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I came up with an idea for a parasitic fungus for my world, and I was wondering if it would be biologically viable/possible. Here are its traits.

After the target organism breathes in the spores, they travel to its brain. They form a mycelium covering the host's brain and take control of its bodily functions, but it DOES NOT KILL THE HOST. It then forces the host to gorge itself on whatever food is available, while all of the nutrients go towards the developing fruiting body. After a few days of feasting, the host promptly dies, and the fruiting body of the fungus erupts from the corpse and releases its spores.

Would this be biologically possible, and what would its effects be on Earth's ecosystem?

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    $\begingroup$ there is a similar fungus already on Earth, cordyceps. youtube.com/watch?v=XuKjBIBBAL8 $\endgroup$
    – Allan
    Commented Mar 30, 2021 at 13:58
  • $\begingroup$ it sounds like its based on cordyceps, which actually is a real fungus, so this isnt as unrealistic as you'd think. the problem comes in when you realize this fungus must now find some way to redirect a large portion of these resources the host takes in not to the rest of the body, but to the fungus. if it redirects too much the host will die, if it doesnt redirect enough than the parasite cant be sustained, and if it redirects in with the wrong method than the host still dies. in real cordyceps, the fungus lives mostly around vital organs to pull nutrients from many sources and not just brain $\endgroup$
    – zackit
    Commented Mar 30, 2021 at 13:59
  • $\begingroup$ @Allan I am aware of the cordyceps fungus' existence, but this can control all animals instead of just ants, and it works a bit differently too. $\endgroup$
    – random internet person
    Commented Mar 30, 2021 at 13:59
  • $\begingroup$ @zackit that's the whole point. The host dies of starvation shortly after the host's death. $\endgroup$
    – random internet person
    Commented Mar 30, 2021 at 14:00
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    $\begingroup$ the main problem here is infecting any animal with a brain. A) its much easier to control thing without brains than things with brains since brains will try to resist the fungus's commands. B) anatomy is complicated. cordyceps can only control a small number of species, despite infecting many different species, because they need a full neurological, anatomical, and biological map of the animal in order to control it. this would mean the fungus would need a full map of every species it ever infects, and encode this genetically into its spores without evolving and just adding, and more. $\endgroup$
    – zackit
    Commented Mar 30, 2021 at 15:05

2 Answers 2

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Crash and recovery.

I feel like this widespread cordyceps for everything idea is sort of a zeitgeist. Inspired by politics? There is at least one video game with the zombie fungus people theme. Maybe 2? But the question of long term ecological effects is interesting.

  1. Things with brains are infected with fungus.

  2. They die and release spores.

  3. More things with brains are infected with fungus.

  4. Things with brains get scarce. Things without brains that are not potential fungal hosts all dance a merry jig, because the world is theirs. Jellyfish jiggle back and forth which is their way of dancing.

  5. Maybe there are some fungi / host interactions where the fungi does not take all the nutrients. The host still gets some. Maybe in some fungi / host interactions where the fungus can release spores without killing the host. In a world low on hosts, these less virulent fungi will have a selective advantage because they don't burn thru hosts as fast.

  6. Some hosts are able to reproduce despite being infected with the fungus. Their children have the fungus too.

  7. Fungus / host interactions evolve towards commensalism. Creatures without brains watch suspiciously. Jellyfish jiggle back and forth which is their way of watching suspiciously.

  8. Fungi become full commensals. Personal hygiene products are sold to creatures with brains to manage overgrowth and odor of fungal commensals.

I think of viruses on cruise ships. Remember cruise ships? Those noroviruses can be maximally virulent and burn thru hosts one after another. There are lots of hosts and they cant get away. Viruses on land are often less virulent. If you incapacitate your host, she will stay home. A host that can still get to the bar and forget to wash his hands can infect more people. Actually he never washes his hands so he did not really forget.

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  • $\begingroup$ Good idea. I never thought of that. $\endgroup$
    – random internet person
    Commented Mar 30, 2021 at 14:15
  • $\begingroup$ with this set up the fungus actually has a really good chance of becoming a mutualist, maybe managing automatic functions of the body so the host can use the rest of its brain for other tasks. $\endgroup$
    – zackit
    Commented Mar 30, 2021 at 14:15
  • $\begingroup$ This is basically the conclusion came to by the (quite excellent) movie The Girl with All the Gifts. $\endgroup$
    – In Hoc Signo
    Commented Mar 30, 2021 at 14:32
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The hunger of various creatures and other biological functions are controlled in part by biosynthesized chemical structures like hormones.

The adipose tissue (fat) actually does signal to our body to become hungry when it is depleted, by releasing a hormone.

Also you could say that increased levels of dopamine in certain portions of the brain would spark repetitive behaviors, so... theoretically if the fungal cells communicated with each other in response to say rising glucose levels in the brain, which they were feeding on, and responded to increased blood flow and neurotransmitter levels that accompanied the increase in glucose and had some kind of ability to store information, that they could increase the sensations and feelings that accompanied this by stimulating the sections of the brain that accompanied the increase in feeding by creating something akin to a agonist or antagonist that would increase or lower the activity noted during the increase or decrease in nutrient levels.

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  • $\begingroup$ So, essentially, the victim becomes addicted to food. $\endgroup$
    – random internet person
    Commented Apr 1, 2021 at 13:38

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