[Testicular activity in Orychtolagus cuniculus, a wild rabbit from Zembra island (Tunisia), during short days and long days. The effect of pineal gland deafferentation].

Several male wild rabbits from Zembra island were used to determine the effect of the photoperiod and of the cranial sympathectomy on testicular activity. Two groups were used (G1 and G2), including each 4 control rabbits and 5 cranially sympathectomized by removal of the superior cervical ganglia. The G1 animals were reared in natural photoperiod at room temperature; the others (G2) were exposed to alternating three-month periods of short days (8 L-16 D) and long days (16 L-8 D). The changes in the testicular function (testis volume and plasma testosterone levels) were studied during one year. Our data show that: (1) The control animals, reared in natural photoperiod at room temperature, showed a decrease in testicular activity during the winter season (December to February) characterized by short days. However, testis volume and plasma testosterone seemed to be maintained at low levels during the other months of the year. (2) The artificial short days (8 L-16 D) induced an increase of the testis volume and of the plasma testosterone. A significant decrease of these parameters was observed when transferring the animals to long days (16 L-8 D). (3) The deafferentation of the pineal body by bilateral superior cervical gangliectomy blocked the testicular activity either when the animals were maintained in natural photoperiod or transferred from (8 L-16 D) to (16 L-8 D). Thus the testicular activity of wild rabbits from Zembra island is controlled by the photoperiod. Light action on the pineal is carried via the superior cervical sympathetic ganglia.