Speaker 1: Hey, Welcome to Stuff to Blow Your Mind. My name
Speaker 1: is Robert Lamb and I'm Joe McCormick, and it's Saturday,
Speaker 1: time for a Vault episode. This episode originally aired on
Speaker 1: January and it's about horseshoe crabs. I remember this was
Speaker 1: a lot of fun. Yeah, it sounds fine, but this
Speaker 1: is one of those. When I was putting it in
Speaker 1: our schedule for the Vault episode, I realized I had
Speaker 1: no memory of this one at all. Really. I mean,
Speaker 1: I vaguely remember researching some of the stuff about the
Speaker 1: blood and the usefulness of horseshoe blood, but I really
Speaker 1: don't remember this episode. Otherwise, I don't know why. I remember.
Speaker 1: This episode led me to discover a really cool book though,
Speaker 1: that was about horseshoe crabs and uh and an evolution.
Speaker 1: So yeah, yeah, it was a good one. Alright, let's
Speaker 1: dive in Welcome to Stuff to Blow Your Mind, a
Speaker 1: production of I Heart Radios has to work. Hey, you,
Speaker 1: Welcome to Stuff to Blow your Mind. My name is
Speaker 1: Robert Lamb and I'm Joe McCormick, and today we're gonna
Speaker 1: be talking about an underappreciated evolutionary marvel, the horseshoe crab. Robert,
Speaker 1: this this episode was your idea, and I'm so glad
Speaker 1: you you thought of this. Yeah, and I'll bring up
Speaker 1: a little later in the episode. What what reminded me
Speaker 1: that the horseshoe crab should be a topic of discussion.
Speaker 1: But but really, this is a creature I feel like
Speaker 1: that I've been admiring my whole life. It's frequently brought up.
Speaker 1: It's frequently pointed out to me. I remember as a
Speaker 1: kid being if not shown an actual horseshoe crab, I
Speaker 1: mean maybe I was shown like the remnants of one
Speaker 1: that had washed up, or picture of one, and it
Speaker 1: was explained to me that, like, this is a unique
Speaker 1: organism that you don't find many things that I really
Speaker 1: like it on this earth, on the Earth today, and
Speaker 1: if you went back far enough in time, you would
Speaker 1: find them in in ages of of strange biological diversity
Speaker 1: that what otherwise seem alien. But the horseshoe crab has
Speaker 1: remained largely constant. It is an olive colored lump from
Speaker 1: the Jurassic period and beyond. So one of the great
Speaker 1: things about it is it's sort of perfect fodder for
Speaker 1: our show, I think, because it's something that if you
Speaker 1: don't go deep on it, it might be uh, you
Speaker 1: might think of it as a kind of like lowly
Speaker 1: and uninteresting, just sort of lump in the mud with
Speaker 1: with some scuttling claws, and you know that there's not
Speaker 1: really much to it. There's a lot to it. This
Speaker 1: creature is marvelous. And to start us off, I want
Speaker 1: to inspire some wonder by by reading a passage with
Speaker 1: a few abridgements from a really excellent book I've been
Speaker 1: reading this week by the British paleontologist Richard Forty, called
Speaker 1: Horseshoe Crabs and Velvet Worms, The Story of Animals and
Speaker 1: Plants that Time Has Left Behind. It was published into
Speaker 1: the two thousand twelve Now velvet Worms by the way
Speaker 1: we spoke about them recently, it was potentially buried if
Speaker 1: you skip our movie episodes, and you shouldn't. Uh. We
Speaker 1: did an episode on the Tangler, that old Vincent Price
Speaker 1: horror movie, and the title character in or the title
Speaker 1: monster in that film, the tingler very closely resembles a
Speaker 1: velvet worm, so we discussed its unique biology so to
Speaker 1: be mentioned in the same sentence as the velvet worm.
Speaker 1: That should I let you know that the horseshoe crab
Speaker 1: is no joke totally so. Richard Forty, the author of
Speaker 1: this book, is a former president of the Geological Society
Speaker 1: of London. He spent much of his career as a
Speaker 1: staff paleontologist at the British Natural History Museum, where his
Speaker 1: research included a special focus on our old friends, the
Speaker 1: trialo bites uh. And he's also done a lot of
Speaker 1: public natural history communication, appearing on BBC documentaries and stuff
Speaker 1: like that. So in the opening chapter of this book,
Speaker 1: Forty is describing a massive gathering of horseshoe crabs that
Speaker 1: he witnessed one night on a beach in Delaware. So
Speaker 1: I'll begin reading here deep in the night, along the
Speaker 1: shores of Delaware Bay. The horseshoe crabs are stirring. The
Speaker 1: tide is now high, and there is no moon. Darkness rules,
Speaker 1: But even in the feeble starlight, the overwhelming flatness of
Speaker 1: the countryside can be made out, except along the room
Speaker 1: of the bay, where old sand dunes have built up
Speaker 1: a levee heave with gentle movements. First, I noticed some
Speaker 1: very odd sounds. There is a general hollow clattering, a
Speaker 1: tapping and grinding sound somewhat like that made by knocking
Speaker 1: coconut shells together, once used on the radio to imitate
Speaker 1: horses hoofs, but altogether less rhythmic and with a kind
Speaker 1: of underlying push. Then, as my eyes get used to
Speaker 1: the darkness low shelly mounds, the size of inverted colanders
Speaker 1: can be seen slowly pushing and jostling all along the
Speaker 1: shore and perhaps six meters up into the sands. They're
Speaker 1: bumping and clambering together. Is the source of those tap
Speaker 1: tapping percussive sounds. The flash of an infrared torch reveals
Speaker 1: more details. The head shield of the horseshoe crab is
Speaker 1: domed upwards and carries a few weak spines at its
Speaker 1: back end to hinge marks a jointed boundary with a
Speaker 1: second large plate spiny at the edge, which can flap downwards,
Speaker 1: and beyond that again projects a stout triangular spike as
Speaker 1: long as the head, which can waggle up and down.
Speaker 1: Here at Kit's stomach. More crabs are gathered on the
Speaker 1: mud flat seaward of the sands, waiting their turn. Strange green, black,
Speaker 1: slowly animated lumps further offshore again in the shallow seawater
Speaker 1: Tail Spikes project briefly above the gentle waves like raised
Speaker 1: radio antenna and are gone, showing we're still more horseshoe
Speaker 1: crabs vie with one another to get their place on
Speaker 1: the sand. So if that doesn't attempt you to buy
Speaker 1: the book, I will say that the whole thing I
Speaker 1: think is great like that Forty is uh he's a
Speaker 1: great scientist but also a really great writer. In this
Speaker 1: book is just a fabulous read. Yeah. I like the
Speaker 1: details he gives to describing it. Like, one thing that
Speaker 1: I think stands out for me is the horseshoe crab
Speaker 1: always looked like an element from a suit of armor.
