Transcript
Speaker: I'm Katherine Pultz and this is Plant Kingdom. Plant Kingdom is a conversation series about awe and sublime in nature and environment, featuring scientists, artists, researchers and writers.
Speaker: Today's conversation is with Dr. Frank Ashwood. Frank is a soil ecologist based in New Zealand and author of the new book, The World Beneath Our Feet, The Hidden Life of Soil and Why It Matters to Us All.
Speaker: In our conversation, we look at the amazing adaptations of life in the soil, touching upon species of mite that have been exclusively female for hundreds of millions of years, how an earthworm experiences its world, and how you don't need to travel to the ends of the earth to discover new species. All you need to do is look down.
Speaker: Here's our conversation.
Speaker: Thank you, Frank, so much for chatting today. Really looking forward to it. And before we get before we start, could you just please introduce both yourself and also tell us a bit about your incredible new book, The World Beneath Our Feet, The Hidden Life of Soil and why it matters to us all.
Speaker: Yeah, so my name is Frank Ashwood. I'm a soil ecologist, which means I studied life in soil. And I'm also a macro photographer, so I photograph life in soil. And now I guess I can call myself an author as well, which is very exciting. The book is sort of somewhere between a love letter to soil and its life and a safari kind of journey through soil around the world to try and bring people on board as to why I think they should also love soil.
Speaker: I love that, a safari of soil around the world. it is It is just that. And I love this passage from the introduction, which I'll read. You write, I've been fascinated by soil and its inhabitants since I was a child. Growing up surrounded by heathland and broadleaf forests in southeast England, I walked over astonishing ecosystems all the time without realizing it.
Speaker: And I just felt for many of us, so many of the systems that we live we encounter every day without really language that tells us how to see and how to know it and puts words to the observations. It can be hard for some of these systems to come alive for us. And I think... Your book does a really beautiful job of making soil alive for us and making it visible and just giving us the language to appreciate and understand it. So thank you for that. And really looking forward to jumping into the mysterious world or hidden world of soil. I guess basic question. I know soil ecologists hate
Speaker: question i know soliologist hey the word dirt when it comes up. So just tell us, what are what are we talking about when we talk about soil? Is it a substrate? is it an ecosystem? is it living? what What are we talking about?
Speaker: So yeah, it's kind of it's kind of everything really. So soil is is both a and material, but it's also an ecosystem and at the same time. It's the most biodiverse ecosystem on the planet. It's estimated that over well around 60% of the world's biodiversity is actually in in the soil in some way, shape or form.
Speaker: Probably more than that. So it is a really rich ecosystem, but it's a iss the material that is made from a few key things. So you've got ah Any true soil is made of minerals. So that's weathered rocks, basically that what soil scientists call parent material, which is like bedrock that's been eroded over time.
Speaker: And that releases the sand, the silt and the clay particles that people may have heard of. But it's also got a few other things in there that make it soil. So there's also water, there's air.
Speaker: and there's organic matter and that organic matter is really important so that comes from decomposing plant material or decomposing animal remains that are being recycled and that brings us onto the final component which is life so soil is only really soil because there's life in it and that keeps the nutrient cycle turning keeps this gives the soil structure and helps to turn it from some sort of inert chemical substrate into something that's the foundation for basically all all life on on land on our planet just that right um no no small no small feat and you mentioned it ah a little bit in your introduction but what does a soil ecologist do i guess there's many different ways to be a soil ecologist aren't there
Speaker: There are, yeah. there's um There's lots of people who call themselves soil ecologists that do lots of different and wonderful things. I'm a i' in the small group of soil ecologists that look at the animals, not the bacteria and the fungi. So a soil ecologist, just to back up, is um anyone really, I guess, that is interested in the life in soil and works.
Speaker: interact with life above ground or just the wider environment so ecology is the study of how organisms interact with their environment and just put the word soil on in front of it and that kind of explains that gives you the context And i I love to talk to scientists about like the relationship to the system that they study and spend years thinking about. And I guess for for you, is it is it possible to talk a little bit about your relationship to soil and kind of what does this inquiry and the study of soil, what does it kind of provide with?
Speaker: Yeah, so ah for me, soil, I've been thinking about this a bit lately with the book and everything, and I think really the reason I like soil is because, or the reason I love it is because it gives that sense of mystery. It's like um it's when you're a child going on a a treasure hunt and you have that excitement of not knowing what you're going to find and that sort of that thrill of discovery. And I think because soil is a sort of dense soil,
Speaker: dark impenetrable kind of material and and even including things like rolling over logs and stones to look at what's living underneath them because their soil organisms do it's that kind of that potential that really keeps me fascinated. And it's, um, in, and in in terms of areas of science in which to study, it's one of the few areas where, um, there's a lot of discoveries, basic discoveries that can still be made quite easily because there's just very few people looking. So it's this kind of,
Speaker: the the last great unexplored frontier, excuse me, the last great unexplored frontier in science, in nature, i think. and So I find it really fascinating. I find it endlessly fascinating. And you never know when you roll over the next log or the next stone or you dig up the next soil sample and see what's in there. You just, you can never be entirely sure what you're going to find. And you could find something completely new to science, which I find amazing.
