The Japanese spider crab, known scientifically as Macrocheira kaempferi, is one of the largest arthropods on the planet and is native to the waters around Japan. They inhabit the deep ocean floor, typically at depths between 50 and 600 meters (164 to 1,969 feet).

One of the most striking features of the Japanese spider crab is its size. On average, they have a leg span of around 3 to 4 meters (10 to 13 feet), although some individuals have been recorded with even larger spans, reaching up to 5.5 meters (18 feet). Their bodies, or carapaces, can grow to be around 40 centimeters (16 inches) wide. Despite their immense size, they are relatively light, as they are made mostly of chitin, the same material that makes up the exoskeletons of all arthropods.

These crabs have a unique appearance, with long, spindly legs covered in small spines and a triangular-shaped body. Their coloration is often a reddish-brown to orange, which helps them blend in with their surroundings on the ocean floor. Their eyes are small and situated on stalks, allowing them to detect movement and changes in light levels.

Japanese spider crabs are scavengers and opportunistic feeders, primarily consuming dead fish, mollusks, and other small marine animals. They use their powerful claws to break open shells and tear apart their prey. Despite their formidable appearance, they are not aggressive towards humans and are not considered dangerous.

Due to overfishing and habitat destruction, the population of Japanese spider crabs has declined in recent years, leading to conservation efforts to protect their habitats and regulate their harvest. They are also popular attractions in public aquariums around the world due to their impressive size and unique appearance.