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Residential Life Goes
West • Chewing
on Evolution •
Atmospheric Ambiguities
Lobsters Play Biological Violins • Remembering
Wannamaker
When is a Platypus Not a Kangaroo? •
Solution for Smokers
• In
Brief
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Lobsters Play
Biological Violins
Duke graduate student has discovered that spiny lobsters make sound
using the biological equivalent of a violin—the first time such
a mechanism has been found in nature. “Lots of people have tried
to explain how these lobsters make sounds, and most of them were wrong,”
says Sheila Patek, whose research is reported in a May issue of Nature.
“We’ve never seen this before.”
Using an underwater microphone and tiny sensors attached
to the lobster’s antennal muscles, Patek showed that when a lobster
moves its antennae in a certain way, a nubbin of tissue called a plectrum
rubs over a file near its eyes, creating frictional pulses of sound.
Unlike crickets and other animals that produce sound by scraping a
hard “pick” over a ridged “file,” a lobster’s
plectrum is made of soft tissue, and the file’s surface is macroscopically
smooth. So, although the sound they produce is hardly musical—it
resembles a cross between a stick dragged across a washboard and a
moist finger rubbed on a balloon—the underlying mechanism is
similar to a violinist drawing a bow across the strings of her instrument.
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| Fiddling around:scary
music |
Since lobsters cannot hear except at very close range,
the sounds they make are probably not used to communicate with each
other, Patek says. Instead, the sounds serve as a defense against
predators, which may be startled long enough for the lobster to escape.
“If you were reaching down to pick up a sandwich, and it squeaked,
you might pause.”
Sound-based defense mechanisms are relatively common in
nature, Patek says, but the lobster’s is unusual from an evolutionary
as well as a structural standpoint. Not all lobsters are noisy—only
certain species in the Palinuridae, or spiny lobster, family. These
lobsters bear little resemblance to the docile creatures found in
supermarket tanks: Aside from their mottled coloring, their most striking
characteristic is a pair of long, stiff, spine-encrusted antennae,
and several faded scratches on Patek’s arms bear witness to the
antennae’s effectiveness as defensive tools.
During the molting period, the spiny lobsters’ antennae
and shell are too soft to protect them against predators. Instead,
the lobsters must rely on scare tactics—sound
—to drive away predators like sharks, grouper, and triggerfish.
A sound-producing mechanism that relied upon hard surfaces would be
of little use during this vulnerable stage. This suggests that the
lobsters’ soft-tissue-based sound structures are an evolutionary
response to predation, says Patek.
“Organisms face many mechanical problems. In this
case, lobsters are able to make sound without relying on hard parts,
and therefore they can make sound when their exoskeleton is softened
and they are most vulnerable to predation.”
Patek says future research might turn up other examples
of animals using the same violin-like “stick-and-slip” method
to produce sound. She adds that she hopes her research will spur others
to investigate sound-producing mechanisms and their evolutionary
history. Patek’s own future includes a three-year postdoctoral
Miller Fellowship at UC-Berkeley, where she intends to study the evolution
of signals and communication in mantis shrimp.
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