Amino acid requirements of Schistocerca gregaria (Forskal)

David Colin Williams
The development of a chemically defined artificial diet for Schistocerca gregaria (Forsk.) is described,. The diet that permitted the best growth of S. gregaria was used to determine the amino acid requirements of this animal. Further studies were performed to determine whether amino acids were required as nutrient per se or as phagostimulants. The moist artificial diets initially used in growth trials showed signs of deterioration after 20-days storage at -15°C. This deterioration was
more » ... ration was evidenced by reduced growth of animals on 20-day-old diets, and by the loss of ascorbic acid from such diets. Freeze-or oven-drying diets increased their storage life and their stability under experimental conditions. Growth trials showed that dried diets were stable for at least 2 months when stored in vacuum desiccators. Little ascorbic acid was degraded in diets kept under experimental conditions (30°C, 55% E.H.) for 2 days, suggesting that such diets could be kept under these conditions for at least 2 days without being replaced. S. gregaria showed poor growth on artificial diets containing either an ad hoc mixture of amino acids or a mixture of amino acids based on analysis of lettuce protein. However, growth of animals was improved by using an amino acid mixture based on analysis of cabbage proteins. Diets could be prepared mere rapidly if the vitamin solutions used in compounding the diets were replaced by vitamins triturated in sucrose. The physical properties of the diet were important, and fine-powder diets caused heavy mortality of S. gregaria hoppers.. Powder diets had to be formed into granules or tablets before they could be utilized by S. gregaria. Although few animals reached the adult stage on artificial diets, the best diet did allow S. gregaria hoppers to develop to the 5th instar (with a mean weight of approximately 550 mg) after 33-days growth. To determine which amino acids were essential for S. gregaria, the growth of animals reared on test-diets lacking an individual amino acid was compared with grow [...]
doi:10.14288/1.0094924 fatcat:pz4uz3xd7zbwrbz5hpf6xqqm5u