I have well over a thousand draft posts in a 51-page list on this site’s dashboard, and most of those posts will never appear, moving ever father back in the unrecovered past. But sometimes I go back a bit to see if I’ve forgotten anything cool. Today, on page 3, I found three nice animal videos, two of them showing the famous snapping shrimps that kill their prey by stunning them with pressure waves. The first two videos are self-explanatory, but Wikipedia tells us a bit more:
The snapping shrimp [also called a “pistol shrimp”] competes with much larger animals such as the sperm whale and beluga whale for the title of loudest animal in the sea. The animal snaps a specialized claw shut to create a cavitation bubble that generates acoustic pressures of up to 80 kPa at a distance of 4 cm from the claw. As it extends out from the claw, the bubble reaches speeds of 60 miles per hour (97 km/h) and releases a sound reaching 218 decibels. The pressure is strong enough to kill small fish. It corresponds to a zero to peak pressure level of 218 decibels relative to one micropascal (dB re 1 μPa), equivalent to a zero to peak source level of 190 dB re 1 μPa at the standard reference distance of 1 m. Au and Banks measured peak to peak source levels between 185 and 190 dB re 1 μPa at 1 m, depending on the size of the claw. Similar values are reported by Ferguson and Cleary. The duration of the click is less than 1 millisecond.
And another:
The snap can also produce sonoluminescence from the collapsing cavitation bubble. As it collapses, the cavitation bubble reaches temperatures of over 5,000 K (4,700 °C). In comparison, the surface temperature of the sun is estimated to be around 5,800 K (5,500 °C). The light is of lower intensity than the light produced by typical sonoluminescence and is not visible to the naked eye. It is most likely a by-product of the shock wave with no biological significance. However, it was the first known instance of an animal producing light by this effect. It has subsequently been discovered that another group of crustaceans, the mantis shrimp, contains species whose club-like forelimbs can strike so quickly and with such force as to induce sonoluminescent cavitation bubbles upon impact.
Although I had a striped skunk for about six years, these spotted skunks (this species is probably the western spotted skunk, Spilogale gracilis) have a unique behavior. I can’t think of another mammal that stands on its forepaws (of course some captious reader will name one), although plenty of species, like meerkats and bears, stand on their hind legs. Ignore the stupid breakdancing in this video and look at that skunk!
h/t: Michael
Bull’s eye!!
Look up “pug handstands” on Youtube. BOOM
Stunning! I did not expect that.
Family lore is that Aunt Margaret once surprised a spotted skunk in the hen house and got the full-on hand-spring aerosol…
Somedays you eat the
bearshrimp and somedays thebearshrimp eats you.I can’t mention another mammals that stands on its forepaws, but I remember when Matthew and you last spotted [sic] this behavior:
https://whyevolutionistrue.wordpress.com/2015/11/17/spotted-skunk-does-handstand/
There’s more videos and squee photos in there.
Does the territorial marking behaviour of male Pandas count? They use the tree to support their hind legs while doing a forepaw stand. Presumably they do this to micturate as high as possible on the tree.
The adaptations of those shrimp is absolutely amazing. It would seem to me that they must expend a significant amount of energy to create the sonic/cavitation/light effect. So, if there are any shrimp specialists out there, is their system just really efficient at gaining high quantities of calories through hunting, or is it just that they are really efficient at converting chemical into kinetic energy during the hunt?
I wonder if pistol shrimp’s mechanism may depend partly on cavitation. The closing claw blasts out an expanding jet of water. The momentum of the water makes it keep expanding, and with nothing behind to replace it a vacuum bubble forms. When this collapses, with nothing to cushion the impact of the water ‘hitting itself’, extremely high pressures can be generated.
(Pump engineers know cavitation only too well, if cavitation bubbles form then collapse on a surface they can eat hard steel impellers quite rapidly. https://jacpump.files.wordpress.com/2011/04/thermalchgo-017w2.jpg )
The slow-mo shows the cavitation bubble is clear of the shrimp’s claw when it collapses, which is just as well for the shrimp. Still, it must be pretty well armoured to withstand the shock wave it has just generated.
It’s unclear whether the prey is stunned by the jet of water or by the shockwave, or possibly a combination of both.
cr
Actually on re-reading the article, I see the effectiveness is indeed put down to cavitation.
Clever shrimp!
As to how it discovered cavitation (evolutionarily), I’d guess it just started with proto-shrimps blasting a jet of water at their victims. As their mechanism improved, it would have reached the stage where cavitation started to occur, vastly enhancing the effectiveness of the technique. (I wonder if the first few shrimps to get that good were, literally, stunned by their own prowess. Mental picture of shrimp looking at its claw in amazement and saying ‘bloody hell, I didn’t know I could do *that*!’)
cr
Yes, why doesn’t it stun itself?
I suppose, firstly, the jet of water and the resulting cavitation shock wave are somewhat directional, and second, maybe it has thicker tougher skin than ordinary shrimps? I don’t know, I think it must have something like that.
cr
I recall seeing a video of a chihuahua (sp?)
walking on its forepaws while peeing, almost writing its name on the curb.
Do marine mammals count?
Great couple of critters!
Speaking of sea critters, David Attenborough’s new show, The Great Barrier Reef (Ep.1), has recently aired on BBC and CBC, and it’s fantastic!
For folks in the UK, here’s the BBC link for Episode 1 :
http://www.bbc.co.uk/programmes/b06t4j41
For Canada, here’s the CBC link:
http://www.cbc.ca/documentaries/great-barrier-reef-builders