Ryukyu Islands

This species appears to exist in a number of different forms which exhibit differences in colour pattern, morphology, or both, and it's currently unclear whether all of them are truly conspecific or not although to avoid confusion we list all together here.

As with all members of the genus sexual dimorphism is pronounced. Males are brightly-coloured, with a reddish-orange stripe extending posteriorly from the pectoral-fin, with the posterior portion of the body entirely suffused with red. A darkish band extends from behind the eye to the edge of the opercle, and the basal third of the caudal-fin is reddish-orange.

Known only from the Ryukyu Islands, Japan, and thus far recorded from just 4 streams on Okinawa island and two on Iriomote island. The type series derived from both islands with Okinawa given as type locality. It may be more widely-distributed than this however, and was possibly transported to the Ryukyu Islands via the Kuroshio Current, an ocean current similar to the Gulf Stream transporting warm, tropical water northward from an area east of Taiwan past Japan towards the polar region.