THE BITTERLING FISH RESPONSE TO MALE SEX HORMONES*

Abstract

The male bitterling fish (Rhodeus amarus) develops the typical mating coloration when treated with female sex hormones. Logically it would appear that the female fish might display the spawning season changes, when treated with male sex hormones. The Japanese bitterling (Achelognathus intermedium), was employed in the study here reported. Methods. The males were stocked separately from the females. In the test, individual aquaria containing 1 liter of water were used. The water temperature was 20 C. and the pH 6.53. Materials tested were added directly to the water or painted on the food particules. In interpreting results a lengthening of the external ovipositor in the female to at least 3 mm. was regarded as positive. In the male fish two of the following changes were considered as positive response: development of a red tip or red edge on the dorsal fin; production of a red cast to the eyes; the appearance of a red orange tip or reddish edge on the anal fin; the development of a pinkish body cast or flush.