Artificial Production of the “Wedding Dress” in Chrosomus Erythrogaster. ∗

Abstract

Summary and Conclusions

While the results are not complete enough to reach definite conclusions, it would seem that in view of similar and better known conditions in rodents the mechanism of the production of the “wedding dress” in Chrosomus erythrogaster is due to the action of substances having either a stimulating effect upon the sex glands of the fish, such as prolan, or having an effect similar to that of the estrus producing hormones, such as Yohimbine.

Recent reports 1 , 2 , 3 have made it probable that certain species of fish may be used successfully as test animals for the demonstration of either the gonadotropic or the sex hormones. For some time it has been known that certain male fish, such as Rhodeus amarus, Gastrosteus, Phoxinus laevis, belonging to the Cyprinidae group, assume striking color changes during the spawning period, lasting for several weeks in the spring. This so-called “wedding dress” or “mating coat” is due to the expansion of the chromatophoric cells of the skin and is considered to be an expression of heat in order to attract the females. Thus it would be comparable to the well-known estrus of the rodents.

Wunder, 1 working with Rhodeus amarus, obtained a “wedding dress” with subcutaneous injection of testis extract, variable results with prolan, and no effect with the female sex hormone. Glaser and Haempel 2 reported the castrated Bitterling as a suitable test animal for the demonstration of the male sex hormone. Zondek 3 used the expansion of the erythrophores of Phoxinus laevis as a test for the demonstration of his pituitary pigment hormone intermedin.

While these experiments were conducted on fish, domestic and very abundant in central Europe, they are not inhabitants of this country and are difficult to obtain. For this reason and for the purpose of producing the “wedding dress” artificially in an American fish, Chrosomus erythrogaster was considered the most suitable fish. This attractive and hardy fish, commonly called “red bellied dace”, belongs to the group of Cyprinidae and is found in various parts of this country from Maine to Alabama in small, clear streams, where it breeds in May and June. No record exists of its having bred in captivity. 4 The breeding dress consists in a vivid and brilliant red discoloration of the otherwise white belly and the part just below the mandible on each side. 5