 Yeah Hello everyone and welcome for another vision web seminar if you are new to this talk series I would like to mention that these talks are part of the worldwide neuro initiative It's a coveted inspired platform that for the last year has allowed fellow neuroscientists to present their ongoing work and a load Continued interaction with their peers within their own respective field of city So you might be interested in looking at the upcoming talks and topics. There's also plenty of podcasts already available Including our own from the University of Sussex vision series But also from to begin neuro campus group and also from the bar Elon University vision sites And of course you have also all the topics not related to vision You will find all the relevant links as usual in the description Today, we are glad to receive Michael Bock Michael obtained his PhD at the University of Maryland under Thomas Croning supervision He then moved to Sweden and John Danielsson for a postdoctoral position Is now a senior research associate the University of Bristol here in the UK His work focuses on unusual visual systems of a variety of marine invertebrates ranging from the Regimentary compound or silly of a farm worm to the Spectacular if sophisticated eyes of a mantis shrimp It's currently working on farm worms and aims to unravel the developmental neurological and behavioral factors that drove the evolution of these simple eyes and Perhaps also influence the origins of nature's very first visual systems In completion of his lab work, Michael is also a seasoned diver and a talented photograph I will encourage you to visit his website where he posts stunning pictures of his model of study Actually also in the description Some of these pictures were actually used as journal covers and I'm pretty sure that you've seen Already at least one of them. So hello Michael. Thanks for being with us today. How are you doing? I'm good I'm very happy to be presenting here so What do we have for us today? Oh, I go now. All right. Let me share my screen and Hello, thank you very much for the invite to present at World Wide Neuro Sussex Vision Talks I'm really excited to talk to everybody today and I'm gonna be presenting to you a bit of a combination of some various things I've been working on for the last 10 years or so Both from starting in my PhD come through my postdoc and all the way up to what I'm researching now At loon's where I'm back now I've moved from Bristol back to loon just recently Where I'm a researcher now at in the vision group at loon University And I'm gonna be talking to you about the blurry beginnings What nature's strangest eyes tell us about the origin and evolution of vision and the two animals that I'm going to be speaking about today are Mantis shrimp and bandworms They're both marine. They're both quite pretty and quite a lot of fun to work with in my opinion And I hope you agree by the end of the presentation The main thing in Research that I'm very interested in personally is thinking about how do eyes evolve? How do we get all these wonderful complicated? Precision visual organs and all these different kinds of animals. How did they get this way? What do they do and how do they function? The one reason I evolution I think is a very special fun thing to study is if you look at the history of life on the planet earth Back in the pre-Cambrian before the Cambrian explosion life in the ocean was a bit simpler a lot of filter feeding Some animals sifting through the sediment jellyfish floating around But not not very much excitement and then suddenly Suddenly in geologic terms after the Cambrian explosion you get this incredible diversity of animal forms You get a lot more Drama happening you have predator predators hunting things you have prey running from predators You have animals foraging and orienting and navigating and there's some Speculation that a lot of the factors that may have been driving this Cambrian explosion are sensory And I like to really think that once an animal once animals evolved eyes that really gave them the ability to Facilitate these much more complicated behaviors Of course, it was probably multiple factors that contributed to the Cambrian explosion But once you have vision you can assess your world at essentially the speed of light So that's an incredibly advantageous Development that you can then exploit in evolutionary time So the eyes I'm going to talk about today in nature. There's basically two types of eyes There's compound eyes and simple eyes compound eyes There's a single photoreceptor unit behind each individual lens or facet in the compound eyes and insects These are called omatidium. I'll be calling them Ocelli today. These individual Optical units with a single photoreceptor and you put many of them together to make a compound eye Then there's the simple eyes which is closer to what we have which is what we have Where there's a single lens element and behind that single lens element light is focused on to a whole array of photoreceptors from single lens so those are the two types of eyes you find in nature with some Exceptions and all kinds of crazy modifications If you look across all the different phyla of animals you can see examples of these two different eye types You'll see some phyla have both in different species. For instance, the mollusks have compound eyes and some clams And simple eyes and a lot of cephalopods and some mollusks some other bivalve mollusks but this is incredibly a Beautiful diversity of eyes from different animals from different phyla and you there's exact There's examples of convergence here and all kinds of diversification. So there's lots of good things to study in an eye evolution I'm thinking down to basics about how a precision instrument like an eye Gets to where it is today in humans being able to do very complicated tasks related to resolution and color vision and polarization vision and all these other types of visual modalities You'll often see on creationist websites this quote from Darwin from the origin of the species Where he professes that to think about an eye which