Speaker 1: You know, it has a looks it looks like a
Speaker 1: little tank um thing along the shoreline. Well, yeah, exactly,
Speaker 1: And there's a good reason it looks like that. I mean,
Speaker 1: that is quite literally what it is. This is a
Speaker 1: creature that is mostly a suit of armor, especially if
Speaker 1: you're looking down from above right, it is quite literally
Speaker 1: biological armor. Now, Forty goes on to explain the marvels
Speaker 1: of the scene. He says, there are thousands of these
Speaker 1: creatures gathered on the beach and coming onto the beach
Speaker 1: from the waves. Uh. He at one point finds one
Speaker 1: horseshoe crab upturned on its back in the sand, desperately
Speaker 1: bending its tail spike up and down in an attempt
Speaker 1: to flip itself back over, which is a strategy that
Speaker 1: I believe would probably work in the water, but not
Speaker 1: so much on the land. Um And despite his status
Speaker 1: as a scientific observer, Forty admits that he's unable to
Speaker 1: resist the urge to right the animal, and he does,
Speaker 1: grasping it by its head shield, and he flips it.
Speaker 1: But once upright, of course, it doesn't say any thanks.
Speaker 1: It just kind of trundles away and gets back to business.
Speaker 1: But what is this business? It is mating. This is
Speaker 1: a giant convention of hor shoe crabs essentially for the
Speaker 1: purpose of an invertebrate orgy. And that's not forty. Forty
Speaker 1: himself uses the word orgy. I think that is the
Speaker 1: correct term for this. So he notes that the largest
Speaker 1: animals on the beach are digging down in the sand,
Speaker 1: so while their dorsal shields hide most of what's going on,
Speaker 1: their jointed limbs underneath our industriously removing sand. And then
Speaker 1: some of the larger crabs end up digging themselves so
Speaker 1: far down that they're almost completely buried, and these larger creatures,
Speaker 1: the ones doing the digging, or the females, they will
Speaker 1: ultimately be burying their freshly laid eggs in the sand
Speaker 1: here on the beach. Meanwhile, smaller crabs are fighting to
Speaker 1: climb on top of the buried females. These smaller ones
Speaker 1: are the males, and the reason they're fighting for positioning
Speaker 1: is that they're competing for a chance to fertilize the
Speaker 1: female's eggs with their sperm cells, which are called milt
Speaker 1: and Uh Forty realizes that much of the tapping he's
Speaker 1: talking about in that passage, I read that clacking noise
Speaker 1: that he heard in the dark comes from what he
Speaker 1: calls tussles for dominance. Male horseshoe crabs knocking one another
Speaker 1: about by the exo skeletons as they fight for a
Speaker 1: chance to be the first in line to reproduce, and
Speaker 1: this can get really violent. Forty notes that finally, uh,
Speaker 1: many of them don't survive this night of mass invertebrate
Speaker 1: sex on the beach. In the morning, the shore is
Speaker 1: just littered with assorted chunks of horseshoe crab carcasses. It's
Speaker 1: an amazing scene, and I wish I could be present
Speaker 1: to see this something I would go to Delaware for that.
Speaker 1: That would get me into Delaware. Yeah, they should put
Speaker 1: it on the license plate, right. Yeah, this does remind
Speaker 1: me of of a story that I've heard before. My
Speaker 1: wife's grandmother had an amusing tale of horseshoe crabs. I
Speaker 1: believe this is a tale from the Great Outer Banks
Speaker 1: of the United States. Uh, though she also lived in
Speaker 1: Australia for a time when she was younger, so it
Speaker 1: might be a tale from Australia, but I'm pretty sure
Speaker 1: it's Outer Banks anyway. The story goes that she happened
Speaker 1: upon a bunch of horseshoe crabs on the beach and
Speaker 1: thought they were in danger. So um, my wife's grandmother
Speaker 1: then devoted an hour or so to collecting them and
Speaker 1: hurling them back into the sea, only to learn later
Speaker 1: that they had come ashore to make so she thought
Speaker 1: that they were like beached whales essentially. Yeah, you know,
Speaker 1: they're usually not there here, they are in mass maybe
Speaker 1: something is wrong. They need help, you know, thrown back
Speaker 1: in before the birds get them, that sort of thing.
Speaker 1: So she meant, well, but it turns out she was
Speaker 1: interfering in their natural process. I bet those were some
Speaker 1: frustrated invertebrates. Uh. Now, these mass matings on the beach
Speaker 1: bear a and actually pretty great ecological significance. Forty describes
Speaker 1: the eggs they lay as tiny and green, and he
Speaker 1: writes that they're they're laid together in these golf ball
Speaker 1: sized clumps of about four thousand to six thousand eggs apiece. Uh.
Speaker 1: He says up to fifteen or so males will have
Speaker 1: the opportunity to fertilize the eggs of a single female,
Speaker 1: and during a reproductive cycle, a single female horseshoe crab
Speaker 1: might lay about eighty two a thousand eggs total. And
Speaker 1: yet Forty notes that on average, it's estimated that only
Speaker 1: about thirty three out of every million eggs survive into adulthood.
Speaker 1: So again this comes back to kind of in the
Speaker 1: invertebrate numbers game, much like we talked about in our
Speaker 1: Christmas Island Crabs episode. Uh. You know, there's a lot
Speaker 1: of larva and only a tiny fraction of them actually
Speaker 1: ever become adult crabs. Uh. But this massive eggs and
Speaker 1: juveniles that don't survive, they're ecologically very important because like
Speaker 1: the Christmas Island crabs. They are an important food source
Speaker 1: for lots of animals living in and passing through the region.
Speaker 1: Longerhead turtles prey on the crabs even into adulthood. That
Speaker 1: is kind of weird imagining eating a horseshoe crab, because
Speaker 1: if you look at one, it just really does not
Speaker 1: look like it would have much good meat. It looks
Speaker 1: like an animal made entirely out of shell and bone.
Speaker 1: So I was looking around on this and in some
Speaker 1: parts of the world that they are sometimes harvested for food,
Speaker 1: but only the eggs or row are edible, according to
Speaker 1: Malaysia Best dot net so, which is a blog post
Speaker 1: about this and some photos. You'll find them on the
Speaker 1: menu and some restaurants either grilled and flipped over for
Speaker 1: row consumption, or someplaces you can get the row already
Speaker 1: scooped out and served to you. And I read that
Speaker 1: the eggs basically have a rubbery texture and a salty taste,
Speaker 1: so nothing really all that exotic in terms of you know,
Speaker 1: eating uh, you know, the the eggs of marine creatures
Speaker 1: like this, But again, the end of the air favorites
Speaker 1: among birds and other creatures, and the horseshoe crab is
Speaker 1: a keystone species for this reason, Like it's we're gonna
Speaker 1: spend a lot of time on this show talking about,
Speaker 1: you know, how ancient they are in their ancient origins.
Speaker 1: It's easy to maybe fall into this notion that they
Speaker 1: are an outcast, that they're not really important, they're just
Speaker 1: a throwback. But no, they have a very important role
Speaker 1: in a number of species. Again, like migratory seabirds depend
Speaker 1: upon them. Yeah, you're exactly right about that. And Forty
Speaker 1: talks about this at length that you know, the birds
Speaker 1: will peck around in the sand to find the hidden caches,
Speaker 1: buried eggs. Um. So this scene that Forty describes so
Speaker 1: vividly is not just an amazing spectacle of nature. We
Speaker 1: sort of alluded to this earlier, but it's also a
Speaker 1: window into the deep history of planet Earth and a
Speaker 1: way to think about the wonders of evolution across geologic time.
