There
were many times when I was on the Langkawi mangrove tour especially at low
tide, I always wonder what made the popping sound like opening a bottle
of champagne. Someone told me that it was the result of the air bubble
popped when a crab emerged out of the burrow. Or could it be another
creature like this one here that emerged in front of us be the answer?
We
were checking out a nest of sedentary tube worm (polychaete) when it
suddenly emerged out of the mud! It was a real lucky day for us
especially for me. I am not sure if my guests were excited about it but I
was surely 999% excited to see it. It didn't stay out very long for us
until it dug itself into the mud again.
Snapping Shrimp was starting to dig into the mud
Digging in!
Do
have a closer look and try to notice one of its claw that is very much
larger than the other. This is possibly the mangrove snapping shrimp
(Family Alpheidae). However, I am not sure exactly of which species this
one is.
This
mangrove snapping shrimp we saw was less than 10cm. How a little
crustacean can make a sound so loud and powerful to stun a fish and be
heard many hundreds of metres away?
According to the book PRIVATE LIVES - An Expose of Singapore's Mangroves:
It
is because of its large claw that is packed with muscles and has a
uniquely structured tooth on the finger that fits into a socket on the
opposite. The muscles pull the toothed finger back and hold so much
elastic force that when it is released, it hammers into the socket at an
incredible speed and force, causing a high speed jet of water to
emerge. The high speed causes a sudden drop of pressure (Bernoulli's
principle) resulting in the formation of a tiny vapour bubble - what
physicists call a cavitation bubble. The bubble violently collapses
under the pressure of the surrounding water in a small "underwater
explosion" causing a loud sound. During the collapse, the temperature in
the bubble reaches the surface temperature of the sun! Snapping shrimps
make these "snaps" to fend off rivals, deter enemies and rivals, and
probably also to communicate with one another.
Researchers
in the Acoustics Research Laboratory of the Tropical Marine Science
Institute of the National University of Singapore have shown that
in tropical waters, the snap density can range from 0.01 to 0.1
snap/second/square metre. Although this noise limits the performance of
most traditional man made underwater acoustic systems, a novel technique
known as "ambient noise imaging" uses this noise for underwater
sensing.
Read
about how the sound of the snapping shrimps interfere with the sonar
detection in shallow seas and how a snapping shrimp rely on goby in Ria's WildfactSheets.
A
HUGE THANK YOU to Iris Flock for taking the pictures of this snapping
shrimp and kept your promise in sending them over to me. And also thank
you to Ria for the confirmation.
This is my first time seeing a real live snapping shrimp. Amazing! Hmm... I wonder if it tastes good...??
References:
1) Private Lives - An Expose of Singapore's Mangroves
Written by Peter K. L. Ng, Wang Luan Keng, Kelvin K. P. Lim
Published by National University of Singapore
Links:
