The 34,XY1,der(13) chromosome constitution with loss of Y2 is associated with unilateral testicular hypoplasia in the endangered Indian blackbuck antelope (Antilope cervicapra).

The present study is the first report of unilateral testicular hypoplasia in 3 of 15 (20%) Indian blackbuck antelopes (Antilope cervicapra). Interestingly, the condition was restricted to only the right testis in all cases. Cytogenetic analysis revealed chromosomal aneuploidy in the affected individuals which had a 34,XY(1),der(13) karyotype with loss of the acrocentric (autosomal) Y(2) and an aberrant chromosome 13. We further determined that the semen output and the circulating testosterone levels were markedly low in the males with hypoplastic testes as compared to fertile males.