Testicular response to melatonin or suprachiasmatic nuclei ablation in the spotted skunk

Abstract

Testes of the Western spotted skunk enlarge and regress seasonally. The pineal hormone, melatonin, may be important in timing this seasonal reproductive activity. Likewise, the suprachiasmatic nuclei (SCN) have been implicated as possible neural regulators of pineal and reproductive events. These experiments were conducted to determine whether ablation of the SCN or constant administration of melatonin alters timing of the seasonal pattern of testicular regression and recrudescence. Male skunks (n = 24) were treated as follows: six received two empty Silastic capsules, six received two melatonin-filled Silastic capsules, six received sham lesions to the SCN, and six received lesions to the SCN (SCNx). All skunks were exposed to a natural photoperiod and had regressed testes at the onset of the experiment. Four of six males from the SCNx group had an average of 94 +/- 11.3% of these nuclei destroyed. Sham SCNx, animals with less than 40% of the SCN ablated, and males with empty capsules did not have fully enlarged testes until October. SCNx and melatonin-treated skunks exhibited a hastening of testicular recrudescence with maximal testis size being reached in June. Skunks with lesions to the SCN maintained enlarged testes for 5 months while all other groups exhibited rapid regression after attaining maximal testis size. Testicular regression occurred from July through October in animals receiving continuous melatonin, while controls exhibited recrudescence during this same period. Our data suggest that the SCN, melatonin, and thus the pineal gland, play a role in regulating the seasonal testicular cycle of the spotted skunk.

Influence of season on seminal characteristics, testis size and serum testosterone in the western spotted skunk (Spilogale gracilis)

“…Testicular function in western spotted skunks exhibits seasonal variation. The seasonal changes in testis size reported in this study agree with previous results in this species (Mead, 1968a;Berria et al, 1990), the greatest testis size being observed during the autumn breeding season. The peak in mean testis size was approximately twice the basal size.…”

“…The western spotted skunk, Spilogale gracilis, is a seasonally breeding mammal; the testes reach maximal weight and most copulations occur in late September and early October (Mead, 1968a). Testicular recrudescence occurs from July to October in skunks maintained on a natural photoperiod (Berria et al, 1990) and the pineal gland is considered to be involved in entraining this testicular cycle. Other attributes of the male reproduc¬ tive cycle, such as seminal characteristics and testosterone concentrations, have not been reported for this species. Electroejaculation has been used successfully to obtain semen from a few mustelid carnivores including domestic ferrets, Mustek putorius (Shump et al, 1976;Atherton et al, 1989;Wildt et al, 1989), black-footed ferrets, Mustela nigripes (Kitchin et al, 1988; Curry et al, 1989), and mink, Mustek vison (Aulerich et al, 1972).…”