Quorum Sensing

by Wise Cracker

Rating: everyone
Tags: Slice of Life, My Little Pony: Friendship is Magic, Sad, Cutie Mark Crusaders
Length: 3835

Scootaloo learns her Cutie Mark will never come. How can she break the news to her friends?

Everything has fallen apart for Scootaloo.

Her Cutie Mark will never come. The doctor said so. Her blood is just wrong.

As she stays in the Cutie Mark Crusader's Clubhouse, her friends show up. Now she has to explain that her crusade is over, and that there's even worse news.

Life as she knows it is over.

A/N: Kind of a sad story, with an upbeat ending. Listed as Slice-of-Life because it contains headcanon that makes some modicum of sense. Pretty light (Scoot's not even an orphan in this), and may have been done before, but this idea's been bothering me for too long, so here it is. Bonus points if you know what the title means. Avoid comments for massive spoilers, even if you do know what the title implies.

And yes, I do have some background in genetics, but I'm skimming it a bit for show feel.

Edit 28/7: Made the whole thing a little longer, and I think better in general. Hope you enjoy!

Watch out for the sequel, being worked on now.

Published 2012-07-10 17:34:02 UTC
Last updated 2012-07-10 17:34:02 UTC

Quorum Sensing

Quorum sensing

Scootaloo lay in the Cutie Mark Crusader clubhouse, alone. Her stomach was groaning. A nervous knot had settled there a while back and today had only made matters worse. She rubbed her head, the bandage on her bump itched. And then there were her flanks. Her blank flanks. Her burning blank flanks. She couldn’t think, she couldn’t even cry. She wanted to cry, but she couldn’t, she just felt empty inside. But then, somehow she wasn’t surprised. Deep down, she had to have known. But she’d been so happy once... she’d never wanted to face the facts.

You can’t argue with doctors.

“Hey, Scootaloo.” Apple Bloom and Sweetie Belle walked in, a little confused at seeing their friend in the fetal position.

She looked at them and dreaded what had to happen to now. She had to tell them. Her voice came out a weak croak as she got to her hooves.

“Hey.”

“What’s wrong? Rainbow Dash said you ran away from the hospital.” Sweetie Belle looked her friend over and winced at the sight.

Scootaloo caught her friends were staring at the bandage over her head. Then their eyes turned to the feathers she’d shed while moping alone. Her wings looked even more stubby than usual without the orange feathers adorning them. She followed their gaze and sighed at the sight.

Everything just seems so… final…

“This is a very complicated matter,” the doctor spoke to the unicorns in front of him,” have her parents been informed yet?”

“Yeah, I sent a letter to my sister as soon as we got your message,” Vinyl Scratch replied,” I just don’t understand how she could have gotten this. Is she gonna be…you know…”

“Let him explain, Vinyl,” Twilight interrupted. She’d tagged along for moral support and for her expertise on the matter. Granted, she wasn’t that knowledgeable on hereditary diseases, but it was the closest Ponyville had.

“Well, for starters: it’s in her blood. We’ve checked it three times now, and there’s no question about it, we did not get a false positive. The real problem is: her condition isn’t purely genetic, or at least not like other genetic disorders. It’s at a far smaller level than we can operate.”

Vinyl cringed at the word ‘disorders’.

“Scootaloo is a homozygote for the gene in question. She got the correct code from both her mother and father’s side. If she’d had only one, it might not have been an issue. But these things hide for generations. We’re talking centuries, maybe even millennia,” he pondered aloud.

Twilight shook her head.

“But then why is she the only one like that? It doesn’t make any sense. There ought to be more, or there should have been more like her. Wouldn’t anypony have noticed by now?”

“That’s just it. The gene in question isn’t the actual cause of her condition, it’s just the the nearest we can get to the root cause. Mitochondrial DNA is inherited from the mother’s side, and it’s the mitochondria that are reacting to her genetic makeup, that's the nearest we can tell. She’s produced an enzyme that triggered the onset of her condition, and her mitochondria are reacting to it. Even if we could counteract the enzyme, the level at which this thing works is so small, so fundamental, that if we try to tamper with it we’ll destroy her. Even her innate magic will be affected,” the brown stallion tried to make himself clear while keeping his cool, which wasn’t easy, given the circumstances. “This defect started at a level we can’t operate on. We can’t alter her innate magic the way it’s being altered right now, not on the long term.”

