 And I guess we can go. Hello everyone and welcome to another virtual vision seminar. We are very happy to see you all live with us every week and have to say I'm very glad to see more and more people from different fields joining us. Lately it's true we have been hosting talks on eventable visions and in consequence it has enlarged our classical audience. So welcome to you all. And that is actually a great opportunity for me to remind you that these talks are part of the worldwide neuroinitiative. It is basically a platform where neuroscientists share their work and insight on their respective fields. And yeah, we have to keep doing that until we can finally meet in person and go on conference. So do pay your visits to the worldwide neural website. There are tons of talks already uploaded as podcasts and there's still many more to come. So as usual, you will find all the relevant links in the description. Today we continue discussing inverted brain vision with Nathan Morhouse. Nathan Epstein is PhD from the Arizona State University where he worked with Ron Rytowski on interactions between female choice and nutritional ecology in butterflies. He then went to France for a couple of years and they joined the Institute of Research for the Biology and Insect Intour where he studied the evolution of seasonal polyphenism in butterflies again. He finally returned to the US as an associate professor at the University of Pittsburgh before moving his research group to the University of Cincinnati in Ohio in 2016. Over there, his research group studies the evolution of vision and visual signaling in butterflies and ducking spiders. So hello, Nathan. Thanks for being with us today. How are you doing? I'm doing great. I'm doing great. It's a sunny day here in Cincinnati and it's springtime. So nothing to complain about. The stage is yours. All right. Thanks, Maxime. I really appreciate the opportunity to share with you and others some of the research that we've been doing over the past few years to understand the evolution of looking and seeing and jumping spiders. You get my pointer going here. We should see a laser pointer. Great. Excellent. So as Maxime said, I've been studying the visual ecology and evolutionary ecology of butterflies and more recently jumping spiders. And my lab is particularly interested in how these animals navigate their world based on what they can see. But I want to take a step back for a moment and think about the broader picture of what we're doing as scientists studying this kind of diversity. This weekend, I started David Attenborough's life in color. And I was struck, as I'm sure anybody is who watches that, by the exuberance of biodiversity shown in that series and particularly things like birds of periodite. Repeatedly you get caught up when you talk about biodiversity. It stimulates human curiosity in a way that's hard to put a finger on really. We really just want to understand what is going on here and what is this male doing? How is the female reacting to this? What can she see? Of course, it feels intuitive that his colors and display are playing some important role in the lives of these animals, helping him to convince her to mate with them, et cetera. At the basis of this curiosity is a fundamental question that my lab seeks to answer, which is how does biodiversity arise and change over time? And when we set out to study this large question, we oftentimes do gravitate towards groups of animals like the birds of paradise, because we have this intuition that there's something special going on here, that the rapid diversification of color traits and motion and pattern must be driven by some fundamental mechanism that we can see when we focus on them. But of course, when we choose a group like the birds of paradise, we choose to overlook other groups that actually even inhabit the same environments. For example, these frog mouths, which cohabitate with those birds of paradise, something entirely different is going on with this group. This is actually three different species of frog mouths here. And unless you were a hardcore birder and ornithologist, you'd be hard pressed to tell them apart. So even though they're in the same place in the world, they're experiencing different selective pressures. So if I think about this in cartoon form, here is a cartoon evolutionary tree where you have some groups, for example, like the birds of paradise, rapidly radiating in terms of their biological diversity. Whereas other groups like the frog mouths are changing more slowly or diversifying more slowly. And yet other groups, for example, horseshoe crabs are in the swan song of their biodiversity on the planet. So in order to ask questions about this, my research group focuses on really two major possibilities here. The first is that there may be major transitions, evolutionary innovations, for example, that sit at the bottom of some of these rapidly diversifying groups that may have opened up a whole new world for them. The other possibility is that there are specific processes within these groups. For example, in this group, processes like sexual selection that in and of itself drive the rapid diversification of form and function that we oftentimes are seeking to explain. So using this paradigm, talking about major transitions, as well as processes within groups, we're going to focus on the biodiversity found in jumping spiders. This is a group of choice in my lab, I think for relatively obvious reasons, these are spectacular animals. The top two animals here are part of a group in North America called the Paradise Jumping Spiders in the genus Havronatus. We'll talk quite a bit about them today. They're relatively easy to hand for us here in the US. And of course, down below are the so-called peacock jumping spiders from Australia, another really vividly colored group. Now, these types of jumping spiders have been front and center in the media coverage of jumping spiders over the past few years. And that's led perhaps members of the audience today to think that jumping spiders are all really brightly colored. But in fact, most jumping spiders are relatively drab in appearance. They may still be accomplishing elaborate displays or dance moves like this Fidipus jumping spider up here. But their body coloration is far more muted. It tends towards the browns and grays and whites and blacks. Occasionally, you'll see something like the bright blue chili tree here of Fidipus audax. But the color palette is more muted. And so we're really interested in understanding why some groups of jumping spiders have really gone bonkers with color and others have not. And one of the important clues is embedded in this image here. And that is that all of the jumping spiders that you're looking at right now are males. And male jumping spiders, especially the colorful ones, use these bright colors during elaborate courtship displays, like the one that you see here. Here's a peacock jumping spider. He's not only displaying with motion and pattern and color. He's also singing to the female at the moment with vibratory songs that transmit through whatever he is standing on. And she hears those vibrations with her legs. You can see her off to the right here. Now you might notice some hesitancy on the part of the male here. And that's well-founded because that female right there has a fairly high likelihood of attacking and eating the male rather than allowing him to mate with her. So he is really, truly dancing for his life. Now you might wonder, well, why are we suddenly learning about jumping spiders? Why are they everywhere we look in the media? And the answer to that is that these animals are incredibly small. This is a real match tip with one of those peacock jumping spiders on top. So they range from anywhere from less than two millimeters, a millimeter and a half, all the way through to about eight or nine millimeters in body size. And animals of that size have been difficult to film until the commercial photography and kind of publicly available photographic equipment caught up. So it's really this move in photographic equipment to allow us to actually film and see and share these animals that has been fundamental to their fame. So today, I want to talk about three topics. First, how to jumping spider see to give you a bit of a primer on that and some of the work in my lab focused on understanding the basic elements of jumping spider vision. I'm going to transition to talking about our work on color vision and finish up talking about dynamic displays and receiver gaze. So let's start here. How exactly did jumping spiders see? Well, if you've ever interacted with