Speaker: Yeah, it's so interesting, that sense of discovery. And I think for, you know, in any system, scientists are always learning more and more about their area. But in something like soil ecology, where still so much is unknown and being discovered and named and every day must be really, we'll just give you endless questions to ask. And I'd love to talk more about the life in the soil, which is the, you know, the main the main character of your of your book.
Speaker: And I guess all we'll have time to do is focus on ah a handful of the thousands or millions of of creatures in the soil. But tell us, tell us a little bit about the life in the soil. And is it is it called the meso fauna? What what lives in there?
Speaker: Yeah, so um as as I mentioned before, so so like 60% we estimate of life on earth is in the soil. So there's a huge variety of things that we could talk about. But um just looking some of the animals, so the miso fauna that you mentioned there, that's one kind of category that we lump them into based on size. So there's three sort of size categories that soil ecologists kind of label and categorize the animals in the soil by. And that's um anything that's less than um or anything that's larger than two millimeters is a um anything that's larger than two millimeters in size is a macro fauna.
Speaker: So that could be things like earthworms or and beetles and things like that. And then you've got and the miso-fauna, is something that between two millimeters and 0.2 millimeters in size. So that's your things like springtails and mites and ah pseudoscorpions and all these incredible little microarthropods, so little and animals without a backbone. And so they've got hard exoskeletons. And so they all live in the soil. They're very small and they tend to do a lot of nutrient cycling and that kind of thing, breaking down organic matter.
Speaker: And then you've got another group called the microfauna. And so those are the nematode worms and little little animals that you need a microscope to see, essentially. And so they sort of swim around in the water in the soil, or they sort of live in little pore spaces in the soil.
Speaker: and uh yeah they are incredibly abundant and incredibly strange creatures and yeah you need to get a microscope out to see those uh but they're well worth the effort if anyone ever gets the chance and that includes things like tardigrades as well which are possibly the most incredible animals on earth i think we can say they're certainly the most hardened survivors there's a colony of those on the moon as we speak and and frank that's amazing tardigrades are they Are they, what where do they fall in the, in the size scale?
Speaker: So the tardigrades would fall into the microfauna because they're very small. You can just about see them with the naked eye. um So anything you kind of can barely see with the naked eye is like um on the borderline of microfauna. And so that can be yeah things like nematode worms or tardigrades or and there's these things called rotifers, which live in high numbers in the soil.
Speaker: um But they're They're small multicellular animals that, yeah, you really need a microscope to see. I did manage to take a photograph once of a tardigrade with my camera, which was hard as a reason that people don't often do that, I found out. But I had to whack on as many lenses and extension tubes as I possibly could and see this thing. But I actually filmed it going into its hibernation state, its tonne state, where they can withstand all of these extreme environmental conditions. So that was really cool.
Speaker: and But I don't recommend it to anybody. That was was a very patient testing experience. We're lucky to have you do that on behalf of us. Just for once. I'm not doing that again. And I guess all these these animals are very different from one another, even in terms of body form and and how they live. Is it and just how amazing to think about creatures living in the pores of soil and what that is is like can you kind of shrink us down to size a little bit like are there some kind of adaptations that are kind of common or or what it like ah what are some of the adaptations or features of these animals that live in the soil
Speaker: there's Yeah, there's quite a few sort of recurring body plans that come up, but they sort of independently e evolve in a lot of these things because they all face these same kind of unique struggles. yeah So one is sort of an elongated worm-like body plan is something that comes up.
Speaker: over and over again quite a lot of the creatures that live deeper in the soil ah tend to have sort of long thin bodies because that's more helpful for pushing through the soil right so long ah so things like the nematode worms but other earthworms but even there's some mites that they're arachnids they're related to spiders and things but there's some mites that have got these long thin worm-like bodies which is crazy and and it's just that there is this kind of selection this evolutionary pressure on um your body ah yeah adapting a more sort of and cylindrical long shape because it's it's just easier to get get through the soil that way
Speaker: so things tend to kind of spaghettify i suppose is' the term ive i've just come up with as spheti yeah yeah which yeah um so yeah as they lived down there um but there's also other really interesting things so because it's dark in the soil you don't need to invest precious energy and resources in things like eyes or pigmentation so a lot of the creatures that live in the deep soil would look quite alien to us because they are kind of ghostly pale they ah don't have eyes they don't their antennae are often reduced because they could just get in the way if if they even have antennae uh it depends they all they have these kind of selection pressures to kind of become these long thin pale, eyeless creatures. And we see it over and over. and but But that's not to say that they're sort of primitive or um yeah simplified in any way, because actually they've kind of evolved new organs in some ways for helping them to get around. So you don't you don't need eyes because there's no light. yeah but instead, some of these creatures are involved have evolved other sensory organs on their heads that help them to sort of taste their surrounding environment or feel vibrations and all those kind of things. So they're they're quite wonderful, weird alien creatures down there. Incredible. Thank you. And a lot of these are really ancient lineages of life, right? Like a lot of the, like, this is this right? The pseudoscorpions, the mites, the, well, the velvet worms, we'll talk about springtails, they're older than insects. They've been on on earth for like hundreds of millions of years. Is that kind of inaccurate characterization of them. Can you reflect a bit on that?
