The Mantis Shrimp Saddle: A Biological Spring Combining Stiffness and Flexibility

Abstract

Stomatopods are aggressive crustacean predators that use a pair of ultrafast raptorial appendages to strike on prey. This swift movement is driven by a power amplification system comprising components that must be able to repetitively store and release a high amount of elastic energy. An essential component of this system is the saddle structure, in which the elastic energy is stored by bending prior to striking. Here, a comprehensive study that sheds light on the microstructural and chemical designs of the stomatopod's saddle is conducted. MicroCT scans combined with electron microscopy imaging, elemental mapping, high‐resolution confocal Raman microscopy, and nanomechanical mapping show that the saddle is a bilayer structure with sharp changes in chemical composition and mechanical properties between the layers. The outer layer is heavily mineralized whereas the inner layer contains a high content of chitin and proteins, leading to a spatial organization of phases which is optimized for load distribution during saddle bending. The mineralized outer layer sustains compressive stresses, whereas the inner biopolymeric layer provides tensile resistance. These findings reveal that the saddle chemical composition and microstructure have been spatially tuned to generate a stiff, yet flexible structure that is optimized for storage of elastic energy.

Effect of some biological factors on the chitin yield of two crustacean species inhabiting the Egyptian waters

“…Previous studies reported chitin values close to those measured in the present study for the mantis shrimp [20][21][22] and crab [11,20,22] ( Table 3). The variability in content of chitin in shells according to species has been documented [20][21][22].…”

“…Crabs, on the other hand, need a hard, highly mineralized shell in order to hold tightly to the ground and burrow into the sand during any attack. Moreover, mantis shrimps are known as very aggressive predators with high swimming and predation abilities [20]. Accordingly, the shell of E. massavensis is less mineralized and therefore lighter and less hard than that of C. natator, a fact that explains the lower levels of both protein and minerals recorded between these two species in the present study.…”

“…The variability in content of chitin in shells according to species has been documented [20][21][22]. Also, several factors were found to influence chitin values in crustacean shells such as season, nutritional and geographic condition [23,24].…”

A Sinusoidally Architected Helicoidal Biocomposite

“…[10][11][12][13][14] The dactyls of the "smashers", those that feed primarily on hard-shelled prey, (see Figure 1A) takes the form of a bulbous club ( Figure 1B), which is used to smash through mollusk shells, crab exoskeletons, and other tough mineralized structures with tremendous force and speed. [11][12][13][14][15][16] Achieving accelerations over 10,000g and reaching speeds of 23 m/s from rest, the dactyl strike is recognized as one of the fastest and most powerful impacting events observed in Nature. [11,12] The club is capable of delivering and subsequently enduring repetitive impact forces up to 1500 N and cavitation stresses without catastrophically failing, demonstrating its utility as an exceptionally damage-tolerant natural material.…”

Bioinspired designs for shock absorption, based upon nacre and Bouligand structures

“…Some of these models were subsequently modified to incorporate related features, from other, suitable geometries such as Bouligand structures [14,20,[31][32][33][34] and biological sutures [25]. Bouligand structures were mimicked by orienting each layer of nacre mimetic aluminum plates at a slightly different angle in the plane of the lamina, while sutures were created as jigsaw interlocks between adjacent tablets in the same plane (L3, L4).…”