a jumping spider on your windowsill or out in a field, one of the first things that strikes you is how curious and intelligent these animals feel. And that's because they really visibly look around the world by moving their bodies to focus their eyes on objects of interest. As soon as they see you, they're likely to turn around and look straight at you. And the reason for that is that, although jumping spiders have eight eyes, the four that face forward provide them with the highest quality vision. So although they do truly have eyes in the back of their head, which they might use to see you in the first instance, to investigate stimuli in their environment that are of potential utility or interest to them, they're going to turn to face it with these four forward-facing eyes. So I want to walk you through what these four eyes allow them to see. Now, if we were to section this individual through the coronal plane here, it would look something like this. They have these two large corneal lenses for what are called the interior median eyes or principal eyes. I use those interchangeably. And then they have this pair of interior lateral or oftentimes called secondary eyes on the right. Let's start with those secondary eyes there. These eyes, we can investigate using ophthalmoscopic techniques where we look in through the lens to image the retina down below, something like this. And although our ophthalmoscope has a fairly limited field of view to look in through, each of these little dots here is a rabdom. We can stitch images together to map out the entirety of the retina of those interior lateral eyes. And they look something like what you're seeing here. This is the interior lateral eye retina of a fitipus audax. This tells us quite a bit. It tells us where these eyes look as well as their visual acuity or their likely visual acuity. And so these eyes provide a wide field of view in front of the animals. There's a considerable space of binocular overlap here. And they actually have pretty decent acuity. Point four degrees is what we estimate to be the distance in angular space that they can see distinct objects or distinct points of light. And that's about as well as the best compound eyes in the insect world can do. We also know that these eyes are only green sensitive. They only express a green visual pigment. And so they're really seeing the world in monochromatic vision. They're highly tuned to motion. They can actually do hyperacute acuity using motion. And so this gives them a kind of black and white peripheral field of view that's sensitive to motion. Let's move to the principal eyes. And these eyes are built entirely differently. As a matter of fact, they're built really differently from just about anything out there in terms of an eye. What you see in the front here is this large lens. And this focuses light down a long eye tube. And the retina down below is this tiny little finger-like thing here. So to better explain this, let's look at a diagram of this. There's an exteriorly visible corneal lens here, a long eye tube filled with vitreous humor, clear liquid. There's a diverging lens, a second lens at the bottom of that and then a layered retina. Now this paired lens system here actually works in principle the same way that a Galilean telescope would with a converging and diverging lens that focused light and then magnified that focused image onto the retina allowing these animals to essentially see the world in a magnified view. Underneath this telephoto or macro lens-like set of optics is a tiered retina here. And it's boomerang-shaped for reasons that we don't fully understand. We don't really understand the function or even the development very well of this boomerang shape. But light is focused down through this boomerang-shaped retina. So this would be an image through that pit lens here, which is going to be positioned right in the center here. And this tiered retina has four distinct tiers of photoreceptive cells. To give you a sense for this, I'm going to show you a video from the ephthalmoscope that we work with here in Cincinnati that's going to focus up from this first retinal tier through the second retinal tier and so that you can kind of see this. So you're going to begin to see coming into the field of view that first tier, the pattern of those rhabdoms. And then as it continues to focus up through, you'll see a second pattern of photoreceptor cells come into view. These are stacked on top of each other. So light coming in through that lens is going to traverse these and be absorbed. So this is what this looks like here. You get a couple of very centrally located and sparse tiers here, tiers three and four. And down below these much more extended tiers one and two. And these tiers are really pushing the optical limits of what's possible in terms of the size of a rhabdom. Their rhabdoms, especially in the central area here, are only about one micron in diameter. This dense packing of these very small rhabdoms in the center paired with that unusual set of optics out front really allows these animals to see the world in extraordinary detail. They have inter-rabdomal angles of about 0.07 degrees in the center here. And I wanna give you a sense for those of you that may not have this number in context of what that actually means. Here's a classic relationship in visual ecology with body size on the x-axis and the spatial acuity I was just talking about on the y. And both of these are on a log scale. And you can see that as animals get larger, their eyes are able to see smaller and smaller details in the world around them, classic relationship here. In other words, in order to see the world around you well, in general, you need to build a bigger eye. So let's put some points onto this to give you a little bit of grounding. There's the fruit fly, pretty poor spatial acuity for those animals. You can feel pretty smug about having pretty extraordinary spatial acuity, especially in your fovea of 0.007 degrees. Of course, your smugness might go away a little bit when you realize that things like falcons can see the world in even higher detail. But where do these jumping spider eyes fall in this? So here's that secondary eye, the interior lateral eye. And it's already well off the curve because although these animals here are quite small, they're still doing really well. They're about as good as a very large dragonfly. As a matter of fact, these animals, the jumping spiders, are smaller than the eyes of these simpetrum dragonflies in total body size. What about those principal eyes? Well, they're way off the curve down here. They've done something truly extraordinary with spatial acuity. And to put that into context, they're doing about as well as a chicken or a pigeon. They're better than the cat that you might have at home. This is the territory where elephants come out. So these animals, even though they're tiny, they're about the size of your pinky fingernail and these eyes are much smaller, are nevertheless seeing the world in extraordinary detail. I wanna point out one more thing here, which is that this layered retina here has a number of unusual properties. One of them is its layered nature. And this was explained at least theoretically by land and others that suggested that perhaps this layering here helped to cope with the feature of the optics I described earlier, which is that it has pronounced linear chromatic aberration. In other words, it focuses short wavelengths of light closer to that lens system than long waves of lengths of light. And so the thinking here was that perhaps this tearing of the retina allowed these animals to place the photoreceptor sensitive to particular wavelengths of light at the right depth behind the lens system so that the image was in correct focus. Now, the best evidence that we have for how these visual sensitivities of jumping spiders are arranged, largely, largely comports with this. So this is work by Nagata et al. from the early 2010s, where they showed that green photopigments were largely expressed in these bottom two tiers where light would be in better focus and UV, rhodopsin or UV sensitive visual pigments were expressed in these upper tiers. So this suggests that this linear chromatic aberration may be shaping exactly where these animals express the different types of photoreceptors that they have in their eyes. This work also showed that these animals are quite clearly dichromats where they're seeing colors of light using contrast between UV sensitive and green sensitive photoreceptors. So to put all of this together, these animals have this unusual visual system where they've got this broad