Speaker: Yeah, yeah, sure. So um there's ah there's a fossil record that we have from a place in Scotland called, the place is called Rhiney, and it's ah a type of rock called a chert, so it's the Rhiney chert. And it's got this this snapshot in time about 400 million years ago when Scotland was tropical and near the equator, if you can believe that.
Speaker: And it's like this kind of really well-preserved early snapshot into what life was like just when life was kind of emerging on onto land from the oceans. And it's preserved these animals in such amazing quality and detail that we can actually kind of compare them to modern day animals.
Speaker: And there's springtails in there, there's mites in there, and there's arachnids that are kind of like spiders and pseudoscorpions and those things. And a lot of them are basically unchanged to the the ones that we see today.
Speaker: And that was 407 million years ago. where So these things are very ancient, very successful. They've survived five mass extinction events on Earth and still going strong.
Speaker: um Barely changed in many cases. ah Yeah. Yeah. Whereas insects appeared much more recently than that. So, yeah, they've they've kind of they've been around for a long time doing what they do. Springtails, for example, were the We think that the first pollinators, so when you think of a pollinator, you think of butterflies and bees and that kind of thing, which are all insects flying around.
Speaker: But actually springtails were pollinating, carrying the spores around of the earliest plants that emerged on land. So they're the first true pollinators. Carrying moving spores around. Amazing. Yeah, powerful to think that soil today looks like soil. Like it's a glimpse into the soil that long ago. the Very successful animals. And in our in our last conversation, you told me some really crazy things about some of these creatures. And, you know, I guess we don't, we're very biased to think about animal life behaves like us in terms of how we think about reproduction, how we think the definition of species and it doesn't,
Speaker: how we live does not apply to a lot of these animals, right? You you told me about mite that males are extinct this in this group. is Is that right? They're exclusively female. Can you can you tell me about this?
Speaker: Yeah, and there's yeah this happens quite a lot. the Males get kicked out of ah species for quite a lot lot of things in the soil, which is fully understandable, really. is They're not needed. yeah ah Maybe humans will do it one day. But ah yeah, so this ah the one that we talked about was this mite called, um the scientific name Platinophorus peltifer, which is a bit of a mouthful, but it's a hard-bodied little thing called an orobatic mite they're very common they you find them under logs in forests or pretty much all around the world but the really interesting thing about them like they fully it fit into this category that we call ancient asexuals which it means that they've they don't reproduce sexually they they clone themselves so they're all they're all female and the females um lay an unfertilized egg which it develops um
Speaker: without being fertilized by a male and it's they're genetically identical to to the mother the offspring are so they basically kind of cloning themselves and they've been doing this for at least 50 maybe 100 million years so this species has been going since erecs walked the earth and if ah if a male does arise then they're sterile so they don't really they don't contribute to the gene pool but They've not really been observed. So probably probably don't happen really. But if they do pop up, then they live quite a lonely existence because the females don't want anything to do with them anyway and don't need them, ah which is absolutely fair enough.
Speaker: But the interesting thing about them is that is that ah kind of the the species, the idea of species that we use in in biology tends to be based on sexual reproduction.
Speaker: So these these animals kind of upend that whole that whole thing. And in theory, um you'd think that they would go through this thing called the genetic bottleneck. So over time, mutations, like negative mutations might accumulate. And so without having sexual production and being able to bring in new genetic material from your partner, um bad, like the sort of bad, um qualities might sort build up and persist and that might cause the species to go extinct. But these ones don't do that. And so people have been studying the genomes of these mites to kind of understand how they get around this problem.
Speaker: And it's kind of interesting when we, when for humans, for example, when we sexually reproduce, you get one, one half of your DNA comes from your parents, each of your parents.
Speaker: So you get one one set of chromosomes from your mother and one set of chromosomes from your father. And that's how we can sort of be so wonderfully varied because you inherit all these different traits.
Speaker: But these mites, obviously they're cloning themselves. um But the interesting thing is that people have spent a lot of time and effort actually trying to study the the genetics of these mites because of how strange it is that they um are still going strong as a species after all this time um by cloning themselves.
Speaker: And it turns out, long story short, that in um when the mites inherit their both sets of chromosomes from the mother, one is preserved perfectly, but the other one is actually allowed to move around and get chopped up and mixed up. And so it does allow them to still uniquely do this kind of get variation in their genetic code even though they're clonal so they aren't necessarily a true clone of their mother um which is quite unusual but it means that after 100 million years maybe these mites are actually still able to adapt to their environment just like any other animal that undergoes um sexual reproduction would be able to so they're kind of this crazy unique thing
Speaker: And it might be that other animals can do that too. But yeah, I don't know if there's much funding to go looking for these things. say Who knows? That's amazing. And you talked about rotifers have so some species have horizontal gene transfer to that also don't have sexual reproduction. Is that?
