12 Mind-Blowing Deep-Sea Creatures You Won’t Believe Exist

6. Japan’s Giant Spider Crab: Titan of the Seafloor

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The Japanese Spider Crab (Macrocheira kaempferi) ranks as the largest arthropod on Earth, flaunting legs that can stretch 12 feet (3.7 meters). Living 150–800 meters below Japan’s coastal waters, it thrives in icy, high-pressure depths. Its spidery limbs let it stride over sediment while its mottled shell disappears into the scenery. Though fearsome in size, the crab is mostly a scavenger, dining on carrion, algae, and small crustaceans. Its powerful claws can crack mollusk shells, and it often “decorates” its carapace with sponges and algae for disguise and defense. With life spans reaching a century, these slow-growing giants molt repeatedly and females carry up to 1.5 million eggs, few of which reach maturity. Overfishing and habitat loss now threaten them, making careful management vital for their future.