KARYOLOGY OF NORTH AMERICAN NATRICINE SNAKES (FAMILY COLUBRIDAE) OF THE GENERA NATRIX AND REGINA

Abstract

Four species of the water snake genus Natrix have a distinctly different pattern of chromosomal morphology than found in two species of the related genus Regina. Natrix all have a karyotype with seven pairs of large or medium-sized submetacentric autosomes, three pairs of medium-sized subtelocentric autosomes, and seven pairs of small metacentric autosomes. All have a 2n of 36 with a submetacentric Z and submetacentric or subtelocentric W. The autosomal complement of Regina consists of seven pairs of large to medium-sized submetacentrics, five pairs of medium-sized submetacentrics, and five pairs of small metacentrics. The Z and W are both submetacentric chromosomes. The sex chromosomes are easily distinguished in both genera. The relationships of Natrix and Regina and Old World Natrix are discussed, as well as chromosomal variation in closely related species in the family Colubridae.