Speaker: Yeah. So there's these groups called podeloid rotifers and ah they've been, I think about 80 million, no, 60 million years, something like that. And they basically, they do something similar um in that they,
Speaker: They have this thing, yeah, this horizonal horizontal gene transfer, which means even though they're clonal, they can actually, um it's like they're going to like a a supermarket. They treat the the world's genetic diversity like a sort of supermarket and they just run around grabbing stuff off the shelves and bunging it into their own genome. um So they can take they can take bits of other organisms, genomes, and incorporate it into themselves. So for example, a yeah, so they can sort of, if they want eat some plants, they can take the cellulase digesting enzyme region from a plant,
Speaker: and then put it into their own genome. And then that enables them to do quite a unique thing, which is actually break down plant tissues, which not a lot of animals can do because cellulose is hard to digest.
Speaker: So they just kind of go around solving problems by pinching things off other animals or or not even animals, plants and bacteria and things. So there's a crazy world down there and I guess things have to adapt on the fly. And so they've developed all these incredible methods for survival.
Speaker: which are completely alien to us on our human scale. We might be the odd ones out if so much life is in the soil. Yeah. I think we're boring. It's really boring.
Speaker: ah Right? Yeah, something a sense feels so like Riot Grrrl to be a hundred million years of just female mites. I want to talk to you next about another creature i know that is very, very dear to you.
Speaker: the velvet worms, an incredible group of animals. I've only been aware of them for a few years. I've never seen one myself. It's high on my on my list. But i just want to read how you describe them in the in the book.
Speaker: You wrote... It's difficult to describe the feeling of awe that comes from seeing a velvet worm in person. These are perhaps one of the most enigmatic soil invertebrates or indeed animals on the planet.
Speaker: They've changed very little in over 300 million years and closely resemble their ancestors, the lipodians Lopopodians. psychedelic multi-legged worm-like creatures that lived in the oceans during the Ordovician Devonian period, just 500 to 400 million years ago.
Speaker: um and then you you take us through to visualize a velvet worm. Imagine a blue and orange striped caterpillar, roughly three centimeters long that has been rolled in tiny sequins. Many pairs of sturdy legs run the length of its soft wrinkly body Now picture the animal's head end as a pair of tentacle-like antennae, beneath which are vestigial-looking antennal stumps, but do not be fooled by the creature's adorable appearance. While these stumps may look harmless, they are actually a pair of glue-firing cannons that eject a gluey webbing to subdue prey for consumption alive.
Speaker: Just a little bit going on there. Frank, when when did you just when did you first see velvet worms, and what do you love about these these animals? Well, so the the amazing thing is they're only in the southern hemisphere already. So yeah, um I had no chance of ever seeing these before moving to New Zealand. You're in Australia, right? So you'll be able to find them there too.
Speaker: But in south, eastern Australia in the forests, they're there as well. So I was really keen to see them when I found out I was going to be moving to New Zealand because yeah, how how else do you get an opportunity to see these these incredible things? And I sort of volunteered to go on a university field trip as a sort of demonstrator and took my camera with me on the proviso that at night i someone would take me out into the forest who had seen these before and try and show me these velvet worms.
Speaker: I promised my guide a ah few beers if if he could find them for me and we spent hours actually, because they're quite rare, so we've spent a few hours at night out in the forest crawling over logs and looking looking inside them to try and find these things.
Speaker: And basically given up hope by the, towards the end of the second hour. And then all of a sudden he he cried out that he'd found one. So I came running and there it was. And they're they're they're smaller than I was expecting until I looked at them down the camera. They were quite, they don't, they don't seem too much, but,
Speaker: yeah absolutely beautiful incredible creatures and then it's it got obviously a bit tired of our um presence because it fired its glue cannons at us so you got to see in action yeah in action yeah uh which was absolutely incredible i'd never seen anything like it but these animals are just so old and weird they don't have a hard exoskeleton like other and arthropods because they're kind of predate arthropods in a way so things like insects and spiders and all those kind of things that there they came before them they use hydro hydrostatic pressure like water pressure in their body to give their body rigidity rather than any kind of hard skeleton so yeah they're kind of like a ah water balloon
Speaker: under pressure with legs that kind of expand and contract based on water pressure in their body. They're these weird creatures. They they look like they could just go back into the ocean and they'd be absolutely fine, um like their ancestors.
Speaker: Back into the ocean. Yeah. Are they related to any living phyla or any any groups or are they really kind of on their own?
Speaker: Well, they're kind of off on their own. they they're um there's this The taxonomy is kind of unresolved, I think, but um they they sit, you've got all arthropods, so all of your spiders, your insects, all of those, you know, crustaceans, all those things, are one branch coming down. And then where those branch off, you've got, at the top, you've got hardigrades as a sister group to all arthropods. And then you've got these velvet worms as another c sister group to all arthropods.
Speaker: So they're in this this group called the Pan Arthropoda, which means they're not quite arthropods. ah they it's not We're not sure, basically. but they kind of Yeah, we're not sure. It's a holding place for them. They're not really an arthropod. We don't really know what they are. there's Yeah, it'll theyll they'll move again and again because we just don't know.
