Karyological Studies of a Female Variable Oystercatcher (Haematopus Unicolor)

The chromosomes of Haematopus unicolor Forster were examined from cultures of embryo cells. The diploid complement for one individual was estimated to be 2n = 72, comprising 35 autosomes and a pair of sex chromosomes. The W chromosome is a medium size submetacentric. It is smaller than the Z and is the only chromosome with noncentromeric constitutive heterochromatin. The only other species of this genus whose karyotype is known, H. ostralegus, differs from H. unicolor in having a smaller diploid complement (2n = 66) and a telocentric W chromosome. Comparative karyological studies of other species will likely provide valuable data for clarifying the systematics of the Haematopodidae.