Tales from the (manus)crypt: Evolved bloodsuckers

We’re diving into the intriguing world of vampire bats and their unique genetic adaptations to a blood-based diet. Shenglin Liu is a researcher at the Senckenberg Natural History Museum in Frankfurt, Germany tells us that vampire bats have evolved specialized traits, from teeth modifications to brain enhancements, to thrive on a diet of blood. The episode also explores the surprising social behaviors of these bats, including blood-sharing among friends, shedding light on their intelligence and adaptability. You will get a picture of these “cute, blood-sucking, smart, and generous bats” and the remarkable feats of evolution that make them stand out in the animal kingdom.

This episode was produced by Anupama Chandrasekaran, and mixed by Collin Warren. Artwork by Jace Steiner.


Shane Hanlon:              00:00                Hi, Vicky.

Vicky Thompson:           00:01                Hi, Shane.

Shane Hanlon:              00:02                When I say vampire, what do you think of? Hot start.

Vicky Thompson:           00:02                Count Duckula.

Shane Hanlon:              00:10                Count Duckula?

Vicky Thompson:           00:11                Do you remember Count Duckula?

Shane Hanlon:              00:12                Is that a DuckTales thing?

Vicky Thompson:           00:14                I don’t think it’s related, but it was a cartoon when we were kids.

Shane Hanlon:              00:20                It was an actual dedicated cartoon called Count Duckula? It wasn’t part of a different one like Looney Tunes or something?

Vicky Thompson:           00:27                No, it was Count Duckula. It’s the same look and feel though, because I actually. But anyway, so yeah, it was a vampire duck.

Shane Hanlon:              00:37                Of course it was, but you saying those two words together is just hilarious.

Vicky Thompson:           00:41                And I don’t remember much about it except for the intro was… I feel like the intro had, this is a fun cartoon, right? It looks like DuckTales, the duck looks like a DuckTales duck, but the intro had scarier images in it, and it was my first introduction to vampires, cover your neck when you’re sleeping.

Shane Hanlon:              01:07                Oh my gosh.

Vicky Thompson:           01:07                Because I think I’ve mentioned this before, because vampires don’t know how to pull a blanket back. So if you keep your blanket over your head, then you won’t get bit by a vampire in the nighttime. So that’s what I think of.

Shane Hanlon:              01:18                Is that the rule that a vampire can’t enter your house without being invited, is that they can’t pull a blanket down unless you pull it down for them?

Vicky Thompson:           01:29                I think the blanket one is based on even less reality than they can’t come in your house unless you invite it.

Shane Hanlon:              01:36                That’s just your reality. That’s what you’ve chosen to.

Vicky Thompson:           01:37                It’s just my reality. It’s just what I had convinced myself when I was a kid that if I kept, so I still sleep with blankets up around my eyes basically.

Shane Hanlon:              01:48                That’s amazing.

Vicky Thompson:           01:50                I don’t want to get bit by vampires.

Shane Hanlon:              01:52                Oh my gosh, I can’t say that mine is any less silly. I think Count Chocula, honestly.

Vicky Thompson:           02:00                Yeah, see?

Shane Hanlon:              02:01                The cereal or something. I mean.

Vicky Thompson:           02:03                Delicious.

Shane Hanlon:              02:04                I’ve taken in a lot of media in my life, specifically movies and books about vampires from the very serious to the origins of Dracula to the very silly, like the silly Nic Cage movie that came out recently about being Dracula. But yeah, honestly, I think of Count Chocula, which is a cereal that I can’t, my parents didn’t care about me eating sugary cereals when I grew up or anything. I wasn’t anything like that, so I could have eaten it. Honestly, I’ve had it, but I don’t only think it was even on my regimen. It wasn’t in my routine though. Yeah, I guess it’s the first thing that comes to mind.

Vicky Thompson:           02:47                That’s funny that we both have cartoon cuddly vampires, more cuddly vampires.

Shane Hanlon:              02:55                If not young in age, we are young at heart.

Vicky Thompson:           02:58                Yeah, emotionally.

Shane Hanlon:              03:04                Science is fascinating, but don’t just take my word for it. Join us as we hear stories from scientist or everyone. I’m Shane Hanlon.

Vicky Thompson:           03:14                And I’m Vicky Thompson.

Shane Hanlon:              03:15                And this is Third Pod from the Sun.

                                    03:21                Vicky, did you know that the word vampire, as we’ve talked about, has its origins? It’s actually in a Slavic word that translates to roughly to one who drinks.

