INVESTIGATION OF NUMBERS AND MOTILITY OF SPERMATOZOA IN REPRODUCTIVELY ACTIVE AND SOCIALLY SUPPRESSED MALES OF 2 EUSOCIAL AFRICAN MOLE-RATS, THE NAKED MOLE-RAT (HETEROCEPHALUS-GLABER) AND THE DAMARALAND MOLE-RAT (CRYPTOMYS DAMARENSIS)

Reproductive tracts and spermatozoa from reproductively active and rep roductively suppressed non-breeding males from two species of eusocial African mole-rats Cryptomys damarensis and Heterocephalus glaber were examined. In two captive colonies of Heterocephalus glaber, reproduct ive tracts from seven non-breeding males removed from their colonies, and housed singly for 5-6 weeks to cause reproductive activation, were compared with reproductive tracts from seven non-breeding males. The body weight of the separated, reproductively active males increased si gnificantly (P < 0.01), and the mean testis weights relative to body w eight of the reproductively active males were significantly larger (P < 0.05) than those of non-breeding males. The number of spermatozoa, i n one half of the reproductive tract, was higher in active males than in non-breeding males (mean +/- SEM: 8.59 x 10(6) +/- 2.69 x 10(6) ver sus 1.78 x 10(6) +/- 1.43 x 10(6), respectively; P < 0.05). In additio n, six of the seven reproductively active males, but only two of seven non-breeding males, had motile spermatozoa. A total of 28 wild Crypto mys damarensis from two colonies were examined in the field. The testi s weights relative to body weight of breeding males (n = 7) were highe r than those of non-breeding males (n = 19; P < 0.01), but the number of spermatozoa did not differ significantly between the two groups (0. 13 x 10(6) +/- 0.06 x 10(6), n = 7 versus 0.29 x 10(6) +/- 0.14 x 10(6 ), n = 21, respectively). Breeding and non-breeding males produced sim ilar numbers of motile spermatozoa. These results suggest that sociall y induced reproductive suppression of males differs in these two speci es of African mole-rats.