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Effects of ciguatera toxin in monk seals under study


Scientists are looking into whether the presence of a toxin in endangered Hawaiian monk seals could be contributing to their decreasing numbers.

A federal study found significant levels of the toxin ciguatera in monk seals in the Hawaiian Islands and in Papahanaumokuakea Marine National Monument.

The findings, published in American Chemical Society’s online edition in May, has led some scientists to believe ciguatoxin exposure is common among the monk seal population.

Scientist Charles Littnan, co-author and lead researcher for the Hawaiian Monk Seal Research Program, said the findings were an important first step. But scientists still need to measure how widespread the ciguatera exposure is among monk seals and the role it plays in the decline of the species, he said.

"We do know that ciguatera toxins can kill other species of seals, but those are seals that may not be regularly exposed to it," said Littnan, a scientist working for the National Oceanic and Atmospheric Administration.

Littnan said monk seals may have developed a resistance to certain levels of ciguatera. "We just don’t know how they process it," he said in an interview yesterday.

Scientists also don’t know the neurological effects, especially in juveniles, and whether it could affect their ability to find food, or reduce their appetite and ability to escape predators.

Littnan said the ciguatera exposure is also dependent on the monk seals’ feeding habits and whether they rely on a high level of reef fish that contain potentially higher levels of ciguatera.

The population of Hawaiian monk seals now stands at between 1,100 and 1,200, dwindling by about 4 percent annually, and scientists have been working to find the cause.

Ciguatera fish poisoning is an illness commonly associated with people eating fish that contain toxins produced by a marine microalgae, Gambierdiscus toxicus.

In humans, symptoms include nausea, vomiting and neurologic problems such as tingling fingers or toes, according to the Center for Disease Control and Prevention.

While people might feed on other sources of food, fish is the principal source of nutrition for monk seals.

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