If the fungi is the mycelium and the protuberances are basically its way of reproduction, then Ellie's Cordyceps is just a network of mycelium on her nervous system without any wishes to parent anything
That’s actually a pretty interesting way to frame it. The mycelium is basically the main fungal body, and the visible growths are usually reproductive structures. I guess the only thing I’d tweak is that fungi don’t really ‘want’ to reproduce (evolution just favors the parts that spread successfully). So Ellie’s infection would probably be more like a stable colonization that never fully enters the sporulating phase.
Okay, first of all, sorry for rambling. Second... It can be quite graphic to picture as well!
If you imagine that the mycelium is wrapped around her entire body's nervous systems--⬇️
--and branching in very tiny strings in her blood system that puncture through the celular walls, much like mycorrhizal networks with trees!! In my head it goes not only in the brain, but in the whole system... It's basically a myriad of white lines entangled with her entire nerves.
She's basically two beings in one body, and since the mycelium is attached to everything, including her brain, it's main objective went from spreading to keeping stable; like the mitochondria that entered a random cell and stayed there.
I picture the Cordyceps feeding on her body in a microscopic level, snatching the base nutrients from the blood cells, which makes her need much more food than your usual teenager girl, and in compensation it boosts electric signals to and from the brain, speeds up information processing and reflective time (humans have a slow reactive times but she'd react to things almost instantly, like a cat, due to the helping mycelium) and makes her TDAH that much faster.
Aside from that, I like to think that the mycelium also helps with her immune system and healing wounds: if she gets a cut deep enough to reach meat, the white lines will be visible and moving across the wound, trying to pull the skin back in a pseudo stitch (which never works because Ellie keeps panicking and pulling as much of it off as she can... It makes her incredibly weak and hurts a lot too).
And her immune system is strong enough to ward off many bacterial infections and even other fungal diseases, but if she uses any fungicide or fungi-based medicine, like penicillin, her body will react poorly... And she gets to be allergic to a few amoebas and the occasional bacteria that prey in fungi too that should have been safe for humans :))
But at least Cordyceps improves (by miles) her hearing and makes her able to eat some poisonous mushrooms. And meat that maybe shouldn't be eaten. And tree trunk, if she's feeling that much desperate; any chemical reaction the fungi has can help with breaking down the intoxication from dubious foods, so Ellie essentially doesn't know why the fuck is Joel panicking everytime she eats the colorful mushrooms around them.
Funny thing is, it's not that off the chart either, since fungi has made a few beneficial relationships with other living beings like trees and lichen (since those are an actual hybrid of two different words, being plants and fungi)
Actually, I found one fic with the Cordyceps moving in her a few weeks ago! It's this one below, from @probssomethingorother and it's got a nice level of body horror and Ellie panicking too, and surprisingly enough I felt sad for the wounded Cordyceps ✨✨
https://archiveofourown.org/works/51145819?view_adult=true
I'm so sorry for rambling, but I absolutely love the pseudo-biologic aspect of the Cordyceps actually being a key aspect in Ellie's morphology; it's freaky. She hates it. Joel... Is thankful for it, since the dude has the single objective of keeping his daughter alive.
omg honestly do not apologize, this is EXACTLY the kind of rambling I come to tumblr for.
the mitochondria comparison is such a good way to frame it, like instead of a purely parasitic infection, it starts to resemble a weird endosymbiotic relationship where the fungus has effectively become part of the host’s baseline biology… that shift from “spread at all costs” to “maintain stability because the host is now the ecosystem” is super compelling.
the mycorrhizal network imagery is also so good (annnd appropriately horrifying). Scaling that kind of distributed fungal structure into a human nervous system turns it into full body horror infrastructure — but it’s a surprisingly coherent sci-fi extrapolation.
I also really like your take on immune interaction. If it’s fully integrated, then parts of it might stop reading as “foreign,” which opens up a really interesting idea of long term tolerance rather than constant rejection. It’s like ellie becomes less “infected vs immune” and more like a negotiated system between human and fungal signaling.
the sensory/reflex changes are speculative, but fun to think about in terms of a rewritten neurochemical baseline, like how much of Ellie is still purely human cognition vs fungal modulation layered on top yada yada yada.
and the wound healing imagery is absolutely nightmare fuel😭 but like also very on brand for fungal behavior pushed into sci-fi extremes. Im defo giving that fic a read you may have just changed my life.
I love this kind of biological overthinking of The Last of Us, it’s for reals exactly my kind of rabbit hole.
(It also makes me wonder if the real limit here isn’t Ellie’s biology but the Cordyceps itself — like if it can’t transmit anymore, does it just… get evolutionarily “stuck” in this weird non-reproductive equilibrium??)
and yeah I love how this whole thing ends up sitting in that space between ecology and emotion… like the Cordyceps stops being just infection and becomes part of how her survival is defined, even if she hates it lool.
Agreeing with everything here and grinning cuz finally someone who's sharing the appeal 🫂🫂!!
Many, many more ramblings with a bit more scientific scheblables below... You were warned.
