Discovery of New Species of Sea Slugs in the Indo-Pacific Excites Scientists

They may not everyone’s favourite creature, but scientists have discovered 18 new species of bright and colourful sea slugs in the Indo-Pacific.

Lead researcher Kara Layton has been studying the molluscs in depth for almost four years, and describes them as “beautiful and diverse”.

But she said there was still much to learn.

“They’ve been understudied, compared to other things,” Ms Layton said.

“They are tiny little slugs that are found on shallow subtidal areas, and a lot of people don’t know about them if you’re not in the underwater community.

“They’re really important, they’re incredibly diverse, they make up a part of our shallow subtidal eco systems.”

She said tiny creatures were often overlooked, so researchers and scientists don’t know a lot about them.

“We want to make sure that we are trying to get a good understanding of biodiversity in general and not just the big charismatic animals that most people know about,” Ms Layton said.

The scientists, from the University of Western Australia, the WA Museum and the California Academy of Sciences are building a comprehensive dataset of these sea slugs.

Of the newly discovered slugs, two of them have been found only in WA.

They are quite large compared to some other sea slugs, and usually hide under rocky outcrops.

“Despite being colourful, they can be difficult to find,” Mr Layton said.

A green and orange-striped sea slug

One species of sea slug — an orange-striped creature found in Port Hedland in the north-west of the state — was so rare it had only been seen in a photo taken many years ago.

“Most of them are actually toxic, because they don’t have a shell to protect them they use toxic chemicals instead,” Ms Layton said.

“When a predator comes to eat them they are pretty distasteful and so they will probably spit them out.”

The scientists were also finding out new things about existing slugs.

Using DNA testing, they discovered the invertebrates could live in disguise — over time they can change colour to mimic the colours of other species in greater abundance.

“One species is mimicking another species that is locally abundant,” Ms Layton said, likely as a method of predator avoidance.

“It’s mimicking the other species that is abundant as a way to protect itself.

“So if a predator knows this abundant species is toxic, it won’t eat it.”

Ms Layton said slugs were hard to find some years.

“Some years we’ll see a lot of them and then we may not see them again for several years,” she said.

Sea slugs, known as nudibranchs, may be a good indicator of marine health and changing sea conditions.

“In some areas, they can act as indicators of ecosystem health,” Ms Layton said.

“The idea that if you have nudibranchs around, it may indicate a really healthy ecosystem.”

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