SELECTIVE EGESTION OF LYSINE BY LOCUSTS FED NUTRITIONALLY UNBALANCED FOODS

The quantitative profile of amino acids egested by fifth-stadium Locusta migratoria fed artificial food differing in protein and carbohydrate content was investigated. Locusts fed foods with high (21%) protein content and low (7%) carbohydrate content selectively egested a large amount of lysine compared with other amino acids, despite its presence in the food at relatively low levels. Previous work has shown that lysine plays an important role in inhibiting feeding in protein-satiated locusts. It is suggested that this selective removal of lysine by locusts fed foods containing a relative excess of protein may counter the inhibition of feeding, thus enabling them to meet their requirements for other, limiting, nutrients.