Matrix-mineral relationships in the scallop hinge ligament

Abstract

The scallop hinge ligament has a large central noncalcified core flanked by two thin calcified zones. In the calcified zones the aragonite (CaCO 3 ) crystals are organized into prismatic units similar to those in totally calcified ligaments of other bivalve species. The individual crystals are surrounded by highly osmiophilic sheaths, which are part of a continuous highly branched framework readily distinguishable from the matrix elastomer. The noncalcified region is also composed of structurally distinct organic phases, the matrix elastomer and a continuous highly branched nonmineralized sheet framework which together are organized into structural units resembling the prisms in the calcified zone. It is proposed that the sheet framework is responsible for the nucleation and orientation of the mineral phase, and that a precursor-product relationship exists between the mineralized and nonmineralized frameworks.