Speaker: The fact that they're still with us at all is just incredible because they basically unchanged in about 400 million years, maybe more. Amazing. And are they just in New Zealand and Australia or are they in South America? No, they're South America and um Africa. So they've kind of got this former Gondwana distribution. So there was once this, you know, the ancient southern supercontinent of Gondwana and then it broke up into South America and South Africa and India and Australia and New Zealand, et cetera. And um so they tend to be distributed there.
Speaker: um in forests, but they're very vulnerable to things like um ah drought stress. So they, because they're quite ancient, they've got quite rudimentary breathing tubes. And so they breathe passively through these little holes on their body, and but they can't close them and like insects can to stop themselves from drying out.
Speaker: So they're exposed to, if they're exposed to too much drought conditions, they dry out because they can't keep the water within their bodies. So you tend to find them only in quite damp areas. So like um humid forests.
Speaker: It's another creature we're going to talk about, Frank. Another one you spent some time um studying, earthworms. um Your book begins with a quote from Darwin. And i i love thinking about Darwin's back catalog, have you, and his books dedicated to plant movements and and worms. um This is a quote from Darwin's 1881 titled The Formation of Vegetable Mold Through the Action of Worms, you quote, it may be doubted whether there are many animals which have played as important a part in the history of the world as have these lowly organized creatures. And he's talking about worms. What what do you think Darwin meant by this? What does he mean?
Speaker: so yes so the amazing thing about Darwin was that he was able to think um kind of outside the box and and think on long time frames and and earthworms kind of epitomized this thought process that he had which also was how he um co came up with the theory of natural selection evolution by natural selection which is that little changes incremental changes over long time frames can make big changes And that was a kind of a new way of thinking about things that people weren't really doing there. And so um he was he was able to figure out that although earthworms might prove, for example, their burrowing activity activity, they move a bit of soil to the surface when they poo a soil out on the so's surface.
Speaker: That's just a little bit of soil that the earthworms moved. But actually, you've got hundreds of thousands of earthworms in a field all doing that every day over the course of a year. That is a large amount of soil that's been moved around in that field, for example. And so he was able to put two and two together in that in that um clever way to realize that actually, you know what?
Speaker: These little animals that aren't doing much and don't seem that important to us actually probably have a pretty big impact. And he calculated how much soil they move and how much organic matter they put into the soil and did all these weird and wonderful experiments with earthworms. It was kind of his life's work, really.
Speaker: He published this that book that yeah quotes from was really his life's work. And um he published it the year before he died. And it actually, in the year that it was published, it outsold on the origin of species in the year. Yeah. Really? a huge appetite for Darwin's work amongst the public at that Yeah. So even though it was a book about earthworms pooing, essentially, and people lapped it up. He had a captive readership for it. Yeah.
Speaker: And thinking about the European earthworm, can you can you help us picture it? Like we know what it looks like, but what's its kind of what's the bit ah about the natural history or or life cycle of of the earthworm? How long does it live?
Speaker: How many offspring might they produce? What are their senses? Can you can you take us into the the world of the worms, for Frank? I will take into the world of the worms. So i'll there's there's a lot of European species of worm, but I'm guessing we're going to talking about Lumbricus terrestris, which is like the most common one, the relatively large one.
Speaker: So we'll go we'll go with that. And that was my PhD supervisor. You tell us. Yeah, that was my PhD supervisor's favorite worm. So I'll honor him. So yeah, so they, oh, where do we start? So yeah, so they can use They can live for a few years in nature. We're not entirely sure how long they live in nature because unfortunately earthworms are basically food for everything. So earthworms don't make old bones in nature. Well, they don't have bones, but they they don't live long in nature. In captivity, that species has been raised for up to maybe five or six years. So they can live for quite some time.
Speaker: um Yeah, they ah they're hermaphrodites, so they're both male and female at the same time. So they don't clone like the other things that we've talked about earlier. they They reproduce, they fertilize each other. So earthworms, when they mate, they sort of, I guess, 69, if you like, they kind of come out as yeah and they have a nice romantic cuddle and ah they exchange sperm with each other.
Speaker: And they'll store their partner's sperm in special pores in their body, and then they'll go back into their burrows. And then for up to 12 months, they can use the sperm that they've received from their partner to fertilize their own eggs. So they've got ovaries. They make their own eggs and they use their partner's sperm. Some earthworms will actually self-fertilize themselves and and can clone themselves as well. But the one we're talking about doesn't do that. That that just will just sexually reproduce.
Speaker: And then when it's time to produce a fertilized egg, they do something quite unique, which is Have you seen on an earthworm, it's got like a ring around its body? Yeah. A saddle.
Speaker: Yeah. So that saddle It's called the saddle, okay. Yeah. So that's kind of the common term. and the The scientific term is a clitellum. and But we'll go with saddle. And so that saddle indicates that it's an adult earthworm.
Speaker: Until they have that on their body, they can't sexually reproduce or they they can't reproduce. and Because that saddle is really important for producing their cocoons. So once they've um got the sperm from their partner and they've got their egg ready to go, they'll fertilize the egg and then the that saddle will produce a layer that rolls down the body of the earthworm, like a sort of tube, and it will pick up the fertilized egg and it will roll off the end of the earthworm.
