The relationships between somatic growth, ovarian growth, and feeding activity in the adult desert locust

Abstract

During the first 10 days of adult life the dry weight of the female desert locust increases by 112 per cent. This increase is largely due to growth of cuticle and flight muscles and an increase in the content of the haemolymph. During this period of somatic growth, protein, lipid, and carbohydrate accumulate in the fat body and proteins accumulate in the haemolymph. Ovarian growth only begins towards the end of somatic growth. During the time when the proximal oöcytes increase in length from 2·0 mm to 5·0 mm a relatively small proportion of protein, lipid, and carbohydrate is deposited in the oöcytes, and materials continue to accumulate in the fat body and haemolymph. During the second half of oöcyte development, when the proximal oöcytes increase in length from 5·0 to 8·0 mm, considerable quantities of protein, lipid, and carbohydrate are deposited in the oöcytes, and the contents of the fat body and haemolymph decline. These measurements of the protein content of somatic and ovarian tissues enable estimates to be made of the amount of protein synthesized during somatic and ovarian growth. Both processes require the provision of large quantities of protein, and it is concluded that these metabolic demands make the two processes of growth antagonistic. Measurements of food intake confirm previous estimates of feeding activity measured by faeces collection. The initial period of intense feeding is largely the result of the selection of bran and coincides with the period of somatic growth. The succeeding lower cyclic feeding pattern is associated with oöcyte development. If bran is omitted from the diet, the consumption of lettuce increases but not enough to provide the same quantity of protein, and consequently growth is slowed down; over several weeks, however, locusts fed on lettuce only ingest the same quantity of protein as do locusts fed on lettuce and bran, but in doing so they ingest twice the quantity of water. It is suggested that water loading might be a limiting factor in feeding activity.