The Development of Mendelian Characters in Aplocheilus Latipes

Abstract

The color varieties of this Japanese fish, which are known to be simple Mendelian characters, are produced by variations in 2 types of pigment cells[long dash]melanophores and xantho-phores. The color of the wild type (BBYY) is due to the full development of both types of cells; in the yellow type (bbYY) both types of cells are present in the same abundance but the amount of melanin is very slight; in the white (bbyy) the same number of cells of both types are again present but with little pigment developed. Studies of fish just hatched show similarly that equal numbers of cells exist in all types. Their presence is revealed by treatment with adrenalin. Mendelian ratios may be detected 2 days after fertilization. The evidence indicates that the Mendelian gene produces its effect not by controlling "division energy" regulating numbers of cells, but by controlling the amount of pigment to be elaborated in cells always present, and that the definitive action is at some stage in cell lineage preceding the earliest appearance of pigment.