Macrocheira Kaempferi is a species of marine crab commonly known as the Japanese spider crab. It is a massive crustacean that can weigh up to 20 kg and has a leg span of almost four meters. The species is found in the waters surrounding Japan and is considered a delicacy in Japanese cuisine. Some synonyms for Macrocheira Kaempferi include giant spider crab, long-armed crab, and monster crab. Despite its intimidating size, the Japanese spider crab is not aggressive and feeds primarily on small fish and shellfish. The species is also the subject of research due to its unique physiology and behavior.