field of motion sensitive, monochromatic, modest resolution vision that's augmented by these principal eyes that see the world in extraordinary detail and in color. So let's move to talking about color vision and color signaling. And the star of this show today will be a jumping spider here in the United States called havernatus pyrethrix or the fiery-haired jumping spider. Pyrethrix means fiery-haired. And here's a male and full courtship display. Females are cute, but much drabber than males. So here's a female pyrethrix right here. These animals live in the American Southwest in places like the lower Sonoran Desert. One of my favorite places in the world is where I did my PhD research. And so some of this is an excuse to get back to these truly extraordinary environments. These animals live in kind of open riparian habitats where we hunt them by hand, capturing them by hand in things like this open Okatio forest. Yeah, that's a forest in the Southwest. Males engage in elaborate courtship displays to females in these environments. And I'll give you a taste for what this looks like in havernatus pyrethrix. So here's the male. He begins this display with a kind of waving display that we've done quite a bit of work investigating to catch the female's attention. Once he's able to get closer, he transitions to a second phase of his courtship where he raises these orange knees over his back while he's flicking those tarsy of his first leg pairs there. And he might transition into this third stage of courtship where he's almost air drumming in front of the female. And if he's lucky, she will allow him to mount her and mate with her. So a prior postdoc in the lab, Lisa Taylor did some work to try to understand whether or not the colors in this display were important to female choice. And she did so by manipulating that bright red face of the males. She actually used Sephora liquid eyeliner to do this, to black out that red face. It's kind of an odd conversation to get in with folks at the mall and Sephora. What are you gonna use this? Oh, I'm painting jumping spiders. But she did this for males. And then she looked to see how far along the sequence of courtship males could get without females attacking or leaving or losing interest. And what she found was that males with their red face intact were actually able to get closer to the female during courtship. In other words, they were able to transition to later and later stages of courtship than males that had had their face coloration blocked out. I wanna point out here and put a pin on the fact that although there's some hint that this may still be occurring in the shade, the results were really only clear in the full sun. And so this difference between sun and shade will become important a little bit later. So we know color is important in courtship interactions in this animal. And we wanted to know whether or not color was also important in some other areas of their life, particularly foraging. So jumping spiders are cursorial predators. They don't build capture webs. They hunt down their prey by stalking their prey and then leaping on it to attack it. And many things in the environments that these jumping spiders live in are brightly colored like this Harlequin leafhopper right here. And many of these things are also quite toxic like this milkweed bug here. So we reasoned that perhaps jumping spiders might actually be using the colors of their potential prey items to make decisions about which prey to attack and which to leave behind. So we did this with what we called the cricket rainbow. We called this the kind of Skittles experiment that tastes the rainbow experiment here where we took pinhead crickets which happen to have pretty translucent bodies. And we provided them with colored water for a period of several days ahead just using basic food coloring. And as the crickets ingest this colored water it actually changes their appearance from the outside. So this allowed us to take a completely non-toxic prey item change its external color and then essentially query these jumping spiders about whether or not they had preferences with regard to the color of the prey they would or would not attack. And what we found was the jumping spiders had strong preferences against yellow and red prey items and actually seemed to have some kind of affinity for attacking blue or green prey items. The problem with this experiment was that we were unable to really adequately control for differences in brightness. So although it seems like these animals are using color and foraging it is still possible that they might be using brightness cues. And so what we wanted to do is follow up on this experiment with one in which we asked the jumping spiders to transfer the property of color from one foraging context to another. And so the way that we did this was we trained jumping spiders that red was either associated with toxicity or with palatability and even profitability. And we did so using a nice feature of a prey item here. These are milkweed bugs. We use milkweed bug nymphs, they're bright red and black. And if you feed these animals on milkweed seeds during development they acquire the toxins that protect them. And jumping spiders are quick to learn that these animals are toxic. They won't attack them after first experience with one of these toxic nymphs. But these milkweed bugs you can also be raised on sunflower seeds at which point they have no access to the toxins that give them protection and they're actually quite tasty to these jumping spiders. So we had cohorts of jumping spiders that developed around these toxic red prey items around these palatable prey items. And we had a control group that were just fed white-eyed fruit flies on a beige diet so that they weren't learning anything at all about color. We followed this up with a test where we looked to see which prey these jumping spiders would attack when we gave them a choice of an uncolored or a bright red colored cricket. So here the exact shade of red is different. The brightness is different. The shape and behavior is different. The only thing in common between their training regime and this predatory context is the color itself. And so what we found was that those that had been taught that red was associated with toxicity attacked red prey items at far lower rates than brown prey items and uncolored prey items. In contrast, those that were taught that red prey items were profitable were tasty attacked red prey items preferentially and those that were only fed fruit flies during their development didn't attack either at any significantly different rate. So this suggests that jumping spiders are not only using color to make foraging decisions but can also associatively learn that color indicates properties of their prey. And what's so exciting about this is that there's almost no work whatsoever at least not carefully controlled work identifying color-based preferences and color learning and terrestrial invertebrate predators. And yet there are a huge number of brightly colored and patterned prey items that are in size classes far smaller than we might expect avian predators to be exerting strong selection on. So for example, that Harlequin leaf hopper on the top left there is only about two and a half millimeters long, barely a snack for a passer and bird but certainly a good meal for a jumping spider. So we think jumping spiders may be really shaping the color properties of the animals that they live with. And evidence for that is quite clear around the world. I have a habit of collecting pictures like those in the bottom left because there's a whole guild of insects in the world that make a living by pretending to be jumping spiders. This helps them to avoid being predated by jumping spiders and actually fantastic work showing the jumping spiders mistake some of these animals, the animal in the far bottom left, the metal mark moth there, actually scares jumping spiders away because they mistake them as another jumping spider. So it's clear that jumping spiders are shaping the appearance of animals in the undergrowth. So jumping spiders are using color and foraging, they're using it in courtship. But if you were paying very careful attention to some of the things I said earlier, you probably noticed that I described their color vision as one of likely dichromacy by using comparisons between UV and green sensitive photoreceptors. And the problem with this is that the picture I just showed you here as viewed through a UV green dichromatic visual system loses most of the color, including the colors that I've just shown you are important in courtship. So this