Vicky Thompson:           03:36                No, I didn’t know that. And is it specifically referencing drinking blood?

Shane Hanlon:              03:40                I don’t think so though. I think there’s only one blood sucking animal. Well, no, that’s not true. Not animal. One blood sucking mammal, let’s go with that. That has vampire attached to it and does in fact drink blood.

Vicky Thompson:           03:54                Oh, you’re talking about bats, right?

Shane Hanlon:              03:56                I am talking about bats, yeah. I learn a new thing every day. What’s perhaps even cooler is that every part of their body of these vampire bats has been modified to cope with the diets, it’s all come around.

Vicky Thompson:           04:13                That’s wild. Okay, so you have my attention now. What’s this about?

Shane Hanlon:              04:20                Yeah, so when we got to pitch and listened to the interview, my curiosity piqued when I learned about this for the first time. And so to more adequately and probably eloquently explain it, I’m going to bring in producer Anupama Chandrasekaran to tell us more. Hi, Anupama.

Anupama Chandra…:    04:35                Hello, Shane.

Vicky Thompson:           04:37                So Anupama, who did you speak to for this episode?

Anupama Chandra…:    04:40                So I had a chance to speak to Shenglin Liu. He’s a scientist who’s basically dissected the genetic sequence of vampire bats.

Shane Hanlon:              04:51                Genetic sequence. So what does that tell us?

Anupama Chandra…:    04:54                I mean, first of all, it was really interesting for me to see that we are not talking to a scientist in the field, but somebody who’s actually looking at all this data that’s been collected and slowly really revealing fascinating facts about a creature. And secondly, what I really, really was very, very surprised to learn about was in the case of vampire bats particularly, it’s not about adding new genes, which has mostly been the case when I read about animals and evolution, but it’s actually about shedding genes and that’s working for these bloodthirsty mammals.

Vicky Thompson:           05:33                Oh, that’s really interesting, let’s hear it.

Shenglin Liu:                 05:44                My name is Shenglin Liu, and currently, I’m a postdoc in the Senckenberg Museum in Frankfurt. I mainly work on vampire bats, which is a really cool group of species that only feed on blood, survive on blood. And what I do is to compare their genome with the genomes of other pet species and see what is unique for the vampire bat genome. Vampire bats as the name indicates, yeah, they feed on blood. But they’re not as horrible as actual vampires you saw in the movies. They’re actually, if you don’t know them, they might be a bit cute, might be. So these animals are quite small actually. But in terms of bats, it’s a medium size, about 30 grams so you can imagine it’s not super big. There are three vampire bat species, as I mentioned, and they are the only mammals that only feeds on blood, the only mammals. There are over 6,000 mammal species and only these three are obligated blood feeders. That makes them really cool.

Anupama Chandra…:    06:55                So could you explain a little bit about that? How these cute mammals that suck blood, why are they unique?

Shenglin Liu:                 07:03                Blood is not a very good source of food or energy because 80 or 90% of it is just water so you really need to suck a lot to get enough energy. And except for that, most of it is protein. It’s very low in carbohydrate and fat, so cannot directly provide you energy. You need to go through some actual procedures inside your body to make it available as energy. For example, their teeth are pretty much gone except for the front teeth and the canine teeth, which are really sharp just to cut the body to get the wound and so that the blood can come out. That’s the main function of the teeth. And then their stomach got really huge, which allow them to store a lot of blood. Their body is around 30 gram and they can drink between 10 to 25 gram of blood, so yeah, that’s a lot.

Anupama Chandra…:    07:57                So could you give us a sense about why these mammals are so fascinating and what the genetic studies actually revealed about these creatures that focus just on drinking blood?

Shenglin Liu:                 08:13                As I said, this is three species as a distinctive group, they are the only blood suckers in bats and also in all mammals. So this creates a very good system for you to study a specific evolutionary question. In this case, it’s just adapting to the blood diet. This is perfect system for studying evolution. That is one of the reasons why we studied it. And besides through the preliminary study, we also found some very interesting results. For example, some genes related to the carbohydrate or fatty acid metabolism, especially the insulin regulative network. Some of the genes in that were lost.

                                    08:58                And also, we also found some gene losses. One gene loss that is related to iron absorption because they drink a lot of blood. Blood contains a lot of iron, which is around 800 times more iron than human consumes. And that, too much iron can be toxic for the body, so how bat can cope with it. And our study indicated that there is one gene loss that might help them to cope with it, that gene loss can allow them to get the iron from the blood into the intestinal cell and then shed those cells through the poop, and then in that way they can get rid of the excess amount of iron.

