Darwin Ate an Owl
Darwin Ate an Owl

Episode · 2 years ago

Dr Angela Crean: Sperm is to semen as rum is to Coke


Ever think about the stuff sperm gets delivered in? Dr Angela Crean thinks about it A LOT.

Woo, welcome to Darwin eight an our. Hello, Hi Mark, I like that mission. That's pretty fantastic. Cools is interesting. Keeps me out of the gym. Anyway. That's people hooked. We're going to find it edlessly fascinated. Fascinating, Darwin ate an OWL, get a mark horsemen. Here today I'm getting out and proud about seamen with a conversation around the kitchen table with evolutionary ecologist Dr Angela cream seamen. Why seemen? Why not seemen? Tell me it isn't fascinating. Well, it is. It makes me a little bit I don't know, I feel a bit almost cringey about it. It was a little awkward talking about it with my parents at first, and now I'm so used to it that I forget that it makes people a little bit uncomfortable. Something about the word seemen is just so visceral. It always made a snigger at school. I of course it did. What kind of response do you get to people when you're chatting at parties and they ask you what you research interest is? When I don't know the person, it's not the first well, depends how much alcohol I've had. I tend to say sperm it's less confronting. Most people just laugh at you, but then when you start talking about the research, it gets people hooked. You mentioned having a drink. Is a fair to say that sperm is to seamen as gins to tonic or run is to coke? From is to coke, the all important mixer. You know what that I'm going to steal that analogy because that's pretty fantastic and if you think about it, it is. It's the main deal. The sperm is what you really want, but the seamen is what supports that sperm, and what we've been looking at is then what it has evolved to become. And it's no longer just coke. It's like a whole cocktail. How did you get into this? But what sparked your interest in the first place? Well, since a little girl, I always dreamed of now, of course I'm joking complete that sentence. So I started off in science because I loved the ocean and I decided from a very young age that I wanted to be a marine biologist and I didn't really know what that was, but I would spend hours just snorkeling and looking at the fish and wanted to know more about them. And at the start of my research career you'd think I was living the dream. I got to do ten weeks out on Lord How Island and I was looking at love of fish recruitment, and then I started working on Lizard Island. I did about six months working out there and we were working on reproduction and I started thinking, well, you've got changing climate and everyone's looking at the adults and thinking o the corals going to survive, but the way they reproduce is they just spawn their sperm and eggs out into the ocean and I thought, well, if they don't survive then it doesn't matter if the adults can cope, it's gone anyway. So I started looking at weather. These simple animals like corals can adapt their sperm and eggs to changing environments. And this was a while ago and when I was working on it we were really only thinking that the eggs could change. And I was working with sea squirts, because nobody wants to kill a bunch of corals, but we had these introduced pests at marinas and so go out collect a bunch of them and they happen to be hermaphrodites. So I was doing these manipulations and changing their densities, making it more stressful for them to...

...see if they change their eggs and the sperm was just sitting there. I thought, well, do they change that too? And to our surprise we saw these huge changes. They were changing their sperm size, the swimming speed and when we'd mix them together with the eggs, this change their fertilization success. Now that's not so surprising. If there's sperm swoons fast star than you'd expect it to change whether it manages to get to the egg or not. But I thought what else happens? And once again we found these huge effects, and not in the direction we were expecting. So the fastest swimming sperm were better at fertilizing an egg, but those eggs didn't tend to hatch out as well. So they seemed to be this tradeoff where you had the super sperm making dodgy offspring. And once again we thought this is super cool and I was telling everyone about how great it was and got dismissed. Oh, that's probably just a weird sea square thing. So we thought okay, well, let's go work with something that is a little bit more normal, that has sex like we do. Let's work with a fly. So that's what drove you from looking at sea squirts two flies and eventually, I guess, two people. But let's go back to the flies. What we're testing there? What did you find out? So I started working with Russell Bondarynski had this really cool system of Narad flies, and what makes them great is he'd found out that if you feed the males lots of food, they come out huge, but more importantly, they also make bigger offspring. So once again, at this time we had the idea that fathers couldn't pass on environmentally acquired traits to their offspring. Thought they just pass on sperm that has the genetic material and that's it. But this manipulation was feeding them something and you see a change in the offspring trade. So because I've been working with the sea squirts and finding these changes in sperm, I went sure, I know what that is. They're changing their sperm quality and that's what's changing the offspring. So we thought we'd go and try and test it. And the difference between the external fertilizers, these corals and sea squirts, and internal fertilizers is that, you know, you can't just squirt your sperm out in a dry in the ocean. They've got something to swim around in. But once you start having sex, the sperm need to be delivered in something and we thought, probably doesn't matter, but we should try and figure out if it's the sperm itself or something else. We should just rule that out. It's nothing else going on. So we designed this experiment where we mate it the females to either a large or small male when she was immature, thinking that if there's something else in the seamen then it might affect the developing eggs, and then left her too mature after being exposed to this seamen from the first male and remaded her to another male that was either large or small, and that second male fertilized her eggs and we collected those offspring thinking that we'd only find a fair x of the second mail or maybe there'd be a bit of an amplification, like an additive effect. And then when we looked at the data, there was no effect on the size of the offspring of the father itself. was completely driven by the first mail that she had made it with, and so not only was that a little bit disturbing, but it meant that it wasn't the sperm, it was something else in the seminal fluid that was affecting the development of offspring. And so now I'm a little bit obsessed with seamen.

