Crabs are decapods crustaceans, that are covered with thick exoskeleton and a pair of claws. Various crab species are found in various waters bodies across the world, from freshwater to the saltwater bodies.
The Japanese Spider Crab, the largest living crab in the world, in terms of its limb reaching 12ft 6in (3.8metres) from claw to claw. When fully grown, the body may grow to a size of 35cm to 40cm. The whole crab can weigh up to 42 pounds (20kg). It may live up to 100 years.
It is during the spring time that Japanese Spider Crabs lay their eggs, typically at depths of around 50metres. Sperm of male crabs are held in a case (sac, or spermatophore). Spermatophores are transferred to the female by the first and second abdominal appendages during mating. After fertilization, the female crab carries the eggs attached to the abdominal appendages. A cement is secreted by the egg-carrying setae to bind them to the abdominal appendages. When the eggs hatch, the young crabs look nothing like their parents. During the larval stage, or zoea, the baby crabs are small, transparent organisms with round, legless bodies. They usually swim at the surface of the ocean. During their growth stage, they tend to shed their skin several times which is an amazing sight to see. When the body and legs begin to form and appear more crab-like, the young crab is in the megalops stage. During this stage, though, the abdomen is large and not folded up. The crab continues to molt its’ skin until it takes on a form that is very similar to the adult.
The Japanese spider crab is primarily an omnivorous species that can be found scavenging for food along the ocean floor at a very slow pace. It feeds on shellfish and animal carcasses on the bottom of the sea. They consume plants, small fish, algae, as well as mollusks. Their large and strong pincers allow them to catch prey easily and tear it apart before consumption.
The males have the longest chelipeds, females have much shorter chelipeds, which are shorter than the following pair of legs. It has eight legs with 2 feeding arms, which are also used to grab and subdue their prey. The male specimen is slightly different from the female specimen, the arms of the male where the pincers of the crab are located, become longer then the legs they use to walk on.
You might think because of its size that this crab would be a monster in its defensive mechanism, but no! Some crabs attach sponges and other sea creatures to their shells as camouflage and defensive mechanism just like any other crab to protect them against other predators. The Japanese spider crab seems big, but in reality, it is a very defenseless creature of the ocean.
As a majestic creature of the wild and predators such as the Octopuses, the main predator is not even from the ocean floor. You see, the meat of the crab is a delicacy and is highly prized, not just in Japan but around the world. They are fished in large numbers on an annual basis and usually to catch them requires large trawling nets, which makes the human species the main predator for the Japanese Spider Crab.
