Ultrastructural analysis of gene interaction and melanosome differentiation in the retinal pigment cells of the albino goldfish.

The genotype of albino goldfish is represented by pp,cc, and the non-albino fish is PP,CC. The P gene begins to control the melanosome formation of retinal pigment cells at St-21; and the C, which is epistatic to P and p, governs melanosome formation in the dermal melanophores and in retinal pigment cells after St-22. Then in the pp,CC fish, between St-21 and St-22, melanosomes of the pigmented retina are albino in type, but after St-22 they become non-albino in type. From ultrastructural observations on the melanosomes of these late-melanizing fish, it is apparent that the imcompletely melanized albino pigment granules can differentiate into normal melanosomes under the control of the C gene. The processes of melanosome maturation in the late-melanizing goldfish are evident from these observations.