“So that’s it? My little niece is gonna die, just like that?” Vinyl asked with a hint of anger.

The doctor sighed.

“We can’t be certain. I doubt she’ll die, certainly not right away. More than likely the mutation will spread throughout her body, every single cell being hit, starting with her extremities and her flanks. Her magic will flare up in response as well, no doubt hastening the process. It could take years, or seconds, we just don’t know. Whether or not her body can handle it is another matter. My recommendation would be that she gets a specialised physician, but given the nature of her case I doubt if even that’s a possibility. She should be okay, but we just can't be sure.”

Twilight bit her lip.

“What about her cutie mark? Is she still going to get one? If what you say is true…”

Reluctantly, he shook his head and shrugged.

“I do not know, Twilight Sparkle. I highly doubt that Scootaloo will ever get a cutie mark like other ponies. As a matter of fact, if she’d gotten her cutie mark earlier, this wouldn’t even have mattered.”

“I still don’t understand how this happened. You said it runs in the family, right? This type of magic got passed down? So why would Scootaloo be the only filly to get this? Why her?” Vinyl sounded a little guilt-ridden.

“Well, from my professional opinion: it was exposure,” the doctor explained,” some genes, particularly in pests and germs, only trigger when certain population densities are reached. It’s called quorum sensing, and certain types of magic work with similar mechanisms. Being in a crowd where so many individuals carry a variant of the gene, or magic, whichever it was, triggered her own, atavistic version of it. The trigger activated it, her body produced the signal molecules, and now, well, the die is cast. She's going to change on a genetic, mitochondrial, and magic level, and there's nothing we can do to change that. Someone’s going to have to explain to her that getting a natural cutie mark is now medically impossible.”

“That’ll be easy. I know my little niece, she’s been eavesdropping the whole time,” Vinyl Scratch casually remarked.

“Umm, the good news is: the bump on my head isn’t so bad. I got my blood checked, and they said I didn’t pass out from anything bad I ate.” Scootaloo tried to look cheerful. Her friends weren’t buying it.

“And what’s the bad news?” Apple Bloom cringed as she braced herself for it.

“The bad news is... I’ve got something else in my blood. And I can’t get a cutie mark because of it now, not ever.” Scootaloo squinted sadly at the admission.

“Come on, that’s not funny. There’s no such thing as blood that stops you from getting a cutie mark.” Apple Bloom closed the distance between her and her friend, Sweetie Belle in tow. That close, Scootaloo couldn’t hold eye contact.

She held her breath for a bit, and had to suck up a tear.

Sure, now I can cry.

“Yeah, there is one thing, actually. And I’ve got it.”

“Wait, you’re not dying, are you?” Sweetie Belle’s eyes widened.

The tears flowed in earnest now.

“I don’t know. Nopony knows, ‘coz I’m the only one like this.”

“Well…what is it, then? Can’t anyone fix it? We could ask Zecora,” Apple Bloom offered.

Scootaloo let her head hang and bit her lip.

“So…basically, your body is reacting to that of others,” Twilight explained.

“Like a disease, or a pest. And because it happened before I got my cutie mark, now I’ll never get it. Did I hear that right?” Scootaloo panted as her anger rose.

A solemn nod answered her.

“Yeah. I'm afraid that’s just how it works. But you’ll be fine, I promise. We’ll find something, your parents are flying over…”

The filly wasn’t having any of it. This was too much. It was impossible, it was supposed to be impossible. Every pony gets a cutie mark eventually. Why couldn’t she?

It just wasn’t fair.

“I don’t want my parents! I just… just leave me alone!” Scootaloo ran off and got on her scooter, barely lucid enough to put on her helmet, despite the awkward bandage. The revelation had left her in a bit of a shock, and Twilight couldn't blame her.

