The blue crab is a crustacean that primarily lives off the Atlantic coast of North America. These animals are more of a grayish brown shade rather than blue, but they do have blue markings on their forelimbs. The blue crab measures between 4 and 10 inches (0.10 to 0.25 meters) in diameter and has 10 limbs, two of which are claws. Males and females look different, with females having more of a triangular shell and red markings on their claws. The blue crab is generally prized as a food item throughout its habitat range.
When it comes to diet, the blue crab isn’t known to be especially finicky. These crabs generally prefer to eat animals like clams and oysters when possible, but they will also eat carrion or nearly any other kind of organic matter they can find. Blue crabs are also willing to indulge in cannibalism when they find a smaller, younger crab. They normally function as ambush predators, generally hiding in soft dirt or underneath objects on the bottom of the sea. When the opportunity presents itself, they will often grab anything that passes by.
Crabs have to molt in order to increase in size. This process involves shedding their shell as a new shell grows underneath it. Right after molting, the blue crab has a soft body, which makes it vulnerable—gradually, the body hardens. The average lifespan of the blue crab is about 2 years, although this is partly because they are often harvested as a food item before they can get any older.
Mating for the female blue crab is tied into the molting process. When she finally reaches her full growth and goes through her last molt, a female blue crab is generally ready to breed. Once the breeding occurs, the females continue to carry the male’s sperm around for several months before actually releasing any fertilized eggs. The length of time before this happens varies, and the crabs generally don’t produce their eggs until their shells harden and they have time migrate to another location.
Once conditions are right, the female generally produces millions of eggs on a spongy mass that she carries under her body. After about two weeks, they are normally released into the ocean as larvae. These larvae are initially tiny and they drift around in the current. Only a very small number of them ultimately survive, while most are taken by various predators or fall prey to bad luck. Once the female breeds once, she will never breed again, but she saves a lot of the sperm, and she is able to produce eggs several times from that single breeding cycle.