Japanese spider crab
Description
The Japanese spider crab has the greatest leg span of any arthropod, reaching up to 3.7 metres (12.1 ft) from claw to claw. The body may grow to a size of 40 cm (16 in) in carapace width and the whole crab can weigh up to 19 kilograms (42 lb)—second in mass only to the American lobster among all living arthropod species. The males have the longer chelipeds; females have much shorter chelipeds, which are shorter than the following pair of legs. Apart from its outstanding size, the Japanese spider crab differs from other crabs in a number of ways. The first pleopods of males are unusually twisted, and its larvae appear primitive. The crab is orange with white spots along the legs. It is reported to have a gentle disposition despite its ferocious appearance. The Japanese name for this species is taka-ashi-gani, (japanese: たかあしがに), literally translating to “tall legs crab.” It also has a unique molting behavior that occurs for 103 minutes, in which the crab loses its mobility and starts molting its carapace rear and ends with molting its walking legs. Their armored exoskeletons help protect them from larger predators such as octopuses, but giant spider crabs also use camouflage. The crab's bumpy carapace blends into the rocky ocean floor. To further the illusion, a spider crab will adorn its shell with sponges and other animals. The way in which spider crabs are able to pick up and cover themselves with such organisms is by following a specific routine behavior. Upon picking up the object with the crab’s slender chelipeds, the chelae is used to twist and tear off the organism, such as a worm tube or sponge, from the substrate that it currently resides on. Unlike other species of crab, like the Chilean crab Acanthonyx petiveri, the Japanese spider crab does not specifically look for matching colors to blend into their environment; they simply camouflage in way that disguises their entire structure. This is most likely because Japanese spider crabs are nocturnally active, so instead of trying to disguise themselves when catching prey, they are actually just trying to avoid predators during the night. Once the material is picked up, it is brought to the crabs’ mouthparts to specifically orient and shape it before it is attached to the exoskeleton. Then, through mechanical adhesion and secretions, the materials attach to the crab, and are able to regenerate, and colonize on the crab.
Japanese spider crab-2