Chromosomal uniformity in the avian subclass Carinatae

Summary

• 1. A method for making two-dimensional measurements of colchicinized metaphase chromosomes was applied to six avian species and one interfamilial hybrid of the subclass Carinatae: the canary (Serinus canarius, 2n=80±), the parakeet (Melopsittacus undulatus, 2n=58±), the pigeon (Columba livia domestica, 2n= 80±), the turkey-pheasant hybrid (♂ Meleagris gallopavo × ♀ Phasianus colchicus, 2n=80±), the Japanese quail (Coturnix coturnix japonica, 2n=78 ±), the jungle fowl of Java (Gallus gallus bankivo, 2n=78 ±), and the duck (Anas platyrhyncha domestica, 2n=80 ±).

• 2. In these species representing five different orders of diverse geographic origin, the total chromosome area varied only from 62.42 μ ² in the turkey-pheasant hybrid to 67.95 μ ² in the parakeet.

• 3. The absolute size of the Z-chromosome was equally uniform, ranging only from 2.3 μ ² in the pigeon and duck to 3.0 μ ² in the canary. A W-chromosome two-thirds as large as the Z was noted in the female canary and pigeon; thus the sex chromosome constitution of the heterogametic sex in all avian species is probably ZW, not ZO.

• 4. Class Aves, subclass Carinatae, constitutes an independently uniform class with regard to the total chromosome area and the absolute size of the Z-chromosome.