Before Twilight could say anything, she was off. A quick look at the sky showed a rainbow trail following the filly. At least Rainbow Dash would stop her if she did anything foolish…

“Nopony can fix it. It’s part of what I am. Or what I could be. Twilight told me that a long time ago, Cutie Pox wasn’t the only disease ponies could get that messed with their Cutie Marks. There were a lot of things, so some ponies just didn’t get their cutie marks, and they were fine,” Scootaloo explained, "at least, as long as the diseases were around. Then those ponies started getting other problems because they didn't have cutie marks, and then it got to where they might get them, or they might not. It depends on a couple of things. My blood was right for a cutie mark, but it was right for something else too. And you can't have both."

“Yeah, but now every pony gets their cutie mark eventually. You can still get yours, right?" Sweetie Belle prodded her.

Scootaloo lowered her head. They were missing the point entirely, but then she wasn’t being too clear on it. She didn’t feel like saying it, either, but it had to be done.

“No. See, what happened is: some things have bodies that can tell when there’s other bodies like it around. With enough of it, they change, sometimes permanently. Most of them are pests and diseases. Germs are harmless, locusts are harmless, but when they swarm, they change. They don’t know they’re dangerous or toxic, their bodies aren’t made that way, but they’re made to turn that way when there’s a lot of them in the same place. I have the switch, it’s part of my magic and it’s part of my blood. It got switched on for me, so now I have it. And now that I have it, I can't not have it. And that means blank flank for life.”

“That doesn’t make any sense. We’ve all been around plenty of ponies all the time. Why would this thing switch on for you if you haven’t been around more ponies?” Apple Bloom frowned.

Scootaloo sighed again.

No sense in stalling.

Canterlot was under attack. The shield above them was shattering, little shards breaking off unto the hotel the fillies had fled into after that Queen thing appeared. Buzzing filled the air as ugly black creatures with holes in their legs came crashing down on the city streets.

Chaos was everywhere. The three panicked and huddled together in front of the window as the buzzing got louder.

Scootaloo bit her lips as pain shot in her hips.

Am I stung? No, it feels like a cramp. What’s with that awful buzzing?

Her wings started cramping up too, like her body needed to buzz along with these weird creatures.

The crashes outside mixed with sounds of battle. The Royal Guard would fight back, they’d be safe. On a whim, they looked up from the battle, and realised they’d been spotted. One of the black things came flying towards the hotel, headed straight for their room. They ducked into a corner, but the thing didn’t veer off. It knew exactly where it was going, even if it didn’t have any pupils.

With a loud bang, the insect-alicorn abomination shattered the window, empty eyes looking over the fillies as it stalked its prey. It hadn't even bothered to scout the place, it had just gone straight down towards them.

Scootaloo stood in front of her friends, ignoring her buzzing wings and burning flank. She wasn’t about to let anything bad happen, not if she could help it. The thing came closer, sniffing the air.

Is it near-sighted, maybe? Are these things blind?

The towering creature came close enough to be able to smell Scoot’s breath. It snorted, and another sharp pain shot through the pegasus’s body, making her sweat in fear all of a sudden. It sniffed her mane, but she didn’t dare flinch.

With a quick turn, the thing headed back for the window and joined the fray, ignoring the fillies.

The three breathed a sigh of relief.

“I guess you scared it off, Scootaloo,” Sweetie Belle patted her friend on the shoulder. They could lay low here for a while still.

Scootaloo was a little shocked. The pain in her hips hadn’t subsided, her wings were still buzzing, and that thing? It could see her just fine, she was sure of it.

Why would it sniff me like that? I don’t look like one of those things, do I smell like one of them, maybe?

Why didn't that thing just attack us?

Sobbing, Scootaloo unwound the bandage on her head. Right on her forehead, dead centre, a black protuberance stuck out like a misplaced nail. The skin around it had turned black, looking like a spreading rot.

It was leathery, it was ugly, it was unnatural.

It was the start of a horn.

“I’m a changeling,” Scootaloo admitted.

To that, the other two Crusaders raised an eyebrow.

“Okay, so… where’s the real Scootaloo and when did you make the switch?” Apple Bloom asked.