Speaker: And it will sort of seal up and it looks a bit like a lemon. And they're yellow and the hard and they look just like little lemons basically in the soil. And that's an earthworm cocoon. And so then within that cocoon is a fertilized egg.
Speaker: And that will depend on the environmental conditions, anywhere between a month to six months to a year. Depends what the soil is like around it. ah But when conditions are favorable, the little egg in there will develop into a little baby earthworm, which look like tiny little pieces earthworm.
Speaker: string normally one per cocoon but not always and they will grow it they will grow in there they don't molt they just get bigger and so they're not like insects or whatever that mulch they just they just grow larger and eventually when it's too big for its cocoon the little baby earthworm will be born it will wriggle out of one of the little ends of this lemon cocoon thing and go off into the soil and just eat and grow and become ah an adult earthworm and the cycle begins again Oh, wow. So one saddle produces one egg.
Speaker: Yeah, they can do it over and over again. Yeah, so they have to regrow this out. Or produce one cocoon. One cocoon. Yeah. That's pretty conservative. But they can reproduce pretty regularly. They can they can makete yeah can mate every sort of week or so. They can kind of keep going. They can pump these cocoons out pretty regularly. They're busy. That brought up this memory. I've seen them...
Speaker: I've seen the mate before and I, it, it's it surprises me. i was, it, i I, would think I was young and it was, I just remember like, it i thought it was like milk. Like what was it? It was sperm that I saw.
Speaker: Oh yeah. It's quite traumatic. It's quite messy. I think it was. I think it was. Yeah. wow Well, if you want to if you want to be even more, well, maybe not more traumatized, but if you want to watch something quite interesting, do you know Isabella Rossellini, the Italian actress? Yes. So she made a um a short film series. Green Porno? Green Porno. Amazing. Yeah, that's right. Yes. And so she had a yeahwrm one on there, which is which is brilliant. Well worth a watch. It makes me think there's this amazing David Attenborough segment too about slug sex. Have you seen that one?
Speaker: Oh, yeah. Incredible. like what comes out of that pore behind their head anyway. Do you know about, well, I can go one further. Do you know about the banana slug? And what happens with them? Tell me. Tell me.
Speaker: but No, I will tell you. it's no bananas So banana slugs have got, and their species name means long penis, and they've actually got a penis length about the length of their bodies. They've got this massive, massive member. And the problem with that is it's unruly. And these are big slugs. Like, yeah.
Speaker: Yeah. They're reasonable slugs. Yeah. No, but when they mate, they're hermaphrodites as well. So they're both male and female. And quite quite often the the male's penis can get stuck in its partner's body and they can't get it back out. And they try and they've been observed. Scientists have observed them doing this. They try and retract it, but they can't get it out. doesn't happen every time, but it happens regularly enough for it to be a thing. And then so they're faced with really one option. Either the the owner of the penis or the recipient will chew it off.
Speaker: and just it just gets stuck in the body and they just leave it behind and it kind of acts like a plug I guess protecting keeping their their um ahp be just from them and not not not allowing it yeah and then the one that's lost its willy can carry on as a female so they can still be fertilized by other males but yeah they won't be doing any more any more um male business themselves Anyway. Dramatic. don't know.
Speaker: Did Isabella Rossellini get to that one? I haven't seen that, but I'd love to see it. I can only Revisit the series. um Yeah. And you told me something. That really fascinated me and corrected an incorrect hypothesis that I had held my my whole life about the very common sight of a worm, what I thought was drowning in a puddle. And you just expanded my my world so much when you told me what is actually happening. Why why are worms coming out of their tunnels in the rain? what
Speaker: What is going on? Yeah, so sorry sorry to upend your entire... um thats reality on that but um yeah so so so they're not actually drowning contrary to popular opinion and you're not the only one that thinks this most people most people think this but they're not actually drowning in the in the soil so um earthworms breathe through they need water on their skin to to breathe essentially so they're fine as long as the water in their burrows isn't hasn't been there for too long and gone stagnant and lost its oxygen they're absolutely fine in wet in wet ground you can actually put an earthworm in a bucket of water for a day or two and it's fine
Speaker: um But what they're doing is they're trying to find greener pastures. So it's it's a lot less effort to move above ground than below ground, as you probably appreciate. um But they are a constant risk of drying out. So when it rains, they suddenly can move above ground without fear of drying out and dying.
Speaker: So they're just making a break for it. They're trying to find areas with maybe fewer earthworms to compete for resources or better soil conditions or whatever. They're just taking their opportunity to to jailbreak, essentially. yeah Yeah.
Speaker: Fascinating. And one of our, one of our final earthworm facts, I think today, but ah Explain it to us. are Are worms our evolutionary ancestors? to What's the relation between us and and worms? Well, some people are more worm-like than others, I suspect. So so not not so much earthworms, although we do we are related to earthworms very distantly. But there's these things called bilaterian worms, which were tiny worms about the size of a grain of rice.
Speaker: that lived about 555, I think, million years ago, they've been found. And this is in fossil records in southern Australia. And yeah, and so most of our really cool fossil records come from Australia, to be honest.
