Uric acid production in larvae of the rice stem borer ( Chilo suppressalis) in relation to post-diapause development

Abstract

Accumulation and distribution of uric acid in larvae of the rice stem borer ( Chilo suppressalis Walker) were studied during diapause in cold storage and subsequent pupal development at 25°C. Uric acid in both diapause and post-diapause larvae increased slightly during cold exposure. A rapid increase of uric acid occurred during post-diapause development to pupation at 25°C (0·5 mg uric acid/g fresh weight per day), but production was slow in diapause larvae even though they were incubated at 25°C. This indicates that uric acid production is associated closely with the metabolic activity of development. All through post-diapause development, a large part of the uric acid was distributed in the fat body and a small part in the integument. Blood did not contain uric acid at any detectable level during cold exposure, and only a trace (maximum level 0·06 mg/ml) was detected after 25°C incubation. Rapid disappearance of injected 1- 14C-glycine and incorporation of radio-activity into uric acid were shown in developing post-diapause larvae, indicating a much higher turnover rate of tissue protein in larvae during post-diapause development than during diapause. Ribosyluric acid (possibly 3-ribonucleoside) occurred in the fat body, increasing its level with pupal development. The ribonucleoside was detected also in the integument but not in the blood. Possible rôles of ribosyluric acid in nitrogen metabolism in this insect are discussed.