Calcification of Gastropod Nacre

Abstract

The growth surface of the nacreous layer of archaeogastropod shells (5 genera) were studied by means of transmission and scanning electron microscopy. Aragonite crytals forming the stacks of nacre grow within pre-formed, multi-layered compartments, partitioned with horizontally-arranged organic sheets. The organic sheets contain an electron-dense central core which is not observed in bivalve nacre and is probably composed mainly of a chitinous substance. Perforations similar to those observed in interlamellar matrices are observed in the organic sheets. Growing crystals within the compartments are always surrounded by a thin organic envelope which is thought to be involved in the acceleration of crystal growth.