Genetic Comparison of Two Choerodon (Osteichthyes : Perciformes : Labridae) Color-types from the Southern Coasts of Japan

Abstract

Mitochondrial 16S rRNA sequences were compared between two color-types (type-A and type-B) of the labrid fish Choerodon robustus (Gunther, 1862) collected from the Pacific coast of Japan and the Ryukyu Islands. The two types differ in coloration of the opercle lower margin and caudal fin. Two type-A specimens each had a unique haplotype, whereas only two haplotypes were found among nine type-B specimens. The amount of mean pairwise sequence divergence within each of the two color-types was very small (0.16% in type-A, 0.035% in type-B), much less than that between the two color-types (4.3%). Phylogenetic analyses using maximum parsimony (MP) and neighbor-joining (NJ) methods, with a haplotype of Choerodon azurio (Jordan and Snyder, 1901) as an outgroup, showed that the haplotypes of each color-type were reciprocally monophyletic with 100% bootstrap values. The sequence differences between the two color-types ranged from 4.2% to 4.6%, such being comparable to those between C. azurio and each of the two color-types (5.3-5.7%). These results indicate that the two color-types of C. robustus represent two distinct species.