is such a complicated organ Having evolved by natural selection seems absurd in the highest possible degree the creationists usually do fail to Say the next sentence that comes from Darwin where he lays out quite nicely that if you can imagine minute gradations each one causing a little bit of increase in Fitness you can go from something that does a light sensitive nerve all the way through to a complicated eye by really small gradations and changes And Darwin and others later used Examples from extant animals to illustrate this point. So the one of the classic examples is in mollusks You can look at extant animals within this group that have all the different gradations On the way towards making a very nice eye. So these simple little um What the heck are these things I forgot what this species was but there's a many species that limpets. I think I have just simple receptor patches Others have a cup eye that gives some more directionality The nautilus famously has a pinhole eye Without a lens but give the working like a pinhole camera to give them some resolution of the world And then a lot of other the squids and cuttlefish and octopus have very nice simple eyes That look a lot like ours, but you can you can learn about how eyes evolve at looking at what Extant animals use these different types of eyes for and how these different types of eyes function And it turns out Eyes can evolve quite fast Even with extremely conservative estimates for these different steps to get from a simple receptor patch all the way through to a complicated lens eye Using computational methods You can get as low as 364 thousand generations, which is quite a lot of generations But evolution in in long evolutionary time. That isn't so bad So it isn't that hard to uh to go computationally from a simple receptor patch to a nice lens eye um But there's a lot more to it than just the structure of the eye So we think about how you go from just simple light sensitivity from having a photoreceptor uh with a photopigment in it, usually an opsin with a chromophore That gives you some very simple idea of luminance in your environment Uh, then you can get a pigment cup around that photoreceptor and that gives you some directionality to the uh The vision you can tell if a light's coming from one way or the other because light coming from other angles is screened by the pigment cup Um, and at that point you can take two different paths You can make an ocellus with a lens on it and then you can start multiplying the ocelli into a compound eye Packing them together and creating more and more complicated compound eyes And then the other route is to make a pigment cup Uh, and then make a cup eye with multiple photoreceptors in the same cup And then eventually put a lens in front of it kind of like the cephalopods did And and that's the the structural level of thinking about it But you have to think about other levels of eye evolution as well Because fitness does not actually work on having a nice eye just because you have a nice eye doesn't mean you Uh are more fit and more likely to pass on your genes um The eyes need also to have uh an increase in neural processing when you make the eye more complicated So the optics can be the information coming in through the optical components can be processed And then they can be used for visually guided behaviors and that's what fitness actually works on If you can do a new task with your eyes, it can make you more fit So if you can spot a predator better, you can you are more fit if you can tell Where the sun is in the sky so you can navigate better you're more fit And then you can pass on your genes and create this continuity all the way from Structure of the eye to the neural processing and then through behaviors And all of these things are required these steps Are required one another in order to advance to a more complicated visual tasks And they're irrevocably tied together So we know quite a bit about How maybe the some of the first photoreceptor systems may have worked from molecular studies and the fossil record You know, uh quite a bit about how high resolution vision works Sort of our eyes or animals with very complicated visual systems But understanding how animals Climb this ladder from non directional photoreception to directional photoreception then to low and high resolution vision That that's a harder thing to study because it's kind of blurry and squishy so I First in this talk today. I wanted to talk about the animals that we've Um highlighted as a a really good way to study how you climb the ladder from simple photoreception up to higher resolution vision by stunning an animal that Seems to have eyes that sit in the middle of this progression and we we call it low resolution vision area but Making the transition from directional photoreception to higher resolution vision And that is the fan worms These are really really spectacular analysts They Are sessile they uh, they live in these tubes on the substrate That they secrete themselves Um, and most of their body is completely hidden within the tube Uh, you can see in this video down in the corner. That's what a fan worm does all day It sticks these tentacles called radial or tentacles out into the water column to filter feed all day And then the rest of the worm the head the thorax the abdomen That's all down inside the tube. The only thing that's sticking out are these tentacles And because the actual head the ancestral head of the worm is hidden inside of the tube all the time They've had to evolve eyes on these tentacles to in order to be able to spot any encroaching threats To make them aware of a predator predator that's coming by to potentially nip at their tentacles And this is what they do when a predator comes by. This is their one simple visually guided behavior And blink and you miss it. Uh, a shadow went over and the worm shot inside its tube as fast as possible He'll come back out again in a second and and repeat the Um performance in one moment so you can see it this time Um And they'll be you'll see a little bit of adaptation here as well to take two shadows