Variations in long- and middle-wavelength-sensitive opsin gene loci in crab-eating monkeys.

We analyzed variations in long (L)- and middle (M)-wavelength-sensitive opsin gene loci in crab-eating monkeys. Unlike humans, most monkeys have a single L and a single M gene. Two variant genotypes, one with only one opsin gene (dichromatic) and one with tandemly arrayed multiple genes, were also found in the monkeys. However, the frequency of the former was 0.47%, and that of the latter was 5% in the monkeys, while 2% and 66%, respectively, in Caucasian males. The two variants were found only in Java Island, Indonesia, and South Thailand, respectively. The data suggest that the frequency of each genotype is different among Old World primates.