Speaker 1: So maybe we should take a closer look at the
Speaker 1: horseshoe crab and its anatomy and its body before we
Speaker 1: kind of zoom out to the evolutionary picture. Yes, absolutely,
Speaker 1: and uh, and we do encourage you look up some
Speaker 1: footage or some images of the creature if you have
Speaker 1: a chance to while while we're discussing it here um,
Speaker 1: because that'll be helpful. Though. I think a lot of you,
Speaker 1: if not most of you, have seen a horseshoe crab
Speaker 1: before and have at least a basic idea in your
Speaker 1: mind what it looks like. I guess maybe let's start
Speaker 1: from looking from above, right the way you would normally
Speaker 1: see one if you're looking down at it on the beach.
Speaker 1: So from above, the horseshoe crab is this closed dome
Speaker 1: of armor that has three obvious body segments. The first
Speaker 1: segment is the headshield technically known as the pro soma,
Speaker 1: which is a solid, rounded, vaguely horsehoof shaped plate of
Speaker 1: protective kitanous material, which forty says is similar to the
Speaker 1: material you'd find making up the wings of a beetle.
Speaker 1: And then it's got on top of that headshield two
Speaker 1: obvious compound eyes poking up on on either side, and
Speaker 1: those compound eyes are used for locating mates. One thing
Speaker 1: I was reading about them that was very interesting is
Speaker 1: that they they have drastically different levels of light sensitivity
Speaker 1: between the night and day cycle. So during the daytime,
Speaker 1: the receptors in those compound eyes are tuned way down,
Speaker 1: I guess, to make them, you know, less likely to
Speaker 1: get blinded by the light coming in from above. But
Speaker 1: in the nighttime they get tuned way up, and that's
Speaker 1: I think primarily used for seeing a mate somewhere on
Speaker 1: the beach and navigating toward it in the dark, because again,
Speaker 1: this a lot of the spawning happens at night. I
Speaker 1: think the eyes are are kind of really key to
Speaker 1: the the human experience of the horseshoe crab, because you know,
Speaker 1: we like things with eyes that we helps us sort
Speaker 1: of connect with them and sort of even think of
Speaker 1: a personality for them. The horseshoe crabs eyes, certainly at
Speaker 1: first glance anyway, they seem to have a certain seriousness
Speaker 1: to them, or even kind of a determination or a
Speaker 1: A seven a sinister quality, and so they're just all business. Yeah,
Speaker 1: they look they look very serious. They don't have like
Speaker 1: goofy eyes. You know, we've discussed animals on the show
Speaker 1: before that from the human perspective may even have googly eyes,
Speaker 1: but like Glenaria, these however, they look very serious and
Speaker 1: so we kind of consider them seriously. I think sometimes
Speaker 1: well it turns out there even more serious than you think,
Speaker 1: because they've got those two big compound eyes that are
Speaker 1: that have that alternating sensitivity good for locating mates. But
Speaker 1: the horseshoe crab actually has something like ten eyes total. Uh.
Speaker 1: These are you know, less easily identifiable as eyes just
Speaker 1: by looking at them, but they've got basically ten photosensitive
Speaker 1: spots or organ that in some way help the creature
Speaker 1: detect light and detect movement. Okay, so that's the big
Speaker 1: first part of it, the domed part of the head shield.
Speaker 1: Then you've got if you're going from front to back,
Speaker 1: you've got the next segment which connects behind the head shield,
Speaker 1: and this is the abdomen, also known as the opus
Speaker 1: the soma. Uh. This is a more flattened plate attached
Speaker 1: to the head shield by a Hinge as forty wrote,
Speaker 1: and uh, and it's got these backward facing spines along
Speaker 1: its lateral edges. And then finally, the horseshoe crab terminates
Speaker 1: in this long, straight, rigid tail known as a telson. Uh.
Speaker 1: And if you've ever seen one of these animals moving
Speaker 1: or being handled, especially if you've seen you know, like
Speaker 1: a demonstration where somebody holds a horseshoe crab upright for
Speaker 1: you to see it's underside. You know, the tail can
Speaker 1: kind of whip up and down dramatically. Now, other Arthur
Speaker 1: pods have Tellson's as well, such as the shrimp, And
Speaker 1: I think the shrimp is a great example because a
Speaker 1: lot of you have probably at least some you probably
Speaker 1: have some experience with shrimp tails, the consuming shrimp tails,
Speaker 1: so in shrimp, lobster's, krill, and crayfish. The the telson
Speaker 1: is important for what is known as the the karadid
Speaker 1: escape reaction, in which a downtail tail flip allows a
Speaker 1: startled individual to dart backwards through the water. Which, again,
Speaker 1: that kind of comes back to you said earlier about
Speaker 1: how the thrashing of the tail would be more useful
Speaker 1: to to right oneself or to escape a stressful situation
Speaker 1: in the water as opposed to on land. Yes, and
Speaker 1: that's a really interesting thing to look at too, because
Speaker 1: when you look at a display like the tail wagging
Speaker 1: up and down, this, you know, the the rigid pointed
Speaker 1: stick there basically, especially when the animal is handled, you
Speaker 1: might guess it's a defensive weapon, right, you'd think, like, okay,
Speaker 1: stinger of a scorpion, and a lot of people do
Speaker 1: assume that about the horseshoe crab that has got a
Speaker 1: stinger on its telson, and that guess would be half
Speaker 1: right and half wrong. The correct part is that there
Speaker 1: probably is an evolutionary relationship at play in the similarity
Speaker 1: with the scorpions tail. Will come back to that in
Speaker 1: a bit, But the wrong part would be to assume
Speaker 1: that it is a stinger weapon. It is not, as
Speaker 1: we were talking about. Primarily, it's used to help the
Speaker 1: horseshoe crab navigate aquatic environment, so it can help the
Speaker 1: animal steer its body while it's swimming. But it can
Speaker 1: also help the animal, like we said, right itself once
Speaker 1: it becomes flipped on its back, and you can imagine
Speaker 1: in its natural habitat this could happen quite a bit
Speaker 1: because this is a creature that's going to be dealing
Speaker 1: with the physical tumult of the title zone. You know,
Speaker 1: you can imagine it might get rolled upside down in
Speaker 1: the surf, where might get rolled over while it's clambering
Speaker 1: around on something in the mud flats, and this popping
Speaker 1: up and down motion of the tail can help flip
Speaker 1: it back over like one of those spring flipping wind
Speaker 1: up toys. Now I just mentioned swimming. One other very
Speaker 1: strange aspect of the horseshoe crab is that when it's
Speaker 1: time to swim, the horseshoe crab usually swims upside down,
Speaker 1: doing a kind of invertebrate backstroke with its head yield
Speaker 1: angled down towards the bottom and it's jointed legs paddling
Speaker 1: towards the sky. If you can find video of this this,
Speaker 1: it will probably recommend you go look at video of
Speaker 1: several things in this episode, because a lot of a
Speaker 1: lot of this animal's movements and behaviors are are fascinating
Speaker 1: to see. But yeah, if you can find video of
Speaker 1: its swimming with its legs inverted up towards the sky,
Speaker 1: it looks very strange, very cool, and it well, yeah,
Speaker 1: it's basically just a backstroke. Well, as long as the
Speaker 1: animals flipped over here, let's discuss what's going on underneath
Speaker 1: the armor. I think that's a great idea. So yeah,
Speaker 1: well you're flipping it over looking at its belly, and
Speaker 1: on this side it is bug city. You've got five
Speaker 1: pairs of jointed walking legs that look kind of like
Speaker 1: crab legs or spider legs, and these are known as pedipalps.
