The reproductive cycle of the male tuatara, Sphenodon punctatus, on Stephens Island, New Zealand

Abstract

Abstract The reproductive cycle of male Sphenodon punctatus is characterised by continuous sexual activity. Spermatocytogenesis is uninterrupted, though abnormal in some cells, and probably very slow in winter. Spermiogenesis is normal from mid spring to mid summer, then becomes abortive and finally ceases during the 5 or 6 coolest months. The epididymal duct, which is hypertrophied during the mating period in summer, remains partly developed during the rest of the year. The kidney has no sexual segment. Many spermatozoa are present throughout the year in the deferent ducts of males, but their number gradually decreases in winter and at the beginning of spring. The reproductive cycle of the male tuatara is similar, but not identical, to that of the few New Zealand lizards that have been studied, but differs markedly from all types of cycles, known in reptiles, from other parts of the world.