Anupama Chandra…:    09:39                Yeah, I mean there’s also genes that have reshaped their organs, right? You’d already spoken about it, could you elaborate a little bit more about that?

Shenglin Liu:                 09:47                Yeah, it is a particular gene. This gene is named that the CTSE. Yeah, cathepsin E. This gene is normally in humankind, is expressed in the stomach, in the parietal cell. The parietal cell are special cells in the stomach that can create the stomach acid.

Anupama Chandra…:    10:05                Okay.

Shenglin Liu:                 10:07                Yeah, this is why your stomach has acidic environment because of these cells and this gene is expressed in those cells. This gene is lost. It may correlate with the shift of the function of the parietal cells, because in other mammals, for example in human and in mice, parietal cell will be secreting the stomach acid. Some other study indicated that in the case of vampire bat, parietal cell probably have specialized into some other function. For example, iron secretion.

Anupama Chandra…:    10:40                So tell me a little bit about your field work and also about what it is to actually be down in the lab and make all these discoveries about acute blood sucking mammal.

Shenglin Liu:                 10:50                I’m afraid I have disappoint you. I don’t have any story to tell about the field work because yeah, I didn’t do any field work. The sample was collected by someone else, and when I arrived in the lab, it was already genome sequenced so my work was a purely computer-based work data analysis, but I like this kind of work.

Shane Hanlon:              11:20                It’s super fascinating how the genetics work that he’s doing and how it’s revealing these really intriguing evolutionary processes.

Vicky Thompson:           11:30                Yeah, who says you need to be out in the field to do really interesting work?

Anupama Chandra…:    11:35                Absolutely. I mean, we need folks to dissect data because otherwise folks are just going to be out collecting the data and we need somebody actually dissecting this data and these things can really reveal fascinating facts. For instance, I was really surprised to know that these bats which consume a non-carb, non-sugary, high on iron liquid diet, when researchers actually went through their genome, they found that this diet actually requires so many tweaks in their internal organs, even their hormones.

Shane Hanlon:              12:09                It is wild if you step back and think about it. And I imagine even though Shenglin doesn’t really do field work, he had to have had some memorable research experiences.

Anupama Chandra…:    12:21                So any particular moment, any days, weeks that you remember very clearly that you mind and you found this peculiarity and were completely amazed by it?

Shenglin Liu:                 12:34                Yeah, for example, one week I just found that, what was that? Insulin receptor gene. That is a very unique gene in the genome. We all have it and only one copy in the genome. That gene is under positive selection in vampire bats and in all vampire bats and that positive selection is quite dramatic. It literally replace quite some segment of the sequence which you would not expect in under normal circumstances.

Anupama Chandra…:    13:06                And what consequence does this have on the adaptability of these vampire bats?

Shenglin Liu:                 13:14                What I can say is purely theoretical. For humankind, we know that insulin is very important. If we have low amount of insulin, then we probably get diabetes. But in vampire bats, they naturally have a low amount of insulin. Also, as I said, their diet contains a really low amount of sugar and fatty acid, so their entire insulin regulative system should be quite different.

Anupama Chandra…:    13:39                There’s this little bit of connection about how smart the vampire bats are and how it also affects their sociability and the friendships and the things that they’re willing to share. So could you talk a little bit about that?

Shenglin Liu:                 13:54                Vampire bats just I have so many unique traits, and another one will be just like what you mentioned, that the social behavior. According to study, they’re also pretty smart. Their social behavior level is quite unique because they share their food. Because blood is quite precious to get, and you cannot guarantee that every night you go out today you can get some blood. And on top of that, they are really bad at enduring hunger. If you starve them for three days, they will die.

Anupama Chandra…:    14:28                Oh, wow.

Shenglin Liu:                 14:29                Yeah. So they really need blood continuously, and some of the nights, one individual probably don’t get any blood and then come back and then they will starve. But they have come up with a behavioral solution for this. Some of the friends or neighbors who got the blood that night who share some of it, they will basically vomit it back.

Anupama Chandra…:    14:29                Right.

Shenglin Liu:                 14:52                And then share it with the individual that didn’t get blood that night. So this regurgitation and blood sharing behavior, it’s very unique, and it shows that they have this kind of social behavior which is very rare in bats. At the beginning, scientists thought probably they will share this blood because they’re related, like mother and daughter, this kind of relationship. But it turned out no, kinship or relatedness in this case doesn’t matter. What matters is that how closely they were interacting in the normal days. For example, they groom each other, so take away parasites from each other’s body and comb their hair. Yeah, just building up this friendship. That is the basis for the blood sharing.

