Females have red-tipped claws. Seasonal appearance: Early spring to late fall. The Blue Swimmer Crab is a popular food in Australia and is targeted and caught in large numbers by professional and recreational fishers. This creature itself is actually very unique shellfish and with great taste, this creature has also become one … This may be an adaptation to low oxygen levels, since the scarlet crab lives at 1000 m, near the oxygen minimum zone. There, however, the crab is invasive. They are mobile predators whose salinity requirements change at different stages in their lives. 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. Juvenile and adult blue crabs serve as food for fish, birds and even other blue crabs. 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. Additional Resources. Thinner legs require less oxygen, hence less energy. 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. Blue crabs are subject to predation throughout their life cycle and are particularly susceptible when they are soft during the molting process. Crabs are crustaceans with five pairs of legs. It weighs 1 to 2 pounds (0.45 to 0.9 kg) when fully grown. During this time females migrate to the mouths of estuaries so that larvae may be released into high salinity waters. 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. Blue Crab (Callinectes sapidus)Color: Olive green carapace, with brilliant blue claws. Blue Crabs. They also store water in their bladder, blood, and specialized pockets throughout their bodies. Size: Up to 9 inches long from point to point, and 4 inches from head to tail. Monitoring blue crab population levels and range shifts to gain knowledge on how changing conditions may be impacting crab populations is a useful first-step adaptation strategy for this species. Striped bass, red drum, catfish and some sharks depend on blue crabs as part of their diet. Florida Fish and Wildlife Conservation Commission Species Profile Blue crab larvae are part of the Bay’s planktonic community, serving as food for menhaden, oysters and other filter feeders. Facts about Blue Crabs 8: the natural predators. Stowaway blue crabs on ship ballasts have even showed up in the Mediterranean. Description. The first pair is modified as pinchers and the last four pairs are walking legs. Land crabs have even more adaptations to prevent drying out. Blue crab larvae have a salinity requirement of at least 20 ppt, and show poor survival below this threshold. The sharks, striped bass, eels, drum, whiptail stingrays, conose rays, and trout are considered as some of the natural predators of blue crabs. They drink water from dew and the ground, they get it from food, and even from water vapor. The scarlet king crab lives even deeper than the golden king crab, and has legs that are much thinner in respect to their length. Blue crabs are sexually dimorphic.Males are slightly larger than females and have bright blue claws. More information about adaptation strategies. Habitat: Shallow and brackish waters, eelgrass beds, muddy bottoms. The blue crab's carapace (or shell) is about 7 inches (17.8 cm) wide and 4 inches (10.2 cm) long. Females have red-tipped claws. As larvae, they are vulnerable to fishes, jellyfish and other planktivores. The megalopae and juvenile crabs are consumed by various fishes and birds, as well as other blue crabs. The blue crab's incubation time is 14-17 days, which is when the eggs are brooded. 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