Seasonal cycles in and effects of starvation on egg development in Mytilus edulis

Abstract

Histological and quantitative cytochemical methods were used to investigate seasonal cycles in, and effects of starvation on, reproduction throughout the gametogenic cycle. Amount and composition of egg cytoplasm in ripe oocytes was found to be variable throughout the season. There was an overall decline in amount of egg cytoplasm as the gametogenic cycle progressed. Eggs developing early in the season had high glycogen levels but low lipid levels; protein levels remained constant from December to May but then declined. Results of experiments showed that during the first half of the gametogenic cycle starvation resulted in an increase in production of ripe oocytes. There was also an increase in volume of egg reserves on starvation but glycogen and protein levels declined. Timing of the gametogenic cycle was delayed by starvation. There was variability in the activities of hydrolytic enzymes throughout the gametogenic cycle; however, starvation did not significantly affect levels of activity.