カワハギおよびアミメハギの体色変化

Abstract

A rapid and marked color change was observed on a filefish, Stephanolepis cirrhifer (TEMMINCK et SCHLEGEL) and four distinct patterns were recognizabl (Fig. 1). Among twelve fish which ranged from 7 to 9cm in length and were kept in a tank of 60 litres capacity in the laboratory, there appeared two dominants assuming the pattern B, whereas the other subordinates indicated no dark pattern (A). When these dominants were removed from the tank, two dominants newly appeared soon. The dominant actively drove subordinates away and fought with the other to occupy the food and space (c and d in Plate I). The excitement in these activities induced the remarkable dispersion of melanophores (C and D in Fig. 1). A rapid and extensive aggregation of melanophores resulting in the excitement pallor was also recognized when the fish were frightened violently. It is the most interesting fact that the time required for change of pattern is very short and the shift from one extreme to the other, for instance from D to A, occurs only in one or two seconds, and this may be the most rapid case so far known on fish (Table 1). Among the fish kept in a large aquarium in the Ueno Zoo, on the other hand, there was recognized no order and every fish assumed the pattern B or C, whereas the same rapid excitement pallor was observed. The behavior of the fish in the laboratory, therefore, must be a specific one induced by the experimental condition, perhaps by the dense keeping of fish. The similar color change due to excitement was also indicated by a different species of filefish, Rudarius ercodes (JORDAN et FOWLER) (Plate II).