That was your light bolb moment in a way. Yeah, it was so taking that forward from s squirts, two flies, to humans. What could that mean for all of us? Well, it is really tempting to be able to say that, of course, you know, we can directly relate from a fly to a human. I would love to be able to, you know, make that leaper for some people. Of might work, sure, but once again we need to go out and test it. So it it came at a time of my life where I was starting to think about my own reproduction as well, and a lot of my friends knew that I was working on sperm and it's sort of always asked me and I'd say I'm well, I've got a lot of crazy ideas, but you know, I work on a fly. Let's not take this too far. And then I've heard, well, hang on, why can't we take it too far? You know, why wouldn't this work? And so now I'm trying to figure out do we find similar things happening in humans and can we use these evolutionary responses to try and boost our own reproductive success? And so that is my new direction. That's what drives me now. So does that have a bit to do with the in vitro fertilization, say, and assisted reproductive technologies? There seems to be a lot of focus on the sperm and the egg, but to what extent is seeming included in those, in the delivery of those technologies? So really interesting area of research that I'm only just starting to delve into. And the thing with the sisted reproductive technologies is they were developed for cases of severe infertility, you know, a real medical condition, but now they've become so common we're just using them more and more and four cases that perhaps we don't necessarily really need such invasive technologies. But because we know it works, it's easiest to jump straight to that. You know, we have these incredible technologies where they can inject a single sperm directly in to an egg, and we love technology, we love this high tech stuff. So if somebody tells you we can do that, then you think, all right, maybe I should jump straight to that because I know where and you really desperate for hope to you'd been trying to get pregnant for a long time. So the problem is is that we haven't had enough time to really track what effects this will have on offspring. So the oldest IVF child is my age. She's like s might have turned forty now. I think TWAS too, babies they were called then. I work for is a little bit harsh, but there is growing evidence that you do find subtle effects on metabolic disease just from the process of artificial reproduction. And we have a lot more data from agricultural systems where they've been doing that to increase production efficiencies for a long time. And so, you know, I think maybe we need to start trying to improve success rates of some of the less invasive technologies where if you're in a case where you don't necessarily need to go to the extent of using exe, where they inject the sperm into an egg, maybe that shouldn't be the first port of call. And so I'm really interested in my research in trying to see if we can improve the success rates of just assisted insemination or intrauterine insemination and try and get these less invasive technologies working a little bit better where traditionally there hasn't been much focus. What would you advise women who are listening to this who want to get pregnant having trouble and a considering IVF? The message that I would like to try and get out there is that, you know, we call it IVF, but that is one technology. There's also...

...a lot of steps you could try out first, so you know, maybe you don't have to wait until you've been trying for a year and then go straight to IVF. Maybe right from the very start you could try learning about these natural fertility cycles and try some simpler, less invasive interventions first and then work your way up, but start early with something simpler and consider seemen. Consider always consider the semen. And how does this kind of work intersect with your personal wife? For example? Do you start thinking more about your partners lifestyle? I have been asked that a lot. I actually, on our very first date my husband did make me promise that I would never use him in an experiment, which is quite sad because it would have been great, but a fascinating conversation to how are your first day? I've had some great first dates. I remember going on a blind date once and talking about my research and he just went gray and I said are you okay? And he stopped. He said I think, I think people can hear us. Said, Oh, if if you can't handle hearing me say sperm, then this is not going to work. But Poor Joe, he he has been enough time around me and my friends at pubs now to not get quite so embarrassed at some of the words that get thrown around in our conversation. But this effective of semen that you're looking at in your various models has to do with the way that the previous life of of the of the male what is what kinds of things were the implications there? So some of my most controversial research has been around this idea of telegany, that the first male that mates with a female can leave an imprint on her and affect all her future offspring. This is much deeper than just first love kind of thing and a bit of no, this is real. This is actual sex. And the most famous case is Lord Morton's Mare, and she was a horse, a mare, and she was mated to a Quagga, which was an animal like a zebra and it had stripes and she produced some folds and they had quagga like traits. But then the interesting thing about her is later on in her life, when she was mated to other pure bred stallions, all her offspring had these quagga like traits. They some of them had stripes, they had this stiff main and it became something that had to be explained in any theory of inheritance. They didn't know about jeans yet at that stage, and so if you look in the origin of SPEC's, it's actually talked about by Darwin. You know, how do we explain this phenomenon of telegany? But then once we forget out genes, we forgot about all that stuff. It was such a nice simple explanation and it didn't fit into that paradigm anymore. So we thought, okay, doesn't work, let's ignore it. Of course, nothing in life or biology ever turns out to be that simple. So now we're discovering that, you know, there must be multiple parts of inheritance and multiple ways that we can influence our offspring or pass on traits to our offspring, and so, you know, there's so much not known yet about what males transfer in their semen and how we know that it affects the female and it can affect her physiology, and so it makes so much sense that it can also affect her developing offspring. could affect the females behavior. It could definitely affect the female's behavior. There's some pretty controversial research out there that has a few flaws in it, but seems to suggest that exposure to seamen can influence depression.

