Alternating Positive and Negative Twist of Polymers in an Invertebrate Integument

Abstract

Here is presented the structure of the organic matrix of the protecting tube secreted by a deep-sea worm. This material shows an extremely original distribution of fibrils, reminiscent of the arrangement of polymers in cholesteric liquids, but it differs from true cholesterics by the twist handedness which is inverted after each 180° rotation. Right-handed layers alternate regularly with left-handed ones. The origin of this particular structure is discussed and, among plausible mechanisms, we consider a cellular control of fibril orientations and the motions of the worm within its tube.