Speaker 1: The first four pairs of legs all end in a
Speaker 1: a pincer claw shaped tip, so imagine kind of a
Speaker 1: regular crab with claws on all of its walking feet.
Speaker 1: But then the final pair of legs ends in what
Speaker 1: looks a kind of strange flower shape, which is apparently
Speaker 1: used mostly for digging, and then towards the front of
Speaker 1: the head. In in front of the walking legs, there's
Speaker 1: another smaller pair of appendages that are known as the chillissary,
Speaker 1: and we'll come back to their significance in a moment,
Speaker 1: but they're primarily used for guiding food toward the mouth.
Speaker 1: So here's maybe one of my This might be my
Speaker 1: favorite partment. Where's the mouth? You might expect, in line
Speaker 1: with other crabs and invertebrates, that the mouth is in
Speaker 1: the front facing part of the head, but nope, in
Speaker 1: horseshoe crabs, the mouth is in the middle of the
Speaker 1: underside between all of the animals jointed spidery legs. So
Speaker 1: as the legs move, any food caught underneath them is
Speaker 1: sort of shuffled inward toward a crevice running between the
Speaker 1: leg pairs, aided by these gripping spines that run along
Speaker 1: the inside of the appendages, so as the legs scuttle,
Speaker 1: the food is also partially chewed up by those legs
Speaker 1: and prepared for digestion. There's this grinding scraping action of
Speaker 1: the exoskeleton parts of the legs and the joints. So,
Speaker 1: in perhaps illicit anthropomorphic terms, the horseshoe crab has crotch, mouth,
Speaker 1: and leg teeth. Yes, But on the other hand, I
Speaker 1: feel like if you really break down how any animal,
Speaker 1: including not especially humans, eat, it's it's all pretty gross.
Speaker 1: Soh No, I'm sure they think the way we eat
Speaker 1: is great, especially when we're eating their eggs. But but
Speaker 1: I do. I do agree that the footage is very
Speaker 1: interesting and one should check it out. Amazing. Yeah, look
Speaker 1: at that there are videos of this online as well. Yeah.
Speaker 1: It also reminds me that a a fictional creature that
Speaker 1: the horseshoe crab is very typically compared to these days is,
Speaker 1: of course, the Zeno morph alien face hugger. Um Like
Speaker 1: even that that Malaysian blog post about eating them eating
Speaker 1: their their eggs at restaurant uh invoked the face hug
Speaker 1: of comparison. It's kind of inevitable at this point, though,
Speaker 1: I'm not sure the face hugger eat. Um No, I'm well, okay,
Speaker 1: I mean that's a whole another description to start talking
Speaker 1: about the face hugger and how it matches up with
Speaker 1: uh with with actual biology. I'll have to save that
Speaker 1: for another episode. But but the face hugger does have
Speaker 1: the you know what, is kind of like a mouth
Speaker 1: that had it definitely has a tubular orifice that emerges
Speaker 1: from the underside and pretty much the same place one
Speaker 1: would find the mouth of the horseshoe crab. But just
Speaker 1: in general, the horseshoe crab and the and the face
Speaker 1: hugger have kind of similar body layouts, even though they're
Speaker 1: they're rather you know, textually different. I can agree with that, though,
Speaker 1: I guess maybe another similarity if the face hugger doesn't
Speaker 1: actually eat, and it's just like a you know, no
Speaker 1: no digestive system, reproductive organism, well I would I think
Speaker 1: you could even class say that the face hugger in
Speaker 1: alien and use a mobile sexual organ Yes, But but
Speaker 1: to bring it back to the horseshoe crabs, forty rights
Speaker 1: that mature adults can sometimes go for months at a
Speaker 1: time without eating, So these things are tough. Uh. And
Speaker 1: then also to continue our exploration of the underside. Behind
Speaker 1: the legs and the mouth crack on the animals underside,
Speaker 1: you will see a series of overlapping leaf like flaps,
Speaker 1: and these are the animals gills, which allow it to
Speaker 1: breathe by absorbing dissolved oxygen from the water. And the
Speaker 1: horseshoe crab can survive out of water for a time
Speaker 1: if it can keep its gills wet. These organs are
Speaker 1: a specific type of underwater breathing apparatus. Unlike many other
Speaker 1: animals gills, these are these are known as book gills.
Speaker 1: Now you might have heard us talk before about other
Speaker 1: arthropods with book lungs, animals such as the spider. And
Speaker 1: with that teasing detail, maybe we should take a break
Speaker 1: and then come back. All right, we'll be right back.
Speaker 1: Thank alright, we're back. So we were talking about the
Speaker 1: horseshoe crab. Ab, we're talking, and we talked. We mentioned
Speaker 1: a little bit about spider. So let's let's get down
Speaker 1: to it. Let's get down to that that basic factoid
Speaker 1: that that I imagine most of you have heard plenty
Speaker 1: of times, and that is that the horseshoe crab is
Speaker 1: not a crab, despite the fact that we will refer
Speaker 1: to it often on as a crab, and you'll find
Speaker 1: plenty of, uh, plenty of studies where scientists will off
Speaker 1: handedly just refer to them as crabs. Everybody keeps calling
Speaker 1: them crabs, but they're not crabs. True. Decapod crabs and
Speaker 1: horseshoe crabs both belong, of course, to the philum Arthropoda.
Speaker 1: They are both are arthropods, meaning they both have hard exoskeletons,
Speaker 1: They've got segmented bodies, and they've got multiple pairs of
Speaker 1: jointed legs, and the sharing of jointed legs is where
Speaker 1: the word arthropod comes from. Arthur pod means jointed leg
Speaker 1: or jointed foot. But after this, the evolutionary histories of
Speaker 1: crabs and horseshoe crabs really diverge. Crabs, along with shrimp, lobsters,
Speaker 1: wood lice, and and many other creatures, belong to the
Speaker 1: sub phil um of Crustacea. We would call them crustations,
Speaker 1: and Forty points out that crustaceans have antennae or feelers
Speaker 1: on the head used for sensing the environment by touch
Speaker 1: and by smell, and Horseshoe crabs don't have these, so
Speaker 1: what do they have? Instead? They have chillissary. Horseshoe crabs
Speaker 1: are not crustaceans their chill serata in evolutionary history, they
Speaker 1: are more closely related to arachnids like spiders, ticks, and scorpions,
Speaker 1: which if you look at the mouth parts of these creatures,
Speaker 1: like spiders and scorpions, you will find these similar little
Speaker 1: mouth parts that that guide food into the orifice. The
Speaker 1: chillis sary. Uh. They're also Horseshoe crabs are also more
Speaker 1: closely related to an extinct branch of chill Serata known
Speaker 1: as the euryptorids, also known as sea scorpions. Now again
Speaker 1: in misleading names. Sea scorpions is somewhat misleading here because
Speaker 1: euryptorids were not actually scorpions and they didn't all live
Speaker 1: in the sea. But they are truly awesome. This is
Speaker 1: one of the great lines of extinct creatures we we
Speaker 1: talked about in the past episode. Didn't I think they've
Speaker 1: come up before? Yeah, So, the Europtorids were briefly a
Speaker 1: diverse order of predatory animals, including the genus of the
Speaker 1: largest arthropod ever known to exist on Earth. Jclopterus, which
Speaker 1: based on some fossil remains found in Germany, is estimated
Speaker 1: to have grown up to about two point five meters
Speaker 1: or over eight feet in length. So that's definitely big
Speaker 1: enough to start its own harmon. Yeah, just try to
Speaker 1: imagine it. So you got an eight foot arthropod, a
Speaker 1: sort of scorpion lobster like creature bigger than your whole body,
Speaker 1: with a plated exoskeleton and claws, scuttling around at the
Speaker 1: water's edge, or just hanging out in the shallows and
Speaker 1: ambush mode h I have before. I sometimes like to
Speaker 1: imagine these types of creatures surviving into modern geologic periods
Speaker 1: and living alongside humans. And I wondered if the ancient
Speaker 1: Egyptians would have had a euryptorid headed god in place
Speaker 1: of the crocodile deity, so back that would be quite
Speaker 1: a quite a god to behold. You know, I mentioned
Speaker 1: that it is something like this would deserve its own
Speaker 1: horror movie. But now I'm remembering the creature in Deep
Speaker 1: Star six, the underwater horror movie from the director of
Speaker 1: the original Friday the Thirteen. Oh. I believe the monster
Speaker 1: in that is a uriptorid. Uh. It is a straight
Speaker 1: up sea scorpion. I remember Miguel Faire exploding in the movie,
Speaker 1: but I do not remember what the creature looked like.
