THE CHEMICAL COMPOSITION AND MECHANICAL PROPERTIES OF THE HINGE LIGAMENT IN BIVALVE MOLLUSCS

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Abstract
The hinge ligaments of 8 spp. of marine bivalve mollusks, Aequipecten irradians (Lamarck), Placopecten magellanicus (Gmelin), Ensis directus (Conrad), Mya arenaria (L.), Spisula solidissima (Dillwyn), Mercenaria mercenaria (L.), Mytilus edulis (L.), and Crassostrea virginica (Gmelin) were investigated. The physical and chemical parameters of the ligment were examined and correlated with strength and resilience. This aspect of functional morphology was related to the life style of the various species. The ligaments tend to have unusual concentrations of glycine; 4 spp. have > 500 glycine residues/1000. Hydroxyproline and hydroxylysine were absent from ligament hydrolyzates, but the S-containing amino acids, methionine and cystine/2, were present. The aragonite phase of CaCO3 was found in 6 spp. A. irradians and P. magellanicus had no detectable inorganic crystalline phase in the ligament. They have the most resilient ligaments of the species examined, but are among the weakest on a per gram of shell basis. M. edulis has the strongest ligament per gram of shell and also one of the most resilient. E. directus and C. virginica have relatively weak abduction systems and low resilience. There is no clear trend relating life style to ligament strength or resilience in the species examined. Resilience is inversely correlated with CaCO3 and cystine/2 concentration. Glycine concentration is directly correlated with resilience. The strength factor (opening moment/gram of shell) is distinct from resilience and does not correlate well with any parameter examined.

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