Morphological differentiation of sex chromosomes in three species of ratite birds

Abstract

Chromosome banding studies allowed us to distinguish the sex chromosomes of the emu (Dromaius novaehollandiae), American rhea (Rhea americana), and Darwin’s rhea (Pterocnemia pennata). In each species, we identified the Z chromosome which is very similar to a carinate Z, and the slightly smaller W chromosome. Contrary to the uniformly heterochromatic carinate counterpart, the ratite W chromosome is euchromatic and retains remarkable banding homology to the Z chromosome.