Speaker 1: Yeah he did, I guess he did explode. Um. He
Speaker 1: There's a scene where they're like, don't get in the
Speaker 1: escape pod, you'll go through explosive decompression, and he's like, no,
Speaker 1: I'm scared, and then he blows up. I just remember,
Speaker 1: I'm the most recent time I watched it, I was
Speaker 1: on an airplane on medication, and I remember just thinking
Speaker 1: it was a wonderful film. We'll see how that would
Speaker 1: hold up over time. But yeah, well, I mean all
Speaker 1: those nine underwater horror movies are worth a watch, but
Speaker 1: certainly I think it was a case where they're, Okay,
Speaker 1: we need it underwater monster. Let's look at some real
Speaker 1: underwater monsters from the past. And they found one and
Speaker 1: they said, heck, let's not try and recreate the wheel here,
Speaker 1: let's do that guy. And so that's what they did. Okay,
Speaker 1: So these would be the ancient closer relatives to the
Speaker 1: horseshoe crabs, the the you know, the arachnids, the scorpions,
Speaker 1: even the uptorids. There are a few extant species of
Speaker 1: horseshoe crab like animals, including a few species found in Asia,
Speaker 1: but the most common by far is the Atlantic horseshoe crab,
Speaker 1: which has the scientific name of Limulus polyphemus. So it's
Speaker 1: got the same name as the the cyclopid monster in
Speaker 1: the Odyssey uh and and Limulus polyphemus. The Atlantic horseshoe
Speaker 1: crab can be found primarily along the East coast of
Speaker 1: North America, roughly from Mexico to Maine. So your wife's
Speaker 1: grandmother's story, I think probably more likely happened in in
Speaker 1: the outer banks on these tis. I'm like American percent
Speaker 1: sure it was. It was outer Banks, but yeah. So
Speaker 1: another thing that's interesting about the horseshoe crabs is something
Speaker 1: that's more common to arthur pods generally. But like other arthropods,
Speaker 1: the development of their bodies as they mature happens through
Speaker 1: a fascinating process called molting. So since these animals have
Speaker 1: a hard, rigid exoskeleton, you might wonder how would they
Speaker 1: ever grow? How do they get bigger? Right? You know,
Speaker 1: if you've got you've got your bones on the outside,
Speaker 1: and molting is the answer. Periodically during its life cycle,
Speaker 1: the horseshoe crab will bust out of its own exoskeleton
Speaker 1: and emerge as a softer critter from within, only to
Speaker 1: quickly have its soft, new larger outline harden again pretty
Speaker 1: rapidly in defense against the perils of the sea. Now,
Speaker 1: a normal horseshoe crab takes about ten years of growing
Speaker 1: and molting before it reaches sexual maturity, which seems like
Speaker 1: a very long time for an animal of this kind. Uh,
Speaker 1: you know, imagine it has to grow for ten years
Speaker 1: before it's ready to mate in that orgy on the beach. Yeah,
Speaker 1: I mean, certainly when we compared to something like say
Speaker 1: a cat or a dog or you know, rat, something
Speaker 1: like that, where the it's pretty short turnaround. But this
Speaker 1: is this is ten years. But especially many other invertebrates,
Speaker 1: we should think reach sexual maturity very fast. But after
Speaker 1: reaching sexual maturity, it never molts again, and instead it
Speaker 1: heads to the beach for mating to leave fertilized eggs
Speaker 1: in the wet sand and start the life cycle over again.
Speaker 1: And so this this life cycle has worked pretty well
Speaker 1: for the horseshoe crab, and it's worked that way for
Speaker 1: quite a long time. Yes, the earliest fossil evidence for
Speaker 1: horseshoe crabs is incredibly ancient. The oldest fossil remnants resembling
Speaker 1: these modern animals, the modern horseshoe crabs, go all the
Speaker 1: way back to the Ordovician period. This is so long ago,
Speaker 1: it's unbelievable. Yeah, we're talking about four hundred and fifty
Speaker 1: million years ago. Um. I mean just consider that the
Speaker 1: for instance, the goblin shark is also something that is
Speaker 1: sometimes referred to as a living fossil, and we'll get
Speaker 1: back to that terminology in a second. But the goblin
Speaker 1: shark own late dates back a hundred twenty five million
Speaker 1: years is an extremely long time. Yeah, um, still incredible.
Speaker 1: Crocodilia goes back some nine million years. Hagfish are virtually
Speaker 1: the same as they were three hundred million years ago.
Speaker 1: Lamp rays go back roughly three hundred sixty million years
Speaker 1: not Alloy's have evolved very little since roughly five hundred
Speaker 1: million years ago. Although that's an example of a creature
Speaker 1: to where they were, there were certainly more varied two
Speaker 1: hundred million years ago. Yeah. About this idea of of
Speaker 1: a living fossil, Richard forty actually he kind of warns
Speaker 1: about this phrase. He calls it quote a paradox and
Speaker 1: an oxymoron rolled into one. Well, yeah, because I mean,
Speaker 1: on one level, it is not a fossil. I think
Speaker 1: that much is probably obvious to most people. It is
Speaker 1: not a fossil. A fossil cannot be alive. A fossil
Speaker 1: is inherently the mineralized remains of something that once lived.
Speaker 1: Though he also sort of uses the word cautiously, his
Speaker 1: point is mainly that we shouldn't be lulled into the
Speaker 1: miss stake, an assumption that a species can exist for
Speaker 1: millions of years with no changes, for example, without significant
Speaker 1: genetic change. Genetic changes are always accumulating, They just build
Speaker 1: up over time, even if the overall form of the
Speaker 1: animal stays very similar. Uh. And also the ecological surroundings
Speaker 1: of these organisms change over time. He talks about how
Speaker 1: even if the the the horseshoe crabs of today look
Speaker 1: extremely similar to the horseshoe crabs of the Jurassic Period,
Speaker 1: the animals all around them would have been completely different,
Speaker 1: and thus they there they were probably you know, they
Speaker 1: had a different ecological niche. They were dealing with different
Speaker 1: relationships and different energy dynamics in the in the environment,
Speaker 1: but eating different things, titially being preyed upon by different things.
