Crabs are classified as decapod crustaceans, which means that their abdomens are hidden under the thorax. Most crabs have a sturdy exoskeleton, which guards their soft insides from predators and other dangers. Crabs exist in all of the world's oceans and come in a variety of shapes and sizes. The smallest crab, the pea crab, measures about three millimeters in width. Moreover, the oldest known crab fossil dates all the way back to the Jurassic era. Crab meat is a popular food item, particularly in seafood-loving countries such as Japan.- Crab larvae
When male and female crabs reproduce, they assume the doubler position, which is when the male carries the female. Mating lasts about five-and-a-half hours, but the crabs may stay in this position for up to three days afterward. The female stores the male's sperm on the underside of her abdomen, where it will be used for two more spawnings that occur within her three-year lifespan. The females migrate to slightly saltier waters after mating and attach between 100,000 to two million eggs to the sperm stored under the abdomen. The incubation period lasts about two weeks, until the crab larvae hatch and are released into the ocean to fend for themselves. For the next 40 days, the crab larvae continue to grow until they reach the adult crab stage. - The crab larvae go through several molting stages before they reach adulthood. First, they morph into the megalopae stage, which is the second larval stage and is characterized by a larger and thicker exoskeleton than the first larval stage. At this point, the megalopae look like a cross between a crab and a lobster. The megalopae migrate to the shore and go through their next molting stage, after which they are classified as immature crabs or "first crabs." This occurs about two months after the first larvae are hatched. These "first crabs" molt at least 18 times before reaching full adulthood.
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