High magnification images from N. norvegicus digestive gland for lipid droplets density determination. (A) March sampling. Digestive glands tubule from male with a very low density of lipid droplets (arrow). It was scored as 1 at the semi-quantitative scoring system. (B) May sampling. Digestive glands tubule from female with a low-moderate density of lipid droplets (arrow). It was scored as 2 at the semi-quantitative scoring system. (C) May sampling. Digestive glands tubule from male with a moderate-high density of lipid droplets (arrow). It was scored as 3 at the semi-quantitative scoring system. (D) May sampling. Digestive glands tubule from female with a high-very high density of lipid droplets (arrow). It was scored as 4 at the semi-quantitative scoring system.