[UK] Spider crabs rub pieces of seaweed against the backs of their shells until they stick, creating remarkable camouflage.
The combe above the beach echoes with the calls of chiffchaffs, and cock stonechats flick and churr on the wind-stunted hawthorns that line the footpath. Around the twin radio masts – a 20th-century riposte to Start Point’s whitewashed gothic lighthouse – a small flock of swallows cut and swerve.
Beneath the sea there are signs of spring too. Common spider crabs (Maja brachydactyla), which have been overwintering in the depths, start to appear close to shore, a sight that has become a feature of my first sea swims of the year.
Today conditions are perfect: on this cloudless May morning the sea is still and translucent. But even with mask and snorkel on, it takes me over an hour to spot one. I’m ready to call it a day, content with views of tropically brilliant ballan wrasse and the sheer joy of being in such clear water, when I’m stopped by a movement beneath me. Even then I almost miss it, so effective is the crustacean’s disguise. But there, coated with algae and bearded with strands of seaweed, is my first spider crab of the season, looking like an aquatic Green Man. Or, given the season, perhaps a May King.
The seaweed tassels are not there by accident. Paul Naylor, a Devon-based diver and underwater photographer, has filmed the crustaceans rubbing pieces of seaweed against the backs of their shells until they stick. They show “remarkable dexterity”, he tells me, adding that slender hooks on the shell act like Velcro to hold the seaweed in place.
Naylor’s footage is of a large group of crabs in late summer. The purpose of such “aggregations” is not fully understood, though they may provide protection in numbers during the delicate moulting stage, or form part of the mating cycle.
The solitary crab I’m watching scuttles down a slab of rock and, with the delicacy of a diner using chopsticks, teases off clawfuls of weed and levers them carefully up to its jaws. After an hour in 12C water my own extremities are numb and tumid, so I leave the crab to its grazing and kick back to shore for lunch.
Photo: A well-disguised spiny spider crab. Photograph: Paul Naylor/marinephoto.co.uk
View original article at: Coated with algae, the crab looks like an aquatic Green Man
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