Speaker 1: But it is truly remarkable to see a type of
Speaker 1: animal that has survived. I think the horseshoe crabs have
Speaker 1: survived five different mass extinction events, definitely four, I think five,
Speaker 1: and they still exist today in in a body plan
Speaker 1: that is pretty close to the same animal you would
Speaker 1: have found four fifty million years ago. And so as
Speaker 1: alternatives to the phrase living fossil, some paleontologists have proposed
Speaker 1: calling these types of organisms stabil a morphs. You know
Speaker 1: that that morph meaning like body basically and stabilo meaning stable,
Speaker 1: meaning that at some point long ago there was a
Speaker 1: body plan that was reached and it just has not
Speaker 1: needed to undergo change much since then. Yeah, this is
Speaker 1: interesting and and definitely touches on something we've discussed in
Speaker 1: the past in terms of of body forms that work.
Speaker 1: And sometimes you see those basic body form that works
Speaker 1: to the degree that it is acquired by by rather
Speaker 1: distantly related relatives, such as such as the basic dolphin
Speaker 1: or the basic dolphin form, and it's you can compare
Speaker 1: that to to various other fish forms and then also
Speaker 1: to the reptilian creatures that preceded them um uh Ichleosaurus,
Speaker 1: for example. I was just looking at a paper a
Speaker 1: while ago. I don't remember where it was, but there
Speaker 1: was something about how nature repeatedly has tried to build
Speaker 1: crabs like crustacean crabs, Yeah, the actual crabs. That it's
Speaker 1: like a form that just kind of nature keeps coming
Speaker 1: back to from different evolutionary pathways and ending up in
Speaker 1: the same place. Yeah, it's like the most logical engineering
Speaker 1: solution to a given environment and a given set of challenges.
Speaker 1: But of course, with the thesaurus, of course went extinct
Speaker 1: for first of some some essential reasons that I think
Speaker 1: we've touched on the past show on the show in
Speaker 1: the past, But with the horseshoe crab, it's rather different.
Speaker 1: It's like they acquired this form and that form has
Speaker 1: remained relatively stable for the duration. Yeah. I mean those
Speaker 1: are two So you can talk in one sense about
Speaker 1: forms that are stable and you see that they're they're
Speaker 1: advantageous because of convergent evolution, different evolutionary pathways sort of
Speaker 1: arrived in the same place. But we're talking about animal
Speaker 1: forms that were achieved at some point in the past
Speaker 1: and then they just kept working over time, and they
Speaker 1: didn't undergo significant changes in their lineages. Uh, you know,
Speaker 1: little changes here and there, but not major changes in
Speaker 1: the body form. And they never went extinct. Yeah, I mean, really,
Speaker 1: to invoke some more alien terminology, this is a perfect organism.
Speaker 1: It it perfectly survives in the environment for which it
Speaker 1: has evolved, and it has remained stable ever since. Then again,
Speaker 1: surviving mass extinction events for four and fifty million years. Crazy. Yeah,
Speaker 1: there's another alternative name for what to call these types
Speaker 1: of creatures that was actually proposed by Darwin's bulldog, Thomas
Speaker 1: Henry Huxley, who just called them persistent types. I think
Speaker 1: that's pretty straightforward. Yeah, but it makes you wonder how
Speaker 1: on Earth is something like this possible? Like what makes
Speaker 1: animals like the horseshoe crab special? How does this type
Speaker 1: of creature persist for so long with out huge morphological changes? Uh?
Speaker 1: And you know, surviving all these extinction events, never you know,
Speaker 1: becoming all that different of an animal fundamentally. Yeah, because
Speaker 1: I can't help but think of think of it in
Speaker 1: comparison to say the business environment, you know, like like
Speaker 1: what are the persistent forms in the business world, Like
Speaker 1: what what brands or franchises or product types just survive
Speaker 1: for the duration through multiple like economic extinction events, and
Speaker 1: also surviving all the things changing around them, you know,
Speaker 1: predators and prey changing the way they behave and the
Speaker 1: way they eat, you know, things in the in the
Speaker 1: natural world that are ever trying to find that new
Speaker 1: niche will allow them to to to themselves survive since
Speaker 1: the early Devonian nature has pivoted to video exactly. Um,
Speaker 1: so it's you know when we say that you know
Speaker 1: they're true survivors, that it's you know action. I mean,
Speaker 1: really you you're tempted to go that far and say,
Speaker 1: like something here is just really working that they have
Speaker 1: not been um surplanted by some of their creature along
Speaker 1: the way. So many terrific seeming organisms have certainly proven
Speaker 1: to have a very tenuous role in the environment, but
Speaker 1: the horseshoe crab remains. Yeah, I mean, we got no
Speaker 1: room to talk, puny, Homo sapiens. What have we been around,
Speaker 1: you know, less than a few million years. Yeah, and
Speaker 1: and we're continuing to work hard and making sure that
Speaker 1: doesn't go too long. Um okay, So actually, so we
Speaker 1: don't know the answer for sure, why the horseshoe crab
Speaker 1: in particular and animals and other organisms like it has
Speaker 1: persisted so long in its basic body type. But Forty
Speaker 1: has some general thoughts about the question of of what
Speaker 1: causes this sort of thing. He's got some arguments, and
Speaker 1: one that I thought was really interesting was that he
Speaker 1: talks about how survival is not just about the endurance
Speaker 1: of the animal, It's also about the endurance of habitat.
Speaker 1: So often the ability of an animal type to survive
Speaker 1: through the eons largely unmodified is a feature of the
Speaker 1: animal's habitat more than the animal itself. Some habitats are
Speaker 1: just better equipped to sustain their adapted inhabitants through ecological
Speaker 1: catastrophe than others. And so what would be an example
Speaker 1: of this, Well, Forty mentions inter tidal zones of the
Speaker 1: ocean and goes into quote shallow subtitle habitats on muddy
Speaker 1: sandy shorelines. Now, why would this be a favored habitat
Speaker 1: for survival through mass extinctions? Well, a big killer for
Speaker 1: ocean dwelling organisms during environment environmental catastrophe appears to be
Speaker 1: antoxy seas, where due to several cascading factors, you know
Speaker 1: and there's a big environmental catastrophe. Oxygen is often removed
Speaker 1: from a lot of the ocean water, and the animals
Speaker 1: in the water can no longer breathe, and they die
Speaker 1: even in these conditions. Fort just that these shallow, muddy
Speaker 1: ocean edge habitats could still be pretty well oxygenated quote.
Speaker 1: After all, the wind still ruffled the waves on shore,
Speaker 1: and so many of the organisms adapted to this environment
Speaker 1: can make it do with very little food to begin with,
Speaker 1: and they tend to bury themselves in sediment at low
Speaker 1: tide and sort of feed on particles of food that
Speaker 1: wash in with the surf. And their access to the
Speaker 1: surface would keep them in oxygen, and their access to
Speaker 1: the tide would keep them supplied with particles of biomaterial
Speaker 1: for food. Uh to quote forty again, I am tempted
Speaker 1: to return to the military metaphor maybe this habitat was
Speaker 1: like a tunnel that simply went under the front line.
