Forget
the fish, whales, dolphins, waves, and boats, snapping shrimp are the
main contributors to ambient noise in subtropical seas around the globe.
Their incessant crackling is a result of their abundance, tendency to
aggregate, and a claw that measures half of their body length. (Imagine
having a three-foot long hand.) Despite its appearance, this enlarged
appendage doesn’t have any pugilistic purpose; being used solely as a
clicking device for communication, defence, and prey capture.
But how do they produce this sound? Early researchers logically assumed that the closure of their oversized claws was at the heart of it. But they were very much wrong. And I’m very happy about that since the real explanation is a breathtaking juxtaposition of crustacean and the laws of physics.
Using slow-motion cameras, hydrophones, and the annoying tickle of a paintbrush, Detlef Lohse and his colleagues at the University of Twente, Netherlands, were the first to explore the secret snap of bigclaw snapping shrimp (Alpheus heterochaelis).
The enlarged claw is first cocked open using a series of antagonistic muscles – making their “pistol shrimp” pseudonym very appropriate – that generate a large amount of tension, which, when released by another muscle, results in the claw closing at a speed of 100km/hr. Then, by analysing the recordings frame-by-frame the scientists observed a phenomenon imperceptible to the human eye. As one portion of the claw (pl) is forced into a deep socket (s), like the closure of a garlic crusher, it literally splits water apart, creating an elongated bubble that emanates from the claw’s edge.
But how do they produce this sound? Early researchers logically assumed that the closure of their oversized claws was at the heart of it. But they were very much wrong. And I’m very happy about that since the real explanation is a breathtaking juxtaposition of crustacean and the laws of physics.
Using slow-motion cameras, hydrophones, and the annoying tickle of a paintbrush, Detlef Lohse and his colleagues at the University of Twente, Netherlands, were the first to explore the secret snap of bigclaw snapping shrimp (Alpheus heterochaelis).
The enlarged claw is first cocked open using a series of antagonistic muscles – making their “pistol shrimp” pseudonym very appropriate – that generate a large amount of tension, which, when released by another muscle, results in the claw closing at a speed of 100km/hr. Then, by analysing the recordings frame-by-frame the scientists observed a phenomenon imperceptible to the human eye. As one portion of the claw (pl) is forced into a deep socket (s), like the closure of a garlic crusher, it literally splits water apart, creating an elongated bubble that emanates from the claw’s edge.
The
mechanics of this process take advantage of one feature of oceanic
water: It contains tiny air bubbles known as nuclei. As the claw closes,
the water pressure inside the socket plummets, causing any nuclei
within to rapidly expand. Then, as it this bubble is released from the
socket’s area of negative pressure, the surrounding saltwater has an
inherent tendency to equalize the anomaly in a process known as
cavitation: Rushing back into the space with enough force to produce a
loud bang. That is, the combination of air bubbles, speedy claw closure
and the concomitant reduction in pressure, and process of cavitation
results in the clicking sound of the sea.
This amazing feat of hydrodynamics has multiple functions for the shrimp. For one, the sensory hairs of their neighbours detect the displacement of water resulting from bubble collapse. In other words, they communicate though cavitation. But if any prey item, rival, or curious crab gets too close then they in for a shock. At a distance of around 3mm from the snap of the claw, they are stunned and sometimes even killed by the collapsing bubble; allowing the shrimp to feed on large prey such as worms, fish, and other shrimp.
Subsequent studies in complete darkness have added to our appreciation of this snapping motion. Bursts of light are also produced as a by-product of cavitation and, due to its exceptional nature, the researchers named this phenomenon “shrimpoluminescence”. (And that is probably the best thing you’ll read today.) The multiple flashes once again cannot be seen with the naked eye, but their detection by sensitive photoreceptors indicates that the snap of a snapping shrimp produces temperatures of around five thousand Kelvin. That’s about the same as the surface of the Sun, albeit only for a fraction of a second in an infinitesimal amount of seawater. But still… the Sun!
