This episode is sponsored by 80,000 Hours. 80,000  Hours is a nonprofit that aims to help people have   a positive impact with their career.

Head to  80000hours.org/microcosmos to start planning   a career that could potentially help solve  one of the world’s most pressing problems. What you’re watching right now is something that  James, our master of microscopes, had never seen   before.

And given how much of the microcosmos he’s  watched, anything that’s new to him is thrilling   to us. What he’d found were those two Loxodes  you see stuck together, waltzing around in a   very public display of conjugation. While  there are ciliates that frequently dally around   in sexual reproduction, for others—including  these Loxodes—it’s just not a common sight.   So James kept his camera focused  on them, following their progress.  But in the process of watching this population of  Loxodes, James would find something much stranger   going on in the microcosmos.

Something  that would start innocently enough,   but that would end up in a place  far darker than he had anticipated.  The scene in front of you now is filled with  loxodes, more of those freshwater ciliates   we were just watching. The smaller  species are called Loxodes striatus,   and the larger ones are called Loxodes magnus. And that’s what we’re following around right now,   a Loxodes magnus navigating a field  of debris and other organisms.  But why?

In a screen full of these  organisms, why are we following this one?  Well, this Loxodes magnus is large—so  large that it was able to eat a rotifer,   those funny animals we often see getting  bullied by their single-celled neighbors.   And James meant to quickly capture another one of  those instances before moving on. As the Loxodes   turns, you can sometimes see the outline of the  rotifer taking up space in grayish oval area.  But what James realized as he was watching—and  maybe you’ve caught on to this as well that rotifer is moving. It’s alive,  twisting and turning inside of   the food vacuole it’s been stuffed into.

And when James realized that, he had to keep   recording. Because there are stories out there  of rotifers fighting back. Of them stretching   themselves and piercing away at the ciliate  that had the gall to eat them until finally,   they poke through the body that’s attempting to  digest them and escape.

So yeah, James wanted to   see if he could watch that happen, to see if  he could watch the rotifer triumph for once.  If only it were that easy. But that’s getting  ahead of ourselves. Let’s just sit here for a   bit and watch the rotifer at work.

This is one  of those episodes where I’ll be quiet for a bit   and then chime in as the rotifer’s journey takes  shape. And for now, the story is straightforward.   The rotifer It tumbles and stretches, and  the shape of its captor shifts in response,   expanding in width as the  rotifer refuses to be digested.  If it seems like the rotifer is  sometimes putting up less of a fight,   you’ll have to excuse it. The conditions it  is facing inside the Loxodes’ food vacuole are   intense, a bath of acid meant to eat away at its  body and render all its multicellular complexity   into a well-digested stew.

The fact that it has  survived this long seems like a small miracle.  At this point, the Loxodes is passing alongside a  field of rotifers—the sisters of the very rotifer   the Loxodes is trying to digest, And you can  see them making that same telescoping motion   as their trapped sibling, just from the  anchored safety of a piece of debris.  Perhaps it seems like the rotifer is making  all this movement for nothing, but just wait…  This. This is the moment where  the rotifer’s escape begins in   earnest. It managed to tear a chunk out of  the Loxodes, ripping out an escape route   that the rotifer’s head  can start to peek out of.   Just watch as it keeps that movement going, the  gaping hole in the loxodes growing larger and   larger as the rotifer continues its  work.

The Loxodes seems unperturbed,   continuing to swim as if its insides aren’t being  torn apart. But with enough time and enough poking   and prodding, the rotifer escapes its acid prison,  making its way once more into the microcosmos.  This is a moment to celebrate, right? We’ve  been watching this rotifer try and try   and try for minutes, and here we are now,  with all the success to show for it as it   sets up a new home for itself.

That’s what James thought too,   except that he quickly realized that something was  wrong. The rotifer wasn’t alone. It was actually   inside another rotifer, or rather what had once  been a rotifer—what had once been its mother.  The acids of the Loxodes’ food vacuole had eaten  her body away, digesting and decomposing it   until all that was left was an exoskeleton that  protected the young rotifer living within her.  While rotifers hatch from eggs, there are  species that hatch from eggs that are still   tucked away inside of their mothers.  This trait is called ovoviviparity,   and it’s found in various amphibians, insects,  and sharks…and yes, rotifers like this one,   using their body to shield their young.

And yes, the young rotifer survived.   But as James watched, a more cruel truth emerged:  the young rotifer was stuck. The same cuticle   that had protected the rotifer from the acids  of the loxodes would now hold it forever,   rigid and uncaring to its former  life as that rotifer’s mother.  The next day confirmed the valiant  young rotifer’s tragic end,   stuck within the confines of its mother’s cuticle   there towards the bottom of your screen, no longer  pushing and shoving, but motionless in death.  And as for the Loxodes, we don’t know  what happened to it. But given the   capacity of its family for regeneration,  it probably survived with little injury.   Perhaps it swam by its former meal,  unaware of their previous encounter a battle waged, a battle lost, and the world  moving on around them both just the same.

Thank you for coming on this journey with us as  we explore the unseen world that surrounds us. And thank you again to 80,000 Hours  for sponsoring today’s episode. 80,000 Hours is a nonprofit that aims to help  people have a positive impact with their career.  The direction of your career path is a  big life decision and 80,000 hours has   a lot of free resources to help you plan and  research what options might be best for you. They’ve got fantastic, free resources  including decision-making tools,   a constantly updated job board, and even a podcast  where they have in-depth conversations with   experts in the world’s most pressing problems,  and discuss what you can do to help solve them. 80,000 Hours wants to help you find a career   that does good in the world and all of their  provided resources are free!

They’re a non-profit,   and their only aim is to help you  find a fulfilling, high-impact career. Click our link in the description or go  to 80000hours.org/microcosmos to be sent a   free copy of their in-depth career guide to start  learning how you could have a high-impact career.   This will also sign you up for their newsletter,  where they send updates on their research   and high impact job opportunities Before we go, we’d also like to thank all of  our patreon patrons, whose names you’re seeing   on the screen right now. If you’d like to help  support this channel so we can keep bringing   you bizarre stories like this one, you can  head on over to patreon.com/journeytomicro If you’d like to see more from our  Master of Microscopes James Weiss,   you can check out Jam & Germs on Instagram And if you’d like to see more from us, there’s  probably a subscribe button somewhere nearby.