“I am the real Scootaloo, that’s what I’m trying to tell you. Turns out a lot of ponies are part changeling, but I happen to have the one in a bajillion part that actually turns you into one! And changelings are a pest, a disease. When we were in Canterlot, when the attack happened, that part of me woke up and made it so I’d turn into a full changeling eventually. It's a switch; changelings evolved that way to dodge epidemics, diseases that hit blank flanks. Because they had a switch, they could stay a blank flank and not get hit by diseases, but that meant no special talents. The ones who can turn never do because they get their cutie marks, which makes it useless. But we got attacked before I got mine, the switch has been turned for me. If I’d just gotten my cutie mark, I wouldn’t have even known I was like this. Now I missed my chance.

Silence fell for a moment, before Scootaloo caught her breath again.

“It’s all over. No finding out who I really am, no special talent, I won’t even be a proper pony soon.”

“So you’re a changeling?” Sweetie Belle asked.

Scootaloo nodded, tears streaming down her face. Her friends would surely abandon her now.

“A full changeling? I mean, you’re just turning into one now, right? But you’ll grow a horn, get other wings…” Apple Bloom continued.

“Yeah,” Scootaloo croaked as she lay down. ”I’ll be ugly, and feed off love. I’ll be poison to everypony around me. Just a pest.”

Scootaloo braced herself for the judgment. The nervous knot in her stomach got worse, feeling like she’d swallowed razors at this point. She just wanted it to end, just to get this horrible moment over with…

“COOOOOL!” the two other fillies fawned.

“Wait, what?” Scootaloo tried, but she was interrupted by the weight of her friends pressing down on her. They were hugging her. She’d never had a hug feel so good before. It actually felt natural for once. They wanted to comfort her, and probably hold her down in case she felt like running.

“Don’t you get it? You’re the only good changeling in Ponyville. That’s like being an alicorn,” Apple Bloom offered.

“Bu-but I’m a monster. I’ll trick ponies into loving me and suck their energies dry.” Scootaloo’s tears were still flowing, mind reeling with consequences.

“I think you’ve got that backwards, Scootaloo. First you do something evil, then you’re a monster.” Sweetie Belle gave her back a friendly squeeze.

“But I can’t be friends with you anymore. I’d be feeding off love.”

Apple Bloom shrugged.

“Kinda like everypony else, then. Love takes effort, just like friendship. Everypony wants friendship and love, you just get something extra from what they give ya, right?”

While it didn’t make her situation any more bearable, she had to admit that logic did make sense.

“But what about our cutie marks? I can’t get mine, ever. And what if I turn ugly?” Scootaloo had never been one for primping, but a girl’s got to draw her line in the sand somewhere.

Sweetie Belle frowned.

“Umm, I’m pretty sure you can’t turn ugly, Scootaloo. Changelings can, you know, change shape. And the one that looked like Cadence had her cutie mark too. You could just pick one out and stick with it.”

That thought hadn’t occurred to her yet.

“But how will I know my talent?”

“I dunno, ask a gryphon or a mule. They never get cutie marks and they can handle it just fine,” Apple Bloom reasoned..

“But… but…” Scoot’s tears kept coming.

“It’s okay, Scootaloo. So what if you’re a changeling? You’re still you, and you’re our friend.” Sweetie Belle rubbed her neck fur gently. She knew her friend had never been one for affection, but she needed it now, so that's what she was getting, like it or not.

Scootaloo smiled. She really couldn’t object anymore. She gave up.

Maybe things won’t be so bad after all.

She lay her head down as the knot in her stomach seemed to unwind and a light burning started in her legs and what remained of her wings. She started glowing green, but she closed her eyes to stop it from bothering her. It felt tingly, and a little hot, but not unpleasantly so.

It did feel... final, though. Like that one step it takes to fall into a bottomless abyss.

It didn’t matter. Whatever happened next, she could face it knowing her friends would be there. The clung to her tightly as the light wrapped around her.

She would never be alone.

The burning stopped, the glow faded, the girls backed off. She felt her forehead, the stubby horn was gone. She felt quite normal, actually.