launched us onto a series of experiments to try to understand how are these animals seeing color in the world around? They shouldn't be at least given what we know. So we went for several sun baked weeks of time and Arizona collected a bunch of spiders and then went to Tom Cronin's lab initially. We now do this in my lab here, but we went to work with Tom Cronin in the outskirts of Baltimore into the dark. This is the yin and yang of science here. So we took our sun burns indoors to Tom Cronin's basement lab to use a technique called microspectrophotometry. And the way that this technique works for those of you not aware is that at least for these animals is that we're cryo sectioning their retinas still physiologically active and we're measuring the light absorption of those rad domes in these cryo sections. You can see over here that we have some rad domes which are kind of the dark spots in the center here. And so we spent a couple of weeks in Tom Cronin's lab measuring the retinas of Havronata's jumping spiders and we found good evidence for UV photoreceptors and those upper two tiers and green photoreceptors in those bottom two tiers. And while this might feel like a success it had not brought us anywhere beyond what I'd shared with you earlier which is this puzzle of how these animals might see color in the world around them. So we're kind of complaining about this to Tom like pulling our hair out, you know how can these animals be seen color? All we're finding is the stuff that we already knew before he came down and was tinkering with some stuff and we had one of these preps up and we had these preps up and under dim red light to avoid bleaching the photoreceptors and the retinal preps. And you don't wanna bleach them except for under specific circumstances. But Tom of course, you know he's been working with a microspectrophotometry for years and so he flicks on the stage light and ruins the sample, totally fine. But I think it's because he had this hint that maybe there was something more to what we were looking at. And he said, guys, I think you need to come look at this. And what he was seeing was this ruby red spot in the center of the retina here. And we hadn't seen it because of course it's transparent to red light. So it was completely invisible under the red light we've been working on. We go to a bunch of our other retinal sections and sure enough in every single animal that we'd sectioned there were a couple of sections in each retina where there was this ruby red spot. And this turns out to be the key to understanding how these animals see the colors that I just spoke about. They have a long pass into a retinal filter built into their retinas right in this acute foveal zone here. And this actually is positioned in front of the light path of a set of green sensitive photoreceptors down below. So incoming light is going to be filtered by essentially a red pair of sunglasses such that only red light arrives at these photoreceptors down below. The consequence of this filtering pigment is that it shifts the functional sensitivity for this population of cells down below here from being largely green sensitive off into the far red. And the result is the ability to move from this situation to this. That filter opens up a whole new world of long wavelength colors for these animals to be able to see. Now, one of the interesting things about this is that when we discovered this mechanism it helped us to understand some of our prior behavior results. So I mentioned that I was going to come back to this. We get this strong response by females under full sun but in the shade and lower light conditions that it responds to red coloration is attenuated. And that can be fairly readily explained by our results for how they're able to see the red because this filter pigment filters out most of the light that these green photoreceptors down below are sensitive to. In other words, their red sensitivity is reliant on this little shoulder of sensitivity of these otherwise green sensitive photoreceptors. In other words, the red photoreceptor class is extremely light limited and needs lots and lots of light to function. So these animals essentially go back to being dichromats when they're in the shade. So we wanted to know whether or not this filter had arrived as one of these major transitions as an evolutionary novelty or an evolutionary innovation. So the red filter is fairly easy to screen for. We began sectioning the retinas of jumping spiders from across the jumping spider family tree. And what we found was that it was highly restricted to habronatus and close relatives here. And so what we think is that this red filter allows these animals access to colors they wouldn't otherwise be able to see. And that this sit at the very basis for the exuberant diversification of color in male courts of displays across this group. It's a new way to tell males apart, males of one species from males of another species, males that are of high quality from males that are of low quality. And this sets the stage for evolutionary diversification of color and male displays. These are just some of the species of habronatus jumping spiders that we have here in the US. I want to return to this because in the exercise of looking for these filters, we sectioned moratus, which is those peacock jumping spiders, and found that they had no retinal filter. So of course, we had to measure their vision and we find measuring them with microspectrophotometry that they're actually tetrachromads with the addition of a blue sensitive visual pigment and a slightly longer wavelength, yellow or orange sensitive visual pigment to the UV and green complement. So now this picture is moving from something like this to repeated major transitions. And this motivated us to begin kind of prospecting across the family tree for jumping spiders using things like bright color and male displays as a tell, a telltale sign that perhaps something has happened to the visual systems of a novel group. And there are quite a few groups of jumping spiders with bright color. One example of these is this animal, Lassertis rainbow spider or stenoluralis Lasserti from India. I just want to say for a moment that my heart really goes out to my Indian colleagues right now, whether at home or abroad because of the situation with COVID at home. And I hope that that situation turns around very quickly. This is a male Lassertis rainbow spider here. You can obviously see that he's using long wavelength colors very conspicuously. And I also want to point out that these long wavelength color patches are restricted to forward-facing surfaces. They're still fairly drab from above, meaning that these are likely to be used into an intraspecific signaling. And so when we measure these in India several years ago, we find again, another instance of tetrachromacy in jumping spiders, again with very different peak sensitivities for these photoreceptor types. So completely independent group of moratus or habronatus in totally different parts of the family tree of jumping spiders, we see evidence for these evolutionary transitions to potentially improved color vision. So we're really beginning to find enormous diversity in the retinal sensitivities of jumping spiders. And if you've been paying careful attention to these little schematics I've been providing here, you can see a kind of organizing principle, which is that all of these actually seem to be organized by that linear chromatic aberration I mentioned earlier. So they really are, their retinas are being organized in a way in terms of where they place their different color sensitive cells by that basic optical feature of their lens system. So this is spun into a really enormous worldwide project that we're having such a delight doing, although COVID has grounded some of our fieldwork plans. Here's a big family tree of the salticity. And this is kind of how it started and where it's going kind of set of slides here. This is the sampling of jumping spider visual sensitivities when we began working on them here. So some work in the late 70s and 80s and then that Nagata paper in the early 2010s. Largely told the story of dichromacy across the group. Yamashita and Tata's results in the late 70s were met with considerable skepticism by people like blessed and devote because they hadn't found evidence for anything else other than UV and green sensitive ones and Yamashita and Tata provided some evidence for blue and red sensitivity. So this was kind of provisionally accepted by the field at the time. Further evidence for kind of an ancestral condition of UV green dichromacy was provided by an out