Jelsacs are aggressive, six legged Phazon-based lifeforms found on the planet Phaaze in Metroid Prime 3: Corruption. They slightly resemble a crab in design, with two large claws in front and its eyes fixed in the carapace. If provoked, the large balloon structure on its back will fill with a highly poisonous and corrosive substance. Eventually, the Jelsac explodes, spraying the venom all over. Samus may safely trigger their self-destruct reaction from afar with any of her weapons, thus disabling the creature's defense mechanism and avoiding the severe damage from the blast. Jelsacs have similar behavior and appearance to Seedlings, and name to Jelzap.