Speaker 1: The luck came in if you happen to belong to
Speaker 1: that special battalion with access to the tunnel. And for
Speaker 1: this reason he points out mud flats as a special
Speaker 1: sort of extinction event survivor zone. Of course, we know
Speaker 1: that you would often find horseshoe crabs scuttling around in
Speaker 1: mud flats and tidal areas. Um. Now, now, why don't
Speaker 1: ancient animal forms in zones like this get out competed
Speaker 1: and displaced by new arrivals. Uh to read from forty quote.
Speaker 1: Populations in many habitats are critically limited by the quantity
Speaker 1: of food available. However, in places such as mud flats,
Speaker 1: food may not be the limiting factor for filter feeding.
Speaker 1: Animals are rich food store is carried into the area
Speaker 1: with every high tide, or is brought from nearby land
Speaker 1: during storms. The crucial things to find living space. The
Speaker 1: problem is not the food in the trough, but making
Speaker 1: a place at the stall. So if it can establish
Speaker 1: itself in its borrow lingula, a creature he's talking about
Speaker 1: is able to compete for food on equal terms with
Speaker 1: a later arrival, geologically speaking, like a shrimp. This habitat
Speaker 1: does seem like a good place to be for an
Speaker 1: organism with conservative tendencies, And so he's sort of talking
Speaker 1: again about many of the creatures that survived these mass
Speaker 1: extinctions and go on for long periods of geologic time
Speaker 1: having kind of behaviorally or ecologically conservative behaviors. Uh. To
Speaker 1: quote him again, in one way, it is survival of
Speaker 1: the fittest, but of the fittest habitat with the right
Speaker 1: design specifications to offer long term security. Stick in the
Speaker 1: MUD's last longest. Now, he also points out a few
Speaker 1: other things, a few other cases of evolutionary survival of
Speaker 1: an organism type over geological time, like if there is
Speaker 1: an animal that's a specialist and a specialist niche, and
Speaker 1: then their particular niche, by luck, persists over time. He
Speaker 1: gives the example of like lampreys and hagfish that survive
Speaker 1: as parasites on bony fish. Um. And then uh, and
Speaker 1: he calls these areas that tend to accumulate long term
Speaker 1: evolutionary survivors together time havens. Yeah. I like that uh
Speaker 1: And And finally he points out also an interesting fact
Speaker 1: that longevity seems to be a common feature in long
Speaker 1: surviving animals, but it alone, of course won't preserve you
Speaker 1: remember again that that it takes horseshoe crabs ten years
Speaker 1: to reach sexual maturity, which is an unusually long period
Speaker 1: of time for an arthropod. Alright, on that note, we're
Speaker 1: going to take a quick break. But when we come back,
Speaker 1: we will venture into the blood. Alright, we're back. All right,
Speaker 1: let's talk about blood. So one of the most astonishing
Speaker 1: things about the horseshoe crab is they're amazing blue blood.
Speaker 1: It's literally blue. Now why would this be Humans and
Speaker 1: other mammals have red blood because of the presence of hemoglobin,
Speaker 1: which is an iron based compound that carries oxygen away
Speaker 1: from the lungs to the rest of the body and
Speaker 1: then transports carbon dioxide back the other way. Horseshoe crabs
Speaker 1: do not have hemoglobin. Instead, they have a protein called hemocyanin,
Speaker 1: which is based on copper instead of iron, and the
Speaker 1: copper content makes the horseshoe crabs blood blue. I can't
Speaker 1: help but think of the I corp of Talos, the
Speaker 1: bronze automaton from Greek myth. But more specifically, I guess
Speaker 1: you have blue blood that shows up in science fiction
Speaker 1: like the alien opera singer in the Fifth Element we
Speaker 1: find out as blue blood. Oh yeah, like everyone else.
Speaker 1: I mainly remember multi pass um. So this hemocyanin based
Speaker 1: blood has has some really amazing properties. So Richard Forty
Speaker 1: writes of how on this beach in Delaware when he's
Speaker 1: walking around looking at all these animals, he comes across
Speaker 1: many horseshoe crabs crawling around with signs of old wounds
Speaker 1: that look really like they should have been fatal, like
Speaker 1: a large hole punched in the middle of the head,
Speaker 1: or just part of the thorax missing, or you know,
Speaker 1: broken off tail, whatever, and the survival of such wounds
Speaker 1: may in part be due to the amazing clotting power
Speaker 1: of horseshoe crab blood. Another anatomy fact that we didn't
Speaker 1: get into earlier was about the circulation of the horseshoe crab.
Speaker 1: Like many other arthropods, the horseshoe crab has an open
Speaker 1: circulatory system, and this is very different from our mammalian system,
Speaker 1: known of course conversely as the closed system, where blood
Speaker 1: is entirely contained within vessels. Right if you cut a
Speaker 1: person open the veins, arteries, capillaries, you have to to
Speaker 1: rupture these containers for the blood to spill out. The
Speaker 1: horseshoe crab is is something closer to kind of like
Speaker 1: a box of free range blood. It has a heart
Speaker 1: type pump that circulates blood oxygenated blood from the gills,
Speaker 1: but then the blood sort of sluices around and bathes
Speaker 1: the creatures organs without being contained entirely within vessels. So
Speaker 1: how do horseshoe crabs survive the carnage of these mass
Speaker 1: mating battles, even having like chunks ripped out of the
Speaker 1: thorax or holes punched in the head. Forty Rights quote
Speaker 1: such endurance as possible because the blood of Limulus polyphemus
Speaker 1: has exceptional clotting powers. The animal does not bleed to
Speaker 1: death because it's blood coagulates and walls off damaged areas.
Speaker 1: So this blood is unique, but it has also proven
Speaker 1: quite useful to humans. Uh specifically, it's been become very
Speaker 1: important to the biomedical industry, which harvests the blood of
Speaker 1: horseshoe crabs to create what is called Limulus ambhisite ly
Speaker 1: sate or L A L, which is used to test
Speaker 1: medical devices and pharmaceutical drugs for indotoxins. And this is
Speaker 1: because their blood contains potent amida sites which function like
Speaker 1: white blood cells, so enzymes are instantly released when they
Speaker 1: come into contact with bacteria, which is observable and less
Speaker 1: than one part per per trillion, So just a tiny
Speaker 1: drop of the blood can help spot contamination. So it's
Speaker 1: important for drug implant and environmental safety tests, and this
Speaker 1: also includes space exploration applications as well. If you want
Speaker 1: to see some footage of horseshoe crab blood harvesting in process,
Speaker 1: you should definitely check out the nat GEO documentary series
Speaker 1: One Strange Rock. We've heard us talk about this in
Speaker 1: the past on the show excellent documentary. Wonderful footage features
Speaker 1: a number of astronauts and Will Smith narrating all of this,
Speaker 1: but they have a section on there. It's on Disney
Speaker 1: Plus right now, so I highly recommend you check it
Speaker 1: out while you're mainlining all of the Mandalorian goodness there.
Speaker 1: In fact, it was while watching One Strange Rock that
Speaker 1: my with my family that I was reminded that this
Speaker 1: would be a great topic because my son was watching
Speaker 1: this and they were showing all these these horseshoe crabs
Speaker 1: being lined up and bled and he just immediately did
Speaker 1: not like it. And he just gets this very stern
Speaker 1: look out his face and he says, human beings are
Speaker 1: the worst and uh, and I had to reassure him, no, Uh,
Speaker 1: these horseshoe crabs are going to be fine. Uh, you
Speaker 1: know that we're not. They're not draining them to death.
