Ornamental Fish Production and Management (1+1)

11.2.4 Platy

Fish of the genus Xiphophorus are amongst the most variable of animals within the natural environment. They also comprise a range of species which hybridize readily amongst themselves and thus provide the breeder with two sources of variation with which to work.

Three sets of colour are inherited: the macromelanophore and micromelanophore patterns are so valuable to scientific study and a series of body ground colour or fin colours. In addition to this, fin shapes and sizes are also developed in the fancy strains. The genetics of the fin shape may derive from hybridization between X. maculates, the common platy of aquarium fame, and X. montezumae or X. xiphidium followed by selection for enhanced expression. The other characteristics have a complex genetic background involving at least 19 loci, but these too seem to have been selected for vivid expression of individual genes. The possible manifestations of this array problems of platy breeding are largely to do with keeping crosses simple and stabilizing the variation. The black and black-stippled forms probably represent another example of duplicate locus inheritance. These fish make excellent material for educational use. Crossbreeding with the readily available short tail also provides good material for demonstrating hybridization and the melanic forms represent a good response to selection.