Slug found on the Worm Incubation Room Wall

So much death and disease down here. I suppose slugs were an inevitability.
Philip Buchanon ~ Penumbra: Overture

These Slug like creatures are first incountered in Penumbra: Overture when you find the Research room with all the dead worms. They do not attack you, they just stay still, seemingly feeding off of mold on the walls.

It's still unclear of the fact if the slugs are poisonous (although, since Red was eating them, it may suggest that they are not). Tom Redwood, aka Red, was rationing slugs as his final meal. Philip then declares, "Still, knowing Red, perhaps he enjoyed them," suggesting that Red has been underground for a very long time, eventually getting used to eating such strange delecacies.