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Tadpole shrimp are neither tadpoles, nor shrimp. They are a little, ancient type of crustacean that swims in water in the driest places on earth.

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Sources:
https://www.britannica.com/animal/tadpole-shrimp
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0034998
https://www.iflscience.com/three-eyed-dinosaur-shrimp-are-waking-up-at-burning-man-70529
https://www.syfy.com/syfy-wire/surprise-three-eyed-time-hopping-crustaceans-emerge-from-seemingly-nowhere-after-arizona
https://books.google.com/books?id=hjwN65nZBE0C&pg=PA75#v=onepage&q&f=false
https://books.google.com/books?id=64jgZ1CfmB8C&pg=PA417#v=onepage&q&f=false
https://academic.oup.com/jcb/article/21/4/991/2679840
https://web.archive.org/web/20110723062941/http://crustacea.net/crustace/www/notostra.htm
https://www.britannica.com/animal/shrimp-crustacean
https://burningman.org/event/preparation/faq/
https://education.nationalgeographic.org/resource/antarctica/
https://earthobservatory.nasa.gov/biome/biodesert.php
https://blackrockdesert.org/about-the-black-rock-desert-playa/
https://eros.usgs.gov/earthshots/black-rock-playa-nevada-usa
https://animaldiversity.org/accounts/Triops_longicaudatus/#habitat
https://animaldiversity.org/accounts/Lepidurus_packardi/#habitat
https://animaldiversity.org/accounts/Lepidurus_packardi/#development
https://www.fws.gov/species/vernal-pool-tadpole-shrimp-lepidurus-packardi
https://animaldiversity.org/accounts/Triops_longicaudatus/#reproduction
https://animaldiversity.org/accounts/Lepidurus_packardi/#development
https://mytriops.com/wp-content/uploads/2020/07/paper11.pdf
https://academic.oup.com/jhered/article/107/6/518/2622894?login=false

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Images:
https://www.gettyimages.com/detail/1013517992
https://www.gettyimages.com/detail/1064483536
https://www.gettyimages.com/detail/1069598202
https://www.gettyimages.com/detail/1077695778
https://www.gettyimages.com/detail/1139993117
https://www.gettyimages.com/detail/1216525882
https://www.gettyimages.com/detail/1226361727
https://www.gettyimages.com/detail/1289843521
https://www.gettyimages.com/detail/1358390661
https://www.gettyimages.com/detail/1358396655
https://www.gettyimages.com/detail/1358397962
https://www.gettyimages.com/detail/1358400090
https://www.gettyimages.com/detail/1358402370
https://www.gettyimages.com/detail/1358412947
https://www.gettyimages.com/detail/1358417851
https://www.gettyimages.com/detail/1358418040
https://www.gettyimages.com/detail/1372104655
https://www.gettyimages.com/detail/1404255511
https://www.gettyimages.com/detail/1498355734
https://www.gettyimages.com/detail/1866221690
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https://www.gettyimages.com/detail/473245425
https://www.inaturalist.org/observations/156008737
https://www.inaturalist.org/observations/3408677
https://www.youtube.com/watch?v=-VnXo_ruGUo
https://www.youtube.com/watch?v=73vLOyYD7wA
https://www.youtube.com/watch?v=AwjwlG52WQw
https://www.youtube.com/watch?v=BzJCkeViWms
https://www.youtube.com/watch?v=gp8YKHArRws
https://www.youtube.com/watch?v=isIlvSupuJo
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https://www.youtube.com/watch?v=ZQacfYW6eZQ
https://zoologicalletters.biomedcentral.com/articles/10.1186/s40851-019-0136-0/figures/1
Thanks to Brilliant for supporting this video!

Because you watch Bizarre Beasts, Brilliant  is offering you a 30 day free trial and 20% off an annual premium subscription  at Brilliant.org/BizarreBeasts. This is a thing called a tadpole shrimp.  It is neither tadpole, nor shrimp.

It’s a different kind of crustacean   that comes from a lineage that first appeared hundreds of millions of years ago, and they’ve looked pretty much the same the whole time. Something about being a small, three-eyed,  horseshoe-crab-looking thing just works. And while they look pretty cute from the  top, underneath is a different story.

You could tell me they inspired the facehuggers  from the Alien franchise and I would not be surprised. And their superpower is waiting.  Which, makes sense, I guess, for an aquatic animal that can live in the desert. [♪♪ INTRO ♪♪] If you want to support the  channel, the Bizarre Beasts pin club is open for subscriptions  from today through February 12th! Sign up now and the first pin you will get  will be one of these weird little guys!

Scientists know these strange critters  as members of the order Notostraca,   which comes from the Greek  words for ‘back’ and ‘shell.’ And there is just one single family in that order: Triopsidae, with ‘Triops’ meaning ‘three eyes.’ That family contains only two genera of  tadpole shrimp and it can be very hard to tell the difference between the species within each genus. And I would be perfectly content to call these little guys ‘three-eyed back-shells,’  because they are both of those things,   though the third eye is more of a basic  light-sensing organ than a real eye. But what they are not is shrimp, in spite  of their common names being tadpole shrimp, dinosaur shrimp, and shield shrimp.

And yes, I realize I’m kind of  stuck calling them ‘tadpole shrimp’ here,   because three-eyed back-shells might be  more accurate, but is a terrible re-brand. Anyway, the whole point of  the Bizarre Beasts channel   is that we explore what makes animals weird to us. And I think calling these little crustaceans  any kind of ‘shrimp’ is really doing them a  disservice, because it makes them seem much  more normal and familiar than they actually are.