Shane Hanlon:              15:52                So I talk about grooming as a survival mechanism in the disease ecology class that I teach. I spoke about a little bit before, and this is mostly in primates, it’s called all grooming, but that’s usually where it stops. They’re just pulling parasites and pests off of one another. It doesn’t usually lead to them becoming close enough to eventually regurgitate blood to feed one another. Your face right now is amazing.

Vicky Thompson:           16:23                I literally have no response. I don’t know what to… That’s really a unique thought that you had there.

Shane Hanlon:              16:30                Oh my gosh, all right. Well, we’ll just get back into it to hear more about it.

Anupama Chandra…:    16:35                They also remember somebody who has probably shared blood with them in the past, and that.

Shenglin Liu:                 16:42                Yeah.

Anupama Chandra…:    16:42                There’s a quid pro quo in a sense which happens.

Shenglin Liu:                 16:45                Yes. It’s mostly the friendship they built up through the normal daily life that enhances this blood sharing behavior. That also means that they need to remember what happened in the past and who they shared blood with. Yeah, that means that they have quite good memory about it. And actually, some study also indicated that their brain relative to their body size, it’s bigger than the other bats, so it means that they are more intelligent. And then our group, by analyzing the vampire genome, we also found that this gene was called CYP39A1. This gene was lost in vampire bats and what this gene does is this gene actually has two functions. One is to produce bile acid. This helps you digest and absorb that from your food. But yeah, this gene is involved in the bile assay production, but it only contributes very little.

                                    17:44                But this gene also has another function. It is in the brain, expressed in brain. It metabolizes the cholesterol in the brain into a special metabolite we call the (24S)-hydroxycholesterol very long name, we can just call it a special metabolite. And some study indicated that this special metabolite can enhance the memory and also social behavior. So basically enhance many cognitive aspects of the brain. So we are thinking that this probably is a very important contributing factor for the vampire bat to gain their intelligence, some level of intelligence in their evolution.

Anupama Chandra…:    18:36                Got it. So these are cute, bloodsucking, smart, and generous bats, so to say, right? Have you been surprised or completely amazed or shocked to know about something or find anything?

Shenglin Liu:                 18:52                Yeah, I cannot say those big moments, but occasionally there were just a small shock wave. The most drastic change that happened in vampire bats is in their gut, gastrointestinal system. So from stomach to intestine and pancreas, all those parts, you know that in humankind after meal, there will be bowel movement. So the intestine will slowly move and to make the food go forward, and even when you are sleeping, there will be rhythmic movement of the bowel so that the remaining undigested stuff will be pushed down together with unwanted bacteria, harmful bacteria. Then it’ll be pooped out eventually. But this moment is gone in vampire bats according to our study, which makes sense because they don’t eat any solid food. It’s a purely liquid food, and so they don’t need a bowel movement, so when they sleep, they don’t move their stomach or intestine.

                                    19:59                And that probably also correlate with another finding, another thing we found. We found some immune related genes under positive selection, and those genes are particularly expressed in the intestine. This may have something to do with the lack of the bowel movement, because if the bowel doesn’t move, then it also means that the harmful bacteria cannot be rid of.

Anupama Chandra…:    20:22                Right.

Shenglin Liu:                 20:25                From the stomach from the intestine. Then they will probably just have to enhance their immune system to cope with it, and to correlate with that, a previous study found that the vampire bat intestine is contains particularly a high amount of immune-related cells actually.

Anupama Chandra…:    20:47                Yeah, I mean it’s no small feat to be a bloodsucking vampire bat in that sense, right? Because that whole thing from your brain to your stomach and intestine and everything, lots of changes have happened to actually enable you to be able to drink blood, process it, excrete it, and so on and so forth, and also share it, right?

Shenglin Liu:                 21:10                I hope people listen to this and then also realize that vampire bats, they’re not all bad. Actually, they’re quite cool. It’s quite an ingenuity of mother nature.

Anupama Chandra…:    21:23                Yeah.

Shane Hanlon:              21:32                Vicky, well, I guess we could have talked about before, but what are your before, and I guess now, what are your feelings on bats? When I say bats or vampire bat, I guess specifically what comes to mind?

Vicky Thompson:           21:46                Oh, like real bats? I learned the other day that from Instagram that if a bat gets in your house that you should just go get rabies shots.

Shane Hanlon:              21:58                Yeah.

