You are walking along the beach when you spy a dead crab on the sand, and being the curious sort, you stop and have a look. You can tell it is a Blue Crab from the color and shape, and you can tell it is female from the red tipped claw. But wait, what is that sticking out behind? Since when do Blue Crabs have tails? Hmmm…it kinda, sorta looks like an itty bitty lobster tail.
Intrigued, you flip it over and have a closer look. It doesn’t look so much like a lobster tail now, in fact, it looks more like a flap of some kind rather than a proper tail. And indeed, a flap is what it is. Many crabs have what is call a “reduced abdomen”, what we call the “apron,” folded against the belly. One way to think about this is to make a crab out of a lobster by folding the tail up under its body between the legs, then press the tail up into its bottom shell until it’s flush. Voilà! You now have a crab… well, sort of! A male blue crab has a long, narrow apron, which I refer to in talks as the “Washington Monument.” The female has an apron shaped like a triangle” (juvenile) or inverted “U” (adult).
Blue Crabs have internal fertilization and mate belly to belly. This mating takes place just after the female has molted and is still soft. What is kinda cool about this is the the male crab will cradle his intended against him for a few days before she is ready to molt and will continue to cradle her afterward, until her new shell has hardened and she is safer from predators. Females may store the sperm for a while before fertilizing their eggs with it. But once fertilized, the eggs are released onto her abdomen, below this flap and they are held in place by a sticky substance secreted with them. They are cradled by modified swimmerets, called pleopods, protected against the mother’s body during their embryonic development, until they hatch and enter the water as zooplankton. Females carrying eggs are called “berried” since the eggs resemble round berries. This egg mass is also called a “sponge”. If harvesting crabs, it is illegal to take a female carrying eggs; they must be released, alive, back into the water they were collected from.
If you would like to know more about our famous Blue Crabs, you can visit my page about them by following this link.
