Does anyone recognise these crabs?
Swimming crabs - I thought marbled - Liocarcinus marmoreus.
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Posted 15 October 2013 - 12:09 AM
I've been down this route a number of times and find them very difficult to separate. The key seems to be to get a photo from above and behind so you can see the legs, carapace shape and the pointy bits between the eyes. I think without a photo like that you will never be 100% certain.
That said, I think your ID is possibly right for the left hand one - not due to the colour which is not a particularly good guide but more because of the carapace and the legs.
I have a .pdf with diagnostic diagrams which I find quite helpful. If you want a copy send me a private message with your email and I will forward it to you
Jim Greenfield - Canon 5D Mark 3/Aquatica
My Web Site
Posted 21 October 2013 - 04:07 AM
I'm not sure that you have sufficient data in the images for an absolute ID to be made either - the most useful guide I have is "A key to Crabs and crab-like animals of British inshore waters" by John & Marilyn Crothers (an AIDGAP guide from the Field Studies Council). Differentiation often relies on relative lengths of leg parts, so you need to take photographs bearing this in mind if you want to be able to identify them.