group, the wolf spiders in the Lycosidae up here, UV green dichromats. And so we've been filling this in with species across this group over the past couple of years. The overarching story is one of largely conserved UV green dichromacy. Lots of these groups out there, Lysamenone, the Hacerone, et cetera, are UV green dichromats. Here's the three unusual systems I already talked to you about down here. But in the process of looking across this group or discovering repeated evolution of long wavelength sensitivity, oftentimes very restricted in taxonomic scope, even within a group like the Spartyines, only some seem to have this long wavelength addition. Asteroids have a long wavelength addition. Hacerius has an additional one here. And so we see this kind of smattering of what we think are probably that mid-wavelength sensitive ops in duplicating and neo-functionalizing into a longer wavelength sensitive visual pigment. And this is work that we're following up with Megan Porter. Her group is doing a lot of the transcriptomics and genomics and expression analyses to understand this better. We also have evidence for a duplication of a UV sensitive visual pigment in the Spartyines here. But the overall this type of duplication event seems to be fairly rare, at least in comparison to this mid-wavelength sensitive ops. Interestingly, just a few months ago, we discovered what we think is probably a second origin or maybe we're seeing reversions but of this filter pigment. So there's a restricted group of plexipines that also have that with a lot of intervening tax of lacking it. So we're gonna need to investigate where that second origin, potential second origin of that filter pigment comes from. We're also kind of looking across this group, looking for red coloration as this tell, as I mentioned. And I just want to point out that sometimes things that we think should be able to see color much better don't. I'm gonna highlight Mexicanus right here because these animals, at least for our microspectrophotometric measurements are UV green dichromats. And yet look at these beasts. I mean, they're using red everywhere. So this is a disappointing in a way but also incredibly exciting because it suggests that these animals are seeing color in some other way or using color in some other way. In other words, we don't really fully understand yet how these animals interact with color in their natural world. But nevertheless, we think this big broad study is really helping us to understand big picture questions about why some groups of jumping spiders are so drab and other groups of jumping spiders are so brightly colored. So we're gonna continue this work asking questions about how these different visual systems shape evolutionary diversification of color traits in all of these groups in the coming years. All right, the last part of my talk is to talk a bit about work. We've been doing on dynamic displays and receiver gaze. And the way that animals allocate their visual attention in complex scenes is a whole area of study in its own right. We as humans, when we encounter a complicated scene with lots of things that might be visually demanding to us have kind of a set of both conscious and subconscious rules that we use to navigate a scene like this to acquire the information. If you're looking at this right now, your eyes might gravitate towards this face. Faces are very appealing stimuli to us. Things like flashing stuff, of course, are there to try to draw our eye to look at things. And some of this exploration of a complex scene like this is under visual control or, sorry, conscious cognitive control. And other elements of this are not. They, that we just have kind of rote ways of looking at things that we really can't help. But of course, jumping spiders are not in 1930s times square. What does a complex visual situation look like for a jumping spider? And it's going to be these displays or the complex environments that they navigate visually. So this is where our work is really focused is to try to understand where are females looking when they encounter a display like this in the midst of everything that's going on in the world around them that might be of importance. Predators or prey items moving around. Now you may be wondering, well, why am I talking about gays? We move our eyeballs around in our head, but these animals have these fixed lenses on the outside of their head. And the females not moving our head around. And that's true. The corneal lenses of these eyes are fixed to the side of their head. But I've concealed one last feature of jumping spider, vision for dramatic effect, which is that the very, very narrow fields of view of these principal eyes pose a challenge for these animals to look around the world. That combined pair of lenses means that these are like binoculars. They only see about two degrees of the world outside of them at any given point in time, at least in the horizontal plane. But what jumping spiders have evolved is the capacity to move their retinas around inside their head using a dedicated set of muscles attached to the back of this eye tube. So these are these blue bands here. Actually gives them something around a 50 to 60-degree range of travel here that they can use to look around the world outside without even needing to move their heads. And if you've never seen a video of this before, I really need to share it with you, because this is just a mind-blowing thing. So what you're seeing here is a juvenile jumping spider that is transparent. And you should be able to see those finger-like eye tubes moving around in its head as it's tracking that brush off to the side. You see this is a tiny animal. There's a Drosophila for scale in the upper right. Lots of people wonder, what's that little dot moving around inside its head? And that's actually something this jumping spider has eaten. If you can imagine moving around things the size of bratwurst inside your head while you're looking around the world, you get a sense for what this feels like to these animals. These are huge structures inside their head. And they move their brain around. They move their digestive system around as they look around. Excuse me, as they look around the world. Now, as these animals develop and become adults, which is, of course, when we want to study them in regard to this courtship, their bodies become opaque. And we can no longer access this information from the outside looking in, at least through the body wall. Instead, we use a second set of ophthalmoscopic techniques in collaboration with Beth Jacob and her lab, which allow us to look through the lens into the interior of the animal to monitor where their eyes are looking using infrared reflections off of these principal eye retinas. And we compare this with a playback paradigm where we present them with stimuli and then we can track in real time where their retinas are looking. And you can see that these boomerang-shaped retinas have XY movements. They also have the ability to do torsional movements where they can rotate those retinas as well. And they're pretty good at tracking objects like this little dot moving past. They also are quite curious about stimuli like potential prey items. So you'd see this increase in those torsional movements as they explore a stimulus like that. These kinds of torsional movements land, Mike Lant, speculated might be these animals using the wings of those boomerangs as line detectors to detect legs. But nobody really had worked on understanding how these jumping spiders look at these complex displays. So that's what our project is largely focused on is tracking the retinas as of females as they watch playbacks of male displays. So here's one of those sequences here with the left and right foveal regions of the retinas labeled here. And what you're gonna see is the female kind of looks around the display for a minute. And all of these females have this bored 1,000-mile stare where their eyes go to rest. In this female, it's off in the bottom right. She's done that now. The male's gonna hike his knees and she's gonna see those in her anterior lateral eyes and then zip over to look at them. And there she goes right there. And there's a little bit of a delay in that because of course she's seeing those knee movements in those secondary eyes which send a signal to the central nervous system which then coordinates the muscle movements to move the principal eyes over to look at the object of interest. So there is this built-in delay. What we can do is track in real time where these females are looking not only from instant to instant but also collapsed over time to try to