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Spider crabs swarm in shallow water on Cornish beach | Animal life

Written by Javed Iqbal

Thousands of poisonous crabs converged on the beaches in Cornwall due to rising sea temperatures caused by the climate crisis. The migrating creatures swarmed in the shallow waters of St Ives and shed their shells before returning to depths of up to 300ft.

Instantly recognizable by their long legs and pincers, the crustaceans have a venomous bite that is poisonous to their prey but harmless to humans.

Their presence at Porthgwidden Beach was enough to deter many bathers from entering the sea.

But Kate Lowe, a marine photographer captured the event just days after a snorkeler was bitten by a blue shark during an excursion off Penzance.

The spider crabs seen gathering at St Ives, Cornwall, to shed their shells before returning to the depths
The spider crabs were seen congregating at St Ives, Cornwall, to shed their shells before returning to the depths. Photo: @cornish.coast/BNPS

Kate said: “I snorkel most of the time throughout the year but I’ve never seen spider crabs in such numbers. When we turned up at the beach it looked like there were lots of dark rocks under the surface.

“But it turned out that there were thousands of crabs just two or three steps down into the water. It was just really incredible, they were only up to the knee. I was able to float on the water above them and tried not to step on them.

“Many of the tourists squealed at the sight of them. Their shells were just floating around.”

Experts say that although it is not unusual to see them in British waters, mass gatherings are becoming more common in the summer due to rising sea temperatures linked to the climate crisis.

Spider crabs – Hyas araneus in Latin – usually congregate in large numbers in shallow water to protect themselves from predators while they wait for their new exoskeleton to thicken and harden.

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Javed Iqbal

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