Chitin Systems Studied by Electron Diffraction, Diffraction-Contrast Electron Microscopy and Lattice Imaging

Chitin the poly β (1-4)-N Acetyl D glucosamine is widespread in nature and occurs normally as a crystalline fibrillar substance. As opposed to most of the crystalline polysaccharides, chitin is quite resistant to the electron beam. In particular, at room temperature, accumulated doses as high as 200 elec/nm2 at 120 kV can be used to record successful images showing crystalline details. For this reason, chitin can be studied without too much difficulty by electron diffraction (ED), diffraction contrast transmission electron microscopy (DCTEM) and lattice imaging. This study presents some of the diversity of chitin morphology.Several chitin rich specimens were studied. They include : 1) cross sections of an ovipositor from an ichneumon fly Rhyssa persuosaria ; 2) cross sections of fragments of demineralized crab cuticle ; 3) cross sections of a tube from the vestimentiferan worm Tevnia jerichonana ; 4) bundles of chitin microfibrils isolated from Tevnia tube fragments after deproteinization.