Seasonal and starvation-induced changes on gonads and lipid reserves of the digestive gland of Nucella lapillus (Caenogastropoda)

Abstract

This study was conceived to evaluate seasonal changes in the lipid reserves of the digestive gland of the carnivorous intertidal caenogastropod Nucella lapillus, using a stereological approach. Volume density of lipid droplets in the digestive gland, digestive gland weight and volume were assessed in animals collected in March, June, September and December on the Portuguese coast. Gonad development was evaluated to detect any relationship between lipid content in the digestive gland and the reproductive cycle. The quantitative light microscopic analysis demonstrates that lipid droplets are a major component of the digestive gland. In males, the digestive gland and its lipid reserves were quite stable without significant variations throughout the year. In females, the percentage of digestive gland volume occupied by lipid droplets was higher in June and December, coinciding with the highest values of digestive gland volume. Due to the conjugation of these two factors, in June and December the total amount of lipids in the digestive gland was substantially increased in females. In both males and females a relationship between the development status of the gonad and the lipid reserves of the digestive gland was not evident. However, significant differences in the digestive gland lipid reserves were detected between males and females in June and December, pointing to a sex related effect on lipid reserves. To evaluate the use of lipid reserves as energy source in N. lapillus, the consumption of digestive gland lipids was followed during a starvation experiment.