Crabs reproduce by laying eggs. When crabs reproduce they assume the doubler position. In this position the male crab carries the female. Mating between the two usually lasts for at least five and a half hours however the crabs maintain this position for up to three days afterward. The female crab then stores the male’s sperm on the underside of her abdomen where it will be used for two more spawning. These spawning occur within her three year lifespan.
The female crabs then migrate to slightly saltier waters after mating and attach between 100,000 to 2,000,000 eggs to the sperm stored under the abdomen. The crab incubation period lasts for about two weeks until the crab larvae hatch and is then released into the ocean to fend for themselves. The crab larvae will continue to grow for the next 40 days until they reach the adult crab stage.
During this time of growing, before they reach adulthood the crab larvae go through several molting stages. First they morph into what is known as the megalapore stage. This is the second larval stage and is characterized by a larger and thicker exoskeleton than the first larval stage. At this point the megalopae often resemble a cross between a crab and a lobster. The megalopae then can be found migrating to shore where they will then continue the 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” or immature crabs usually molt at least 18 times before reaching adulthood.
Crabs such as the hermit crab have been known to live for 30+ years. In captivity, they can even live long lives if cared for properly. Some crab owners have reported crabs living to be the age of 16 or so. Mating between hermit crabs occurs when a spermatophore is transferred by a male to the female as both crabs partially emerge from their shells. Depending on the size of the female, she can lay thousands of eggs and then deposit them with the aid of the gill grooming appendages on her pleopods along the left side of her abdomen. She then carries the eggs as they mature for about a month during which time the eggs will change from brick red to a dark gray color, as the embryos deplete their yolk supply.
The female hatches her eggs in the ocean by passing clusters of eggs from pleopods using her gill grooming appendages to her maxillipeds and forming clusters that are then passed to the tip of the claws and flung out to sea. The crab eggs immediately burst open upon contact with salt water and the new larval hatchlings known as the zoea float amongst the plankton. Each zoea will pass through 4 to 6 different stages that usually last anywhere from 40-60 days and follow the same metamorphosis as other crabs. Something to keep in mind if you are a crab owner is that although hermit crabs do mate in the wild if conditions are right, they will not breed in captivity. They only mate within their natural environments.
In very rare occurrences some crab enthusiasts that live in places like Southern Florida and have kept their pet hermit crabs in outdoor cages that are very large have been lucky enough to have several pregnant crabs from time to time. Unfortunately the zoeas did not survive.