Observation of body colour formation and pigment cells in grey‐black and golden Paramisgumus dabryanus.

In nature, most Paramisgurnus dabryanus are grey‐black (grey‐black loach), although there is a mutant (albino) in the breeding population with a 'golden colour' (golden loach). There are no reports of early body colour formation in albino fishes. In this study, the differences in body colour characteristics between normal body colour P. dabryanus and albino P. dabryanus were compared by comparing body colour formation, skin and fin pigment cells of two body colours of P. dabryanus. It was found that the order of appearance of pigment cells in grey‐black loach and golden loach was melanophores, xanthophores, erythrophores, and finally, iridophores; the composition of the pigment cells in the fins and the skin tissue were essentially the same. However, there were no melanophores in the skin of the golden loach. The melanophores of grey‐black loach skin were distributed with a large number of melanosomes of high electron density; the xanthophore and erythrophores were spherical and contained pteridine vesicles. Melanophores and xanthophores are distributed in both the epidermis and dermis of the grey‐black loach, and the xanthophores of the golden loach are distributed between the scales and the epidermis, and between the dermis and the muscle layer. In this study, we elucidated the body colour composition and pigment cell characteristics of the two body colours of P. dabryanus. Our study provided a scientific basis for the research for fish body colour variation. [ABSTRACT FROM AUTHOR]