As soon as I heard the yell of excitement, I guessed what it might be. This is the species that everyone recording rockpool wildlife in Cornwall has been watching out for. For me, it was especially exciting that this one, found by Jan of Coastwise North Devon, had just turned up in one of my favourite coves, Porth Mear. 

Meet Clibanarius erythropus. Nope, none of us could remember that name either, though we knew it certainly was one. Jan decided to name little hermit crab Sydney to make things easier.

Clibanarius erythropus is a distinctive (if unpronounceable) crab. Most species of hermit crab have one claw that is considerably larger than the other – most are ‘right clawed’. This species is almost unique in having two fairly equal sized claws.  

The white spots on its eyes and its striking red legs are also a good aid to identification.

If you find one, please take a photo and send your record to ORKS, the Cornwall and Isles of Scilly online recording system -it’s quick and easy to do.

This warm-water species, relatively common in the Channel Islands and around the French coast, is at its northerly limit in Cornwall. It used to be found occasionally on our shores, but has rarely been recorded here since the 1967 Torrey Canyon oil spill in 1967. The last recorded sighting was in 1985.

But this year it has reappeared. There have already been at least three records from various locations around Cornwall in 2016. Could these hermit crabs be making a comeback?

One explanation for the reappearance is the high water temperatures of the last couple of years. In 2015 warm currents arrived early in the year bringing a massive bloom of the giant barrel jellyfish. These conditions could have been right for the hermit crab plankton to survive and settle on our shores. 

So now we have to wait and find out whether the conditions remain favourable for this little hermit crab to become a long-term resident in our rock pools.