How Does the Mantis Shrimp Break Glass Without Hurting Itself?
The Harlequin Mantis Shrimp (Odontodactylus scyllarus) typically uses its dactyl clubs to smash shellfish until it gets to the good stuff—soft tissue it can eat. (Check out this video of the clubs in action.) But sometimes, the 7-inch-long shrimp wields its clubs to TKO a tougher foe: aquarium glass. It’s no surprise that it’s possible; this shrimp packs a punch that accelerates to 50mph and delivers almost 160 pounds of instantaneous force. But scientists have long been baffled by how the shrimp can smash glass without doing severe damage to its clubs.
The answer lies in the clubs’ structure and composition, which makes them tougher than the strongest synthetic materials. Researchers analyzed the shrimp’s weapons of blunt force destruction using a slew of high-tech tests and found that the outer layer of the club is made of hydroxyapatite, a very hard crystalline calcium-phosphate ceramic material.
On its own, this material would likely fracture on impact. But underneath that hard surface are layers of polysaccharide chitosan, a much more elastic material. Each layer is parallel to the surface, and each is offset from the preceding layer by a slight angle. Because of this structure, cracks would have to continually change direction to propagate, which is what makes damage to the club unlikely. This area also reflects the force of impact back to the creature being struck, further reducing the risk of fracture. (If the shrimp’s club were a car, this region would be its shock absorbers.)
Chitosan fibers at the club’s edges hold it together during these high velocity impacts. The clubs are so tough that scientists are exploring how this type of structure could eventually be used to create better body armor.
Its powerful punch isn’t the only thing extraordinary about the Harlequin Mantis Shrimp. According to a study by the University of Bristol, the creatures, which have the most complex vision system currently known to science, can see 12 colors (humans see only three) and circular polarized light. Scientists plan to use what they’ve learned from its extraordinary vision to improve DVDs.
If you’re thinking about keeping a Mantis shrimp as a pet, do your research: Experts recommend keeping it in an acrylic aquarium separate from your community tank (putting one of these guys in a populated aquarium is like letting Kobayashi loose in a Nathan’s Hot Dog stand). Make sure to include plenty of nooks, crannies and caves that the shrimp can hide in.