Incidence of testicular lesions in a population of tree shrews (Tupaia belangeri)

Background and Purpose: The sexual activity of male tree shrews is socially influenced; therefore, the testicular lesions in adult male tree shrews we re of interest. Methods: The testes of 229 adult and 9 subadult male tree shrews were obtai ned during routine necropsy and were subjected to light microscopy, At one time, 138 animals were experimentally exposed to social conflicts. Results: Hypospermatogenesis (testicular inactivity) was observed in social stress-exposed males up to two years of age. Seasonality of hypospermatoge nesis could not be statistically supported. Testicular atrophy, observed in 21 animals, was neither stress- nor age-related; it developed unilaterally , with the left testis preferred. Testicular tumors developed in animals ol der than 2 years, with increasing frequency particularly of Leydig cell tum ors in animals more than fours year old. Conclusion: Testicular lesions were more frequently found in male tree shre ws than they were observed in nonhuman primates kept at the German Primate Center. Connections to social stress were statistically supported, particul arly with respect to hypospermatogenesis. Testicular tumors, in contrast, w ere distinctly age related.