Color vision in squirrel monkeys: sex-related differences suggest the mode of inheritance

Behavioral tests of vision in squirrel monkeys (Saimiri sciureus) reveal that there are widespread individual variations in color vision in this species. The variation has a sex-related component: whereas both trichromatic and dichromatic color vision occurs among female monkeys, males appear exclusively dichromatic. This finding suggests that, unlike humans, squirrel monkeys have only a single photopigment locus on the X chromosome.