Striped bass, red drum, catfish and some sharks depend on blue crabs as part of their diet. There are many crab behavioral adaptations for survival that this shellfish do since they need to be able to fight their predators and live in their natural habitat. There, however, the crab is invasive. It weighs 1 to 2 pounds (0.45 to 0.9 kg) when fully grown. The blue crab's carapace (or shell) is about 7 inches (17.8 cm) wide and 4 inches (10.2 cm) long. Blue crabs have been introduced to various international waters such as in Black Sea, Mediterranean Sea, Baltic See, European Water and Japanese water. The scarlet king crab lives even deeper than the golden king crab, and has legs that are much thinner in respect to their length. Stowaway blue crabs on ship ballasts have even showed up in the Mediterranean. Blue Crabs. During this time females migrate to the mouths of estuaries so that larvae may be released into high salinity waters. Blue crab larvae have a salinity requirement of at least 20 ppt, and show poor survival below this threshold. Adult male crabs live in the low-salinity waters upstream, while adult female crabs live in the higher-salinity waters near the mouth of the estuary. Facts about Blue Crabs 8: the natural predators. Florida Fish and Wildlife Conservation Commission Species Profile Blue Crab (Callinectes sapidus)Color: Olive green carapace, with brilliant blue claws. More information about adaptation strategies. Thinner legs require less oxygen, hence less energy. Blue crab larvae are part of the Bay’s planktonic community, serving as food for menhaden, oysters and other filter feeders. Size: Up to 9 inches long from point to point, and 4 inches from head to tail. Additional Resources. Description. If the crab is flipped over, the shape of the folded surface of the belly (the apron) reveals the animal's approximate age and sex. As larvae, they are vulnerable to fishes, jellyfish and other planktivores. It was first seen off Egyptian waters in the 1940s, but reports of blue crab sightings in Italy, Israel, Greece, and Turkey have been made, too. They also store water in their bladder, blood, and specialized pockets throughout their bodies. Land crabs have even more adaptations to prevent drying out. They drink water from dew and the ground, they get it from food, and even from water vapor. Females have red-tipped claws. Blue crabs are subject to predation throughout their life cycle and are particularly susceptible when they are soft during the molting process. The blue crab's incubation time is 14-17 days, which is when the eggs are brooded. These crabs enter estuaries as juveniles and grow quite quickly, maturing after one year. Habitat: Shallow and brackish waters, eelgrass beds, muddy bottoms. Females have red-tipped claws. Crabs are crustaceans with five pairs of legs. Juvenile and adult blue crabs serve as food for fish, birds and even other blue crabs. Seasonal appearance: Early spring to late fall. Blue crabs are sexually dimorphic.Males are slightly larger than females and have bright blue claws. This creature itself is actually very unique shellfish and with great taste, this creature has also become one … The sharks, striped bass, eels, drum, whiptail stingrays, conose rays, and trout are considered as some of the natural predators of blue crabs. They are mobile predators whose salinity requirements change at different stages in their lives. The megalopae and juvenile crabs are consumed by various fishes and birds, as well as other blue crabs. The first pair is modified as pinchers and the last four pairs are walking legs. The Blue Swimmer Crab is a popular food in Australia and is targeted and caught in large numbers by professional and recreational fishers. Blue crabs live in estuaries along the United States' Atlantic and Gulf coasts. 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