The constructional properties of the exoskeleton of homarid, palinurid, and scyllarid lobsters

Lobsters, as members of the Arthropoda, are already endowed with a laminated exoskeleton due to the mineralization of their cuticle. Mineralized laminate structures are found throughout animal phyla and convey, through their multiple surfaces, matrix planes that act as crack-blunting mechanisms. In addition, spiny and slipper lobsters, but not clawed lobsters, add a surface tubercle system that reflects a ventral surface pit system in the carapace. The architecture of these systems coincides with known strategies for crack blunting in composite materials. The division of vertical and horizontal crack blunting systems corresponding to laminate and tubercular systems and pit systems, respectively, may not be so easily separable in a functional sense. Although there is overlap in crack-blunting ability in both systems, separation into horizontal and vertical crack-blunting systems is a convenient way to discuss how skeletons of lobsters resist failure. While laminate structures dissipate forces horizontally in each layer, tubercle and pit systems serve to increase the surface area available to dissipate forces. These systems may represent evolutionary solutions to predation, particularly by predators that strike, crush or bite holes, rather than those that engulf.