Incorporation of 14C-Glucose in the Polysaccharides of Various Body Parts of the Pond Snail Lymnaea Stagnalis as Affected By Starvation

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Abstract
In the present study the incorporation of label in the polysaccharides of various body parts of lettuce fed and of starved specimens of laboratory bred Lymnaea stagnalis was studied after the injection of 14C-glucose in the haemocoel. These polysaccharides are mainly glycogen and, in the female organs, also galactogen. The t½-value for the injected label in the haemolymph of lettuce fed snails was larger than found in previous experiments with non-labelled glucose. It is suggested that this is caused by the presence of labelled intermediates in the haemolymph. It is demonstrated that 20 min after the injection of 14C-glucose a maximum amount of label is incorporated in the tissues (in the total polysaccharides 28-32% of the amount of label removed from the haemolymph is recovered). Of the various body parts, the female accessory sex organs are most important in incorporating the label in polysaccharides (60-83% of the amount incorporated). In the prostate gland the lowest amount is incorporated. Of the other body parts, the muscle fraction is important, followed by the mantle and the digestive gland with the embedded ovotestis. In the heterogeneous rest fraction also some label is recovered. This means that the polysaccharide reserves (glycogen-in the mantle and the digestive gland/ovotestis-) of lettuce fed snails do not increase rapidly. After a starvation period of 14 days the total amount of label incorporated in polysaccharides of the body decreased significantly (with about 75%). It is demon- strated that this difference is mainly due to a decreased incorporation oflabel in the female accessory sex organs. In these organs the decrease is about 95%. It is con- cluded that the synthetic processes in the female organs (synthesis of galactogen, and also glycogen) are very important for the dynamics of the haemolymph-glucose. It is also concluded that the cessation of female reproductive activities is mainly responsible for the difference in the amount of 14C-glucose removed from the haemolymph of fed and of starved snails. The incorporation of label in the poly- saccharides of the female accessory sex organs decreased also when expressed per mg tissue wet weight, whereas it did not change significantly in the other body parts (the muscle fraction excluded). It is concluded that after a starvation period the polysaccharide synthesizing system in the female accessory sex organs is considerably inactivated, whereas this system in the other body parts is not much affected. Therefore, it is suggested that distinct regulatory mechanisms are operative for the control of the synthesis of polysaccharides in the female organs (mainly galactogen) and for the synthesis of polysaccharides in the other body parts (mainly glycogen).

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