to make it jump inside this time um But the point is uh this one they have this one simple visually guided behavior It's a directional alarm or a shadow response um And to be able to work on an animal that's doing one thing with its eyes And uh being able to you can really in a fine tuned level drill down to the the uh neural processing the uh And the behavioral response that comes out of their visual system So that made that made them an initially really attractive group for me to look at um But then we had an idea from the literature that there's some diversity of these eyes and these speed in these creatures so Uh, we want to take a closer look at as broad a diversity of fan worm species as possible to see what the Structure of these various eyes was so this was of course a very nice excuse to go to A very beautiful coral reefs where you get huge species or diversity of marine animals so As usual with my research, this is all a thinly veiled excuse to go diving in the tropics a lot And we did that and we looked at a lot of different species of fan worms And we've really found out that the the structural diversity of these regular eyes is quite spectacular um Many species have our eyeless. They don't have any apparent photoreceptors or eyes on their feeding tentacles Some species have these very simple photoreceptors scattered all over the tentacles These little individual tiny photoreceptive units just scattered all over the place pointing in random directions Other species seem to group them together into these more consolidated masses of photoreceptors And then you start to get into species that have things that look like actual compound eyes You're starting to get nice rounded concave structure to them and lots of these facets organized into a A nice compound eye And you get all the way up to some species that have between 500 and 1500 facets in each one of these eyes and they position them now on the tips of their tentacles So across the group a tremendous diversity at how complex these compound eyes are And just like I showed you earlier with the mollusks, you can then arrange these as nice extant examples of different stages Of eye complexity that you can then test Hypotheses about what behavioral New new behaviors and what new neural processing can be done And needs to be done in order to be able to function at a higher level with your eye at all these different stages and different levels of structural complexity And you can also get some very very strange examples in the fan worms. These are Christmas tree worms if you ever go diving you see these Very brightly colored pear Christmas trees sticking out of varieties coral heads everywhere And if you actually look closely at them, they're they've got a pair of very strange banana shaped compound eyes one of the few concave compound eyes in nature that I'm aware of and really really interesting strange structure that it's not quite sure why it looks like that But anyway the Really these eyes are an evolutionary playground Like as I said, you can see a plausible progression of eye complexity in extant species But there's other really interesting things about these eyes First of all, they use ciliary photoreceptors Ciliary photoreceptors are the kind of photoreceptors we have in our eyes A lot of invertebrates use microvillar photoreceptors for their visual systems So that's a that's an interesting departure that we see in these fan worms And other analytes use microvillar photoreceptors in their eyes Like platinorase or yeah, I mean these other erin polychaetes Also, they have a hyperpolarizing light response, which is fairly typical of certain receptors But again puts it at odds to how the visual photoreceptors work in a lot of other invertebrates They use an unusual opsin gene we found most Invertebrates in their microvillar photoreceptors use a gq type opsin a microvillar opsin The fan worms are using opsins from this strange poorly understood clade of c opsins closer to our visual Opsins than to other invertebrate visual opsins The thing they're most closely allied to are these deep brain invertebrate photoreceptors So it seems like they've just pulled this We don't really know what they're it's used for in many of these animals Pulled this deep brain photoreceptor opsin out of their genetic toolkit and plugged it into these eyes that they've developed on their tentacles Not no other animal uses one of these opsins and something that you would call an eye And every species every species of fan worms that has eyes expresses one of these c type invertebrate opsins As well as some other opsins in some cases, but it seems the c type opsin is the primary driver of their visual system Um, and also the most surprising thing we found was that the structure of the individual cell Eye from one species to another is extremely diverse So we assume that they were just using the same sort of receptive unit and then grouping together more or less of them in a more or less Structured way to create more complicated compound eyes It turns out that is not the case and that almost every individual genus of fan worms that we've looked at has a unique structure of these individual cell Eye Different cells are creating the lenses different the lenses are made out of different material different numbers of Cells are responsible for the overall unit It seems that the in the the the photoreceptor cell is conserved the ciliary photoreceptor cell But then everything else about the optical structure of these the cell eye is Completely unique in each group and there's so many different kinds of optics Some have typical glycogen type lenses others use dense masses of things that seem to arrive from mitochondria as a Sort of an ellipsoid body type refractive structure Other species have a torpedo Where they reflect the light back through the photoreceptor sort of like a cat's eye at night And some species may even have a polarizer built in made out of my my derived mitochondrial rods That might help limit cut through the haze in the aquatic environment a little bit But the point here is that every single genus seems