Part Male, Part Female, Fully Mysterious
Dual-Sex Crab Found in Bay Could Yield Clues to Species' Genetics and Mating Habits
By David A. Fahrenthold
Washington Post Staff Writer
Thursday, June 16, 2005; Page B01
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.
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.
The last time such a crab was caught in the Chesapeake region was about 1980, scientists said. Since then, watermen have hauled in millions of crabs annually without noticing another.
On the day they caught it, Watson and boat captain David Johnson had been crabbing since about 5:30 a.m., dumping females into one basket and males -- who are often bigger and sell for twice as much -- in another.
"What basket should we put it in?" Watson asked the captain.
"I think we're going to put it in one up front," Johnson, 50, recalled telling him.