![]() ![]() These juvenilesgradually migrate into shallower, less-saline waters inupper estuaries and rivers where they grow and mature (Fischler and Walburg 1962). The juvenile "first crab" is typically 2.5 mm wide (from tip to tip of the lateral spines of the carapace). On occasion, an eighth zoeal stage is observed. There are usually seven zoeal stages and one postlarval, or megalopal, stage. ![]() The megalops stage lasts 6 to 20 days, after which the megalops molts into the "first crab" stage, withproportions and appearance more like those of an adult. The megalops swims freely, but generally stays near the bottom in nearshore or lower-estuarine, high-salinityareas (Tagatz, 1968). The megalops larva is more crablike in appearancethan the zoeae, its carapace is broader in relation to its length, and has biting claws and pointed joints at the ends of the legs. Development to this stage requires 31 to 49 days. The final molt of the zoeae is characterized by a conspicuous change to the second larval stage, called a megalops (also termed megalopa or megalopae. The finalzoeal stage is about 1.0 mm in width (Hopkins, Rogers 1944). Zoeae molt four to seven times before entering the next stage of development. Zoeal developmentmay require 31 to 49 days, depending on salinity and temperature, but development time has been shown to be variable even in a singlesalinity-temperature regime (Williams 1965). The zoeae and all subsequent life stages can increase body size only by molting (Hay 1905 Pyle and Cronin 1950). Theselarvae may migrate vertically in the water column to reach flood and ebb tides, which transport them back into the bay area. Evidence suggests that blue crab zoeaehatch in the Chesapeake Bay, Chincoteague Bay, Delaware Bay, and other estuaries and drift out to sea, where they feed and grow. Tagatz (1968) found more zoeae near the water's surface than at the bottom. They bear little morphological resemblance to adults (Hopkins1943), are filter feeders, and live a planktonic existence in the high-salinity surface waters near the spawning grounds (Pyle and Cronin1950 Darnell 1959). Larvae Stage 1 - Zoeaeįirst stage larvae, called zoeae, measure approximately 0.25 mm at hatching. The stage between moltsis termed intermolt. The new shell is initially soft, but it expands and hardens in a few hours. Before molting, a new shell is formed underneath the old exoskeleton,which then loosens and is cast off. These changes are most dramatic when the animal molts(sheds its rigid exoskeleton) permitting growth and changes in body shape. Crab openin underbelly flap series#Growth and development of the blue crab, as in other crustaceans, consist of a series of larval, juvenile, and adult stages duringwhich a variety of morphological, behavioral, and physiological changes occur. The average sponge contains about two million eggs and is formed in about two hours.ĭevelopment - Growth Stages Growth Stages The female extrudes fertilized eggs into a cohesive mass, or "sponge," that remains attached to her abdomenuntil the larvae emerge. Most females spawn for the first time two to nine months after mating, usually from May through Augustthe following season. They over-winter beforespawning by burrowing in the mud. Spawning SpawningĪfter mating, females migrate to high-salinity waters in lower estuaries, sounds, and near-shore spawning areas. Once the female's shell has hardened, themale will release her and she will migrate to higher salinity waters to spawn. ![]() During mating, the female captures and storesthe male's sperm in sac-like receptacles so that she can fertilize her eggs at a later time. Following this molt, when the female's shell is soft, the pair will mate. Male crabs vie for females and will carry and protect them, called "cradle carrying," untilmolting occurs. Female blue crabs mate only once in their lives, when they become sexually mature immediately following their pubertal molt (immediatelyfollowing this molt, the female is known as a "sook.") When approaching this pubertal molt, females release a pheromone intheir urine which attracts males. ![]()
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