Abstract
The desert locust, Schistocerca gregaria (Forskål, 1775) (Orthoptera, Acrididae), may feed in the Sahara desert on Lotus corniculatus (Fabaceae), which is rich in linamarin, a cyanogenic glucoside that is usually toxic for herbivores. The relationship between food consumption and the activity of five isoenzymes in the motor muscles of desert locust was investigated. Nutritional indices were estimated in fifth instar female nymphs. Consumption and assimilation rates on L. corniculatus were significantly lower than those on wheat seedlings (Triticum aestivum) as control plant. The efficiency of ingested (ECI) and digested (ECD) food conversion was significantly lower in the nymphs fed on L. corniculatus than for those fed on wheat seedlings. The relative growth rate (RGR) and relative consumption rate (RCR) for nymphs feeding on L. corniculatus were significantly lower. The development duration of nymphs fed on Lotus was relatively longer than that for those fed on wheat seedlings. Nymphs fed on L. corniculatus lost weight. Electrophoretic assays of five enzymes were assessed in adult females to examine the feeding effect on L. corniculatus and T. aestivum on the isoenzymatic patterns of these enzymes. Considered enzymes were acid phosphatase (Acph), alcohol dehydrogenase (Adh), β-esterase (β-Est), malic enzyme (Mal) and malate dehydrogenase (Mdh). Enzymes were tested in femur and wing muscles of adult females. Feeding on T. aestivum seemed to be more efficient for the activity of the metabolic enzymes (Acph, Mal and Mdh) than feeding on L. corniculatus. Their isoenzymes were relatively more expressed in the case of feeding on T. aestivum. The activity of esterase isoenzymes (β-Est) was higher in the case of feeding on L. corniculatus thus indicating the role of this particular enzyme in detoxifying plant linamarin allelochemicals.