A 1957 B movie from that fount of B-movies, Roger Corman
A group of scientists land on a remote pacific isle after it was irradiated, in search of a previous group who went missing studying the effects of the radiation from the Bikini Atol tests on the local ecosystem. Turns out they were eaten by Giant Mutant Land Crabs (!) who have absorbed their intelligences by eating their brains. The crabs then go about killing the humans one by one. Once the humans learn of their weakness, the crabs step up their plan to hunt them down, using dynamite to destroy the island bit by bit. Cornered and on the run, the crabs close in for the kill...
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