Seasonal changes in reproductive biology and biochemical composition of the grooved razor shell Solen marginatus (Bivalvia: Solenidae) from Oualidia Lagoon, Morocco

Abstract

The reproductive cycle, condition index and seasonal variation in biochemical composition of the bivalve Solen marginatus were studied from December 2017 to February 2019 at the Oualidia Lagoon in Morocco. The grooved razor shell reproduction was assessed by histological analysis which indicated that the sex ratio did not differ significantly from 1:1. The gametogenesis began in the fall–winter (September–February) with maximum maturation stage in the spring (April 2018). From February to August, the period of sexual activity was marked by the increased water temperature (from 16 to 25 °C), the rise in chlorophyll a (from 0.33 to 1.76 μg/l), and significant variations in condition index. Spawning occurred in spring–summer (March–July 2018), reaching its maximum in May 2018. The summer resorption and resting stages marked the end of the reproductive cycle. Seasonal variations in biochemical composition were studied in relation to reproductive events and environmental conditions. Biochemical analysis showed that proteins and lipids are the dominant components in dry tissue. Their amount increased in association with the gametogenesis. The highest concentration of glycogen detected was during fall and winter seasons when the population was in sexual resting stage.