Construction and nanomechanical properties of the exoskeleton of the barnacle, Amphibalanus reticulatus

Barnacles are some of the major inhabitants of intertidal zones and have calcite-based exoskeleton to anchor and armor their tissues. Structural characterization studies of the specie Ambhibalanus reticulatus were performed to understand the construction of the exoskeleton which forms a light-weight yet stiff structure. The parietal shell is constructed of six compartments to yield a truncated cone geometry, which is neatly fixed onto the basal shell that attaches the organism to the substrate surface. The connections among the different compartments happen through sutured edges and also have chemical interlocking to make the junctions impermeable. Also, the shell parts are furnished with hollow channels reducing the overall mass of the construction. The structure and functions of different parts of the exoskeleton are identified and outlined. Finally, the mechanical properties such as modulus, hardness and fracture toughness of the exoskeleton obtained by indentation techniques are discussed.