It's a happy hormone being delivered within the semen, but in fruit flies it makes the females angry. They will eat a lot more, they get more aggressive. It could also reduce their sleepiness. They have less yester time. You know, anything that the male can do to maximize that investment that he's made so once he's mated with the female, he wants to make sure that he's sperm fertilizers. Many eggs is she can produce? Might not necessarily be good for the female to produce that many eggs, but if he can make her pump out a ton of eggs and actually father those offspring, then that's great for him. So anything he could do to manipulate her would be a great evolution, reinnovation. Where do you think this line of research may take you? Your career. Where do you want it to take you? So the strange thing about my research is it has been a series of twists and turns and a lot of people get a bit confused about what what is it that you do? You know, you were a marine biologist and then you worked on flies and now you're over trying to work in reproduction, and what is it? But it's just following the question, and so I don't even want to predict where I would go, because that that's the most fun part about the science is you don't know where it will take you. It's you do something and it makes you think that's weird and then you get to follow up on that. How exciting is that? I would like to think that that I can make a difference somewhere, and at the moment I have started thinking that I have quite a unique background and a different perspective to a lot of people working in reproduction, and it actually started from I got asked to go and speak at a reproductive conference and realize that there's a whole bunch of people working on reproduction and then a whole separate subset of scientists working on sex and we never speak to each other but it's the same thing and that was really weird to me and then I realized, Hey, okay, they have all this knowledge that it would be great for me to tap into, but I also have, you know, some different ideas that maybe I can bring to the field as well. So is it a difference between biological and behavioral? It's so evolutionary. Biologist work on sex in the context of sexual selection, but none of that theory seems to really be infiltrating into reproductive medicine. Little bits here and there are used. So, for instance, when they collect semen from a ball, they will have other balls around so he can see that he has competition and this makes him produce better. Spurn really not just being embarrassed. No, it's it's a really strong evolutionary, conserved response that we see across all animals and it's because there is such a strong selection pressure there that you know, it's obvious. You can see the premating selection. Males have to compete to be able to mate with the female, but if the female makes multiple times, then the competition doesn't end there. He sperm also have to compete, but it's quite expensive to make sperm and an ejaculate not as expensive as it is to make an egg. But so... don't want to be constantly producing your best sperm if you don't need to. So what we find is that you have, you know, if you have these monogamous couples like the majority of humans now live in, then in males aren't sending in their best swimmers all the time. They're just sending in, you know, blockers and, you know, topping her up all the time. And this is I'm simplifying things a little bit and maybe there's not so much evidence and not everybody agrees with me, but what we do see consistently is if you manipulate a queue of perceived sperm competition, then males will change the quality of their term in that ejaculate. And I want to know if we can use these sorts of evolutionary conserve cues to actually alter the success rates of assisted reproductive technology. Like if women made men jealous, they come up with a better quality product. Well, yeah, that is the idea, but trying to figure out a way that's not so ethically suspect of using the same sort of cues. So, you know, originally I thought, well, you know, this is an easy thing that we could do. We could just change the pornography that we show males in collection rooms to get a better sample, but you know that's not necessarily the best way to go about it. So I've been thinking what else could we do to try and harness the power of this response, and so what I'm working on at the moment is just looking at the seam in itself and if we can use these cues of sperm competition by exposing a sperm to other male seminal fluid, do we see this same response and an increase in sperm quality, or just can we make them swim faster, and would that make assisted insemination work better? So the thing with assisted reproduction is, you know, we find half the time the problem is with the male and half the time the problem is with the female, roughly. But even if the problem is from the male side, it's still the female that has to go through all invasive procedures. At the moment. You know, we pump her full of hormones to make her produce lots of eggs and then harvest those eggs, fertilize them and put them back in and we do that because we we know works and this technology was developed for cases where, you know, the sperm can't swim at all, but more and more we're now using this for cases where we just have subfertile sperm or maybe you have social infertility. So gay couples or single females that want to have a child will still use this technology even though, you know, maybe it's not required. And so I think you know what about if instead we try and focus on boosting the sperm and trying to increase the rates of these less invasive technologies and try to help women that, you know, I just subfertile, help them try and boost their reproductive success and, you know, get over that hurdle a bit quicker instead of completely take over exactly with an invasive process. So if you're interested in IVF you're talking to a doctor about it, should you ask what do you do with seemen? What do you know about that and what response do you think you might get? There was a really interesting article published by a few evolutionary biologists a few years ago and it started with a personal anecdote of them and they said when they went to get an IVF procedure, the doctor sort of quipped you should go...

