Gynogenesis and triploidy in the viviparous fish Poeciliopsis.

Three all-female strains of the viviparous fish Poeciliopsis occur in the Río Fuerte of Sinaloa, Mexico. Poeciliopsis lucida, a bisexual species, provides sperm for these monosexual forms which I designate as Cx, Cy, and Cz. Form Cy is a triploid that when test-mated to males of various species produces all-female, triploid offspring devoid of paternal characters. Both Cx and Cz are diploid and express characteristics of both parents.