Speaker: So you could be proud of that. But yes, these things, these these worms, they were the first animals that we know of that had essentially a head end and a t and ah and an anus. linked by a gut and they have one plane of symmetry so if you sort of cut it down the lower put a mirror on it from head to pi tail um it's symmetrical on either side and so that was a very novel and groundbreaking body plan at that time everything else just had one hole that you ate in and that you pooed out of and some animals still have that so the relatives of those other creatures uh things like jellyfish and starfish and those things they just have one one hole for everything but these yeah different planes of symmetry Yeah. A different plane. Yeah, exactly. Like five planes of symmetry or more, you know, whereas
Speaker: we and horses and dinosaurs and birds and slugs everything yeah um have these two planes of symmetry because we come from these bilateral worms so this successful head anus joined by a gut one plane of sin but one plane of symmetry kind of vibe was incredibly successful and it's it's also the reason that we have all of our sensory organs on our head because once you've got a mouth and an anus it may you need something to direct you towards food and sense where food is so that stuff goes at the mouth end not the anus end so we have these kind of little and then if you've got those things you need something to coordinate coordinate all that so you need a brain so we owe our entire sort of existence to these tiny little rice-s size rice sized rice grain sized worms that invented an anus and a mouth um with one planet symmetry so yeah we are basically all just worms we've we've come a little way since then and adapted to different conditions and But you know, if we've learned anything from all of the creatures that live down in the soil, it doesn't take too much of a change in your environmental conditions before evolution could push us back towards worm shape, really.
Speaker: I love that. I think Darwin would have liked that too. And you write about ah one giant mythical folkloric worm in your book that is it's I just had to to bring up. The giant rainworm of of Baden, Europe's largest earthworm species, up to 60 centimeters long. i think it's its Latin name was Lumbracus badness. Badensis. Badensis, not badness. Okay, that's not as cool as my typo. Badness would be better.
Speaker: I know, it's great name. cant Can you tell us about these these worms? Where do they live and how unusual is it to be that big? Yeah, so they're this, yeah, they're very quite locally restricted in terms of range, earthworm in the Schwarzwald in this region of Germany in the mountains near Baden. And yeah, so their habitat's actually kind of threatened in that area. So whilst they're really cool and big and incredible, and they're also at risk. So I write in the book that actually my PhD supervisor, Dr. Kevin Butt, who's up, he runs the earthworm research group, In Preston, in Lancashire in the UK, he's got the only, probably the only population of Lumbrogus bedensis outside of the Schwarzwald. He's rearing them in incubators as a kind of backup community, I guess, should they go extinct. And he's even there doing experiments with the Natural History Museum in London in terms of trying cryogenically freeze the cocoons from this earthworm species and others. So you can make a kind of millennium seed bank of earthworms, of earthworm species. So yeah, it's this incredible earthworm. It's very big for Europe. Europe doesn't tend to have these massive worms like you find down in in places like New Zealand and even Australia. yeah I mean, Australia's got one of the largest earthworm species on earth, the gitsland the giant Gippsland worm. Get up to, is it meteor or two? Thanks. Incredible, incredible thing. Yeah. But...
Speaker: I did not know this. Yeah. Yeah, but that, like the Lumbicus pedensis, is at risk of extinction from land use change. Because people just love to cut down forests where these things live. And they they have to they'll go extinct with them if the forest goes away. So yeah, it's it's amazing. But also these things are at risk. and But luckily there's some people out there that are trying to help conserve these incredible, incredible things.
Speaker: I've never seen one, I should say. I would like to see Lumbicus pedensis. Yeah, yeah it sounded like amazing lab and menagerie of different earthworm varieties and and species.
Speaker: Yeah, an amazing new science of preservation and in conservation. Seed banks were very familiar with and the significance of conserving plants, you know, like that's major. And so it's so interesting to think of that technology or some of those same approaches working with many different kinds of creatures, right? Yeah.
Speaker: And just as important to the ecosystem and habitats. And in your book, you use this analogy that soil is actually like the the deep sea, that there's so much to discover and so much unknown about what lives there.
Speaker: Can you reflect a bit a bit on this? And it's interesting thinking about the deep sea being so foreign, whereas soil feels so more familiar and part of our lives. What what did you what what what are you thinking about new when you write this? Yeah, so the everyone always says, you know, we know more about the surface of the moon than we know about what lives in the bottom of the oceans. And and that's entirely true and fair enough. But yeah, but i I kind of think really, if we're talking about what's the the most unexplored frontier on Earth in terms of biodiversity, then probably know a lot more that's going on at the bottom of the ocean than we do what's going on in in the soil because we can we can swim down to the bottom of the ocean with submersibles and film those things but actually soil is quite impenetrable or quite difficult to see what's in there so it takes ah quite a bit of work so we know about the sort of rate of species new rate of species discovery from the oceans and there's statistics on that but there's no equivalent statistic for what the new rate of species discovery is from the soil because we're not really counting people aren't necessarily looking
Speaker: in the same way. But we know that there's a lot more biodiversity in the soil than in the ocean. So yeah, it's this massive treasure trove of stuff that we've yet to discover. Who knows?
