Space Amoeba is a 1970 Japanese kaiju film directed by Ishirō Honda, written by Ei Ogawa, and produced by Tomoyuki Tanaka and Fumio Tanaka, with special effects by Sadamasa Arikawa. Produced and distributed by Toho Studios, the film stars Akira Kubo, Atsuko Takahashi, Yukiko Kobayashi, Kenji Sahara, Yoshio Tsuchiya, and Yu Fujiki, with Haruo Nakajima portraying both Gezora and Ganimes.
Space Amoeba tells the story of amoeba-like extraterrestrials that hijack a space probe and, after crash landing on an atoll in the Pacific Ocean, create gigantic monsters from native lifeforms (a kisslip cuttlefish, stone crab and mata mata) for the purpose of conquering the Earth. The film was released theatrically in Japan on 1 August 1970, and received a theatrical release in the United States in 1971 by American International Pictures, under the title Yog-Monster From Space.
The Helios 7 space probe is sent on a mission to study the planet Jupiter. While on its outward journey to the gas giant, the probe is overtaken by the Space Amoeba, an amorphous parasitic extraterrestrial. The probe returns to Earth and crashes into the South Pacific, where the Amoeba leaves the device and inhabits the body of a cuttlefish, causing it to mutate into what is called "Gezora". The tentacled kaiju begins attacking ships and islands in the area.
A photographer named Kudo and his entourage land on Selgio Island for a photoshoot, but their camp is attacked by Gezora. Because of its mutation, the creature can create extremely cold temperatures with its body. When the survivors discover that Gezora is vulnerable to high temperatures, Kudo and his friends use a leftover Japanese World War II munitions bunker to set fire to the monster. Severely burned, the creature retreats to the water, where it dies.
Later, the Space Amoeba possesses a stone crab, mutating it into "Ganimes" and attacks the surrounding islands. Luckily the humans manage to lure Ganimes into a pit and destroy it with explosives. The Amoeba survives a second time and flees into the surrounding jungles, plotting its revenge.
The Space Amoeba decides to control two Earth creatures this time: another Ganimes and a mata mata named "Kamoebas". The two monsters raid the human camp. Luckily Kudo realizes the two monsters' weakness: supersonic waves. By releasing a storm of bats, the Amoeba loses control of its creations. Ganimes and Kamoebas, no longer under control, go berserk and begin to battle one another. The humans, using more explosives, cause the volcano to erupt, engulfing the Space Amoeba and the two monsters.