Testicular Hypoplasia Or Atrophy

Abnormally small testes were discovered in three males, one of which (SB 356) was an individual with Stunted Development Syndrome (see Chapter 7). However, two normal-sized adult males (SB 323 and 345) had only a single, normal-sized testis in the scrotum. The contralateral testis was hypoplastic or atrophied (see Chapters 4 and 7). The retained testis was situated adjacent or perhaps within the inguinal canal and could be palpated for measuring. An examination of the pedigree as well as photographic records revealed another male (SB 181, now deceased) also with a single hypoplastic testis.

There was no obvious aetiology to this condition - the only common factor being that SB 181, 323 and 345 had been housed at one time at a single breeding facility. For example, at the time of the Biomedical Survey, SB 323 was a robust 12.5-year-old male and a consistently successful natural breeder. SB 181 (deceased) was the sibling of SB 323's dam, suggesting, perhaps, a heritable, genetic defect, similar to the phenomenon of cryptorchidism observed in other mammals, including in wildlife (Thomas & Howard, 1975; Burton & Ramsey, 1986; Roelke et al., 1993). Curatorial records also curiously indicated that both testes in SB 345 were at one time descended (although one testis was always smaller) with the onset of unilateral testicular atrophy occurring at 7.5 years of age. Until this condition's aetiology is well understood, males from this genotypic line are not recommended for breeding.

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