Seasonal variation in some reproductive parameters of male vicunña in the high andes of northern chile
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Experiments were undertaken to obtain information on the effects of season on endocrine function and testicular morphology in male vicunña. Serial blood samples were taken every 15 min over 4-8 h in February and August: testes size was measured and testicular biopsies obtained. Plasma testosterone was higher (p < 0·001) in February (6·60 ± 0·35 nmol l-1) than in August (4·45 ± 0·37 nmol l-1). Longitudinal and transverse testes diameters were greater at 3·3 ± 0·22 cm (p < 0·001) and 1·89 ± 0·24 cm (p < 0·003) in February than they were, at 2·64 ± 0·18 cm and 1·50 ± 0·25 cm, in August. Seminiferous tubules had greater diameters in February (163-49 ± 29·64 μm) than in August (137·90 ± 25·15 μm); Leydig cell nuclei diameters were also greater (5·88 ± 0·97 μm vs. 4·19 ± 1·03 μm), both sets of data differing significantly (p < 0·001). February is an active spermatogenic phase and August a regression phase. © 1994 Academic Press Limited.
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