The Japanese spider crab, known for its immense size and unusual appearance, often prompts questions about its potential danger. This deep-sea inhabitant captures public attention and curiosity. Exploring the reality behind its formidable looks clarifies misconceptions surrounding this unique marine creature.
Physical Attributes and Perceived Threat
The Japanese spider crab (Macrocheira kaempferi) possesses distinctive physical characteristics that contribute to its intimidating image. It is the largest known living arthropod, with a leg span up to 12 feet (3.7 meters) from claw to claw. Its body, or carapace, can grow to about 15 inches (38 cm) wide and weigh up to 44 pounds (20 kg). Male crabs have longer claws than females.
The crab’s body is orange with white spots along its legs, and its pear-shaped carapace is covered in small, spiky projections. Two thin spines protrude between its short eye stalks. These impressive, almost alien-like features, particularly its extended limbs and unique shell texture, contribute to a perception of danger. Despite its large size, the legs are considered weak, and it is common for these crabs to be missing a limb.
Habits, Habitat, and Temperament
The Japanese spider crab inhabits the deep waters around Japan, primarily off the southern coasts of Honshu, including areas like Suruga Bay. They are found at depths ranging from 160 to 1,970 feet (50 to 600 meters), preferring sandy and rocky continental shelves and slopes. Adult crabs prefer water temperatures around 50-55°F (10-13°C).
These crabs are primarily scavengers, feeding on dead animals and detritus found on the ocean floor. Their diet includes decaying fish, mollusks, smaller crustaceans, and algae. While they can use their long claws to pry open shells or tear meat, they are not active predators of large creatures. Their slow movement along the seabed reflects their scavenging lifestyle rather than aggressive hunting behavior.
The Japanese spider crab is known for its calm and gentle disposition despite its appearance. They are not aggressive towards humans or other creatures and rely on camouflage and their tough exoskeleton for defense. When threatened, they may use their large size and sharp spines as a deterrent.
Actual Risk to Humans
Despite its formidable size and appearance, the Japanese spider crab poses virtually no threat to humans. Encounters with these crabs are extremely rare due to their deep-sea habitat, limited to deep-sea fishing operations or specialized aquariums. When they move to shallower waters, it is during their mating season, around January to March, at depths of about 164 feet (50 meters).
The crab’s docile temperament means it lacks aggressive behavior towards people. While its claws are substantial, they are primarily adapted for foraging and defense against natural predators, not for attacking humans. Any potential “pinch” from a Japanese spider crab would be accidental or a defensive reaction if provoked, and it is not considered life-threatening. The strength of their claws is not sufficient to cause serious injury to a human.