She got up and looked herself over. Aside from the moulted feathers, she looked like her normal self.

“Huh. Maybe the doctors were wrong after a--”

Rainbow Dash had taken up post right above the clubhouse, not daring to leave for fear of losing track of the little filly. It must be harsh, thinking you’re a pony all your life and then finding out you belong to a race that’s declared war on your home. Even worse if you consider it could have been avoided if she hadn’t had the misery of being a late-bloomer with her cutie mark.

It was a rotten deal, no matter how one looked at it. Dash wasn’t even sure if the filly would be able to live in Ponyville anymore. There were so many questions that needed answering, she couldn’t imagine what Scootaloo herself must be feeling.

Still, with the other two Crusaders in there, at least nothing serious would happen.

A loud boom quickly dispersed that illusion. A green beam tore a hole straight through the clubhouse roof.

Of course things would blow up; it was the Cutie Mark Crusaders, for crying out loud.

In a flash, Rainbow went down through the hole in the roof.

“Everypony okay?”

“COOOL!” Sweetie Belle and Applebloom admired the sudden display of power that had enveloped her friend.

Rainbow Dash turned her head to the subject of said compliment.

Coughing and spluttering, a black filly dusted off some wood chippings from her chest, noting a dull sound when she tapped it.

“What the… I have a chest plate?”

The other two fillies inspected Scootaloo.

“Yeah, and a back shield, too.” Apple Bloom patted the green chitinous mass as Sweetie Belle got a mirror ready.

Her face didn’t look all that different, actually. No tusks, the chitin plates on her neck were barely noticeable, and her eyes hadn’t even changed at all. Her mane had turned a little pale, though, as had her tail. The horn didn’t look too big or weird, either, aside from the curling. She could probably pass for a unicorn if she dressed up.

That thought made her freeze and snap her head. Her wings. She actually had wings now, not feathered stubs. And they looked pretty good, too: gauzy, transparent, they looked like those of a faerie, or a dragonfly, only sharper and with small indents at the edges. They buzzed just like her old wings, too. Forget dressing up, if anypony asked, she cast a spell to get them. That brought another thought to mind: she could cast spells now.

Great, now I’ll have start actually reading spellbooks.

But the real relief was her legs. No holes. Thank Celestia, she didn’t have the holes. Being called a blank flank was one thing, being called a cheese grater was another.

“Are you done looking at yourself, kiddo?” Rainbow Dash gave her a friendly smile.

Scootaloo rushed up to her and resisted the urge to hug. It probably wasn’t too appropriate, since she wasn’t sure how the whole ‘hugging’ thing went to the ‘feeding’ thing yet. She really didn’t want any accidents of one turning into the other.

“Umm…well, what do you think?”

Dash chuckled.

“I think now we know why you couldn’t fly yet.” Rainbow pointed at the ground to illustrate the fact that her number one fan was finally at eye level with her.

Scootaloo wanted to cry with joy, but she didn’t have any tears left. Instead, she just quivered as her idol gave her a surprise pat on the head and a rub over that back plate.

“Trust me, this looks good on you. Now come on, we should get you checked up back at the hospital.”

Scootaloo nodded and went along as the mare slowly trotted off. Sweetie Belle and Applebloom trailed after her as the questions of her new existence came flooding in.

How would she go to school? Same shape or make up a new identity? Would anyone really mind if she decided to look like an alicorn from now on? Would it be considered poor form if she joined the hoofball team and kept her chitin armour under her uniform? Would ‘making boys cry’ fall under the header ‘playing with your food’? Actually, how was she supposed to handle boys at all?

Would she get mind control powers? Just a few minutes as a changeling and she was already pondering waving her hoof and going “These aren’t the ponies you’re looking for”. Would that work? And how would her shapeshifting go, exactly? Would it make a difference if she turned into a colt?

More to the point, what could she get away with now? Everything seemed so distant to the new changeling, like everything had just changed for her in the blink of an eye.

“You realise what this means, right?” Apple Bloom asked, snapping her friend out of her reverie.

“What?”

“Now you can really be a chicken.”

Well, maybe not everything.

The End