Space Amoeba

Original title: ゲゾラ・ガニメ・カメーバ 決戦!南海の大怪獣

Synopsis

When a space probe crash-lands on a far-flung Pacific atoll, the craft's alien stowaways decide to take over their new world one creature at a time. Soon, the parasitic life forms latch onto three indigenous critters -- a squid, a crab and a snapping turtle -- and transform them into colossal mutant monsters.