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INCORPORATION OF 14C-GLUCOSE IN THE POLYSACCHARIDES OF VARIOUS BODY PARTS OF THE POND SNAIL LYMNAEA STAGNALIS AS AFFECTED BY STARVATION by J. P. VELDHUIJZEN and GREET E. DOGTEROM (Departmentof Biology,Free University,Amsterdam, The Netherlands) SUMMARY 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 Lymnaeastagnalis 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). 248 INTRODUCTION In a study on the dynamics of the haemolymph-glucose of the pul- monate pond snail Lymnaea stagnalis it was found that injected glucose was removed at a lower rate from the haemolymph of starved than of fed snails (VELDHUIJZEN, 1975b). It was demonstrated also that injected glucose is removed faster from the haemolymph of snails kept at higher temperatures than could be expected from the results ob- tained at lower temperatures. It was concluded that in starved snails as well as in snails kept at low temperatures, the stop of oviposition and growth possibly is the main cause of the lower rate of the removal of glucose from the haemolymph. This suggestion is corroborated by the fact that the haemolymph-glucose content of starved snails shows a rapid increase after the restart of feeding (VELDHUIJZEN, 1975a). This high value decreases to the control value when egg mass production starts again. Growth will be probably of little importance in the removal of glucose from the haemolymph as in protein synthesis primarily amino acids are involved. However, it can be expected that some glucose will be converted to amino acids. Processes in the ovotestis, such as the development of oocytes in which protein synthesis dominates, will be probably also of minor importance. It is likely that the processes related to oviposition are most important: the female accessory sex organs contain large amounts of galactogen and also glycogen and acid mucopolysaccharides are found (GOUDSMIT, 1972; DE JONG- BRINK, 1973; PLESCH et al., 1971) Galactogen is synthesized exclusively in one of the female accessory sex organs, the albumen gland (GouD- SMIT & ASHWELL, 1965) and is deposited in the eggs where it is a major component of the perivitelline fluid. Smaller quantities of polysaccharides are present in almost all body parts. Glycogen is found in particularly large amounts in the vesicular connective tissue cells (VCTC) (SMINIA, 1972; MEULEMAN, 1972; DE JONG-BRINK, 1973). These cells are found throughout the body and are abundant in the mantle and between the lobes of the digestive gland and the ovotestis. In most pulmonate snails glycogen seems to serve as the main reserve material (voN BRAND et al., 1957; EMERSON, 1967; VELDHUIJZEN & VAN BEEK, unpublished). To investigate the removal of glucose from the haemolymph in more detail, the incorporation of label in polysaccharides by the various body parts ofL. stagnalis was studied after the injection of 14C-glucose in the haemocoel. Experiment I was performed to study whether the ti-value for the injected label equals that found in similar experiments with non- labelled glucose. It was also studied at what time after the injection .

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