A case report of conjoined twins in medaka fish.

Conjoined twins have been reported in trout, catfish, guppy, tilapia, and other fishes under natural conditions. However, they are rarely reported in medaka fish. As far as we know, only one case where two fries were connected to the same yolk sac was reported before. Here, we report a case of conjoined twins in medaka fish (Oryzias latipes).