Aquaculture for all

Scientists Study Toxic Sea Slug


Next month, traps will be lowered into the waters of the Hauraki Gulf in a renewed bid to find out more about the prevalence and impact of the toxin that is threatening seafood safety, writes the Cawthron Research Institute.

Nelson based Cawthron Institute is collaborating with the Hauraki Maori Trust Board in a quarter million dollar research project funded by Nga Pae o te Maramatanga to see whether tetrodotoxin, the poison also found in Puffer Fish, might pose a risk to the collection of kai moana (seafood) from the Gulf.

Nga Pae o te Maramatanga is one of eight Centres of Research Excellence. It is based at Auckland University and facilitates projects deemed important to Maori.

Cawthron’s Maori Business Development Manager, Shaun Ogilvie will be leading the project, working with David Taylor, an ecologist, who recently made the link between the tetrodotoxin containing sea slugs and a little known exotic shellfish which is relatively new to New Zealand, as part of on-going sampling work for the Auckland Regional Council.

The pair will be joined by chemist Paul McNabb, who will be developing robust methods to test samples that will come out of the project.

During a diving survey, David Taylor discovered large populations of sea slugs living amongst large beds of the Asian Date mussels off Narrow Neck and Cheltenham beaches where the dog poisonings occurred.

The invasive mussel species, which arrived here in the 1970’s, live on sand beds off shore.

Paul McNabb says while it's not thought the mussels carry the deadly toxin "they are clearly providing a habitat where the slugs are able to build up and wash ashore in large numbers."

"That’s new information that suggests if we tidy up the Asian Date Mussels, while not getting rid of the slugs, their populations would go back to normal densities and we might not have the same problem.

Paul McNabb says this new research is essentially aimed at determining the risk, if any, of harvesting seafood from the Hauraki Gulf, from a toxin point of view.

"The discovery, last year, that tetrodotoxin in sea slugs was killing dogs on Auckland beaches was surprising and we are still uncertain about the potential for this lethal toxin to enter the food chain."

Hauraki Maori Trust Board Policy and Planning Manager, Liane Ngamane, sees their involvement in the project as a natural extension of the kaitiaki role Hauraki Iwi have with Tikapa Moana and a response to concerns about the impacts of toxins on Tikapa Moana.

"Tikapa Moana is highly valued as a pataka kai (food basket) of the Iwi of Hauraki who have gathered kaimoana from its shores for centuries. This research will help us to better understand this toxin and any emerging and potential health risk there might be to whanau today."

"It will also build capacity within the Iwi to manage this new toxin in the long term."

The project will run for two years starting this September.

Cawthron, the agency that discovered the presence of the deadly toxin in the sea slugs, will apply its expertise in testing the samples for tetrodotoxin and other toxins.

The Hauraki Maori Trust Board will also be going back through its records for any incidences of poisoning historically, which at the time were not thought to be linked to toxins, as part of the project.

At the end of the two years, Cawthron Technical Manager, Paul McNabb says they hope to be able to provide a detailed assessment of the prevalence and impact of tetrodotoxin, and any risks that might be associated with harvesting kai moana.

"Our findings will help iwi around Tikapa Moana (the Hauraki Gulf) take the appropriate actions to reduce any risk to people from tetrodoxin."

While the research is specific to the Hauraki Gulf, Paul McNabb says the project will also help, at least in part, to answer a number of questions around the existence of tetrodotoxin in New Zealand, including whether it is truly a new phenomenom or whether there is any knowledge from people who have lived here the longest time about toxic things washing up on the beach.

Because the sampling will continue throughout the year he says it should also point to whether this is only a seasonal problem or one that we need to be alert to all year round.

"While it is unlikely to show there is something really dangerous out there that we are eating every day, we don’t really know what else could potentially also contain the toxin. There are a lot of things that live in a similar area to the slugs, that we actually eat, that might also have it, albeit in low levels."

"After all this work we still won’t know how the slugs got it’s toxin. By looking at sealife similar to these slugs if we find they don’t have it then it does lead us to assume there has to be something special about the slugs themselves, and that in itself would be significant."

The Nga pae o te Maramatanga funded project is the first ‘major’ piece of research into tetrodotoxin since its discovery on Auckland beaches last year following the deaths of a number of dogs.

Cawthron CEO Gillian Wratt sees it as a significant investment not only by Maori but also in building confidence among the general population that it is safe to return to the beach, and to enjoy the treasures of the sea.

"While there have been no dog deaths this season, there have been new cases over just this past month involving dogs on Torpedo Bay, Narrow Neck and Milford beaches, and the discovery of toxic slugs also on Kohimarama Beach for the first time."

“The truth of the matter is toxin containing slugs could have been washed up on our beaches for years. But it is only now, that we know the connection with dog deaths, that we are able to match the symptoms to a cause. The question now is what can we do about it.

Cawthron hosted a tetrodotoxin workshop in Nelson with three eminent scientists from Australia, Albany and the University of Waikato, in a bid Gillian Wratt says "to take the research forward. This is something Cawthron is funding and promoting in our role of providing science for the good of New Zealand."

She says there are big and scientifically exciting questions that Cawthron and their collaborators are keen to research. Auckland Regional Council and Nga Pae o te Maramatanga funding are making a significant contribution, but while everyone wants to know the answers, no-one else seems able to step up to fund the level of research that is really needed to understand this phenomenon.

"The ocean has thrown up this amazingly toxic slug which somehow, somewhere has developed a mechanism to cope with one of the deadliest toxins in the world. And it is right here on our doorstep. While there is a large amount of evidence that says species take up tetrodotoxin from their food what’s not clear is why it is fatal to some and not others. Why this particular sea slug can handle it where other species can’t. From an evolutionary and a genetic perspective the reason this particular sea slug can handle it where other species can’t remains the big question."

"Scientists in Japan have been trying to address this for a long time, something like 30-40 years without success. While they’ve made a lot of discoveries, they haven’t managed to crack it. We could – the sea slug is more amenable to research than the Japanese puffer fish or fugu - and wouldn’t that be phenomenal if we did. "

February 2011
Filed as: Health
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