Similar use of sound to stun enemies is exhibited by one Marvel character in particular. Created in 1967, and named after an Irish ghost, Banshee could induce a state of unconsciousness with a narrowly focused beam of sonic waves. But he is not alone in his superhuman acoustics; Ulysses Klaw, a physicist that eventually transforms into a near-immortal body of sound, possesses a vibranium-powered prosthetic hand that emits high-frequency sound waves for a whole host of purposes. But such fictional noisy hands and high-pitched screaming was created well before the discovery of the snapping shrimp’s phenomenal powers.
Since then, other cartoon designers have been paying attention to studies from the natural world. With a greatly enlarged claw producing water jets potentially 50% more powerful than other water-types, the snapping shrimp has obviously influenced a Pokémon character known as Clauncher (of whom evolves into Clawitser) in the recent generation VI. And the reference to its living inspiration is also encompassed in its Japanese name Udeppou, meaning water gun arm.
This amazing feat of hydrodynamics has multiple functions for the shrimp. For one, the sensory hairs of their neighbours detect the displacement of water resulting from bubble collapse. In other words, they communicate though cavitation. But if any prey item, rival, or curious crab gets too close then they in for a shock. At a distance of around 3mm from the snap of the claw, they are stunned and sometimes even killed by the collapsing bubble; allowing the shrimp to feed on large prey such as worms, fish, and other shrimp.
Subsequent studies in complete darkness have added to our appreciation of this snapping motion. Bursts of light are also produced as a by-product of cavitation and, due to its exceptional nature, the researchers named this phenomenon “shrimpoluminescence”. (And that is probably the best thing you’ll read today.) The multiple flashes once again cannot be seen with the naked eye, but their detection by sensitive photoreceptors indicates that the snap of a snapping shrimp produces temperatures of around five thousand Kelvin. That’s about the same as the surface of the Sun, albeit only for a fraction of a second in an infinitesimal amount of seawater. But still… the Sun!
Similar use of sound to stun enemies is exhibited by one Marvel character in particular. Created in 1967, and named after an Irish ghost, Banshee could induce a state of unconsciousness with a narrowly focused beam of sonic waves. But he is not alone in his superhuman acoustics; Ulysses Klaw, a physicist that eventually transforms into a near-immortal body of sound, possesses a vibranium-powered prosthetic hand that emits high-frequency sound waves for a whole host of purposes. But such fictional noisy hands and high-pitched screaming was created well before the discovery of the snapping shrimp’s phenomenal powers.
Since then, other cartoon designers have been paying attention to studies from the natural world. With a greatly enlarged claw producing water jets potentially 50% more powerful than other water-types, the snapping shrimp has obviously influenced a Pokémon character known as Clauncher (of whom evolves into Clawitser) in the recent generation VI. And the reference to its living inspiration is also encompassed in its Japanese name Udeppou, meaning water gun arm.
But
it’s not exactly bubble cavitation and shrimpoluminescence is it. Each
of these fictionalised characters doesn’t do justice to the
awe-inspiring natural phenomena found in nature. Even the world of comic
books and video games can’t compare to millions of years of descent
with modification.
References
Versluis, M., et al. (2000) How snapping shrimp snap: Through cavitating bubbles. Science, 289: 2114-2117.
Lohse, D., et al. (2001) Snapping shrimp make flashing bubbles. Nature, 413: 477-478.
Images
Snapping shrimp from themagazine.ca; Anatomical images from Versluis, M., et al. (2000); Bubble series from Lohse, D., et al. (2001); Banshee from comicvine.com; Klaw from marvel.wikia.com; Clauncher from archives.bulbagarden.net
References
Versluis, M., et al. (2000) How snapping shrimp snap: Through cavitating bubbles. Science, 289: 2114-2117.
Lohse, D., et al. (2001) Snapping shrimp make flashing bubbles. Nature, 413: 477-478.
Images
Snapping shrimp from themagazine.ca; Anatomical images from Versluis, M., et al. (2000); Bubble series from Lohse, D., et al. (2001); Banshee from comicvine.com; Klaw from marvel.wikia.com; Clauncher from archives.bulbagarden.net