Fungi are that exact living being you can safely describe that might make people think you're talking about sci-fi tho, even without the extrapolation 😅 and yeah! I used to go with Ellie being just immune and that's it, but having the human and fungi system work with each other has made things that much interesting for me.
Yeah, I kinda got the sensory and reflex from just wanting some beyond human stats for Ellie, but the hearing in those infected gets extremely strong so at least that is canon... Now going for the scientific reason:
Since runners have an average hearing, we're led to believe that what makes clickers and bloaters that much better at listening isn't truly the humane version of eardrums, but more likely thin strands of 'fur' on the fungal protuberances in their body that are extremely sensible to air currents and can detect sound by mechanical vibrations (aka: sound waves)... I'd say it would be like a bat's echolocation of sorts?
Obviously it would be much weaker in Ellie seeing as she leans in other senses, but if we wanted to make her biologically capable of this sound sensibility, we could say that the fungal network inside her also branches through the epidermis, and its thin roots reaches the external skin and mimics the normal human body hair - we see this in insects that are able to react extremely fast to the environment due to micro hairs in their limbs that can feel each shift on the air; due to her basically growing since a baby with this network, she'd think it was just the normal for everyone else.
This would make the mycorrhizal network that much creepier seeing as we are now talking about the mycelium not only spreading along the nervous and blood system, but also branching to pierce flesh and exist outside her body. Seeing as it is white, unlike the rest of her dark body hair, those hyphaes would camouflage with the normal fur by being so thin they're barely visible.
About the neurochemics.... Well, I haven't yet started on anything more complex about fungi, I'm still starting on my biology college, but I know Cordyceps is not the specific shrooms used for the psychedelic experiences; regardless, the shrooms used for these things are known for strengthening the connections between neurons and making the brain more potent and flexible, essentially making the human mind able to perceive things that in a normal state it wouldn't be able to sense.
The problem is, big dosages of psilocybin may increase human sensory intake but it also lowers the brain's capacity of processing information, causing sensorial overload and the tripping-high hallucinations that come with it and it... Wouldn't be really good in a life or death situation, but seeing as Ellie would be either adapted to a much higher production of it/ would have been micro dosing the substance since birth, we could say that her brain neural network is extremely strong and much more efficient/faster than the usual human. So, any sensorial intake would be processed and reacted upon much faster.
Again, I know Cordyceps doesn't produce psychedelic chemicals butttt I'm sci-fi-ing my way into this headcanon so let's just put it in the same family tree.
But now focusing in Cordyceps, we can also mix the branch from The Last of Us with the Cordyceps militaris, which are used to improve endurance during high-intensity activities through improvement of lungs and efficient oxygen distribution, and are also capable of maximizing energy by increasing ATP production, besides aiding with the general immuno responses and acting as a antiviral substance... It's called cordycephin the specific chemical, if I'm remembering right.
The antibiotic chemicals are produced from yet another fungi, the mold Penicillium, that I'm also mixing with our sci-fi-ed bucket of fungi-related chemical reactions produced inside Ellie.
The bad part of it is, taking any antifungal medicine would be a big no-no for Ellie, which is bad since no one even knows that Ellie is extremely allergic to those things... Same with other medicines made from fungi, since they might start a chemical disturbance or a self-degenerative disorder inside her.
One of the best things in Fandoms oughta be the biological overthinking ✨ and how it would either help or offer some unexpected problem to the character... I like to think that Ellie is simply not aware of how far the Cordyceps actually goes; maybe she someday gets a cut too deep to heal on its own while her and one of the Milers are in a trip, maybe she panics the moment she sees those tiny threads moving and pulling the opposite edges of the wound close and tries to rip it all off... But in any way, it is quite unlikely that she'd ever discover how connected she is to the fungal network without fireflies putting her through a few inner body exams
I mean, in canon it only exists in the brain, but we are kinda pushing it to exist as an adjacent full body system. I got a headcanon to just why exactly the Cordyceps in her has not developed and instead fused with her biology, but in short Ellie was a premature stillborn baby and the Cordyceps was the only reason she hadn't died at birth... since Cordyceps prevents tissue from dying out, I'd say it somehow kept the few working organs active while the rest of her body fought to reach stability. Due to having already spread from another being (her mother) and entering a dead body, the fungi entered a state of needing to save the local ecosystem instead of taking over it.
The emotional rollercoaster goes crazy cuz it also kinda killed her mother and her best friend, and Tess, and Sam, and a lot more people she doesn't know, and it's inside her and it's keeping her alive. She absolutely hates it. Joel searches Jackson's library for the best nutrients for fungi. His enemy's enemy is his ally and all that. Also sorry for rambling again I love fungi
PS: I JUST REMEMBERED CLICKERS FUCKING CLICK.
So rewording my sentence, it's likely that these fungal protuberances are filled with thin strands of hairy fungi that react strongly to any sound wave, which means that they can either feel these waves and sense anything close or 'see' their surroundings by echolocation; so by making Ellie's network reach across her skin in the same way, she would be always aware of everything going on around her. It's like exposing her nervous system to the world in every step or word she says/hears...she'd probably have severe overload crisis after adrenaline crashes during life or death situations, and going to much populated areas with unknown people probably burns the double of her social battery than it would in a normal human.
