Molecular composition of the wall of insect olfactory sensilla - the chitin question

Identification of chitin in sensory hairs of olfactory sensilla of silkmoths was performed using two independent methods. Firstly, ultrathin sections were labelled with gold-conjugated wheat germ agglutinin and showed positive labelling in the cuticule of sensilla as well as in the antennal cuticle. Secondly, isolated sensory hairs and body scales were subjected to analytical pyrolysis in combination with gas chromatography and mass spectrometry. Chromatograms of both sensory hairs and scales, included several pyrolysis products, which unequivocally demonstrate the contribution of chitinous moieties to the chemical composition of both types of cuticle. This study supports the notion that even the very thin cuticle of olfactory sensilla is composed of both an epi- and a true exocuticle. The carbohydrate components of the latter cuticle most probably are responsible for the extremely high resilience and breaking limit of these delicate structures. (C) 1999 Elsevier Science Ltd. All rights reserved.