After mating, the two crabs resume the cradle carry until the female's shell hardens. Shortly after mating, the now mature female crab, known as a sook, migrates to the saltier waters of the Bay near the ocean. The female crab lays her eggs from 2 to 9 months after mating, depending upon when the mating took place. For example, a spring mating would result in a late summer spawn, while a fall mating would result in an early summer spawn the following year. Females develop an external egg mass on the underside of their abdomen which may contain between 750,000 and 8 million eggs, depending on the size of the crab.
Young sponges are orange and gradually turn to brown and then black as the sponge matures.
The newly-hatched larvae are called zoea and look nothing like an adult crab. These young crabs are microscopic in size and drift about in the water currents. It is believed that the majority of these eveloping larvae are transported into the ocean by an interaction of seasonal winds and bottom water circulation patterns, and eventually returned to settle on seagrass beds in the spawning area. After approximately 6 or 7 molts, the zoea changes into a post-larval form known as the megalops. The megalops has claws like a crab, but can swim and crawl on the bottom.