Feeding activity, respiration, and lipid and carbohydrate content of the male desert locust during adult development

Abstract

Somatic growth in the male is completed during the first 8 days after the final ecdysis. In this period the dry weight of the insect increases by 80 per cent. The materials for growth are obtained during a period of intensive feeding which occurs during the first 4 days after emergence. Analysis of the carbohydrate, lipid, and protein content of the diet and faecal pellets show that the insect ingests sufficient protein to meet its growth requirements. The carbohydrate content of the haemolymph and fat body increases during the period of intensive feeding, but the lipid content of the haemolymph and also of the flight muscle remains low and constant. Only a third of the lipid ingested during this period is stored in the fat body, the remainder is oxidized to provide energy for growth. Between 6 and 8 days after emergence the insect synthesizes lipid from dietary carbohydrate and this is stored in the fat body. Analysis of the fat body lipid shows that the major storage component is triglyceride. Only small amounts of monoglyceride, diglyceride, and free fatty acid are present. A small amount of phospholipid is also present and is probably mainly structural lipid. After maturation the insect utilizes its reserves of lipid through adult life. Studies on the respiration of the whole insect and its tissues show that although the respiration of the whole insect is constant there are changes during development of the individual tissues. Respiratory quotients derived from these figures suggest that the fat body oxidizes lipid throughout development whilst the flight muscle oxidizes a mixture of carbohydrate and lipid at all stages of development. Changes in the diameter of the corpus allatum during development were also measured in an attempt to define the particular stage of development at which the gland secretes the hormone.