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We examined the histology of testes of 134 capybaras (Hydrochoerus hydrochaeris) and the relationship among mass of testes, body mass, and the ratio of seminiferous tubules to interstitial tissue. The capybara had a low gonadosomatic index (0.14% of body weight, epididymides included) and one of the highest known proportion of nonspermatogenic tissue (72% interstitial tissue) among mammals. Seminiferous tubules in testes of capybaras developed earlier than interstitial tissue. Older adults had testes with larger volumes of interstitial tissue and narrower diameters of seminiferous tubules than younger adults.

Original publication




Journal article


Journal of Mammalogy

Publication Date





1096 - 1100