Interspecies comparison of the mechanical properties and biochemical composition of byssal threads.

Several bivalve species produce byssus threads to provide attachment to substrates, with mechanical properties highly variable among species. Here, we examined the distal section of byssal threads produced by a range of bivalve species (, , , , , , , and ) collected from different nearshore environments. Morphological and mechanical properties were measured, and biochemical analyses were performed. Multivariate redundancy analyses on mechanical properties revealed that byssal threads of , and have very distinct mechanical behaviours compared with the remaining species. Extensibility, strength and force were the main variables separating these species groups, which were highest for and lowest for Furthermore, the analysis of the amino acid composition revealed that and threads are significantly different from the other species, suggesting a different underlying structural strategy. Determination of metal contents showed that the individual concentration of inorganic elements varies, but that the dominant elements are conserved between species. Altogether, this bivalve species comparison suggests some molecular bases for the biomechanical characteristics of byssal fibres that may reflect phylogenetic limitations.