Thousands of spider crabs have been filmed congregating in shallow waters off a British beach.
The eerie-looking crustaceans, known for their long limbs and ghostly appearance, have gathered en masse to moult – shedding their hard outer shells to allow for growth.
The seabed near Porthgwidden Beach, St Ives, Cornwall, has been left strewn with discarded exoskeletons – creating a scene that looked more like a tropical reef than the British coastline.
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The footage was captured by marine expert Matt Slater, as reported by Need To Know.
It revealed vast numbers of crabs carpeting the ocean floor in a natural phenomenon rarely seen by the public.
According to the Cornwall Wildlife Trust, the sight is both spectacular and significant.
While mass gatherings of spider crabs are not unheard of, they appear to be happening more frequently and over wider areas of the Cornish coast.
“Known for their eerie appearance but harmless nature, these long-limbed crabs are massing in huge numbers to moult,” a spokesperson for the Trust said.
“Footage shows the scale of the event, with carpets of crabs scuttling across the sea floor in scenes rarely witnessed by the public.”
Experts suggest that climate change and warmer sea temperatures could be contributing to the increased frequency and distribution of these gatherings, as the species may now be thriving further along the British coast.
The Wildlife Trust emphasised that events like this are a striking reminder of the richness and vitality of the UK’s marine ecosystems – and why they deserve stronger protection.
The organisation is calling for urgent action to safeguard the marine environment, including measures to address pollution, habitat disturbance, and destructive fishing practices.
The spokesperson added: “These moments show just how full of life our seas really are.
“We’re incredibly lucky to witness such natural spectacles here in Cornwall, and it’s a powerful reminder of the need to protect them for future generations.”
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