The Influence of Starvation and of Increased Carbohydrate Intake On the Polysaccharide Content of Various Body Parts of the Pond Snail Lymnaea Stagnalis

Abstract

In the present study the haemolymph-glucose concentration, the tissue wet weights and the amount of polysaccharides in the various body parts of the pond snail Lymnaea stagnalis were determined after feeding lettuce ad libitum, and after various periods of starvation or of feeding on a carbohydrate rich diet (Bemax). During starvation the haemolymph-glucose concentration remained rather constant, at the same level as in lettuce fed snails (about 15 µg/ml). Feeding Bemax caused a significant increase in the glucose concentration (3-4 fold). Tissue wet weights decreased significantly during starvation (by about 40%) but did not change in snails fed Bemax. The total amount of polysaccharides of all body parts together was about 25 mg in lettuce fed snails. During 15 days of starvation this value decreased till about 9 mg (-65%), whereas after feeding Bemax during the same period this value increased till about 51 mg (+ 100%). This suggests that the metabolism ofL. stagnalis is carbohydrate orientated. Of the various body parts the mantle, the digestive gland/ovotestis and the muscle fraction are very important both in the mobilization (83% of the total amount lost) and in the storage of polysaccharides (84% of the total amount stored). The storage function of the mantle and also of the digestive gland/ovotestis is mainly due to the glycogen storing properties of the vesicular connective tissue cells (VCTC). In the muscle fraction, the muscle cells will be important in the storage. The other body parts (female accessory sex organs, prostate gland and rest fraction) are of little importance in the mobilization and the storage of polysaccharides. It is noted that the polysaccharide content of the female organs is not indicative for their synthetic activity, as at the end of the experiment the synthesis of galactogen will be doubled in Bemax fed snails, due to the doubled amount of eggs produced. It is suggested that the increase in the haemolymph-glucose of Bemax fed snails stimulated the synthesis of polysaccharides (glycogen and galactogen). After saturation of the main storage centres (VCTC and muscle cells) an equilibrium is reached between the influx of dietary glucose and the loss of polysaccharides via the female reproductive system. The stimulation of the polysaccharide synthesis may be either directly or via hormone producing organs.