HEMOLYMPH AMINO-ACID AND SUGAR LEVELS IN LOCUSTS FED NUTRITIONALLY UNBALANCED DIETS

Aspects of pre- and post-ingestive compensation were investigated in l ocusts (Locusta migratoria) fed nutritionally unbalanced artificial di ets containing 7% protein and 21% digestible carbohydrate (7:21) or 21 % protein and 7% digestible carbohydrate (21:7). Feeding behaviour and haemolymph levels of amino acids and sugars were measured in locusts fed ad libitum on these diets. Locusts fed the high-protein diet had c hronically elevated haemolymph levels of 15 out of 19 amino acids meas ured compared to locusts fed the low protein diet. However, haemolymph levels of lysine, alanine, aspartic acid and glutamic did not differ between diets, suggesting some specific regulatory mechanism for these amino acids. Haemolymph glucose and trehalose reflected levels of car bohydrate in the diets, being high in insects fed diet 7:21 relative t o those given diet 21:7. These data are discussed in relation to the p hysiological and behavioural bases of nutritional homeostasis.