The Colgate Scene
January 2003

Something well beyond lowly
For Damhnait McHugh, studying worms has been the journey of a lifetime

Damhnait McHugh, associate professor of biology, examines a terebellides, more commonly known as a spaghetti worm. One of the world's leading authorities on annelids, McHugh and her research were featured in the 2002 PBS television series The Shape of Life. [Photo by Timothy D. Sofranko]

For 20 years, Damhnait McHugh (whose first name is pronounced "down-it"), associate professor of biology, has been enthralled with some of the most remarkable and, in her opinion, under-appreciated creatures on earth. There are an estimated 15,000 species of them. They come in practically every color of the rainbow and they propagate, motivate and feed themselves in ways almost too varied to count.

Some are decorated with feathery whiskers in garish, iridescent hues. Some explore their world with elaborate fans of spaghetti-like tendrils. Some are plain Janes who eschew the decorations but are nonetheless impressive for their tenacity.

They exist as nearby as your backyard. They exist in places where humans can only venture with the most sophisticated life support equipment available on earth. And without them, the world as we know it might not exist.

McHugh, whose research was featured in the 2002 PBS television series The Shape of Life, is one of the world's leading authorities on the annelids, the lowly worms. More specifically, she says, "I am interested in the ecology and evolution of marine invertebrate animals, particularly the diverse and beautiful polychaete annelid worms."

She first began to explore the polychaete annelids in the early 1980s, as an undergraduate zoology major at University College Galway, in her native Ireland. As an honors student, she was required to write a senior thesis and found an opportunity to assist an ecologist who was surveying shallow marine habitats in and near Kinsale Harbor, on Ireland's southern coast.

McHugh spent much of each day that year exploring muddy tidal flats. It was her task to collect and identify worm specimens to determine whether contaminants they might have been exposed to in the near-shore environment were affecting their abundance and variety.

It was an eye-opening experience. Up to that point, most of her experience with worms involved fishing and the back garden. But when she recalls that, "I identified almost 100 species of worms from that one small harbor," she still gets excited. In the Kinsale mud, McHugh learned the true meaning of diversity in the animal world.

A fellow student was assigned to collect mollusks. His name was Pat Reynolds. Like McHugh, it was his first exposure to that sort of work. Both fell in love with it, though . . . and with each other. Twenty years later they are married, have a young daughter, and are still studying worms and mollusks. (Reynolds is a professor at Hamilton College.)

Since Kinsale, McHugh's fascination with worms has taken her around the world. She completed her masters degree at the University of Victoria in Canada, and her Ph.D. at the University of California --Santa Cruz. She has studied worms in Iceland, South Carolina, Maine and South Africa and, while a graduate student at the University of Victoria, in one of the most inhospitable places imaginable.

This mature autolytus is budding off a chain of young at its posterior end. The fleshy lobes along the body of the worm are used for crawling along the sea bottom. [Photo by Greg W. Rouse]

Realm of the black smokers
In the late 1970s, scientists were exploring the Juan de Fuca Ridge, a stony spine a mile or more below sea level and 300 miles west of Seattle, Wash. There they discovered something spectacular: deep-sea volcanic vents, chimneys of rock that spew toxic, super-heated mineral fluids into the ocean around the clock.

The vents, which some scientists call "black smokers," were weird enough. But what researchers found living there was even stranger. Dense populations of animals -- mussels, clams, albino crabs and worms that live in pipe-like tubes -- were colonizing the vents. Thriving in temperatures near freezing, under immense pressure, in proximity to vents that emit water heated to 300 degrees Celsius, the animals lived off bacteria and other tiny creatures that actually metabolize the chemicals released from the vents. Each of the smokers was like a small island of life. Between them, the ocean floor seemed nearly lifeless.

In the mid-1980s, along with two other scientists, McHugh descended to the ridge in a three-person submersible. Through its small window, they could observe the worms and other animals that spend their entire lives in absolute darkness, clinging to the walls of these tiny volcanic apertures. When they went too close to one of the vents they discovered that not only was the fluid it emitted hot, but it was also under great pressure.

The submersible was abruptly thrust away. And when the trio returned to the surface they found, disconcertingly, that its window had been scorched by the super-heated volcanic water.

McHugh has made no further trips to the netherworld of the annelids since that experience. But her interest in those worms and their behaviors remains acute. She is currently working with Jamie Knowles '03 to find out if worms at these island-like vents can disperse to other vents hundreds to thousands of kilometers away. Knowles and McHugh extract DNA from vent worms collected at 15 different sites along the Juan de Fuca Ridge, and sequence their genes. By comparing the letter code sequence in genes from the worms, they can infer the parentage of the worms from each site. Their comparisons indicate that offspring from parents at one vent can end up at another vent 50 kilometers or more away. Given that these worms have no known way of swimming, they must rely on deep-ocean currents to carry them to new habitats.

Splendid diversity
Why do annelids captivate McHugh? The answer is not simple.

First, there is the matter of respect. "I think we should see ourselves," she said in The Shape of Life, "as custodians of the great diversity of animals that we see around us today. But we should also remember that we are not masters of this diversity. In fact, we depend very much on the diversity of animals around us . . . even the lowly worm."

To underscore this statement, she references an important theory that worms, emerging along with a dazzling array of other creatures in the sudden burst of animal life that was the Cambrian explosion, may have played a significant role in ending the dominance of ice over the earth. Consuming eons worth of decaying carbon-based plant matter that had drifted to the floors of the oceans, the theory holds, the worms may have released sufficient carbon dioxide to build a denser, greenhouse atmosphere that warmed the planet.

In addition to the worms' ancient history, the study of their variety also captures McHugh's imagination. Through analysis of their genetic makeup, she rebuilds the tree of worm relationships to look for patterns in their "splendid diversity" that help explain how and when they evolved. Understanding such timeless mysteries of what she calls "the evolutionary tree of life" is what she strives for.

The roots of that tree, McHugh will tell you, are deep in the mud of places like Charleston, Oregon, and Kinsale Harbor, Ireland, and Penobscot Bay, Maine. The history of life smells like the ocean.

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