This is a blue crab, named for its strikingly blue legs. The blue crab’s scientific name, callinectes sapidus, celebrates a combination of color, ability, and tastiness. “Calli” means beautiful in Greek, a tribute to the crabs’ color. “Nectes” is swimmer in Greek — by using their rear legs as paddles, these crabs swim very well. “Sapidus” is savory in Latin, because people like to eat them (see fine dining).
The savoriness of blue crabs means they are widely fished and eaten everywhere they live, from Nova Scotia in the north to Uruguay in the south. One of their favorite places is Chesapeake Bay, where in 2018 an estimated 147 million adult female blue crabs made their homes. Females have reddish tips on their pincers, and thus we know the crab posing for us at the top of the page is a female.
On the way from birth to adulthood, blue crabs molt several times. This means they outgrow their shells, shed them, and grow new ones. They typically live for one to three years, if they aren’t scooped up for dinner, and during that time they must deal with two things important to all living creatures, food and sex.
First, food: Blue crabs are not picky eaters; they will eat just about anything they can find. This means the tasty blue crab you just consumed likely ate, in its turn, clams, oysters, mussels, smaller crustaceans, dead fish, and plant and animal debris. Your crab may also have been a cannibal, having happily eaten smaller blue crabs, as well as fellow crabs who chose a bad time to molt and so were not protected by shells.
And now, let’s address matters of sex. Male blue crabs mate frequently, probably as often as they can. To attract a female, they wave their legs as though dancing. A female blue crab, however, mates only once during her lifetime. Could this difference demonstrate superior female morality? Maybe not. Perhaps it’s just the result of simple fatigue, since, after she mates a female blue crab produces from 750,000 to 2,000,000 eggs.
___
The photo at the top of the page is in the public domain from the U.S. Environmental Protection Agency.