Perhaps when you were on holiday, you risked eating mussels. You may have noticed a red blob inside or crunched on something hard as you chewed the soft mussel tissue. In the dim evening light you probably didn't realise that the red blob was a female crab, and the crunchy 'nut' a male one. They are pea crabs, Pinnotheres pisum L., frequently found in mussels and other bivalves – especially in the Solent.