Speaker: And something that you do so beautifully is you make this biodiversity visible, right? Through writing about it and describing it in your book, also through your incredible macro photography. And I first came across your work on Instagram where you have an amazing collection of images of these creatures we've been talking about, springtails, velvetworms, mites at frank.ashwood. What has kind of been... the importance for you in communicating about soil or making this world more visible and connecting people to it? It's been it's been the part of my career that I've enjoyed the most, I think. that i kind of I hadn't really set out to consciously do it any point, i don't think. I do now. it comes a bit naturally to me to try and engage and interact with people. And and then i built as I've built up this kind of knowledge and this this resource set of resources in the photographs it kind of felt like it would be a crime not to try and use these things to kind of communicate to other people how about how important soil is and how much we depend upon it but also how incredibly amazing it is and and unique and wonderful the the creatures that live there and they tell the story for themselves i mean the photography is a really useful tool because it's it's quite it can be quite striking photographs of springtails and mites and even earthworms can be so surprisingly beautiful
Speaker: and alien looking but and in an interesting way that it it really helps to grab people's interest and attention and then you can communicate why these things are important alongside that so for me I found that the macro photography has just been such an amazing tool for helping me to reach out to people and get people's attention and then slip in some useful information along alongside that if you like and originally my idea for the book was going to be him I wanted to write a macro photography coffee table style book and because I thought so I actually thought maybe the photography was the main thing but I was convinced by my agent to my literary agent now and to write you know a proper nonfiction book and with the proviso there would be photographs sections in it to macro images and yeah I'm delighted that he kind of convinced me to do it that way because I think actually these things can come across cross in writing just as as well as in in images hopefully
Speaker: Yeah, it's it's just a wonderful thing and it's really helped me to enjoy my career as a soil ecologist a lot more as well. when I'm feeling a bit sort of stagnant at the desk, if I just go out with the camera and observe these creatures in life, because a lot of scientists look at the things, you know, dead and pickled down the microscope, which isn't isn't quite as enjoyable and rewarding as seeing this. Or just looking at the DNA or something. Yeah, yeah it's kind of a bit cold. and But if you actually go out and see these mating creatures, feeding and mating and escaping predators and doing all of the things that they do on a daily basis, just like we do, really, um you kind of it puts everything in perspective and you can kind of appreciate that they are actually part of this this big food web this natural system that's going on around us and that we're all connected to so yeah for me it's it's just been amazing it's just it's helped me to really enjoy my career a lot and science communication is something I want to do as much of as possible yeah well I see a lot of that um ahead for you and i think that's so beautiful thinking, you know, like at the beginning of the conversation, you're talking about that sense of discovery being really motivating for you in your career and through the photography and through the writing, like you're, you're sharing that sense of discovery, right? And you get to see it come alive for your audience and for other people and to build that connection to people and the soil and, you know, to have gratitude for the role of soil and the creatures in it is really...
Speaker: i can I can really see that, like that cycle. Yeah. I mean, and I'm in a privileged position to be able to do that really. you know, not everyone can, I've just found myself in this unique situation where I'm able to do this thing that I love, but also go out and and experience this sense of discovery on a daily, more or less daily basis. I get to do every day now. Not since having a baby. the budget Next year, next year.
Speaker: but But then the writing's been fun too. So yeah, but yeah, it's a, it's a real privilege and I'm, and I'm, I'm so pleased I get to do it. And I hope that people enjoy that sort of that adventure that the the book hopefully takes them on if they, if they read it. Yeah. Well, I think maybe you've just, you have just said it, but is there, i guess, I guess what do you hope people gain from reading The World Beneath Our our Feet? Yeah, just that really. I hope that people hope people enjoy it. I hope that people are pleasantly surprised that soil isn't this inaccessible thing. It's there. you can
Speaker: You can learn about it and and enjoy hopefully learning about it. and But also beyond that, I hope people feel empowered to take an active interest in soil themselves and the life in the soil because most people have access to some soil in some somewhere around them, whether it's a public space or a garden or some nature in their area hopefully and know most people live in cities these days but you know there's still soil around and yeah and if people feel empowered to investigate that soil for themselves and see what's living there and take an interest and then hopefully protect it and conserve it and do things manage the soil around them in a way that's better for the soil and better for the life in the soil then i'll feel like the book's done its job i'll be very happy with that yeah to get their hands to get their hands dirty and yeah it's so interesting thinking about all like the metaphors that we have in in writing and literature in life about being grounded being on home soil like it is something very there very grounding very meaningful like what it what it means to be connected to the soil and to the ground it's not new it's just kind of remembering that a bit isn't it
Speaker: Well, the term human is related to soil. So humus is the organic matter in soil, is a form of matter in soil. And the the the word human means of earth, basically.
Speaker: we are We are of the of the earth. We are humans. We are of the soil.
Speaker: That was my conversation with Dr. Frank Ashwood. Thank you for listening. Plant Kingdom is hosted and produced by me, Catherine Paltz, and our music is by Carl Deiter. Listen to us wherever you get your podcasts and check out our website at plantkingdom.earth.
