Nucleus (細胞核 Saibōkaku?) is the boss of stage 6 in Gradius.


The Nucleus is the boss of level 6 in the original Gradius. It consists of a pink amoeboid core and a large crystal structure formed of the same material as the rest of the stage.

Attack patterns

The Nucleus will constantly spray random projectiles from the vents to each side of its head. Aside from that, it's only attack is to occasionally spawn Amoebas.


Nucleus makes a very brief appearance in the third episode of the Salamander anime. In the anime, it is pink colored and doesn't contain the core.



  • Due to sprite limitations, the pink core of the Nucleus does not appear in the NES version of the game.
  • Various lifeforms that look almost identical to Nucleus's Core (complete with a sphere of latticed webbing) appear in the background at various points in Stage 5 of Gradius Gaiden. Unlike this boss, however, these are purely background elements and do not attack the player in any way.
  • In cell biology, the nucleus is an organelle that contains almost all of a eukaryotic cell's genome.
Ships Vic Viper
Stages VolcanoStonehengeMoaiReverse VolcanoWasteland (PCE) • TentacleCellBase
Sub Bosses VolcanoZub RushMother and ChildIron MaidenTentacleElectronic Cage

Re-Bone (PC Engine) • Tornado (MSX) • Tyran Pace (MSX)

Bosses Big CoreCell NucleusXaerous Brain
Organic bosses
Space entities NucleusIntruderPhoenix (Geezer Butler)GoliathBubble EyeWyvernVulture DragonBlizzard CrawlerYorogaton ChimeraGilladorVolleoneDoomLynyrd SkynyrdTriumph KicksGawGigaKiller Dwarf
Body horror AbadonGolemZylomBig EyeGregolMad SkinBrachion EyeBiterBerialHuge HeartCrawler (X) • Infected Statue
Plantlife Choking WeedStinger KidHunter FangGiga's RoseDendrodiumHans Naughty
Salamander (OVA)
Episodes Episode 1: SalamanderEpisode 2: Paula's MeditationEpisode 3: Gofer's Ambition
Characters Ike Lord BritishDanStephanie McBainEddie EvansDoromoMinistersLee McBainPaulaGofer
Enemies RugalSharp CrossGolemGigaZelos ForceIntruderTentacleBig Core MK IMoaiXaerous BrainFire DragonDeath HandBig EyeDee-01PhoenixAmoebaNucleus
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