Horseshoe Crabs: Blue Blood of the Ancients


The Horseshoe Crab Robert this This episode was your idea. And I'm so glad you thought of this. Yeah and I'll I'll bring up a little later in the upset what Quite reminded me that the horseshoe crab should be a topic of discussion. But they're really. This is a creature. I feel like that I've been admiring my whole life. It's frequently brought up. It's frequently pointed out to me. I remember as a kid. Being if not shown an actual horseshoe crab thing maybe it was showing the remnants of one that had washed up or picture of one and it was explained to me like this is a the unique organism that you don't find many things that are really like it on this earth on the earth today and if you went back far enough in time you would find them in in ages of Of strange biological diversity that would otherwise seem alien but the horseshoe crab has remained largely constant. It is an olive colored lump from the Jurassic Period and beyond. Yeah so one of the great things about it is it's sort of perfect fodder for our show I think because it's something that If you don't go deep on it might be You might think of it as a kind of like lowly and uninteresting just sort of lump in the mud with with some scuttling clause and you know there's not really much to it. There's a lot plot to it The this creature is marvelous into start us off. I want to inspire some wonder by by reading a passage with few bridge minutes from a really excellent Poland book. I've been reading this week. By the British paleontologist. Richard Forty called a horseshoe crabs and velvet worms the story of animals and plants. That time has left behind. It was published in two thousand twelve now velvet worms. By the way we'd we spoke about them recently it was potentially buried. If you skip our movie episodes and you shouldn't. We did an episode on the Tingler. That old Vincent Price Horror movie and the title character in or the title monster in that film. The tingler very closely resembles of velvet worms. So we discussed its unique biology so to be mentioned in the same sense as the velvet worm that should let you know the horseshoe crab is no joke totally so Richard Forty. The author of this book is a former president of the Geological Society of London. He spent much of his career as a staff paleontologist colleges at the British Natural History Museum where his research included a special focus on our old friends. The trial of Bites And he's also done a lot of public natural history communication appearing on BBC documentaries and stuff like that so in the opening chapter of this twenty twelve book fourteen is describing a massive gathering of horseshoe hugh crabs that he witnessed one night on a beach in Delaware So begin reading here deepen the night along. The shores of Delaware Bay the Horseshoe. Crab are stirring the tide is now high and there is no moon darkness rules but even in the feeble starlight. The overwhelming flatness of the countryside can be made out except along. The Rim of the bay. Were old sand. Dunes have built up a levy heave with gentle movements. I I noticed. Some very odd sounds downs. There is a general hollow clattering a tapping and grinding sound somewhat like that made by knocking. Coconut shells together once accused on the radio to imitate horses hooves but altogether less rhythmic and with the kind of underlying push then as my eyes get used to the darkness low. Shelly mountains the size of inverted calendars can be seen slowly pushing and jostling all along the shore and perhaps six meters up into the sands. They're bumping and clambering together is the source of those tap tapping percussion sounds the flash of an infrared torch reveals more details. The head shield of the horseshoe crab is domed upwards and carries a few weeks spines at its back into hinge marks at jointed boundary with the second large the plate spiny at the edge which can flap downwards and beyond that again projects a stout triangular spike as long as the head. which can wagle up and down here at kits helmet more crabs are gathered on the mudflats seaward of the San waiting their turn strange green? Black slowly animated lumps temps further offshore again in the shallow seawater. Tail spikes project briefly above the gentle waves like raised radio antenna and are gone shopping. Doing were still more horseshoe crabs vie with one another to get their place on the sand so if that doesn't Tempt you to buy the book I I will say. The whole thing I think is greatly that forty really is He's a great scientist but also a really great writer in this book is just a fabulous. Read Yeah I like the the details it gives to describing like one one thing that stands out from me is the horseshoe crab always looked like An element from a suit of armor has a it. Looks like a little tank moving moving along the shoreline. Well yeah exactly and there's a good reason it looks like that. I mean that is quite literally what it is. This is a creature that is mostly a suit of armor. especially if you're looking down from above above right it is quite literally biological armor Now forty goes onto explain the marvels of the scene says there are thousands of these creatures gathered on the beach. Each coming onto the beach from the waves He he at one point finds one horseshoe crab up turned on its back in the sand desperately bending its tail spike up down in an attempt to flip itself back over which is a strategy that I believe would probably work in the water but not so much on the land And despite his status says a scientific observer forty admits that he's unable to resist the urge to write the animal and he does grasping it by its head shield and he