Seasonal reproduction and sexual maturity in Odontocymbiola magellanica (Neogastropoda, Volutidae)

Abstract. Members of Odontocymbiola magellanica (Volutidae, Odontocymbiolinae) inhabit Argentinean waters from 35°S to the Magallanes Strait. The reproductive biology of this potential fishery resource has not been studied before. Male individuals reach maturity at 80 mm and females at 90 mm, corresponding to ～7 and 8 years of age, respectively. Mating was observed in the field in all seasons and females possess live spermatozoa in the bursa copulatrix all year round, suggesting that living sperm can be preserved for several months. Major oviposition events occurred July (winter) to December (summer) during the 5 years sampled, as characterized by aggregation of females coincident with increasing photoperiod from winter to summer solstices, and not, apparently, by increase in water temperature. Males showed gametogenic activity throughout the year. Gamete resorption occurred in both sexes. Ultrastructural studies showed that oocytes are attached to companion cells, which enables cell–cell communication and provides support until evacuation; males showed normal sperm cells and two types of parasperms. If populations of O. magellanica are commercially exploited in the future, we propose a minimum catch size of 100 mm, and a ban on the collection of females and egg capsules during the reproductive season.