...home and have sex and then you'll never really know whether it was the procedure or you just happen to get pregnant and said. You know, that was a little bit of a ridiculous thing to say, but it turns out that it might have been really good advice, because we now have this evidence that regular exposure to seamen can prime the females immune system and make it more likely that that embryo will implant, and there's also evidence that, further along with the pregnancy, regular exposure to seamen can reduce the chances of pregnancy complications like preclaimsia. But it has to be the right seamen. So if you're getting this constant message that your partner is around and there to help, then it's a good thing to invest in this child, whereas if you're getting the message that you know you're pregnant to a child but then coupling up with another male, then maybe this isn't the best time to invest in that child. So if we can start understanding these kind of feedback and messages and, you know, find a way to try and harness that power and use it to help us increase our own success, then that would be that's where I would love to go. You have a personal experience with IDF. I didn't go down the IVF fruit, but I think that is only because of my science background. So I was told that I should. You know, I went to the doctor because I had had trouble getting pregnant and she said, oh well, that's fine, or refer you just go and get IVF. You know, it's no big deal. I thought, well, hang on, we've done tests and there doesn't seem to be any problem. And if there's no medical reason to be getting IVF, why would I be jumping to that straightaway? Is there something else that I could try first? And she kind of looked at me strangely like, you know, what do you mean something else that you could try? We know this works, this is what people do. Why wouldn't you just go and get IVF? Which seems like a valid question. And you know women are so desperate to have a child and you know, I said I'm not maternal. I didn't think I would get this way, but it's one. The idea was in your head and you wanted to do it. You do feel like you would do anything that anyone suggested to have a child. And so I probably would have been willing to go and do anything that anyone suggested for me. But because I had this science training and I work on paternal effects and maternal effects and you know how early develop mental environments affect your offspring, I was a little bit reluctant. And I know that I don't handle hormones well. I've always had troubles going on the pill and the thought of pumping myself full of hormones terrified me. And so I thought, okay, well, I'm going to start doing some of my own research to see if I can figure out what's going on. I've always had a very regular cycle and you know, once I started researching, I thought, how is it that I know so little about my own reproduction? You know, I can know so much about a C squired and so much about a fly, but I didn't even know that. You know, my own cervical fluid changed in a predictable way that could tell me when I'm ovulating. I didn't need to go out and get a test kit. You...

...know, your own cervical fluid changes to become more like seamen around the time of ovulation. Most of the time it's trying to block anything from getting into your uterus. You know you don't want any pathogens or bacteria to get in, but for a small window around the time when you're fertile, it's completely the opposite changes so that it can help the sperm get in there. And if you know these fertility signs, then you can boost your own chances of becoming pregnant. And then as soon as I started tracking my own cycle with my temperatures, it's straightaway I became pregnant. And obviously that's not going to work every time and it's not going to work for everyone, but if I hadn't done that own that research myself, I would have gone straight to IVF. You became your own experiment. In a way I often become my own experiment. What a revelation to go from C squords two flies to and cree sure. Well, all the best. Thanks very much. been lovely. Speaking to you to been absolute pleasure. Thanks for listening to Darwin. Eight an OWL and production of spectral media, Bigger Street and Crowsnest media with host Mark Horsemen. Research and writing by me, Margot Adler and Mark Horsemen, recording and editing by Fraser Johnston and Andrew Tarrell, sound design and music by Nick Sullivan. You can get new episodes automatically and for free by subscribing wherever you get your podcasts. You can get in touch with us on facebook.

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