Seasonal changes of testicular parameters in southern pudu Pudu puda in relationship to circannual variation of its reproductive hormones

Seasonal variation of testicular and epididymal parameters in the smallest deer, the southern pudu Pudu puda Molina, 1782 were related to the circannual fluctuation of plasma levels of its reproductive hormones. The diameter and the length of testes, the diameter of epididymis as well as the diameter and the heights of epithelium of seminiferous and epididymal tubules were measured. Morphological evaluation of spermatogenesis were performed on histological sections of testicular and epididymal tissues. Most of these gonadal parameters exhibit a seasonal variation which is in accordance with the reproductive pattern as well as the variation of reproductive hormones. Seasonal fluctuations of LH and testosterone indicate two seasonal activations of the reproductive system, one in the spring (antler mineralization), the other in the fall (rut). FSH exhibit one prolonged peak (summer to fall) whereas prolactin follows the expected, photoperiodically-dependant time course with peak levels around the summer solstice. The measurements of testicular parameters indicate a prolonged period of gonadal activity in southern pudu but the period of maximal reproductive stimulation is limited to the time around the rut.