The world’s largest terrestrial crab
Meet the coconut crab (Birgus latro), which holds the title of the world’s largest terrestrial crab (and indeed the world’s largest terrestrial arthropod). Found on islands of the Pacific and Indian oceans, it can reach a length of up to 1 m (3 ft 3 in), and a weight of up to 4.1 kg (9.0 lb) (see an especially large individual here: http://bit.ly/1UXlLhF).
Like all arthropods, coconut crabs do not have an internal skeleton. Instead, they wear an exoskeleton like armour, which sheds as they grow. Fuelling their massive growth requires a lot of food, so the crabs eats anything they can get its claws on - from carrion to fruit, chickens to other crabs. But as their name suggests, coconuts are their favourite.
As anyone who has lived on a tropical island will know, coconuts are notoriously difficult to open. But these crabs have no problem. Equipped with a pair of massive claws, they tear away the outer fibres (which can take many days and more than one crab), and use one of their legs to puncture a hole to pry the shell open further. If this fails, some crabs have been observed to lift coconuts up trees 10 metres (33 ft) high, then drop them to reveal the inner white flesh. In fact, the crab’s claws are capable of lifting weights up to 28 kg, so this is rarely an issue.
And it seems their love of coconuts is worth it. Crabs living in coconut-rich habitats have double the average mass of those living in coconut-free habitats. I guess it’s similar to how many of our own favourite foods greatly increase our mass, though this is perhaps not so much of a good thing.
References: http://bit.ly/1T6E5DQ, http://bit.ly/1OjRIzb Image credit: USFWS (https://flic.kr/p/8x28HH)