Hereditary Basis of Melanosis in Hybrid Fishes

Abstract

In reviewing the work on the generic hybrids between Platypoecilus maculatus and Xiphophorus hellerii, one is confronted by evidence which seems to point to a definite correlation between melanotic conditions in the hybrid fishes and their characteristic color pattern. In some cases, normal and pathological hybrids occur together in the same brood, born and reared in the same aquarium. But it is only in hybrids of certain specific color patterns that melanosis appears. Since the various color patterns have been shown to be heritable, the evidence seems to indicate that heredity plays an important rôle in determining the physical condition of each generic hybrid.

Abnormal conditions in certain hybrids were recognized by the early fish hybridizers, Lösslein (1912) and Haffner (1912). It is only recently (1928) that a confirmatory note, with respect to the origin of the pathological conditions arising under controlled breeding practices, has been presented by Häussler, writing from the Institut für experimentelle Krebsforschung, Heidelberg. His results and interpretation agree in the more important details with those of Kosswig (1928, 1929).