to have rolled the evolutionary device and come up a dice and came up with a different fundamental Ocellus unit and then grouped them together to greater or less complexity So it's a much more complicated story of the evolution of these eyes and we originally thought we're working Uh a lot harder on trying to understand that right now how these different Outcomes are apparently being used for the same exact task And the other really interesting things about these fan worms is that they have many species have distributed eyes There's a few examples of these in the invertebrates box jellies for instance have These rupalium that have a bunch of different optical units on them pit Little cup eyes as well as two big lens eyes and there are four of those around their bell Um the kind of worms like starfish have eyes on the tips of their tentacles A lot of mollusks have dozens or hundreds of little eyes all over their mantle This is an example of a scallop I'm less thrilled to eat scallops now that I know that I have pretty little shining blue eyes all over the place Uh a little bit too cute in a way And then also the analytes these fan worms have Many species have dozens or hundreds of these simple compound eyes scattered all over the place And these sorts of individual systems depart very heavily from our visual system where we have two consolidated eyes On our heads that we very nicely control where they're pointing Um it becomes much more hard to understand what kind of behavior can be controlled when you have dozens or hundreds of eyes pointing in every direction At the same time often with poor control over what they're pointing at. How do you Filter out all the overlapping redundant chaos of a visual system like this in order to actually control uh visually guided behaviors And the fan worms are a very nice species with which to answer this question Because uh we have species that have nice a pair of nice big consolidated compound eyes And then they live right next to Species that have dozens or hundreds of much simpler eyes And they're using them for that same exact behavioral escape response So it's a really great system in which you can study the trade-offs. So these two different strategies to imaging the world And we're doing this from a very narrowly ethological perspective We're looking at how the uh photo receptors actually function How the brain is processing that information and then what's uh the actual behavioral outcome what visual stimuli are these Uh distributed versus consolidated eye designs able to actually help the animal achieve So we've done a bit of work um on the actual electrophysiological response of these eyes And we found that they respond to blue-green light which makes sense in a shallow marine environment It's good to spot a silhouette of something coming at you if you see the green light behind it Which predominates in that habitat? We've also found surprisingly that the uh the temporal resolution of the eyes the flicker fusion Of the eyes is actually quite high for a distributed eye shadow response alarm system They can respond to around 35 to 40 hertz Which is on par with some of our photoreceptors So so quite fast for a startle response system Usually you'll see in in mollusks in scallops for instance a much slower temporal response And that helps them to actually filter out a lot of the chaotic wave flicker and other visual information in a marine habitat and be able to simply resolve on something coming Coming at them So it somehow this is complicating things downstream in the brain for the fan worms Because then they have to process a lot more Temporal information about their light habitat out in order to actually see a threat And we've worked a little bit about how these photoreceptors are being processed in the brain They project all the photoreceptors from the eyes project directly into the brain of the animal And they synapse into these mushroom shaped Structures in the brain Directly adjacent to the giant axons the giant axons are the the darker pink Thing the pair of darker pink pink circles you can see here So you can see the eyes communicate very nicely to this giant axon startle response system that they use to then shoot themselves inside the tube We want to learn a lot more about how what the processing that's happening in these mushroom shaped nervous structures Is what what is actually going on there? And I really quickly I wanted to show you some experiments that we've done very very recently Looking at behavior of these fan worms. What visual stimuli can they actually respond to? And so to do that I went for the species that actually had the most complex Eyes that we could find the most complex consolidated eyes And unfortunately it was in the uk instead of the tropics, but Cornwall is a nice enough place So I was not too sad to have to go there Um, and this is uh acromegaloma vesiculosum. It has a pair of these very nice compound eyes With each eye having between a thousand and fifteen hundred uh facets in it So those are putting it on par with a lot of insects And here they are in their native habitat uh all these little brown tufts you see everywhere are actually the fan worms If I was diving here, I would never see them out like this But I have a little white colored drone driving around right now And they're not afraid of white objects. Um, they're more interested in a dark silhouette coming at them So this is the only way to really see them hanging out Uh, if I go in the water, I never see them But you sometimes when it drives really close See they see the camera on the drone the black circle of the camera and they'll jump inside So we we collected these down in Cornwall and then brought them into the lab in Bristol And I set them up in these cubicles in the lab So they're all fixed in with their tubes in a little clamp in front of a screen And they have dividers between them so they can't see each other But uh, they get to have this Little arena where they can look at what's on the screen kind of like uh office workers in a cubicle And then onto the screen I can project various stimuli And