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Cinema Bayville

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Creatures and Critters

Oyster S.O.S.

Narrator: Tangier Sound was once one of the Bay’s most productive oyster fisheries. But an oyster population survey there today brings up more dead oysters, known as boxes, than live ones.

Chris Judy: On many surveys when the disease is quite active, we bring up the dredge, and it’s filled mostly with dead oysters, and just the year before they were live. So we’ve seen this time and time again, and it’s really disheartening to see this trend.

Narrator: Overfishing started the decline, reducing Maryland oyster harvests from fifteen million bushels a year in the 1880’s to two million bushels a century later. But the crushing blow was dealt by two mysterious diseases, called Dermo and MSX. Although they’re not harmful to humans, these parasites began to ravage the remaining oyster stocks since the mid-1980s.

Chris Judy: Since the mid-1980’s, we’ve had about one-fifth the oyster harvest that we had in the pre-disease era. So that’s a dramatic decline.

Narrator: And it’s not the economic impact alone that is cause for concern. For these filter-feeding, algae-eating oysters are critical to the Bay’s ecological health.

Chris: Oysters, of course, filter the water. They spawn and produce more oysters. A thriving oyster population attracts other organisms to the bottom, so a thriving oyster bar is actually a community of other organisms as well.

Narrator: But now there’s new hope for the beleaguered oyster. The science of marine biotechnology is offering tools never before available for diagnosing and attacking the disease. Some of the leading research in the field is being conducted by Dr. Gerardo Vasta at the University of Maryland’s Center for Marine Biotechnology. He’s focusing on the Dermo parasite.

Vasta: The breakthrough for us came about eight years ago when we were able to culture the parasite in the lab, and this is a first step in addressing questions of any infectious disease, whether this is affecting humans or this is affecting oysters.

Narrator: Using these cultured parasites, Vasta and his associates have been seeking answers to a question that has been plaguing scientists for years. How is the Dermo parasite able to outsmart the oyster’s immune system?

Vasta: In the natural environment, oysters are continuously exposed to large numbers of microbes that could be potential pathogens. But oysters have blood cells, which could be analogous to our white blood cells, that will take these microbes and kill them. When these blood cells are confronted with the Dermo parasite, they cannot do this.

Narrator: Vasta’s lab is gaining insight into how derma blocks the oyster’s immune response. With the hope that scientists could eventually employ selective breeding techniques or use gene transfer technologies to create oysters that are better defended against the parasite.


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