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What Mysterious Disease Is Plaguing the American Lobster?

February 28, 2012

By Lisa M. Gerry

Patrick Gillevet

Patrick Gillevet

On the Discovery Channel show Lobster Wars, lobstermen battle rough seas and brutal weather in hopes that they’ll hit the jackpot and bring home a boatload of what is considered an American delicacy. But what the cameras do not catch is the real drama taking place beneath the ocean’s surface on the lobsters’ shells.

More than 50 percent of the American lobster (Homarus americanus) population off southern New England has been affected by epizootic shell disease. The afflicted lobsters develop a shell-eating bacterial infection that can kill the lobster before it has the chance to molt, or shed its shell. The economic impact of the disease on lobstermen is great because lobsters with the disease are covered in unsightly dark spots and cannot be sold.

To find out more about the disease and why lobsters are contracting it, the National Oceanic and Atmospheric Administration provided a $2.3 million grant to the New England Lobster Research Initiative. Mason environmental biologist Patrick Gillevet is part of this research consortium, which consists of scientists from 11 institutions across the country.

In Gillevet’s particular research, he studies the microbial community, or all the bacteria present in an ecosystem, by comparing samples of tissue from healthy lobsters and diseased lobsters. The hope is that the bacteria present in the diseased tissue can offer clues as to what is causing the disease and why.

To compare the bacteria present in the different samples, Gillevet uses a technique he developed and patented called multitag pyrosequencing. This new technology, which essentially creates a barcode to tag the bacterial sequence of a sample, dramatically reduces the time it takes to compare samples and has been used to study a variety of microbial communities—from the human gut to diseased coral in Key Largo. In fact, Gillevet says that analyses that previously took 50 years to complete can now be done in one afternoon.

What Gillevet has learned from his research is that the bacteria in the lobsters’ lesions are probably always present on the lobsters’ shells, but the lobsters are suffering from some sort of opportunistic infection. In other words, while the bacteria that are killing the lobsters are always there, it isn’t threatening until an environmental stressor weakens the lobsters’ defenses.

According to Gillevet, environmental stressors could include warmer water temperatures as a byproduct of climate change, ocean acidification, or pollution. There is even speculation that plasticizers that have made their way into the ocean from environmental runoff may be softening the lobsters’ shells.

While they don’t know exactly what is triggering the deadly infection, Gillevet feels confident that the shell disease is not being caused by a foreign pathogen. Some lobstermen had been concerned that large ships may have been discharging dangerous bacteria through their bilge pumps when they entered shallow water. That, however, does not appear to be the case.

The research supported by this particular grant has come to an end, and now the research teams are combining and reviewing their findings.

“What I would like to do is apply a systems biology methodology,” says Gillevet, who is the director of the MicroBiome Analysis Center at Mason. “Take the data from all the groups, correlate it, and come up with new hypotheses.”

Gillevet and his fellow researchers are planning the next step, which will be to apply for more funding to continue their research. And until they get to the bottom of what’s causing epizootic shell disease, Gillevet and his associates will be hot on its (lobster) tail.

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