Exploring chitin morphologies in cuticle fragments of Xiphopenaeus kroyeriby atomic force microscopy

Shells of Xiphopenaeus kroyerishrimp were submitted to mild acid and alkali ne treatments to produce alpha chitin films, which were characterised by in frared spectroscopy. Dynamic AC operational mode atomic force microscopy (A FM) was used to image the external surface and regions of an inner surface of the cuticle. All samples were scanned in air. No modification of the sur face structure was observed even while scanning for a long time. Chitin was visualised as microfibrils of varying thicknesses and shapes. Bundles of c racked microfibrils, as well as nearly straight microfibrils occur in the e xocuticle. Scanning of an inner region clearly disclosed a bundle of microf ibrils in helicoidal pattern. Non-straight microfibrils were visualised in the rostrum, as well as bundles of straight microfibrils. Estimation of the crystals thickness showed that those pertaining to bundles generally have the largest diameters. (C) 2002 Elsevier Science Ltd. All rights reserved.