While the precise reasons for the secondary mutation remains unknown, it appears that if a Standard Headcrab and their host survive for an unspecified period of time or are subjected to certain conditions, the Zombie will develop into a Gonome. The host experiences a growth in overall body mass, and the gash in the chest cavity develops into a functional, vertical maw. The Gonome also obtains the ability to spew organic projectiles from their maw.
While the host body appears to grow dramatically, the Headcrab controlling the host appears to wither or deflate; the outlines of the host skull's eye sockets and nose are visible through the Headcrab's skin.
Gonomes generally stay with groups of lesser Zombies and Headcrabs. If they observe any threat, they will first use their ranged attack. Should the enemy get closer, they will resort to manually attacking with their claws. They can sprint if they spot a distant target. In many ways, the Gonome's behavior is similar to that of a Bullsquid.
According to Black Mesa scientists, as Headcrabs can take over the host's nervous system, one of them asks Adrian Shephard; "Can you imagine what the next stage of mutation looks like?"
Behind the scenes
It should also be noted that the Soldier zombies and Security Guard zombies were also created by Gearbox. It could be assumed that Gonomes are critically mutated scientists since they're only depicted with plain white scientist pants as seen in the standard-definition models.
- In Half-Life 2 no Gonomes are seen in Ravenholm, despite the fact that the Humans there were transformed into Zombies a fairly long time prior to the beginning of the game's events, evident by the fact that Father Grigori had clearly been setting up traps and living alone for a long time.
- The Gonome has an unused dancing and jumping animation.
- The Hunter from Left 4 Dead, also published by Valve, uses a very slightly modified Gonome attack sound for one of his melee attacks.
List of appearances
- Half-Life: Opposing Force (First appearance)