Reproductive cycle of the Neotropical Crotalus durissus terrificus II Establishment and maintenance of the uterine muscular twisting, a strategy for long-term sperm storage

ABSTRACT

Crotaline snakes store sperm by means of a uterine musculature twisting (UMT). We investigated the inXuence of plasma levels ofestradiol and progesterone and vasotocinase cystine aminopeptidase (CAP) activity on UMT formation and maintenance, and the invitro uterine reactivity for AVT in Crotalus durissus terriWcus in primary or secondary vitellogenesis with or without UMT. Frequencyof females in secondary vitellogenesis with UMT is signiWcantly higher than in primary one. Estradiol levels did not vary inall conditions studied, however, signiWcantly low levels of progesterone were found in snakes in secondary vitellogenesis with UMTcompared to those without it. UMT is always observed when high levels of estradiol and low levels of progesterone are detected.CAP activity did not change in the presence of UMT. AVT produced concentration–response contractions of the isolated uterus ofsnakes in all stages analysed and the pD2 value and maximum contractile response were signiWcantly higher in primary vitellogenesiswithout UMT than in other reproductive conditions, indicating that uterus of those snakes presents a higher contractile capacitywhich may favour UMT establishment. In conclusion, we show a relationship of UMT and estradiol/progesterone balance and apossible participation of AVT in UMT formation and maintenance in the Neotropical rattlesnake.