What exactly is a species, anyway?

A common definition is a group of organisms that  can reproduce together and have fertile offspring. Although, that doesn’t  really account for microbes… A species could instead be defined as the unit  of common descent you can divide down to – kind of like elements, but alive!

Or maybe it’s just something to  do with patterns of gene flow? Annoyingly, it turns out there  are at least a couple dozen   conflicting definitions officially out there. So maybe forget about species for a minute.

There must be some categories of  animals that we can agree on, right? Like rodents, or beetles, or… snakes. Like, we can all agree on what a snake is, right?

Well, today’s beast probably isn’t one  of the first snakes to come to mind. And what’s more, it really challenges  our ideas about “species,” too – because every single one of these  snakes is female and a clone… and maybe also a hybrid. [♪♪ INTRO ♪♪] The Bizarre Beasts pin club is open  for subscriptions for the whole month! Sign up by June 20th and your first pin  will be one of these weird little snakes.

The Brahminy blind snake, Indotyphlops braminus,   is a tiny, non-venomous snake that  both looks and acts like a worm. It’s only 11.2 to 16.5 centimeters long, it spends  most of its time burrowing through the soil,   and its tiny mouth is best suited to eating the  eggs, larvae, and pupae of ants and termites. The scales over its eyes make it  practically blind, hence the common name – and after all, what’s it really  gonna see down there under that dirt?

Though, that dirt can vary dramatically: this snake can live anywhere from forests of any  kind, to grasslands, to semi-deserts, to swamps. And like a worm, we only ever really see it  above ground after it rains or if we dig it up. It has a pointy tip on the end of its tail  that it can use for a mild, pokey defense,   but it’ll also make a literal stink about  being caught via some musk glands in that tail.

And that just about concludes the “normal”  portion of this snake’s list of traits.   Because even just talking about where  it lives opens up a whole can of… snakes that look like worms. Before we dig more into the many ways  that these snakes challenge our old   assumptions about how species work, we  want to take a moment to challenge some   outdated assumptions about plant based  meat, with today’s sponsor Beyond Meat. Plant-based meat has been a thing for a while now,  but there’s still a lot of noise surrounding it - including misleading social content,   and fear-based narratives fueled  in part by the meat industry.

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Check out the link in the  description to learn more. The Brahminy blind snake is only known for  sure to be native to India and Sri Lanka,   but its exact origins have been muddled,  because its range has… expanded a bit. Living in tropical soil seems to  at least partly serve the snake as   a means of temperature regulation,  but it has also become a means of   getting accidentally spread all  over the world in potted plants.

Which is how it earned another of its common names, the “flowerpot snake.” This snake now spans the tropical and subtropical biomes of every continent, except for Antarctica. It doesn’t seem to be necessarily invasive  in some parts of its introduced range,   though the potential has definitely been noted  in others as something to keep an eye on. But our love of houseplants is not the only reason  these tiny snakes have spread around the world – and it’s definitely not the weirdest.

No, the real reason that they’re able to  gain such a successful global foothold – so to speak – comes down  to the way they reproduce. Because the Brahminy blind snake seems  to exclusively reproduce asexually – we’ve only ever found females, and they can lay  unfertilized eggs that grow up into adult clones. While we usually think of animal reproduction as a  pair of individuals mating to make offspring that have their combined DNA, there are actually a lot  of forms of asexual reproduction in animals, too.

In today’s case, we’re talking  about “parthenogenesis,”    which means a female having offspring  without the need for a male. And this can happen in a couple of ways. In species like ants, bees, and wasps,  females lay eggs fertilized the old   fashioned way to produce female offspring, and  they lay unfertilized eggs to produce males.

In other species, parthenogenesis just entails  a female giving birth without mating, period. This is usually only a part-time strategy,   or even just a Hail Mary when  mates are too hard to come by. And we covered this before  with the bonnethead shark,   and even with another snake  species, Australia’s coastal taipan.

But the flowerpot snake is  completely parthenogenetic – not just sometimes – and there simply are no males. Male-free parthenogenesis like this occurs  in about 0.1% of known animal species,   and in very few known vertebrate species. In fact, for vertebrates, full-blown,  all-the-time, female-only parthenogenesis   seems to only happen in some populations  of snakes and lizards, specifically.

As for entire species of snakes that use  this as their only reproductive method? Well that just leaves the Brahminy  blind snake and no one else. A female will lay 1 to 8 eggs at a time… and she can just, like, do that.

All on her own. To make matters weirder,  this snake is also triploid,   meaning that it has three copies  of every one of its chromosomes. Most of the time, animals are diploid,  with two copies of every chromosome – one from each parent – in every cell.

Polyploidy – having more than  two copies of each chromosome – only happens in less than 1% of animal species. Now this is common in plants, but  it is pretty weird in animals. But both polyploidy and parthenogenesis   are associated with a third  strange thing: hybridization.

Which brings us back to this  whole “species” question. Of the numerous definitions out there, the  “biological species concept” is the one that   says a species is when two individuals  can mate and produce fertile offspring. Since we’re talking about virgin snake births,   a reproduction-based definition  feels kinda relevant here.

When two different species mate  and produce infertile offspring,   the result is considered a “hybrid” that  does not get species status under this model. For example, a mule is a hybrid: the sterile offspring of two different  species, a horse and a donkey. But just like how the definition of  a species isn’t 100% locked down,   this rule about what a hybrid is or  can do, also has some flexibility.

Hybrid sterility is a pretty big barrier  keeping hybrids from naturally proliferating,   but it’s really more of a problem for  male individuals than for females,   due to the weird interaction of opposite sex  chromosomes from parents of different species. So if a female hybrid could reproduce asexually,   that is, without the need to even bother  mating, then she could be good to go! Parthenogenesis therefore may actually act as  a happenstance workaround for hybrid sterility.

