The reproductive cycle of the ‘blunt’ sea urchin

Abstract

The reproductive cycle of the blunt sea urchin, Sphaerechinus granularis (Lamarck), was studied in the Bay of Brest, West Brittany, from monthly samples by examining seasonal changes in gonadal index, in the stages of gonad development and in oocyte diameters. This echinoid exhibited an annual cycle of gonadal growth, with a short breeding season occurring in May and June, and a decrease in gonadal index during the winter attributed to the use of nutrient resources. Histological examinations defined long mature stages during autumn, winter and early spring, where the vitellogenic oocytes accumulated in the lumen of the gonad. Changes in oocyte diameters showed a short pre-spawning period in April and May. The brief breeding season was followed by rapid post-spawning recovery and gonad growing stages during the summer, where the gonads mainly grew through the development of nutritive tissue. The features of this reproductive cycle show that the species can be commercially exploited and these results are used to make recommendations in terms of the management of S. granularis fisheries in Brittany. The influence of temperature on the initiation of spawning was noted again. This exogenous factor could be monitored to improve gonad production and availability of mature gametes in mariculture projects. © Rapid Science Ltd. 1998