Developmental changes in urea in the haemolymph (determined by a urease-indophenol method) in hybrid strains of the silkworm, Bombyx mori and the effect of starvation in the fifth instar larvae, fed an artificial diet, on urea level in subsequent development

Abstract

1. 1. Developmental changes in urea in the haemolymph in hybrid strains of the silkworm, Bombyx mori were determined by a urease-indophenol method in silkworms fed an artificial diet or fed fresh mulberry leaves. 2. 2. Lower concentrations of urea in the haemolymph compared to our previous results determined by a chemical method (Suraida et al., 1990; Comp. Biochem. Physiol. 97A, 373–379) were observed in the fourth and fifth larval instars, approximately 0.1–0.2 and 0–0.05 mg urea N/ml haemolymph in the silkworms fed an artificial diet and fed fresh mulberry leaves, respectively. 3. 3. Concentrations of urea in the haemolymph in pharate adults, approximately 0.7–0.8 and 0.001 mg urea N/ml haemolymph in the silkworms fed an artificial diet and fed fresh mulberry leaves, were similar to our previous results. 4. 4. Based on evaluation of the assay method, it was concluded that the changes in urea in the haemolymph in a hybrid strain of the silkworm, Bombyx mori in the larval stage was established for the first time in the present study. 5. 5. Starvation from 72 hr after the fourth larval-larval ecdysis in the silkworms fed an artificial diet resulted in a further elevated concentration of urea, approximately 1 mg urea N/ml haemolymph in the pharate adult stage, a 20% increase against non-starved control silkworms.