Scientists Determine How Chemistry Keeps Weird Worms

Contact: Tracey Bryant, Marine Outreach Coordinator
University of Delaware Graduate College of Marine Studies
Newark, DE 19716-3530
Phone: 302-831-8185
E-mail: tbryant@udel.edu

Using a novel detector attached to a submarine, a research team led
by University of Delaware marine scientists has determined that water
chemistry controls the location and distribution of two species of weird
worms that inhabit deep-sea hydrothermal vent sites. The study, which
is the first to demonstrate through real-time measurements how different
chemical compounds control the biology at the vents, is reported in
the April 12 edition of Nature.

The interdisciplinary research team included chemists, biologists, and
marine engineers from the UD Graduate College of Marine Studies, Woods
Hole Oceanographic Institution, Rutgers University, and Analytical Instrument
Systems, Inc. The research was supported by the National Science Foundation,
the National Oceanic and Atmospheric Administration’s National Sea Grant
College Program, and the National Aeronautics and Space Administration.

UD’s George Luther, a marine chemist, and Craig Cary, a marine
biologist, worked with Don Nuzzio, president of Analytical Instrument
Systems in Flemington, New Jersey, to develop a chemical detector capable
of withstanding the harsh conditions at the vents. Their “electrochemical
analyzer” consists of a foot-long wand that houses several needle-like,
gold-tipped electrodes, which are coated in super-tough plastic to protect
them from heat. The wand, which resembles a large, hand-held hairdrier,
is connected to a 3-foot-long, 8-inch-diameter tube that houses the
system’s electronics. The tube is mounted to the bottom of the
submarine Alvin.

Once attached to one of Alvin’s highly maneuverable arms,
the analyzer’s wand can be placed near a vent to instantaneously
reveal the ingredients in the sulfur-rich stew rocketing out of the
Earth’s crust.

“One of the analyzer’s greatest benefits is its ability to
detect a number of sulfur compounds simultaneously, such as iron monosulfide,
hydrogen sulfide, thiosulfate, polysulfide, and others,” says Luther.
“Previous techniques could not identify these compounds, which
are the lifeblood of the vents.”

During the past two years, the research team tested the analyzer at
vent sites in the Gulf of California and in the Pacific Ocean. They
examined the microhabitats of two different vent worms: the tubeworm
(Riftia pachyptila), which looks like a giant lipstick and can
grow to 9 feet tall, and the hairy, 5-inch Pompeii worm (Alvinella
pompejana), which currently holds the record as the “hottest”
animal on Earth.

The tubeworm lives on the seafloor near hydrothermal vents. It has no
eyes, mouth, or stomach. Instead, this worm relies on the billions of
bacteria that live inside it to make food. Using the analyzer in a tubeworm
colony, the scientists confirmed that this animal resides in waters
up to 30°C (86°F), and its bacteria require hydrogen sulfide
for survival. If the chemical is not present, the tubeworms die.

Unlike the tubeworm, the Pompeii worm eats helpful microbes. “A
fleece of bacteria also occupies this worm’s back,” says UD
marine biologist Craig Cary. In 1998, Cary and his team confirmed that
the Pompeii worm is the most heat-tolerant animal on Earth, capable
of surviving nearly boiling water.

“The Pompeii worm forms tube-dwelling colonies on the sides of
certain vent chimneys,” says Cary. By replacing the analyzer’s
hairdrier-like wand with a more slender attachment, the scientists were
able to insert the device right into the Pompeii worm’s home. They
found that the Pompeii worm resides in much hotter water than the tubeworm,
with temperatures fluctuating from 40° – 90°C (104°
– 194°F).

According to Luther, this hot water causes an important chemical reaction
critical for the worm’s
survival. “The higher temperatures allow for the formation of soluble
iron monosulfide, a compound that reduces the toxicity of the hydrogen
sulfide in the surrounding water,” he notes. “So figuratively
speaking, you might say the worm’s hot-water home helps keep it
out of ‘hot water.’ ”

While this research demonstrates how differences in chemical compounds
control the unique ecology of vent environments, Luther says the study
also may aid astrobiologists.

“The interplay of oxygen, iron, and sulfide compounds in controlling
biology in primordial environments on Earth could provide a paradigm
for the detection of life on other planets,” he says. “Europa,
one of Jupiter’s moons, is covered in ice. But recent findings
suggest that portions of the ice move, which is strong evidence that
liquid water lies beneath it, maintained by hydrothermal vents. If hydrothermal
vents exist on Europa, there’s a possibility that ancient microbes
could live there, too.”

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