Reproductive cycle of Bolinus brandaris (Gastropoda: Muricidae) in the Ria Formosa lagoon (southern Portugal)

Abstract

The purple dye murex Bolinus brandaris is a commercially valuable gastropod in Portugal. However, there is a lack of knowledge on the reproductive cycle in Atlantic populations of this species. In this context, the reproductive cycle of B. brandaris from the Ria Formosa lagoon, southern Portugal, was studied using standard histology and light microscopy and the calculation of bio-physiological indices (gonadosomatic indices for both sexes, penial index for males and capsule gland indices for females). Monthly variation in gonad developmental stages and biophysiological indices revealed that B. brandaris has an annual reproductive cycle, long gonadal activity and a relatively short resting phase. Spawning occurred mainly between May and July, with a clear spawning peak from June to July. Gonad maturation and spawning appear to be synchronised with the seasonal variation in seawater temperature. Slight asynchrony between the peak of male gamete release and the peak of female spawning might be interpreted as a modality to increase the reproductive success. The timing of spawning was compared with analogous information available for other regions throughout the species distributional range. The present study provides baseline information for proposing fishery management measures, particularly a closed season in the fishing or harvesting activity during the spawning peak of B. brandaris aimed at protecting the female broodstock and collective spawns. The overall results from the bio-physiological indices (especially the penial index and the area-based gonadosomatic and capsule gland indices) encourage the adoption of similar approaches with other gastropod species, namely in routine analyses that do not require a detailed histological description.