Abstract
A common polymorphic freshwater goby, “Yoshinobori” Rhinogobius similis Gill, was divided into the three ecological types of an amphidromous type, a lacustrine type and a fluvial type; and these types were compared on the subject of life-historical features.
Both the amphidromous type and the lacustrine type spawn in summer a great number of small eggs (Fig. 1, A; Table 1), from which swimming larvae hatch (Fig. 1, B). Their larval stages are spent in the stagnant waters like seas (in the case of the former), lakes and ponds (in the case of the latter). They are distributed all over Japan.
The fluvial type spawns in summer a small number of large eggs (Fig. 2, A; Table 1). in which their swimming stages are passed. The newly hatched larvae (Fig. 2, B) transform directly into benthic young fish of the essential form of adult. They spend their whole life in the mountain streams in the southwestern province of Japan.
As a result of the above comparisons, the fluvial type may be considered to belong to a different species from the other two types.
