 um).A.rhombea has more round tubercles, and tubercles of unequal sizes coexist in A.lognipinnis.
Classification of rhodeine species by the morphology of tubercles well supports the phyletic relationships among them suggested by Miyadi et al. (1976).
