The popular blog BoingBoing ("a directory of wonderful things") has once again found its interest piqued by crustaceans (see BoingBoing, Bubba, and the Acronym Wars). Today BoingBoing ran an amusing story on an unusual Chesepeake blue crab that showed up in a waterman's trap: on one side of the crab's body it was male; on the other, female.

Despite what you might think, this was not a case of hermaphrodism. Hermaphrodites change gender. This was something far stranger: the crab was literally two genders at the same time. It's called gynandromorphy, and occurs only in bilaterally symmetric animals, including crustaceans and insects, when they undergo what one scientist has referred to as a "chromosomal mishap." The word "gynandromorph" is Greek for "woman-man-shape."

Gynandromorphy occurs in lobsters, too. Last summer, Bruce Fernald's wife Barb (whom you know if you've read THE SECRET LIFE OF LOBSTERS) e-mailed me a photograph of a rare half-male, half-female lobster that Bruce had caught in one of his traps. Here is Barb's photo. You can see the hardened top swimmeret (=penis!) on the right, but not on the left, which has the soft swimmeret of a female.

Gynandromorphy is a particularly tough situation for a lobster; normally the male has two of those little pensises, one on each side. Sadly, the gynandromorph gets only one, plus part of a female seminal receptacle (=vagina!) nearby. In theory, this arrangement might allow the lobster to have sex with itself. But it's not clear that lobster gynandromorphs have much sex drive at all -- when one was paired with a willing female, it treated her like a rock. Intrigued? Here is where I learned what I know about gynandromorph lobsters.