Vicky Thompson:           21:59                Did you know that?

Shane Hanlon:              22:00                So yes. Okay, this is actually funny because I love bats and I think they’re absolutely adorable. I talk a lot about them in the class that I teach about all the harms they’re facing, like fungal diseases wiping them out among other things.

Vicky Thompson:           22:14                Fungal disease.

Shane Hanlon:              22:16                Yes, we talk about rabies because I teach a disease class, and so we talk about rabies a lot, and I basically, yes. Bats, this is my PSA. You can get bitten by a bat and you will never know.

Vicky Thompson:           22:32                Right.

Shane Hanlon:              22:32                And many of, at least a handful of the more well-known rabies cases in America happen happened because folks were bitten by a bat and never knew. So I don’t want to spread misinformation or anything. I’m not saying you’d have to kill the bat or have to go, but.

Vicky Thompson:           22:49                The best practice, go get fixed up.

Shane Hanlon:              22:51                Best practice is probably just to figure out, try to determine if you were bitten. They can carry rabies. I didn’t really think about going in this direction, but we’ll pull back around. So I do love bats. With all those caveats aside, I think they’re really great people to know. They’re really great for the environment, they’re good for economies, all that type of thing, even if they do suck blood. Anupama, what do you think about bats? Has your perception shifted at all or anything like that?

Anupama Chandra…:    23:25                Actually, there are lots of fruit bats in my neighborhood, and it’s quite fascinating to go to this ficus tree and watch these fruit bats hanging upside down during the daytime. It’s really quite interesting. But I have never particularly been affectionate towards vampire bats, and now that’s surely changed because these really seem like evolved blood sucking machines.

Shane Hanlon:              23:53                I want a shirt with that, with a picture of a vampire bat that just says evolved blood sucking machines. I think that’s pretty good.

Anupama Chandra…:    23:53                Yeah.

Shane Hanlon:              24:01                I think where we’re ending here with positive attitudes about bats, bloodsucking, otherwise. So with that, that is all from Third Pod from the Sun.

Shenglin Liu:                 24:12                Thanks so much to Anupama for bringing us this story, and to Shenglin Liu for sharing his work with us.

Shane Hanlon:              24:19                This episode was produced by Anupama with audio engineering from Collin Warren and artwork by Jace Steiner.

Vicky Thompson:           24:25                We’d love to hear your thoughts on the podcast, so please rate and review us, and you can find new episodes on your favorite podcasting app or at thirdpodfromthesun.com.

Shane Hanlon:              24:34                Thanks all, and we’ll see you next week.

                                    24:42                Oh, I’ve never heard of Count Duckula, which is funny because I feel like I knew a lot of really silly cartoons back in the day.

Vicky Thompson:           24:54                Well, when were you born?

Shane Hanlon:              24:56                ’86.

Vicky Thompson:           24:57                Yeah, so you were two. I Googled it. You were two when it came out, and I was six.

Shane Hanlon:              25:03                How long did it run for?

Vicky Thompson:           25:06                Yeah, I was six. Let’s expand this Wikipedia article, hail Wikipedia, to ’93.

Shane Hanlon:              25:14                I mean, I would’ve been seven. What was it on?

Vicky Thompson:           25:19                I don’t know because it’s British.

Shane Hanlon:              25:25                Oh. Then what did you see it on? Were you watching it on PBS?

Vicky Thompson:           25:25                Not to be confused with the unrelated 1979 cartoon also based around a vampire duck, Quackula.

Shane Hanlon:              25:33                Quackula’s better. That’s just a better name.

Vicky Thompson:           25:36                Based on Danger Mouse. I don’t understand how any of this. Nickelodeon. ITV and Nickelodeon.

Shane Hanlon:              25:43                Oh, I didn’t have cable.

Vicky Thompson:           25:48                You poor child. You didn’t have cable.

Shane Hanlon:              25:48                I didn’t.

Vicky Thompson:           25:52                I thought I was dead because I didn’t have the Disney Channel. We have to pay extra, so I would wait. I think we’ve talked about this before. I would wait for them to have the free, they would give you a free week of the Disney Channel so that they would get the kids hooked on the Disney Channel. So I would just wait for that free week and just watch TV the whole week.

Shane Hanlon:              26:10                Yeah. I didn’t have cable. My parents literally got satellite dish TV, because cable didn’t run to my house actually up until a year ago, frankly, because where am I from?

Vicky Thompson:           26:23                Rural Pennsylvania.

Shane Hanlon:              26:24                There we go.



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