Occurrence of Natural Hybrid between Pufferfishes, Takifugu xanthopterus and T. vermicularis, in Ariake Bay, Kyushu, Japan.

Abstract

Six unidentifiable pufferfishes of the genus Takifugu collected in Ariake Bay, Kyushu, Japan in 1985 and 1986, were examined enzyme electrophoretically and morphologically. Electrophoretic analysis showed these specimens to be natural F1 hybrids between T. xanthopterus and T. vermicularis, since they were heterozygous of having one allele from T. xanthopterus and another from T. vermicularis at all the eight diagnostic loci. Morphological examinations showed intermediacy of the hybrid specimens, and supported the findings of the electrophoretic analysis: (a) mean values of five meristic characters of the hybrids fell between those of the parental species, hybrid indices ranging from 16.7 to 73.3, with a mean of 44.4; (b) the first principal component (PC1) extracted from the values for three meristics and seven morphometrics clearly separated T. vermicularis from T. xanthopterus, with the hybrids situated between them; and (c) coloration and body prickles of the hybrids were intermediate between those of the parent species. The incidence of hybridiza-tion was quite low (0.4%), as recorded for some other marine fishes.