The Spore Spawn is a large, genetically engineered plantform created by the Space Pirates, which inhabits the upper levels of Brinstar (specifically, a part of Jungle Brinstar above "Pink Brinstar"). Its huge, thorny tendrils make up for most of the jungle's environment, since it appears that they originate from the Spore Spawn. Samus Aran defeated it on her first visit to Brinstar when she pursued Ridley to Zebes. After defeating the Spore Spawn, she obtained a set of Super Missiles.
The Spore Spawn is located in a secluded chamber in the upper levels of Brinstar, which is guarded by Ki-Hunters in the room that precedes it. Its central nervous system is found here, within a spiked globe attached to the wall by a large vine. Four pods are found on the ceiling above the "head" that generate poisonous spores, which the plant uses to defend itself. The Spore Spawn has green skin like most terran plants, but as it takes more damage, it gradually darkens to a rotten brown.
In battle, the Spore Spawn attacks by swinging its head around the room like and dropping spores from the ceiling at a very fast rate. Samus can shoot the spores to get pick-ups which restore Energy and Missiles. Every now and then, the head stops and opens up to reveal its core, a pulsating column of nervous tissue with a ring of crimson "eyes" in the middle. The core, obviously, is the only weak point on the Spore Spawn, and it must be attacked quickly (with the Charge Beam or Missiles) before it closes up and starts swinging around the room. As the plant takes more damage, the head starts to move faster, eventually getting fast enough to being nigh-unavoidable. When it is defeated, the head retracts and the whole room appears to wither away, changing from deep green to brown. Samus can then use the dead Spore Spawn's head as a stepping stone to get up to a shaft that eventually leads to the first Super Missile upgrade.
- There are three enemies in Metroid Prime, Metroid Prime 2: Echoes and Metroid Fusion that resemble the Spore Spawn, which are known as the Puddle Spore, Dark Phlogus and Nettori respectively.
- The Puddle Spore and Dark Phlogus greatly resemble the Spore Spawn's head, moreso for the former, but they dwell in liquid environments (the former lives in lava pools in the Magmoor Caverns and the latter lives in dark water pools in Dark Torvus) and use ranged attacks by snapping their shells closed (former spits acid and latter shoots a stream of dark water).
- Nettori has two Samus Eater Buds on the ceiling of the room where it is fought, which spit out spores much like how the Spore Spawn did. Additionally, the room dries up after Nettori is defeated, but it is only seen when Samus leaves and returns to the room.
- Spore Spawn and Crocomire are the only bosses that leave remains (the former left its dried husk and the latter left its skull).
- The Spore Spawn's battle theme is also used for Botwoon in Super Metroid, Nettori in Metroid Fusion and the Imago Larva in Metroid: Zero Mission.