It sounds like an old black and white sic-fi classic. But giant killer crabs do exist and, in some places, they act as the top predator on land. One particularly nightmarish club-a-crab hotspot is the Chagos archipelago several hundred miles of the southern tip of India. Some of these small islands play host to the coconut crab, so named because it can literally break open adult coconuts and feed onf the yummy sweet juice and pulp inside. It sounds like a wonderful place to not visit:
In the decades to come, of course, coconut crabs would be photographed not only climbing trees but hanging from them like enormous hard-shell spiders. Researchers in our own century once left them a small pig carcass to see what would happen, Smithsonian Magazine wrote. The crabs quickly disappeared the pig.
Now we know they are the largest invertebrate to walk the earth - more than three feet long, pincer to pincer, with claws so strong that a researcher once tried to measure the force, and described it as “eternal hell” after a coconut crab caught his hand. But what, wondered Mark Laidre, do they eat?
Crabs are often thought of as a tasty bit of seafood slathered in butter. But they live in freshwater and even on land. There’s even a species that has specialized in living inside the hollows of carnivorous plants that grow in the rainforests of Malaysia. Crabs have radiated into these surprisingly diverse, non-marine echo-niches in part because they’ve had a lot of time to evolve.
The first creatures roughly similar to crabs appear at the dawn of the cambrian explosion over half a billion years ago. The best known, ancient representative of these arthropods being trilobites. Today, this
hugely successful phylum includes insects, spiders, and lobsters. But whereas bugs like centipedes and ants were constrained by a less organized circulatory system that depends a great deal on osmosis and could literally — if inaccurately -- be described as heartless, crabs and their well armored cousins like lobsters hit on the ingenious idea of developing in the more buoyant media of water and evolved a more efficient central pump, both of which helped them to grow to larger sizes than their creepy crawly insectoid kin.
In fact, at least two extinct members of the arthropods that were fairly crab-like were
basically the crocodiles of their time and place in both
size and ferocity. Today the largest crab, and thus the largest extent arthropod, is the
giant Tasmanian crab which can weigh in at almost 40 lbs! But that one lives in deep water.What makes these coconut crabs so eerie is they are unabashed predators happy to stroll in land, climb trees and hang out in ambush like a giant spider from the worst nightmares. Sleep well tonight!