flips it But once upright of course it doesn't say any thanks it just kind of trundles away and gets back to business. What is this business? It is made ing. This is a giant convention of Horseshoe Horseshoe Crabs essentially for the purpose of an invertebrate orgy. And that's four. Forty himself uses the word orgy. I think that is the correct term for this. So he notes that the largest animals on the beach are digging down in the sand. So while their dorsal shields hide most of what's going on there jointed to the limbaugh underneath our industriously removing sand and then Some of the larger crabs ended up digging themselves so far down that they're almost completely buried and these larger creatures the ones doing the digging the females. They will ultimately be burying their freshly laid eggs in the sand here on the beach. Meanwhile smaller crabs jobs are fighting to climb on top of the buried females. These smaller ones are the males and the reason they're fighting for positioning is that they're competing for a chance. To fertilize is the female's eggs with their sperm cells which are called milt and Forty realizes that much of the tapping. He's talking about in that passage. I read that. clanking noise is that he heard in the dark comes from what he calls Tussles for dominance male horseshoe crabs knocking one another about by the EXO skeletons as as they fight for a chance to be the first in line to reproduce and this can get really violent forty notes that finally Many of them don't survive this night of mass asked invertebrates sex on the beach in the morning. The shore is just littered with assorted chunks of Horseshoe Crab Carcasses. It's an amazing scene. And I I wish I could be present to see this. I would go to Delaware for that. That would get me into Delaware. Yeah they should put it on the license plate right. This does remind me of a of a story that that I've heard before My Wife's grandmother had an amusing tale of worship crabs. Believe this is a tale from the outer banks of the United States Though she also who lived in Australia for a time when she was younger so it might be a tale from Australia. But I'm pretty sure it's outer banks anyway. The story goes that she happened. Upon a bunch of horseshoe crabs on the beach. I thought they were in danger. So my wife's grandmother then devoted an hour or so to collecting them and hurling them back into the sea only to learn later that had come short to make so she thought that they were like beached. Whales essentially. Yeah you know they're usually they're here. They are in mass. Maybe something is wrong. They need help you know. Throw them back in before the birds get them that sort of thing so she meant well but turns out. She was interfering in their natural process. ooh I bet those were awesome. Frustrated invertebrates Now these mass meetings on the beach bear an actually pretty great ecological significance Forty describes The eggs they. La is tiny and green and he writes that they're they're laid together in these golf ball sized clumps of about four thousand six thousand eggs a piece He says up to fifteen or so males will have the opportunity to fertilize the eggs of a single female enduring a reproductive cycle a single female horseshoe crab might lay about eighty to one hundred hundred thousand eggs total and yet forty notes that on average. It's estimated that only about thirty three out of every million eggs survive into adulthood. Did so again. This comes back to kind of in the invertebrate numbers game much like we talked about an hour. Christmas Island Crabs You know there's a lot of larva and only a tiny fraction action of them actually ever become adult crabs but this massive eggs and juveniles. That don't survive their ecologically very important. Because like like the Christmas Island crabs they are important food source for lots of animals living in passing through the region loggerhead turtles prey on the crabs even into adulthood The the that is kind of weird imagining eating horseshoe crab because if you look at one it just really does not look like it would have much good meat. It looks like an animal made entirely entirely out of Shell and bone. So it's looking around on this. And in some parts of the world that they are sometimes harvested for food but only the eggs or roe or edible according to Malaysia best dot net which has a blog post about this and some photos. You'll find them on the menu and some restaurants either grilled and flipped over for row consumption or or someplace where you can get the row already scooped out and serve to you. And I read that the the eggs basically have a rubbery texture a salty taste so nothing really all that exotic attic in terms of Of eating the eggs of of marina creatures. like this but again the end of their favorites among birds and other creatures in the horseshoe crab is a keystone species for this reason. Like it's going to spend a Lotta time on the show talking about how ancient they are their ancient origins. It's easy to maybe fall into this notion that they are an outcast that they're not really important. They're just a throwback but no they have a very important role in a number of species sees again like migratory seabirds depend upon them. Yeah you're exactly right about that and forty talks about this. At length the birds will peck around in the sand to find the hidden caches buried daggs. So this scene that forty describes so vividly is not just an amazing spectacle of nature. We sort of alluded to this earlier. But it's also also a window into the deep history of planet Earth into way to think about the wonders of evolution across geologic

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