Multiple Sex Chromosomes in a Mexican Cyprinodontid Fish

Abstract

THE chromosomes of the killifish^1–3 family Cyprinodontidae are being studied in many laboratories and the karyotypes of forty-eight of the approximately eighty-five species of North American killifishes have so far been determined (refs. 2 and 3 and our unpublished results), twenty-seven of them by us. All but three of the fifteen or sixteen North American genera of the family have been studied, and of the largest genera, Fundulus (twenty-nine species) and Cyprinodon (about twenty species), twenty-two and thirteen species, respectively, have been karyotyped. The diploid chromosome number of American killifishes is usually 48. The known exceptions are species of the genus Fundulus^3,4 and Lucania parva (46), L. interioris (36) and Adinia xenica (32). The latter three species have large metacentric chromosomes indicating centric fusions; they can be enumerated by subtracting the total number of chromosomes from 48. For example, Adinia has sixteen large metacentrics, the thirty-two chromosomes being subtracted from 48.