Mantis Shrimp Mate Selection

Originally posted to reddit:

Mantis shrimp produce multi-bubble cavitation sheets when they strike prey with their hammer claws. With a shelled organism, you’re just trying to get over the elastic-inelastic threshold because once a shell is cracked it loses structural integrity. Cavitation, especially when the boundaries of adjacent bubbles interact mid-expansion, can redistribute force that was initially applied over the length of time the bubbles take to expand. A sheet of cavitation bubbles can produce a very powerful shockwave orthogonal to its surface.

The shrimp’s hammer strike would just be an asymmetrical bump of impulse if not for the cavitation phenomenon. Instead, you get a bump with a little divot taken out of the left side (that’s the force required to expand the cavitation bubbles) and a skinny sharp spike on the right side (that’s the shockwave from the collapsing bubbles) that has roughly the same area as the divot.

Cavitation produces sonoluminescence, which is a quantum phenomenon. Some people will tell you that it’s actually just plasma or something “like totally classical.” Those people are stuck in the 90s. The spectrum produced by cavitation is discrete and changes based on the pressure, temperature, solutes, and the overall geometry of the multibubble system. It probably has something to do with the surface at the last stages of collapse resembling distinct quantum states that only emit specific photon energies due to symmetry conditions or somesuch.

Anyhoo, mantis shrimp are monogamous and have ~16 cone cells. No other animal (known) has that many. They can also see circularly polarized light. I noticed this and wanted to write a paper proposing that mantis shrimp employ mate selection tactics that perpetually “tune” their hammer claw geometry to successfully cavitate. This coupling might be necessary for survival considering how easy it is to disrupt a cavitation sheet. You just need to have a shell surface that is locally uneven. This might partly explain why the shells of marine life often have very basic fractal patterns on their surface:



Edit: Here be an update.