red claw, blue claw

The WaPo has a story about a fascinating crab:

Watermen say that female blue crabs 'paint their fingernails,' meaning the tips of their claws turn bright red as they age. The male crabs, on the other hand, have sky-blue claws -- a sign as masculine as a mustache in the world of crustaceans.

So when Robbie Watson dumped out a crab trap and found a specimen with one red claw and one blue one, the discovery stopped him.

'I set it aside for a while,' Watson said. 'I really wasn't sure what to think.'

As his boat, the Wharf Rat, moved on to other crab pots, Watson, 42, studied the crab. Underneath, its shell should have had a design looking roughly like the U.S. Capitol dome if it were female, or a Washington Monument pattern if it were male.

Instead, Watson found a wavy arrow, which seemed to be a combination of both sexes.

'It was unreal,' Watson said. 'I've never seen anything like that, and I've worked the water all my life.''

Scientists said the crab, caught May 21 near Gwynns Island in the lower bay, is an extremely rare creature called a 'bilateral gynandromorph' -- that is, split between two genders -- with its right side female and its left side male.

There's a photo.