Brand new species of delightful sea creature discovered off the British coast

Finding a new species can happen in a variety of ways, from reclassifying species based on new genetic information with a little help from Will Smith, finding them hiding in trees, or spending months closely examining museum specimens. Scientists are always learning more about the species that surround us. Now a new species of sea slug has been discovered almost by accident in British waters.

Scientists from the UK’s Center for Environment, Food and Aquaculture Science (Cefas) and the University of Cadiz in Spain collected fourteen specimens while conducting routine surveys of fisheries off the south-west coast of England and one in the Gulf of Cadiz. More than 100 species of sea snails are known to live in British waters, but there was something unusual about this one.

The new species, described as “cream and clay colored with white spots”, has been given a name Pleurobranchaea britannica and is approximately 2–5 centimeters (0.7–1.9 in) long. Initially, researchers thought it might be a different species because of the distinctive side gill on the creature’s right side Pleurobranchaea meckeli, which typically occurs in Senegal. However, this species has never before been seen in British waters, leading scientists to doubt the true identity of the sample they had collected.

“It’s exciting to see that routine fisheries surveys can still lead to such discoveries. It only took a brief inspection of two specimens to ensure we had stumbled upon a species. Pleurobrancheaea. This was exciting as no other species of this genus had been documented in British waters, or even this far north,” said Ross Bullimore, marine ecologist at Cefas and co-author of the paper describing the sea snail, in a statement sent to IFLScience.

Ultimately, the specimens were sent to a team in Spain, where researchers both scrutinized the DNA and compared the structures to those of known species. They concluded that the specimen was a brand new species.

Top view of the new sea snail.  The animal has opaque white spots over most of its body with some brown coloration.

This new species increases the number of sea snails in the genus Pleurobranchaea to three.

Image courtesy of Ross Bullimore ©

Sea slugs are one of the most brightly colored and diverse groups of animals, some of which exhibit incredible features and unique appearances. They can also take over parts of their prey, reusing cells for photosynthesis or becoming poisonous by consuming venomous animals.

“When Cefas scientists contacted me and told me that they had collected individuals belonging to the genus sea snails Pleurobrancheaeabut whose specific identity was not clear, I was really surprised,” said Dr. Juan Lucas Cervera Currado of the University of Cadiz. “Firstly because species of this genus have never been found in the British Isles, and secondly because the possibility was really exciting to have found a new species of this genus in European waters.”

Pluerobranchea are commonly known as side gill sea snails, their gills are located on the right side of the body, allowing them to extract oxygen from the water. No other group of sea snails found in British waters has this anatomy, so the distinctive blade-like – or ‘canoe paddle’ structure as the team describes it – side gills alerted them to the fact that they had found something not previously found in British waters had been found.

They suggest that it could have range as far south as Spain and even off the coast of Portugal. The two other species in the genus include Pleurobranchaea meckeli And Pleurobranchaea morosa. The former lives in the Mediterranean Sea and can even be found off the coast of Senegal. The second is much rarer and less known. However, this is not good news, as the researchers suggest that climate change could see this species move to more northerly waters as temperatures rise.

However, the team is thrilled to have discovered a brand new sea snail species. “It is often assumed that we know all there is to know about species found in British waters, but this just goes to show that there is still so much to learn in our own backyard,” says Bullimore.

The study was published in Zoosystematics and Evolution.

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