better understand where females concentrate their attention during male displays. And one of the powerful things about this playback paradigm is that we can manipulate what females see. So we can create a full display like this. We can eliminate elements of this display. We can change where the colors are positioned on this display. To begin to tease apart whether movement or color or specific traits are involved in female gaze capture and retention. And so we can take a group of females and play them the same stimulus and then track the kind of group or population level behaviors of these gaze like you're seeing here. And this allows us to look at this data in a number of ways which I wanna share with you right now. This is very much ongoing not only in methods development but also in deriving insight from this data. But if we collapse this information over time you can see that females spend a lot of time looking in some areas and not others. And what was so exciting about receiving this data from my postdoc Daniel Zurich at the time was that he sent it to me without the male display under lane below it as I have it here. And yet I knew exactly where the male display elements were where those knees were going to be placed in the display and where those Tarsi flicks were going to be just by knowing where the female looked. I could see the male display. We are looking into manipulating this so if we remove those knee movements in the videos what we find is a significant decrease in the amount of attention. Obviously that females pay to this region of space where those knees would be. But rather intriguingly females still spend a lot of time looking just above the head in the location where those knees would normally be emerging which suggests some kind of perhaps even built in template for looking at these that could be even species specific. There's some anticipation for where salient or important male display elements might be. We can do grayscale manipulation such that females are really not seeing colored things but we remove the color and removing color really shifts where females look in space when they're viewing these male displays. Suddenly the things that females spend a lot of time looking at that were very colorful become less interesting and this is becoming true across species as I'll mention in a minute. So I wanna share with you a little bit more what this data looks like if we don't collapse it across time. We've called this a space time cube. It's really a three-dimensional histogram of where the majority of females are looking at any given point in time. And I'm going to try to swap over and load a more interactive version of this here so that I can walk you through what we're seeing. What you're seeing here with time going from left to right is a series of events. We've got them labeled as flick. That's those first leg tarsal flicks and then those knee pops coming up over the back. And so let's just look at it from the top down. It's just incredible to watch this as a narrative. Females become very interested in one of those two wrist flicks as we call them up here and then those male knees emerge above his back and she immediately begins looking at them. His other knee comes up on the other side. She switches over to looking at them there and she continues looking some proportion of the females then look up to these flicks again. But what the male is really doing is manipulating where in space females are looking. Now it turns out that if we look at removing color not only does it reshape where females are looking in space but it also shapes female attention or female interest by changing the length of time that females persistently look in a given area. So what we're calling attentional half-life goes down as we remove color. So these are really kind of rich representations of where females are looking here. So you can kind of see the concentration of female attention across space and time. So where we're taking this now is hang on I've just got to get back to my presentation here. This was working great. There we go, excellent. Where we're at now is we're looking across this group. Again, another large comparative study in Habernadas over a hundred species in the US to work from lots of variety in their displays and we're doing the same gaze tracking paradigm with them. So here's an example of this from Habernadas to Corus. Again, we get this concentration of female attention that's concentrated not only just on his abdomen but on his face and we get more information about how females evaluate displays over time. So this male abdomen is kind of wiggling off to the left here and you can see that she engages with it once then twice but her attention begins to shift more and more over to his body and to the rest of his display. So this gives us some sense for how females essentially consume the available information in the male display. The other thing to note here is that these animals are really diverse in terms of their habitat usage. So some of them live in leaf litter or on rocky cobbles and sand and montane forest clearings. And so we're using this ecological diversity to really explore how the circumstances, the visual ecology of these animals shapes properties of the colors that they use in their displays as well as the properties of the movements that they use when courting to achieve saliency, contrast with the background, not just in color contrast, which has been studied quite a bit but also in motion contrast with the background. So what you're looking at here are all videos of their environments. And you can see that some of them have almost no movement in them at all like this red rock scree here whereas others are gonna have more motion like this one here, a grassland habitat that has a lot of horizontal motion. And so we're processing this using computer vision algorithms to monitor kind of optic flow in these different environments and then asking whether or not that might drive selective pressures for particular colors and motions in these displays. So I just wanna end today by sharing some of the diversity of displays that we find in this group here. Here's Habernanus Hursutus named Hursutus for being, so Hursutus, so Harry, these are our boreal species. And we think that the twitchiness of these male display movements may actually be really quite salient against the largely swaying motion and the mesquite bosques within which these animals live up in the bushes and in the canopy. Here is Habernanus Halini, this animal here, we like to call Mr. Sparkle Pants in the lab because he's got these iridescent under surfaces to his legs here. And he actually reminds me a lot of those birds of paradise that we keep seeing footage of in the way that he kind of moves side to side orienting all of that iridescent color with the occasional flash of some of the colors in his movement here. And see him come back across here. Really spectacular animals. All different strategies for capturing and retaining female gays and hopefully eventually convincing the female to allow the male to mate with him. Here's another one here, this is Habernanus Organensis, we call him Popeye for the obvious reason here. And he's just a weirdo, he just kind of ogres his way around like this here. And the last one that I wanna show you here is Habernanus Americanus. And he's named of course, because he's red, white and blue but he's also a spaz, he's the subject of lots of Fourth of July memes in my lab. But again, look at that incredibly brilliant red underbelly that he's got here. I never get sick of watching these animals do their thing and they'll do it on an arena the size of a CD or a small dinner plate, which makes them incredible behavioral models. So to return to the kind of broad schematic of the talk here I hope I've convinced you that not only is our work discovering major transitions for example in color vision, driving diversity across this incredible animal group but we're also making some headway and thinking about processes within clades, things like attentional processes and sexual selection that might be driving the particular forms that this diversity takes on and how that interacts with the environments that they live in. So if you'll stick with me for just two more slides I wanna talk a little bit about why we do this kind of work. Of course, we're interested in diversity of life but I wanna point to some of the broader value to human society for this. Things like jumping spiders provide us with exceptional inspiration for novel technologies that can solve some of the pressing technological challenges that we face. You might not think