A group of scientists will gather this week in an attempt to unravel the mysteries of the poison found in sea slugs which have reappeared on Auckland's shores this winter.

The workshop, initiated by the Cawthron Institute, comes as the spread of the toxic sea slug reached an east Auckland beach - Kohimarama - for the first time.

The slugs - scientific name Pleurobranchaea maculata and usually about 2cm long - were found last year to contain tetrodotoxin (TTX), a potent neurotoxin.

The poison was blamed for the deaths of five dogs on North Shore beaches.

There have been no deaths this season, but dogs which visited Torpedo Bay, Narrow Neck and Milford have become sick.

Cawthron Institute chief Gillian Wratt said the sea slug's ability to handle a strong poison has baffled scientists in Japan for forty years, and it was a good time for New Zealand scientists to research the organism in greater depth.

"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."

It was evident that sea slugs took up tetrodotoxin from their food chain, but it was not clear why it was fatal to some and not others.

"This remains the big question," said Ms Wratt. '

Japanese researchers had made a lot of discoveries, but had not solved the mystery.

"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."

It is likely that the sea slugs are not the only carriers of the toxin, and the institute wants testing of beach sediment, kina, limpets, crabs, spotties and other sea creatures in the Auckland region to make sure they do not contain TTX.

A study last year showed sea slugs may have carried TTX for many years.

It is not yet known why it has only come into contact with dogs in the past year - this mystery will be one of many which tomorrow's workshop in Nelson hopes to address.

Auckland Regional Council spokesman Grant Barnes said it was also important to establish whether the toxin was present outside the Auckland region. Sea slugs are found on both islands, but testing has only been carried out in the Hauraki Gulf.

Mr Barnes said it was fortunate that no child had become sick or been seriously harmed by the poisonous slugs.

Slugs found on the North Shore contained deadly amounts of TTX - enough that 0.25g of sea slug could kill a dog and 2g could kill a human.

Scientists are intrigued by the presence of the toxin in New Zealand waters, as it is more likely to be found in the tropics, in puffer fish or blue-ringed octopus.

If you find a sea slug, do not touch it. Mark the spot and call the Auckland City Council on (09) 379 2020.
BAFFLING
* Sea slugs' ability to handle a strong poison has baffled scientists.
* The slugs are found on both islands but testing has been done only in the Hauraki Gulf.
* The slugs carry tetrodotoxin, which is normally found in the tropics.