Sabotage, Implosions, and Regeneration
Alpheus randalli’s Spooky Story

    After reading about Alpheus randalli, you may wonder what is so spooky about this shrimp.  It is so tiny, how could it cause any harm?  Truth is this shrimp can stun its prey, enemies and other organisms with just a snap of its claw!  

    This snap creates a loud crack that can be audible up to one kilometer away.  When large groups of Alpheid shrimp are making the snapping noises, it can interfere with sonar systems, which have caused a lot of investigations ever since World War II.  There have been multiple incidences reported from U.S. submarines.  In 1942, a submarine in the Macassar Straight went through a group of Pistol Shrimp which spooked many sailors on board.  Luitenent Commander W. D. Wilkins said “the Japs may have some newfangled gadget that they drop.”  Thus it is evident that these snapping shrimp of any Alpheus species caused quite a scare during World War II. (Johnson, et. al. 1947)  

    So what allows this tiny creature to pack such a punch?  The major chela, the larger of the two claws, has two parts, the dactylus, the movable finger, and the pollex, the immovable.  The two work together by the dactylus quickly closing onto the pollex.  The dactylus and pollex are normally held open, but when they do close, it happens very very quickly (BBC news 2000).  This is very similar to the hammer of a pistol, hence the name Pistol Shrimp (Spence and Knowlton 2008).  The noise, however, does not come from the claw itself closing.  It comes from the air bubble created after.  When the claw closes, it creates a high velocity jet of water.  Tiny bubbles expand because the pressure of the water around them is lower than the vapor pressure of water due to the high velocity of the water jet.  The pressure quickly comes back up to normal, imploding the bubbles on themselves, which creates the popping noise (BBC news 2000).   As you learned in the Interactions section of this website, Alpheus randalli uses this process to stun its prey and to communicate with other members of its species (BBC news 2000).  

    There is something even more impressive about this process.  The jet of water can reach velocities up to 60 miles per hour, which makes it understandable how this creates a drop in pressure.  When the bubble collapses, the snapping sound that it makes can get up to 218 decibels, which is louder than a jet engine.  If that’s hard to believe, the next part will be even more unbelievable.   This same bubble creates a small flash of light and, for a fraction of a second, the temperatures inside can reach 8000 degrees Fahrenheit (Derbyshire 2008).  This is just under the surface temperature of the sun!  And to think this all comes from a tiny shrimp that can fit in the palm of your hand.  No wonder the goby fish love forming a symbiotic relationship with these shrimp.  

    To see this claw in action, check out this video!

    If this is not crazy enough for you, Pistol Shrimp in the Alpheus genus can regenerate!  This is not quite like bringing Frankenstein back to life, but it is still pretty impressive.  If the shrimp loses or permanently damages its snapping claw, it will grow it back with one minor change.  The smaller claw, or pincer, on the opposite side will grow into the large snapping claw, while the damaged appendage grows a pincer.  This is possible because both sides have the ability to grow into a large snapping claw.  Now you may ask why they both don’t grow into snapping claws.  This is because as one grows into the large snapping claw, it inhibits the other one.  When it is damaged or removed, the inhibiting factor is gone and the pincer grows into the large snapping claw.  The newly grown snapping claw then inhibits the pincer, growing where the last snapping claw was lost, from getting too large.  This could potentially go back and forth infinitely (Read and Govind 1997).
    For more interesting facts, head to the Fun Facts section of the website!