Team of scientists find Smeagol sea slug on remote mainland marine reserve

When a team of scientists travelled to the country’s most remote mainland marine reserve, they did not expect to discover Smeagol lurking in its depths.

Hautai Marine Reserve, South Westland

Hautai Marine Reserve in South Westland. Photo: Spencer Virgin / Marine Ecology Research Group

The extremely rare gravel maggot – named after the Lord of the Rings character – has been detected for the first time in the Hautai Marine Reserve in South Westland.

Before the discovery, the Smeagol sea slug was only found in two places – both hundreds of kilometres from the remote beach.

Earlier this year, a team of three scientists from the University of Canterbury Marine Ecology Research Group and two Māhaki ki Taiao rangers travelled to the reserve to undergo marine monitoring work.

The team used a new technology to detect the presence of species called eDNA.

It works by passing a litre of seawater through a very fine filter to capture DNA fragments left behind by plants and animals that have been in the area recently.

These fragments were sent to Wilderlab in Wellington for analysis with about 500 species detected, ranging from bacteria to dolphins.

West Coast marine ranger Don Neale said they were delighted to confirm the presence of Smeagol.

The Smeagol sea slug Smeagol Climoi.

The Smeagol sea slug Smeagol Climoi. Photo: WildWind / iNaturalist

“The gravel maggot has a similar lifestyle, living up to 30cm down under the gravel beach surface. That makes it very hard to find and study, but the eDNA method is one way to do that,” Neale said.

“It has previously only been found in two places – a small beach on the south coast of Wellington, which was thought to be its only home, until it was discovered that a genetically-distinct population also exists in Kaikōura.”

It was unknown whether the new population was its own species or related to one of the known populations, he said.

“To figure this out would be a pretty major undertaking.

“We would need to go back in to Hautai and spend some time digging carefully around gravel or under boulders to see if we can find any live gravel maggots there.”

That was no easy task.

The study area requires a helicopter or a two-day walk from the nearest road en, and it also helped to time a weather window.

During the recent trip, university researcher Shawn Gerrity said they managed to squeeze in a tight weather window as a large storm approached.

They got helicoptered out just before it hit, he said.

Neale hoped there would be another opportunity to search the next time they have monitoring to do around the Hautai Marine Reserve.

There was little known about the Smeagol sea slug or its ecological role, he said.

“Although they’re very small and inconspicuous, coastal animals like Smeagol likely have some role to play in recycling nutrients from beachcast kelp back into the thriving ecosystems of the surrounding oceans.

“Their name, ecology, and threat status all give Smeagol a bit of an iconic status.

“And it goes to show how much more there is to learn about our marine environments, with dozens of new species discovered in New Zealand every year.”

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