INFLUENCE OF SEASON ON SEMINAL CHARACTERISTICS, TESTIS SIZE AND SERUMTESTOSTERONE IN THE WESTERN SPOTTED SKUNK (SPILOGALE-GRACILIS)

The western spotted skunk is a seasonally breeding mammal: most copula tions occur in late September and early October. This study was perfor med to characterize the seasonal changes in concentrations of testoste rone and in ejaculate quality. Captive males (n = 22) were maintained on a natural photoperiod for 15 months. Semen samples were collected b y electroejaculation; testis size was measured; and blood samples were collected. Of 110 electroejaculation attempts, 104 (95%) resulted in successful fluid collection and 101 (97%) samples contained spermatozo a. Significant increases (P < 0.05) in serum testosterone concentratio n, testis size and ejaculate volume were observed from August to Novem ber. Mean concentration of testosterone in serum ranged from 0.15 +/- 0.05 ng ml-1 in mid-January to 6.42 +/- 1.79 ng ml-1 in early October. Mean testis size ranged from 1.22 +/- 0.25 cm-2 in February to 2.68 /- 0.08 cm2 in October. Mean ejaculate volume ranged from 11 +/- 3 mul in March to 129 +/- 22 mul in October. Seasonal changes in the number of spermatozoa per ejaculate or motility of spermatozoa were not obse rved. Mean number of spermatozoa per ejaculate was 8.14 +/- 0.85 x 10( 6) spermatozoa (n = 97); motility was 56 +/- 2.4% (n = 93); semen pH w as 7.76 +/- 0.20 (n = 6); osmolarity was 3 94 +/- 13 mmol kg-1 (n = 10 ); and 70.3 +/- 1.5% of the spermatozoa were morphologically normal (n = 47). Concentration of testosterone in serum was highly correlated w ith testis size (r = 0.484, P < 0.001, n = 137), but none of the semen characteristics was found to be correlated with either concentration of testosterone in serum or testis size (P > 0.05). These data suggest that concentration of testosterone in serum, testis size and ejaculat e volume increase seasonally as photoperiod decreases.