快猫短视频

LURKING in the oceans are creatures that can create balls of plasma almost as
hot as the surface of the Sun, a Dutch researcher has found. No, they aren鈥檛 the
stars of a monster movie, but shrimps that live on coral reefs.

Snapping shrimp (Alpheus heterochaelis) have an outsized claw that
they use to fire jets of water at their prey and each other. The noise that they
make pervades the ocean, drowning out the sounds of ships and other animals.
鈥淪ubmarines can use the shrimp to hide,鈥� says Detlef Lohse of the University of
Twente in the Netherlands.

To understand the source of this cacophony, Lohse and his colleagues filmed
the shrimp with a high-speed camera and found that the snapping sound comes
before the claws shut. The noise is generated not by the clicking claws, but by
tiny bubbles in the water jet that expand and then collapse violently鈥攁
process known as cavitation (Science, vol 289, p 2114).

But the researchers also suspected that these cavitating bubbles might be
producing light as well as sound through a phenomenon called sonoluminescence.
When the bubbles collapse, any gas or water vapour inside them is compressed,
which can raise its temperature to startling levels and give off light (New
快猫短视频, 21 November 1998, p 27).

Further experiments suggest that sonoluminescence is occurring in the water
jets fired by the shrimp. 鈥淭he preliminary results hint at light emission, but
more work is in progress,鈥� Lohse reports.

He estimates that the temperature inside the collapsing bubbles is around
5000 掳C. 鈥淚t鈥檚 a cold plasma,鈥� he says. These extreme conditions only last
for around 200 picoseconds, however, and are most common 3 millimetres from the
tip of the shrimp鈥檚 claw, so it seems unlikely that the animals are using the
balls of plasma as weapons.