Barbelith Underground > Laboratory > Zombie biology: how ghouls work.

There's at least one other form of zombie that hasn't been addressed yet: there have been zombie outbreaks that have been traced to an organism that appears to be a species of parasitic fungi.

The infection begins when the spores of this fungus come in contact with the bodily fluids of the host organism. Unlike most other species, this fungus spreads its spores through the medium of water. This accounts for the infectious qualities of the host's blood and saliva.

Upon infection, the fungus quickly spreads through the body of its host, creating a mycelium-like web of tissue that permeates the host's organs and tissues. When the mycelium has grown and the infection has progressed to the extent that it interferes with the normal functioning of those tissues and organs, the host dies.

While the host body is, in fact, dead, the mycelium continues to grow and feed upon the tissues of the corpse. After 2-3 days the mycelium has grown throughout the entire structure of the host corpse. Here is where the host organism officially becomes a zombie.

The mycelium of this parasitic fungus has special fibers that can expand and contract in roughly the same manner as animal muscles, and since it is spread throughout the host, can achieve a form of locomotion using this secondary musculature. Under normal circumstances rigor mortis would have set in due to the deadened nerves failing to move potassium within the muscles of the corpse, but a consequence of the mycelium's feeding is a partial digestion and liquefaction of the host bodies muscles. This renders the body of the host pliant enough for the specialized mycelium to move.

The slow, shambling zombies are "young" ones. About a month after the initial infection the parasitic mycelium has spread throughout the host to an extent that it is capable of faster locomotion and greater exertion. These advanced cases are also "smarter" in the sense that the mycelium has also by this point reached maturity and grown beyond its initial rudimentary nervous system. (capable of little more than stimulus/response) The fully formed mycological nervous system is capable of functioning at roughly the same level as lower-level predators such as reptiles.

The "juvenile" zombie must hunt in order to feed the organism governs its un-life, else the parasite will have to use its host for food. A zombie deprived of external fuel sources will eventually be eaten from within by its infection. In order to stave off the need to cannibalize its host body, the parasitic fungus will cause the host hunt and ingest other animals to feed its biological processes. Due to the poor control the fungus exerts over the host body, very little of its victim's flesh ends up within the host's gullet (where it is utilized as fuel once it reaches putrefaction) and the hunt must begin anew. Like most messy eaters, most of the food ends up unusable and befouled.

The groaning sound that zombies of this sort make, often mistaken as a form of communication is actually the byproduct of the contractions of the mycelium musculature. The contraction causes the chest cavity of the host to expel air past the vocal chords, causing a wide range of sighs, grunts and moans. Any actual communication between organisms of this sort appear to be in the form of airborne chemicals similar in function to mammalian pheromones. This is how zombies from miles around may congregate at a specific point and not eat each other. (though zombie cannibalism has been witnessed in situations of extreme hunger)

Finally, this form of zombie is vulnerable to head wounds due to the fact that the central control organ of this fungal parasite is most likely to form in the empty and protected cavity of the host's skull. (the skull usually having been emptied during the 2-3 days of incubation) When the protective barrier surrounding the control organ is removed it has proven remarkably sensitive to physical trauma and outside pathogens, and often dies within a matter of minutes. A less common occurrence is for the control organ to form in the host's torso, which results in sightings of motile legs and headless zombies. Authorities suspect that the torso-inhabiting fungus is a rarity due to its inability to feed once the head of the host is removed, and therefore a less viable genetic trait.