that an iPhone or phone technology is pressing technology until you realize how much of the ability to enact change in our world in terms of abuses and police violence, et cetera come from the simple devices of our phone cameras and the telephoto lens, wide angle lens pairing of the most recent generation of iPhones is really very similar to the ways in which jumping spider vision works. So perhaps there are ways of learning novel algorithms or novel techniques for even improving upon that. Actually, one of the early Mars rovers contained a system with a moving sensor that was very much inspired by jumping spider vision. We've been talking with folks in the self-driving car industry because they face the challenge that jumping spiders face which is that they have an enormous inflow of information that they need to use to make sometimes life or death decisions on split second behavioral timelines. And of course, these Ubers like the self-driving Uber here do so by crunching all that data in a liquid cooled supercomputer in the trunk but that's just not sustainable as a mechanism for rolling that out more broadly. So are there particular ways in which jumping spiders down sample types of information that could be used as an analogy for novel technologies for self-driving cars? And of course, something as small as the jumping spider eye with its visual capabilities could provide real inspiration for biomedical sensing. And I just wanna give a quick shout out that we've started a brand new research institute that I'm leading as director here at the University of Cincinnati with wide reaching collaborations across campus and medicine and engineering and across arts and sciences here with external partners called the Institute for Research and Sensing or IRIS that seeks to bridge this gap between natural and engineered sensors in new ways. But these applications really aren't what drive me personally. And so I guess the note I wanna end on is that what drives me personally is curiosity about the world, that boyhood joy and discovering the intricate and unusual alien lives of things that we share the planet with. I really fell in love with this planet as a boy and have retained that love over time in part because of this extraordinary opportunity to continue to look carefully at the world around us. And I think that curiosity is something that is a deeply human thing. Oftentimes curiosity driven sciences is a pejorative designation. And I don't think it should be because I think part of what it is to be human is to be curious and we should value that and we should honor that. And part of the way of doing so is to look carefully at nature with curiosity. And perhaps that will allow us to fall in love with nature which is really what we need to do in order to save the planet from many of the harms that we bring to it every day. So that's where my passion comes from is that this is me with my younger sister. I still feel like that inside. And so I just wanna end by thanking lots of folks, collaborators that have kept me sane and stimulated my thinking and gone to the field with me. We've had really extraordinary luck with funding from the National Science Foundation. I really appreciate their support. The University of Cincinnati is just an absolute joy of a place to be doing this kind of work with strengths and sensing and sensor technology development and sensory biology all across campus. And I'm happy to answer questions in the session that follows up on this but that's what I have to share today. So thanks again for being with me and look forward to questions in the discussion afterwards. Well, thank you and that was very interesting. I mean, it's a mesmerizing complexity for such a tiny animal. I would like to ask you something about the four remaining eyes. Do we know anything about their composition? I mean, are there other spectral absorbance? Well, so they have in jumping spiders that have two secondary style eyes that face backwards. So that gives them almost a 360 degree view of space. And again, they're much like those anterior lateral eyes, green sensitive, motion sensitive, modest resolution eyes. And then those are called the posterior lateral eyes and then they have a very small, almost vestigial pair of posterior median eyes that face skyward. And one of the unusual features of those eyes is they're not always properly image forming and they express a blue sensitive visual pigment in those. So those may be guiding, they're kind of an up-down response, their attitude stabilization in a way as well as their circadian rhythm. Whether they do anything with polarization, we don't really know, but yeah, that seems to be how those are distributed. And I just wanna say that what's unusual is we almost never find that blue visual pigment expressed in the principal eyes, which is odd. They have the ops and in their genome as part of their ancestral ops and complement, but it seems to only ever be expressed in those posterior median eyes for reasons that we don't understand. It would obviously be really useful in all of vision. That's a bit of a mystery still. Sorry, very positive indeed. I have a question, sorry if I said the name wrong from Schumann-Kars-Saha. So he has a question related to your experiment about matings. How do you take away the probability of actually getting rejected by a female when you have colored the male with red? Does a female have any idea about the male population of the female? And by that he meant that rejection acceptance can be a function of multiple parameters and not any color. Technically, how can you, how do you control all your parameters to drive the decision of mating? Or addiction in these cases? That's a great question. Obviously there's a lot more going on in the male display than just the color of his face, right? And males can differ in the amount of time they spend courting and the vigor of their courtship. And in a separate set of experiments with the same species, which I didn't have the time to share today, we also measured those kinds of courtship effort measurements and those are very influential in the male's ability to court and move through his sequence of courtship events. So the amount of time the male spends courting, the vigor of his display, both very predictive of male courtship success. Obviously we cannot control for that in this circumstance, but Lisa worked very hard to try to kind of size match males between the two treatments and to monitor what's called male conditions. So his weight versus his body size to make sure that anything we could control ahead of time was controlled for. But again, differences in male motivation can vary and we couldn't control for that there. But the one thing we knew for sure different between those treatment groups was whether or not the male had experienced this blackening of his face. So we think it's pretty good evidence that that at least plays some role here. I agree. I forgot to tell the audience that if they want to come here and as they question themselves they can follow the link that was post on a YouTube chat or if you just want to join us for a post-poking formal session, please do so now. I have a follow-up question actually about this regarding your gazing experiment. So you actually showed what it's an array of interests a female may have during the courtship behavior. Did you estimate what was the wrong move, let's say for the male to be rejected or eaten? Do we know what's the wrong move might be in your gazing experiment? No, I mean, that's of course very difficult in that situation to do because the females are tethered and they're presented with this playback stimulus. So we don't have any real way of knowing whether or not they might lunge at a male if he's made some kind of wrong move. We're now to the point where we're using track ball methods to track where females fictive path might be in response to some of these displays but that was not part of our original formulation of that paradigm. So we don't really know. I would say that mating is fairly rare as an outcome for these interactions as well. It certainly is in the lab. One of the reasons for this is that females only typically mate once, sometimes twice over the course of their lifespan and these animals live for a year and a half, probably about a year as adults in many instances. And they can be courted by males as at peak population densities once an hour. So that's a whole lot of rejection, right? And not a whole lot of acceptance. So one of the limitations of this system is having enough of these acceptance events in our dataset to know what truly predicts that. We can look at