A giant marine slug found marooned on an Anglesey beach may be a sign of things to come, experts believe. The alien-like creature was spotted by a dog walker at Traeth Treaddur Bay this week.
It was identified as a sea hare, a marine snail more commonly called a “sea slug”. They are named for their prominent, “rabbit ear” scent receptors on their heads.
Smaller sea hares are native to the UK but the Trearddur find is thought to be a much rarer depilatory sea hare, usually found in the Mediterranean. Historically, it was mistakenly believed that touching one would cause hair loss – hence its name.
Emma Leese came across the sea hare some 20 metres from the water’s edge at low tide. Worried that local dogs might take too much of an interest, she returned it to the sea.
“When back in water, it sort of unfolded,” she said. “It began wriggling – slug-like – and its stalks began going back up.” Get the best island stories from our Anglesey newsletter – sent every Friday
As sea slugs cannot absorb atmospheric oxygen, they typically die relatively quickly after stranding. When disturbed in water, they release a dramatic cloud of purple ink derived from the red algae they eat. Like the octopus, this ink is thought to provide a screen or act as a decoy to confuse predators.
Thoughts the Trearddur Bay find might be a black sea hare have been “99%” ruled out. This would have been astonishing: black sea hares are only found in the Pacific Ocean off California, USA, and can grow to enormous sizes – the largest on record measured 99cm and weighed nearly 14 kg.
Black sea hare found on the Pacific coast near San Diego, US. These are much larger than the Depilatory sea hares usually seen in the Mediterranean – which are in turn are much bigger than UK native Spotted sea hare. Black sea hares have features said to resemble a hippo(Image: Madeleine Claire/Wiki)
“Without examining the sea hare, we can’t be absolutely certain,” said Frankie Hobro, owner and director of Anglesey Sea Zoo. “It would be ever so exciting to find a black sea hare here but it’s extremely unlikely.
“More probably it’s a depilatory sea hare. This is still a rare UK species, found occasionally in southwest Britain. However it’s a species we’re likely to see more of in the future as the seas warm and they keep moving north.”
According to the Global Biodiversity Information Facility, the Isle of Man has three confirmed sightings of the depilatory sea hare, and north Scotland has one. Wales has none, though there have been anecdotal reports in Pembrokeshire.
As a mollusc, sea hares are related to the common garden snail. Instead of an external shell, they have a thin, transparent internal shell.
Their fleshy mantles have become modified into large, wing-like flaps. The depilatory sea hare can use these to gracefully swim through water – it is said to be surprisingly agile.
Trearddur Bay’s sandy beach and gently sloping waters(Image: Lesley Scott)
Much more commonly found in the UK is the native spotted sea hare. This is usually around 7m long but can grow to 20cm. In contrast, depilatory sea hares can reach 40cm, dwarfing their British cousins. They’re also much bulkier.
Frankie advises anyone finding a sea hare not to touch them without gloves as their skin stores noxious chemicals from their algal food. Reputedly, Roman Emperor Titus was poisoned by his brother Domitian with a sea hare.
“They are quite revolting to touch,” said Frankie. “As they have quite strong suction, they should never be prised off a rock as this may damage them.
“I always say it’s best to leave marine creatures alone as it might not always be what you think they are.”
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