Identifying harmful marine biotoxins

Reliable and cheap tests to detect harmful toxins in oysters lie on the horizon as a Franco-American science team identify how two toxins found in micro-algae actually make consumers ill.

For the first time, scientists at France’s publicly-funded CNRS laboratory say they have identified why the toxins harm humans. The discovery could pave the way for new testing techniques to identify harmful marine biotoxins.

Marine biotoxins, or phycotoxins, accumulate in fish and shellfish from their diet and can cause diarrhea or possible neurological problems when the seafood is consumed, say the researchers.

In 2005, oysters contaminated by phycotoxins were identified in France’s major oyster-producing area, the Atlantic-facing Arcachon Basin. The outbreak led to an immediate ban on oyster sales, which was costly for producers.

The French researchers and their American counterparts found that two particular types of phycotoxins, a spirolid and a gymnodimin, explained the neurotoxicity of these phycotoxins in several animal species.

“Better understanding of their action is a first step toward developing suitable antidotes. In addition, the development of reliable and sensitive tests that are practical and inexpensive could detect the presence of these phycotoxins in seafood for consumers,” the researchers said this week.

According to their findings, these “fast-action” neurotoxins attack an essential receptor in animals, the nRACh, which plays a major role in neuromuscular and neuronal transmission.

“More precisely, these toxins work by rapidly blocking, in an almost irreversible manner, the canal-receptor function for the nRAChs. This inhibition can lead to muscular and/or cerebral malfunction,” reported the authors.

The study was published online in the Proceedings of the National Academy of Sciences journal on 8 March. Its authors include Yves Bourne, Zoran Radic, Romulo Aráoz, Todd T. Talley, Evelyne Benoit, Denis Servent, Palmer Taylor, Jordi Molgó and Pascale Marchot.

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