The moulting fluid of silkmoths contains numerous proteins, mostly in the range of 20,000 to 70,000 molecular weight. Only a fraction of these proteins have known enzymatic activity. Approximately ten bands are resolved by polyacrylamide disk gel electrophoresis. The moulting fluid is a distinct secretion differing from blood in almost every parameter studied: pH, visible absorption spectrum, protein content, enzymatic activities, and protein electrophoretograms; the u.v. spectrum and possibly the electrophoretic mobilities of a few proteins are similar in blood and fluid. Proteolytic activity appears in the moulting fluid at the beginning of the last week of the pharate adult stage (on day 12 of adult development in Antheraea polyphemus) and shows a time-activity profile that correlates well with the rate of digestion of pupal endocuticle. By contrast, general esterases of moulting fluid show a relatively constant level of activity. As adult development proceeds, the fluid becomes enriched in dialysable components. Endocuticle digestion was studied in vivo and in vitro. The amount of proteinase in moulting fluid (ca. 9 μg trypsin equivalents in 150 μl, less than 1% of the total protein) is consistent with the quantity of protein in the pupal endocuticle (ca. 85 mg) and the period of time (2-4 days) required for full digestion in vivo.
ASJC Scopus subject areas
- Insect Science