Speaker 1: They are draining them and then uh a certain portion
Speaker 1: of their blood and then releasing them into the wild.
Speaker 1: So there is some mortality. Yes, yeah, I was looking
Speaker 1: around on this. Uh there's a paper from the Department
Speaker 1: of Fisheries and Wildlife Sciences and Horseshoe Crab Research Center.
Speaker 1: This is Virginia Polytechnic Institute and State University from LINKA Hurton. Uh,
Speaker 1: this is a this is a small study, but it
Speaker 1: it looked at them the morality the mortality rates for
Speaker 1: horseshoe crabs. It's gonna vary depending on the sex of
Speaker 1: the of the horseshoe crab and the amount of blood drawn.
Speaker 1: And also not every specimen that is collected is ultimately
Speaker 1: deemed suitable for a draw. So the source I was
Speaker 1: looking at place male mortality rate anywhere between zero percent
Speaker 1: at ten percent of blood drawn to thirteen points six
Speaker 1: percent at thirty percent blood drawn, while females it range
Speaker 1: from zero at zero to fifteen point four percent at
Speaker 1: blood drawn. And wait, hold on, no, no, go ahead,
Speaker 1: Well wait why did they ask zero percent drawn? This
Speaker 1: comes down to the fact that it was such a
Speaker 1: small study that there were zero that word, that had
Speaker 1: zero percent drawn on this particular study. So, like I say,
Speaker 1: the very small sample size makes these numbers, you know,
Speaker 1: not the gospel, but they give some idea of of
Speaker 1: what you're looking at here. For the females, the more
Speaker 1: standard blood draw was came with a mortality rate of
Speaker 1: ten point three, So thirty percent of a of a
Speaker 1: crabs blood is generally extracted before it is returned to
Speaker 1: its natural environment within seventy two hours and their placed
Speaker 1: further out, usually to prevent repeat capture and draining. However,
Speaker 1: this is still a physically stressful situation. You know, not
Speaker 1: to anthropomorphize the creatures experience or anything, but the crabs
Speaker 1: take three to seven days to regain their blood volume
Speaker 1: and up to four months for those amata sites to
Speaker 1: return to baseline levels. And they're also usually harvested during
Speaker 1: spawning periods because this is when their easiest to catch.
Speaker 1: A June nineteen study published in the University of Chicago
Speaker 1: Press looked at the stress placed on the crabs following
Speaker 1: their bleeding and how it might be uh impacting their
Speaker 1: re productive potency um so owings at All found the following.
Speaker 1: First of all, overall, biomedical bleeding may impact the reproductive
Speaker 1: output of female horseshoe crabs during the season in which
Speaker 1: they were bled. Week one following the bleeding, bled animals
Speaker 1: appeared to spawn less than the controlled animals, and they
Speaker 1: also found that control females appeared to spawn on average
Speaker 1: four point eight times uh the rate of bled females,
Speaker 1: which spawned on average just two times. They also found
Speaker 1: that bled animals tended to stay clear of shallow zones
Speaker 1: places that they actually needed to be for breeding purposes,
Speaker 1: and this might this might be due to disorientation in
Speaker 1: the animal following the blood draw or it also just
Speaker 1: might all of this might come down to weakness, like
Speaker 1: the creature is going to be weakened for a state
Speaker 1: of you know, a week or even months following of
Speaker 1: what's gone on here, and that may impact their reproductive
Speaker 1: health as well. So all of this can ultimately alter
Speaker 1: the sex ratio at those breeding areas that we talked
Speaker 1: about at the top of the program, which is then
Speaker 1: going to impact reproduction overall for the species in these
Speaker 1: areas where blood harvesting is taking place. So the harvesting
Speaker 1: of horseshoe crab blood probably has saved thousands or millions
Speaker 1: of lives over the years that it's been done, but
Speaker 1: it's still not good to be hurting these populations like this,
Speaker 1: it is, you know, and again like this is a
Speaker 1: study from just last year, so you know, we're still
Speaker 1: learning more and more about the impact as we are
Speaker 1: also looking for ways to get better, ways to get
Speaker 1: away from the use of horseshoe crab blood because there
Speaker 1: are some synthetic solutions now, right, Yeah, there are, and
Speaker 1: we're generally we're looking at a future where we're going
Speaker 1: to depend less on it. Another thing to keep in
Speaker 1: mind is this is not the only risk factor for
Speaker 1: horseshoe crabs. It would be one thing if it were,
Speaker 1: but uh, they are also harvested for their eggs, so
Speaker 1: they can be used as bait for eels as well
Speaker 1: as features known as welk. Yeah, forty was talking about
Speaker 1: this in his book, and the welk is some kind
Speaker 1: of conk like animal that people fishing for it have
Speaker 1: used horseshoe crabs as bait. So you know, these are
Speaker 1: two different human practices that are having varying degrees of
Speaker 1: impact on their reproductive health. And we have to come
Speaker 1: back again to the fact that this is not just
Speaker 1: some mirror outsider species. It's just left over from a
Speaker 1: bygone age. They are keystone species. Their eggs are important
Speaker 1: food source for a number of organisms, again including migratory
Speaker 1: sea birds. So the future promises new biomedical tests as
Speaker 1: well as hopefully alternative baits for the fishing industry, and
Speaker 1: hopefully all of this will come together to ensure the
Speaker 1: long term survival of the horseshoe crab. I hope it
Speaker 1: is not the sixth extinction that wipes them out. But
Speaker 1: that's the thing, isn't it. The great sixth mass extinction
Speaker 1: event is proving to be the human occupation of the planet. However,
Speaker 1: the one thing we have going for is is that
Speaker 1: this extinction event is largely self conscious, or at least
Speaker 1: it's self consciousness is growing. I'm going to be an optimist,
Speaker 1: and it can do things like curb it's uh, it's
Speaker 1: fishing practices. It can do things that are self reflective
Speaker 1: and hopefully sustainable. Yeah, save the limuli folks, they're scuttling
Speaker 1: masses are precious, absolutely all right. So there you have
Speaker 1: at the horseshoe crab. Obviously, we'd love to hear from everybody,
Speaker 1: especially those of you who have you know, any firsthand
Speaker 1: experience with the horseshoe crab. If you have ever eaten
Speaker 1: the row of horseshoe crabs, let us know. We'd love
Speaker 1: to hear about that as well. In the meantime, you
Speaker 1: can find us wherever you get your podcasts. Go to
Speaker 1: stuff to Blow your Mind dot com and that'll redirect
Speaker 1: you to a place where you can find the episodes.
Speaker 1: But wherever you find us, just make sure that you subscribe,
Speaker 1: that you rate, and that you review, and don't forget
Speaker 1: to check out Invention. That's our other show that deals
Speaker 1: with human techno history. Huge thanks as always to our
Speaker 1: excellent audio producer Seth Nicholas Johnson. If you'd like to
Speaker 1: get in touch with us with feedback back on this
Speaker 1: episode or any other, to suggest topic for the future,
Speaker 1: just to say hello, you can email us at contact
Speaker 1: at stuff to Blow your Mind dot com. Stuff to
Speaker 1: Blow Your Mind is a production of I Heart Radio's
Speaker 1: How Stuff Works. For more podcasts from my heart Radio,
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