And that is where today’s beast fits in. Because not only is the flowerpot snake a strange,   triploid, globetrotting clone, but  it also seems to be a hybrid as well. Several studies of I. braminus from distant parts  of the world determined that this blind snake’s   genome makes the most sense as the result of one  or more hybridizations between diploid parents.

A 2022 study then compared Indotyphlops  specimens from different parts of India,   to explore the specifics of hybridization  before the snake’s world tour began. They concluded that the parthenogenetic hybrid   found globally is the offspring of I.  pammaces and the “true” I. braminus – which both reproduce sexually – and that the widely distributed  hybrid should have a whole new name. But the discovery of a genetic match for  the “true” I. braminus in Italy a couple   of years later suggests that either  they are actually the same species,   or that more than one kind of Indotyphlops  is making the international rounds.

Or that hybrid genetics is just  really weird, and comparing only   a handful of genes may not give enough of  the picture to draw very big conclusions. Plus neither study directly addressed the  reproductive situation for the “true” I. braminus,   and there’s still every possibility  that these two-or-maybe-three   Indotyphlops species are continually  hybridizing back home to this day. Luckily, this genetic confusion does  actually address another question: wouldn’t a completely asexual  reproductive strategy sacrifice   the chance for some really  important genetic diversity?

A population of clones would be much  more vulnerable to things like new   diseases than a population with  a bunch of highly-varied genomes. I mean, that was a major reason that sexual  reproduction evolved in the first place! But being triploid and a hybrid may  be how parthenogenetic species like   the Brahminy blind snake avoid the  genetic bottleneck you might expect.

A 2025 comprehensive analysis of the snake’s  entire genome found that yeah, it’s definitely   a triploid hybrid, but also there aren’t an  equal number of copies of every chromosome. Some other funky genetic stuff must be going on. During sexual reproduction in a diploid organism,   chromosomes from each parent couple  up, trade bits with their matches   in a process called recombination, then  split apart into new, reproductive cells.

Meiosis – cell division that produces germ cells – in a triploid organism like the flowerpot  snake gets a bit more complex, and usually   starts with all the chromosomes doubling  first, in order to produce an even number. From there come lots of possibilities, ranging  from recombination between matched chromosomes,   to exchanges of whole chromosome copies  between the three different ancestral sets. The result is more variation than you might  expect for an individual that’s technically   cloning herself, carefully balanced with  enough stability to still keep it all running.

Essentially, the extra chromosomes kicking  around in polyploids provide just enough genetic   diversity to keep the gene pool from getting  too weak without totally breaking everything. Parthenogenesis may not be a first-choice  adaptation for the long term, but because   of the genetic quirks here, it technically works! And evolution is ultimately just  the survival of the “good enough.” Not to mention that evolution  is never on purpose – vertebrates seem to mainly stumble into  parthenogenesis when something big and   unusual happens, like interspecies hybridization.

And polyploidy also largely occurs in  hybrids, so those factors together created   the perfect storm for this little snake’s  accidental but overwhelming global success. We humans try our best to  understand life on Earth,   but life is bound and determined to defy every  rule and definition we come up with for it. Even definitions as fundamental as what  a species is, and how one can work.

The Brahminy blind snake seems like a  species, but turns out to be a hybrid – of… itself and another species? And it can still reproduce,  but only by self-cloning… Really it’s an encapsulation of all the bizarre   contradictions that make our  attempts at labels so futile. And in a roundabout but practical way, this  beast’s very weirdest qualities manage to   cancel each other out, allowing it to keep doing  its tiny, snakey business down in the dirt – where it can quietly take over the world.

Sign up for the pin club at BizarreBeastsShow.com  and help keep this channel going. If you want a blind snake to be your  first pin, sign up by June 20th. We have big news!

Endlings is back! Endlings is our series about the last  member of a species (the ‘endling’),   but it’s also really about people  and our relationship to extinction. We are so excited to announce that after  the success of our first seven episodes,   we are making a whole new season!

The first new episodes about Japanese  wolves and the Galapagos tortoises   are ready for you to watch right now  here on the Bizarre Beasts channel! And now, for some bonus facts… [♪♪ BONUS FACTS ♪♪] Parthenogenesis was quite a big  deal for such a little snake,   but what’s up with the other ways  vertebrates can reproduce asexually? Gynogenesis is when a female lays  eggs that only contain her own genes,   but she requires a male’s sperm to  actually trigger development of the embryo.

Why go through the trouble of actually  mating only to still just clone yourself? Because – you guessed it – you’re a hybrid! Take the all-female hybrid  fish species the Amazon

Molly: in order to reproduce, individuals  need to mate with a male,   usually of any number of other  species in their same genus. The male’s sperm actually do meet the eggs,  but their DNA doesn’t fully incorporate,   and the hybrid is able to pass  on its genes unadulterated! A related phenomenon is kleptogenesis,  which also involves hybrid females using   males’ sperm to make their eggs  go, but which can also result   in the offspring having a higher ploidy  number if the male DNA is incorporated. This can be seen in the  salamander genus Ambystoma,   which may either exclude the male DNA  from her offspring to create clones,   fully incorporate the sperm into some eggs to up  the ploidy, or replace her own DNA in other eggs.

And finally, there’s hybridogenesis,   a complicated method that incorporates some  elements from both of the previous ones. The most well known example  is in the water frog complex,   where three different species in the genus  Pelophylax all mate in different combinations. Reproduction in this system is  partly sexual and partly clonal,   allowing the hybrid to persist  by more than one mating means.

It goes to show that reproduction is always an  option when molecular genetics is basically magic! [♪♪ OUTRO ♪♪]