News - November 16, 2017

Sponge crabs settling in Eastern Scheldt

Roelof Kleis

It looks as if the sponge crab is gaining a foothold in the Netherlands. Divers have come across the crab several times in the Eastern Scheldt estuary.

The sponge crab gets its name from the sponge it carries on its back as camouflage. © Mick Otten

Reindert Nijland of the Marine Animal Ecology group has now reported on the finds in Marine Biodiversity Records.

Crab expert Nijland has a soft spot for the sponge crab, which was last seen in the southern North Sea in 1953. The creature is covered with tiny yellow hairs that give it a woolly appearance. Nijland: ‘That makes the crab look rather cute and cuddly. What is more, its claws have bright pink fingers as if it’s wearing nail varnish.’

Two of Nijland’s friends, the biologists Floris Bennema and Godfried van Moorsel, discovered the crab in August last year near Zeeland Bridge. They brought the crab back in a bucket and phoned Nijland. ‘I jumped in the car immediately.’ The news about the sponge crab was covered in various media, after which reports came in via the ANEMOON Foundation’s Facebook page from divers who had also seen sponge crabs in the Eastern Scheldt. Analyses by the three friends suggest there are at least a handful of different sponge crabs out there, both male and female.

The sponge crab gets its name from the fact that it carries a sponge on its back as camouflage. An almost perfect trick when the seabed is covered with sponges. The crab has two pairs of hind legs that have evolved into little pincers that keep the sponge in place. Nijland says the sponge is hollowed out until it has become a close-fitting ‘jacket’. ‘The sponge is still alive; it can cope with that kind of treatment.’

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The sponge crab normally lives in the Atlantic Ocean off the coast of Portugal and Africa and in the Mediterranean. Nijland thinks the crabs came up here as larvae. It remains to be seen whether they will stay in Zeeland.

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