the amount of time that females spend engaged with the male display. We can look at the number of times females attack males. We can look at how close the male advances in his sequence of courtship display elements. But that final seal the deal on mating is a relatively rare event just given the mating system dynamics here. It probably also places a lot of pressure on the male because he knows that it's unlikely but he really needs to give it his all. So we don't have good information about what leads males to kind of be accepted yet in terms of that final stage. More variables than just the preponents. I have a question from Tom Badden. Who are the main predators of jumping spiders? As a big enough to be interesting to birds? In other words, what is a counter-drivers of then being a couple? As in particular, as a deep red for spider-faces, my two red for most insect visual systems? What about these odd frogs, et cetera? Yeah, it's a great question. Depends on where you are in the world. I'm sure that birds are jumping spider predators. I'm not aware of any jumping spiders that are chemically defended in terms of being toxic to consume so they're gonna largely be a fine thing for birds to eat. What I would say is that perhaps when looking at jumping spider, natural history, physiology, et cetera, I would say that one of the things that seems to be more of a threat to them in terms of the things that they've evolved to be able to detect are wasps. There are a lot of predatory spider wasps that are moving around hunting for them in every field environment that we go to pretty much. There is a guild of spider hunting wasps out and about. They seem to respond very clearly to wasp frequency sounds in terms of wasp frequency, wing-beat frequencies. And they also have those posterior median eyes that seem to be attuned perhaps to looming responses. So I think one of the major things they worry about as jumping spiders is these spider hunting wasps. Of course, there are other things that might capture them to praying mantises and things like that. But my guess is that the thing that keeps a jumping spider up at night are these predatory wasps. I have a question here from James Stone, which is with us. Who's with us? Sorry, if you want to ask a question yourself, you ask if you can say anything about depth perception in spiders. Maybe, James, you want to elaborate? Well, I mean, I can certainly answer that. So that is a really fascinating topic that actually intersects with some of the work that I talked about today. The Nagata paper that I mentioned from 2012, Demonser provided evidence for an image defocus mechanism for depth perception in jumping spiders. Pretty fascinating. So jumping spiders can still judge depth even when they only have access to one of their principal eyes, which suggests that they're doing something within a single eye to see depth. And the notion there was that what these animals were doing was using that chromatic linear aberration to estimate depth by comparing how in focus or out of focus images were in the bottom two tiers of their retina and tiers one and two. So the idea was that light would be in, green light would be in best focus in tier one and less well in focus in tier two and that disparity in focus between those two tiers could give them some estimate for distance. What's interesting about our work in relation to that is that we're showing that they have a variety of sensitivities in that very bottom tier. And so what that implies is that there may be some conflation of color and depth cues. Even in the instance of having both bottom tiers be green sensitive, this system would lead to red stimuli looking closer than they actually were. They would estimate red objects to be closer. And that may actually offer some clues into the use of red by prey and by males because these may present a kind of looming large feeling or when contrasted with things like blue stimuli might create something of a depth illusion, which is something that one of my students is investigating right now. Are these animals and their prey using blue and red contrasting patterns to create a kind of depth illusion? We have the same thing. We have a little bit of linear chromatic aberration in our eyes as well. And when you put like a magenta and teal blue pattern your eye kind of has a hard time of figuring out it kind of vibrates back and forth. And we think that something similar may be happening for these jumping spiders as a consequence in part of this depth perception mechanism. But it's something that we're investigating and of course it involves actually looking at the optics of some of these species with modified color vision and whether or not they tweak the optics and optical parameters to try to focus light at different depths is not really clear. It could be interesting to see how you control this kind of experiment. We'll be looking for that. Yeah, yeah. Well, we're starting with locomotion and looking at whether or not they misestimate depth when they're moving to red platforms or to contrasting platforms and things like that. I have another question from Tambaden. Can you use the gaze tracking approach to estimate the actual visual features? For example, red moving spots that drives specific types of high movement. To make prediction about the neuron doing this, for example, by using a reverse correlation, no stimulation. Yeah, good question. So yeah, absolutely. The playback paradigm is really open for all sorts of psychophysical approaches. What we're using it for right now is to really test color vision. So although I gave you the circumstantial evidence for it from the prey attack experiments, what we'd really like to do is get things like wavelength discrimination curves. And so what we're doing there is we're moving dots of different colors that are isoluminant with a different, with a background of a different color to look at where the boundaries of chromatic contrast exist between stimuli. And we just pulled the trigger on getting a UV green, red projection system so that we can expand that down into the UV as well. So of course these animals see in the UV, we need to be projecting metamers that are UV, green and red. So, but lots of open questions there. Beth Jacob and Ron Hoy are pursuing some of those questions, but we were also working on the kind of color vision side of things. So yeah, exciting to see where those kinds of things. We'd love to hear, Tom, if you have ideas about clever experiments to do with that approach. Ideas we have plenty. Before I continue, I just want to say audience, I'm going to end up the stream on YouTube soon. So if you want to have this discussion, please join us. And if you have any questions that you want to be asked, do that now. Regarding the UV parts that you were talking about, I have a question from Gregor Belichick. Does the addition of long wavelength vision cause any inflation on the brain? I'm not sure I understand what you mean by that. Yeah, that's interesting. So Gregor, I'm assuming that you're asking whether or not brain regions tasked with processing are increasing complexity or size. We don't really know that yet. I would love to know that. There's huge diversity in brain region size in jumping spiders and across jumping spiders in general. There is kind of a separate processing pathway for the principal eyes from the secondary eyes that then is united in the central nervous system that we think maybe in the RQ8 body, but that's not even very well worked out. There was work done to trace some of the kind of first tiers of that already, but we don't have it for any of these unusual color vision systems. So I'd love to know that more. There's also the related question of whether or not there's any proliferation of the number of photoreceptors because you might imagine that these transitions might require especially if the different spectral sensitivities are interdigitated in that tier one, for example, it might compromise to some extent spatial acuity. We don't really know that yet, but we'll have a better sense of that as we begin doing kind of comparative retinal matrix measurements across these jumping spiders. So I guess stay tuned. Do you want to hop in and help? There's a lot to do on this front and looking forward to collaborating with folks on it. All right, so thank you for that. I will end up the YouTube stream now. So thanks for being with us today. We will see you next week. I mean, looking at the audience obviously. We have heavy buyer coming with us next week. So thanks for being with us every weekend. See you next Monday. Thanks so much. Really appreciate it being here.