Pleiotropic effect of the hooded mutation of the rat on male fertility

Several reproductive parameters were studied in males homozygous (hh) or heterozygous (Hh) for the hooded mutation as compared with completely pigmented wild-type males (HH). Histological analysis of the testes was carried out in males of the three genotypes. The proportion of sterile males in homogeneous matings of homozygotes hh was twice as high as in matings of heterozygotes. The proportion of sterile males in matings yielding no progeny was also twice higher in homozygotes hh as compared with heterozygotes. No sterile males were detected in matings of completely pigmented wild-type animals. Unilateral cryptorchidism, a hypoplastic testis combined with a hyperplastic one, or hypoplasia of both testes were observed in some males homozygous for the hooded mutation. Morphologically, these defects were associated with underdevelopment or the complete absence of spermatogenic epithelium or with the presence of gaps and cells with large nondivided nuclei in the epithelium. The results showed that the hooded coat-color mutation exerts a pleiotropic effect on male fertility in rat.