Without getting too far into the taxonomic weeds of ‘what even is a shrimp..?’   I’d say you can recognize a shrimp by these features… They have long bodies that are  flattened from side-to-side,   whip-like antennae, eyes on stalks, a  tail that ends in a fan, and ten legs,   some of which are skinny, and some of  which are modified into swimmerets. And tadpole shrimp just…don’t. It’s actually kinda strange to me that  someone saw them and thought ‘shrimp.’ Instead, they have a broad, oval-ish  shell at the front of their bodies,   a relatively skinny tail with two  long thin projections at the tip,   up to 70 pairs of legs in some species,  and eyes that are not on stalks.

I think they really look more like mini-horseshoe  crabs, but it would also be misleading to call them that, because they’re even less closely  related to tadpole shrimp than true shrimp are. And if you have heard of  these little weirdos before,   it might be because Triops crashed the  arts festival known as Burning Man in 2023. Burning Man takes place every year in the Black Rock Desert in Nevada right around the last week  of August or first week of September.

Now, when you think of a desert, you might  picture rolling sand dunes or big cactuses or,   if you’re really into deserts, Antarctica… Because deserts can be cold, too,   as long as they don’t get more  than 25 cm of rain per year. But the Black Rock Desert is a  different kind of landscape – it’s a playa, a semi-arid, windswept  ancient lakebed covered in fine sediment. It’s really hot in the summer,  with temperatures regularly hitting 37 degrees Celsius or  more during the day   before dipping to 7 degrees Celsius at night, and  it gets down to freezing in the winter.

And it only rains an average  of 17 cm per year... but aquatic animals still live there. Which seems pretty weird to me,   and it only works because tadpole  shrimp are just really good at waiting… or, at least, their eggs are. See, tadpole shrimp are found  worldwide, but they generally only live in environments where pools  of water are temporary and seasonal.

And this means their eggs have to be  able to survive the pools they were laid in drying up  and somehow make it to  the next time conditions are favorable… which, in some species, can  be up to 10 years later. While they wait, the eggs dry out and can  survive pretty extreme environmental conditions,   like the temperature swings on the playa, as well  as being literally eaten and excreted by animals. Then, when it finally rains,  like it did during Burning Man,   the eggs hatch and the juveniles  mature really quickly, ready to reproduce and start the whole thing  over again before their pool dries up.

But, the thing is, having a life  cycle that’s kinda unpredictable like this  can have some weird  consequences for reproduction. Being entirely dependent on specific environmental conditions means there’s no guarantee that they’ll happen again or, if they do, that there will be suitable mates around. What’s the point of your eggs being able  to hang out for a literal decade if,   once they hatch, it’s the  end of your lineage anyway?

Well, tadpole shrimp reproduction has  gotten wild as a way to deal with this – it can vary between species and even  between populations of the same species. There can be equal numbers of males and females,  lots of one sex and very few of the other,   no males at all, or males that don’t seem to  contribute genetically to their offspring. And in the populations with no males  at all, the single sex that exists   can either produce both eggs and sperm,  or it can reproduce via parthenogenesis,   essentially cloning itself  from an unfertilized egg.

If you thought our episode on aphids had  some weird reproductive shenanigans going on,   I’d say tadpole shrimp have them beat. But, given the particular environmental  pressures tadpole shrimp have to cope with,   it makes a lot of sense that extreme  reproductive flexibility has evolved. They have to pass on their genes somehow.

And, in that, they’re just like every other  organism that has evolved on our planet: bizarre in the way that works for them. Along with our fantastic tadpole shrimp pins,   we also have two new special  things for you this month! First, because it is February,   we’ve turned the art of some of our  favorite beasts into valentines!

And second, because at least for us it is  February in Montana, we’ve made a scarf! It has sea slugs on it! You can get the pins and the cards and the scarf and everything else at BizarreBeastsShow.com Tadpole shrimp live at the  whims of the water cycle.

Maybe this year they will  swim around and maybe next   year they will just hang out as dry little eggs. They’ll never have any real way  to predict either outcome,   but you can with the Explaining  Variation course on Brilliant. This online course starts with correlation   and then covers everything from linear  regression to Simpson’s paradox.

And that’s just one of the many courses  you can explore with Brilliant, the online learning platform with thousands of interactive  lessons in science, computer science, and math. Brilliant lets you learn anywhere at any time  and if you aren’t sure what course to take,   Brilliant has a quiz you can take when you sign up    to be matched with content that  fits your skill level and interest. You can try it for free for 30 days  at Brilliant.org/BizarreBeasts    or by clicking the link in the description down below.

That link also gives you 20% off an  annual premium Brilliant subscription. Thanks to Brilliant for supporting  this episode of Bizarre Beasts! We mentioned in the video that  it can be really hard to tell the difference   between different species  of tadpole shrimp in the same genus,   but telling the two genera, Triops and  Lepidurus, apart is actually much easier: it all comes down to the tail.

Both kinds of tadpole shrimp have  an elongated tail, called a telson,   which is just the final segment of the  body of certain kinds of arthropods. At the end of the telson, they have two skinny,  spine-like projections called caudal rami. And between those caudal  rami, Lepidurus has a rounded,   plate-like structure, while Triops does not! [♪♪ OUTRO ♪♪]