Abstract
It is known that bitterling larvae of Acheilognathus and Pseudoperilampus have minute scale-like tubercles on the skin surface.These remarkable structures are considered to be an adaptation to prevent the larvae from being ejected from freshwater bivalves (Uchida, 1937, 1939; Nakamura, 1969).Recently Fukuhara et al. (1982) described morphology of minute scaly tubercles distributed on the surface of the yolksac in the larvae of Acheilognathus.However, they did not mention minute tubercles distributed on the surface of winglike projections of the yolksac in the larvae of Rhodeus species.
The present paper deals with minute tubercles found in larvae of the following species, Rhodeus ocellatus smithi, R.ocellatus ocellatus, R.atremius and R.suigensis.Minute tubercles are small and hemispheric (ca.3-10μm in height).Their distribution is limited to the outside of the yolk projections in the larvae 2 days after hatching.With growth of the larvae, minute tubercles appear on the ridges, such as eye cups, dorsal and hind parts of the head, and ventral and posterior parts of the yolk projections.
From our observations, it was shown that all species of Japanese rhodeine fishes share minute tubercles during developmental stages.
