The Morphology of Melanotic Over-growths in Hybrids of Mexican Killifishes

نویسنده

  • H. D. REED
چکیده

Genetic studies of hybrids between the Mexican killifishes, Platypoecilus maculatus and Xiphophorus hellerii, have shown that when the black-spotted varieties of Platypoecilus are crossed with Xiphophorus, melanosis appears in some of the hybrid offspring. The distinguishing feature of these black-spotted varieties of Platypoecilus is the presence in the skin of a large type of black chromatophores. These pigment cells have been called macromelanophores and in normal fishes are confined to the cutaneous tissues of the body. Varieties of Platypoecilus possessing the small type of black chromatophores (micromelanophores), when crossed with Xiphophorus, do not produce hybrid offspring which become afflicted with melanosis in any degree. The two general types of hybrids are illustrated in Plate XV. Fig. 89 is a photograph of a melanotic individual possessing the macromelanophores arranged as black areas or blotches over the surface. Fig. 90 shows a specimen lacking melanophores of the large type but possessing the small melanophores (micromelanophores) condensed as a crescent about the base of the caudal fin and also scattered over the whole body. The two specimens shown in these figures were brood mates. It appears conclusive that the macromelanophores alone among black pigment cells are involved in melanosis and the melanotic over-growths under consideration.

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تاریخ انتشار 2010