Reproduction in the male Cape fur seal Arctocephalus pusillus pusillus: age at puberty and annual cycle of the testis

Abstract

Seasonal changes in the reproductive anatomy and histology of the male Cape fur seal Arctocephalus pusillus pusillus were examined. Studies were based on 99 specimens collected between Algoa Bay on the south-east coast of South Africa, and Cape Frio, Namibia, during 1974 to 1990. Reproductive organs are briefly described. The presence of sperm in the seminiferous and epididymal tubules indicates that males attain puberty between 3 and 4 years of age. Quantitative measurements of testis weight, testis volume, and the diameter of the seminiferous and epididymal tubules were analysed on a monthly basis and spermatogenesis documented. Although some males may remain in breeding condition until March, the absence of spermatozoa in the epididymis during February to June, when mean testis mass and mean tubule diameter reached a minimum, clearly showed reproductive quiescence following the rut. Four stages of spermatogenesis were observed: (1) inactive (February/March–June); (2) early spermatogenesis (July); (3) late spermatogenesis (July/August–December/January); and (4) epithelial regression (February–June). Individual variation between males, possibly differences in social status and body condition, may influence the duration of spermatogenesis, hence the overlap in duration between epithelial regression and inactivity. It appears that photoperiod may act as an obligatory proximate factor initiating spermatogenesis 3–4 months before the relatively short breeding season from November to December.