Sometimes nature works in mysterious ways, refusing to pigeonhole an animal into one category or another.
David Johnson and Robert Watson of Middlesex County realized that after making a remarkable discovery a few weeks back. While inspecting crab pots near the mouth of the Rappahannock River, they spotted an unusual crustacean.
Any good waterman knows that male crabs, called “jimmies,” have blue claws. Female crabs, called “sooks,” have red pinchers. Jimmies aren’t common in this part of the Chesapeake Bay in June.
“There was one male claw and one female claw,” Johnson said. In other words, one claw was blue and one claw was red.
But that wasn’t the most unusual thing about the crab Johnson caught off Gwynn's Island on May 21.
“We both crabbed for many years and have never seen anything like it,” Johnson said. “We put it in front of the boat and kept it alive.”'
When Johnson called scientists at the Virginia Institute of Marine Science, they were just as amazed at the crab, which they call a “bilateral gynandromorph” because its gender is literally split down the middle.
“I was really surprised because I had never seen one,” said Rom Lipcius, an institute scientist who has been studying crabs for more than 25 years.
Lipcius combed through scientific literature and found out that a similar crab was caught near Smith's Island in Maryland in 1979. But this latest specimen is still alive, and may help scientists answer questions on the cloudy topic of crab sexuality.
Not only did the crab have reproductive organs of both genders, but its underside was shaped on one side like a female and on the other side like a male.
A quick anatomy lesson: A jimmy’s bottom is shaped like the Washington Monument, and a sook’s bottom looks like the dome of the Capitol building.
True, gender identity in the marine world isn’t as simple as it is with humans. Some fish change gender during their lives. But this crab was probably half male, half female from the point of conception, according to Al Place, a geneticist with the University of Maryland’s Center of Marine Biotechnology. “There are multiple potential causes,” Place said. “We don’t know how many genes are involved or what the environmental factors might be.”
Lipcius says answers may come when scientists study the genetic makeup of the crab and its offspring.
That’s right. They’re letting the creature breed. Actually, Johnson conducted his own experiment before handing the crab over to scientists. He put the crustacean in a floating tank with a female crab that was ready to mate.
At first the bi-gendered crab cradled the female crab, as if it was protecting it. That’s male behavior. But a day later, the crab let go and gobbled up half the female crab—a sign of female aggression in a species where cannibalism is common. “It was very confused on what to do,” Johnson said.
The crab is enjoying a diet of chopped clams inside an aquarium at the Watermen’s Hall Visitor’s Center at the Virginia Institute of Marine Science in Gloucester Point.
Lipcius said he will observe the crab for a few weeks to see if, like other female crustaceans this time of year, it produces eggs. It’s possible that the crab can fertilize its own eggs.
“After that, we’ll leave it up to the geneticist on what we will do, dissect it or let it live on,” he said. The crab is about 11Ú2 years old. Most crabs in the Bay live to be about 2 or 3 years old, or up to 5 or 6 years old in ideal conditions.
Lipcius said he has an arrangement with Johnson.“We promise once the crab dies, we are going to have it mounted and sort of take turns displaying it,” Lipcius said. “We’ll probably have it here most of the time, but if he has a family get-together, we’re going to give it back to him.”