Studiesin vivo andin vitro on chitin synthesis during the larval-adult moulting cycle of the migratory locust,Locusta migratoria L.

Abstract

1. Chitin synthesis inLocusta migratoria has been examined by following the incorporation of labelled N-acetylglucosamine into chitin at different stages of the larvaladult moulting cycle from 4 days before to 8 days after ecdysis. With glucose high incorporation rates were measured only during the first 2 days after ecdysis. Acetylglucosamine was incorporated intensively before this period (5 to 7 times higher than glucose). After ecdysis the rate of aminosugar incorporation increases rapidly up to the level of maximum incorporation of glucose and remains at this level for one week. 2. During the days prior to imaginal ecdysis the precursors for chitin synthesis originate almost exclusively from the decomposition of the chitin of the larval cuticle. 3. A few minutes after injection of labelled glucose, acetylglucosamine, or UDP-acetylglucosamine into 24 hour adult locusts, radioactivity is detectable in all chitin precursors. These compounds are found mainly in the integument and in the hemolymph, and to a lesser extent also in the fat body. 4. Preparations of the abdominal integument incorporate chitin precursorsin vitro; under these conditions glucose is the preferred precursor.