February
17, 2001
The
Worm that Boasts Earth's Hottest Lifestyle
Marine scientist finds that a hydrothermal vent worm thrives in near-boiling
waters
by Mike Matz
Scientists have discovered that the Pompeii
worm, an inhabitant of hydrothermal vent ecosystems, can withstand
hotter temperatures than any other creature on earth can -- except
for certain one-celled organisms.
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Scientists
recently granted a hairy little worm found in the deep sea the distinction
of being the most heat-tolerant complex organism on earth. The research
team of University of Delaware marine scientist Craig Cary discovered
that the Pompeii worm (
Alvinella pompejana
) thrives in waters
as hot as 80° C (176°F), easily beating out the Sahara Desert
ant Cataglyphis long considered to be the world's most extreme creature.
Only certain simple one-celled organisms can survive higher temperatures.
The
worm inhabits ocean-floor formations known as hydrothermal vents,
which are geysers found along underwater volcanic mountain ranges
formed by shifting plates in the earth's crust. The chimney-like vents
release jets of "super-heated" water -- more than 300°
C (570° F) -- that is rich in sulfur and metal compounds.
Despite
the absence of sunlight as an energy source, hydrothermal vents are
oases of biological diversity in the otherwise barren deep-sea-floor
environment, teeming with bizarre-looking creatures that have evolved
ways to live off the chemicals the chimneys spew. Most of these species
are found nowhere else on earth, such as an eight-foot long red tubeworm
without a digestive system and a shrimp with a unique organ that may
detect heat and guide it to nutrients.
According
to Dr. Cary, the ten-centimeter-long (4 inches) Pompeii worm makes
its home in papery tubes that it burrows into the sides of the chimneys.
Hot water from inside the vent flushes through these tubes and flows
into much colder deep-sea water from outside. This results in a dramatic
drop in water temperature over just a few inches, from over 80°
C (176° F) in the tube's inner regions to about 14° C (57°
F) at the tube's outer entrance. Amazingly, the worms simultaneously
inhabit both extremes, with their heads positioned at the cooler openings
and their tails withstanding the inner heat.
The creatures more than just tolerate this environment. "The
worm likes it in there," said Dr. Cary.
Marine scientist Craig Cary led the team
that probed into the Pompeii worm's hot lifestyle.
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Dr.
Cary's team made the finding while studying the worm in hydrothermal
vents along the East Pacific Rise, an ocean-floor rift in the waters
west of Mexico. Venturing more than a mile below the surface in the
ALVIN deep-submergence vehicle, Cary's team operated a six-inch-long
titanium probe inside the worm's tubular abode to analyze water temperatures.
It's
still unclear how the worm accomplishes its feat of heat-tolerance,
said Cary. But Cary suspects that the explanation has to do with one
of the worm's most striking physical features -- the hairy shawl that
covers its back. Analysis of this fleecy fuzz has revealed that it's
actually made entirely of bacterial colonies that feed on the sugars
secreted by the worm.
According
to Cary, the hair, which can be up to a centimeter thick, may act
as a protective thermal blanket for the worm. He believes the bacteria
in the hair contain special proteins known as eurythermal enzymes
that can withstand a broad temperature range.
Cary's colleagues are conducting biochemical studies on bacteria samples
collected from the worm to identify these enzymes and determine how
they resist heat. Unfortunately, scientists have yet to successfully
bring the worm itself back alive because, as Dr. Cary says, "They
do not decompress well at all."
These
remarkable proteins may offer enormous benefits to the production
of pharmaceuticals, paper, detergents, textiles, and other products-which
is why many industries are closely following the protein research.
Stunning
discoveries like that of the Pompeii worm are not uncommon in hydrothermal
vents these days. That's because these ecosystems are relatively new
to science -- first spotted just a few decades ago -- and biologists
frequently find never-seen-before species there.
"Almost on every dive something very new and interesting exciting
comes up," said Dr. Cary. "In biological systems, that's
fairly rare."