you see here that many of the animals respond to a black circle encroaching on them and much fewer Are interested in a white circle encroaching on them because the natural stimulus they're Looking for is a silhouetted predator moving towards them To come take a bite out of their feeding tentacles So we were able to use this to test a the consolidated eye species versus a not a species that we got from the tropics that has distributed eyes Scattered all over its tentacles with much lower potential resolution in each of the eyes And we can make comparisons of how well they're able to discriminate Different looms and different rates of looming and different times of stimulus And so you can see here quite clearly that Um, the consolidated eye species is able to detect much smaller truncated looms Uh, so a loom that increases only to a certain size Than the distributed eye cc. So that's a obvious advantage of having a more complex larger eye with more facets You're able to detect smaller threats And also interestingly we've showed them lots of different kinds of stimulus and you see some examples of them on the bottom of this graph here Mostly the two different types of species perform similarly But it seems that the consolidated eye species gets a little bit more of an advantage Being able to detect and respond to a looming or a moving stimulus versus all of these other types of stimulus that essentially affect the same thing In the appearing the fading and the light shrinking All of those have an overall decrease in luminance of the stimulus But these three here the appear fade and light shrink are not very natural of the predator approaching them predators don't appear into existence Right in front of them. They don't fade in While keeping the same size And if you see a light shrinking away into the darkness like that, you've already been smaller than it's too late So it seems advantageous to be able to detect something doing an actual naturalistic predator behavior either coming towards you or uh moving past And we've also found that the consolidated eyes are able to detect Very slowly creeping things looming up on them So these are the examples of the speeds of above 50 response threshold of The angular expansion rate of the looms and you can see that the uh, the this Consolidated eye species has a very broad curve here And so we can see very slow moving things and very quickly moving things coming up on it and respond to them quickly Whereas the distributed eye species has a much more repressed or flattened and decreased sensitivity at the extremes so In summary, you seem to get a lot of visual advantages from having these nice big consolidated eyes They provide improved spatial and motion detection And they are also more economic So if you cram all of your photoreceptors into the same place and organize them nicely You don't have as much Overlap where if you have hundreds of eyes pointing all over in different directions You waste a lot of pixels looking at the same places and create a lot of Processing load filtering out noise in a system like that um But the but also you get the advantage with the distributed system where the eyes are much more redundant So if you lose a tentacle, you don't really lose much information about the world Whereas if you lose one of these nice compound eyes Consolidated compound eyes you lose half your visual world But it's it's really surprising then that The consolidated model isn't more common in these groups. Most species have distributed eyes or scattered eyes Only one genus really has these very nice consolidated eyes And with the visual advantages you get it's really surprising that It hasn't become more purple in the group So I'm gonna Have a halfway point here. You can read more about these fan worms and the work we've done on them here These are some of our recent papers But moving on to the next section of the talk I We I think the fan worms do a very good job of covering this central area of this evolutionary Continuity of eye eye evolution But then it's also interesting to look at eyes that Really elaborate on these simple eye designs and and do some really wild interesting things with it And for that we're going to look at the mantis shrimps And they are probably one of the coolest animals in existence in my opinion The they're really beautiful and they do really interesting things with their visual system. So Uh, they're a colorful and diverse group of a marine Uh, malacostric infestations, uh, they are about They're an order of about, uh, 500 currently described species Uh, they range in size from 40 centimeters down to little thumbnail sized Species and as you can see here, there's a tremendous diversity and in color In size and uh within sometimes within the same species. There's quite a lot of Dymorphism between males and females or between different individuals. So really spectacular to look at Really really pretty animals um The other really cool thing about them is that they're uh, these really feisty aggressive Predators they use these specialized arms called raptorial appendages for hunting um You zoom in on them, uh, they they hold them like this most of the time But if they can then either swing out their arm to hit with the elbow Or they can actually open up their uh, their raptorial appendages and stab with the dactylis uh segment So But you can group the different species of managed shrimps broadly into into two different Classifications uh smashers which have these Bigger elbows for cracking open hard-body things and then there's spears that have more Exaggerated stabbing parts on the dactylis for spear and soft-bodied Prey and you can also sometimes get these really strange versions of the raptorial appendages like this hatchet on a campus Well, uh, and we're not really sure what they use that for but I don't really want to find out to uh to personally um, here's a slow motion videos of their their predatory strike this one is slowed down 30 times of a spear lunging out and uh stabbing a fish head It's a very very quick ambush movement and then here we see a smasher. This is sped down 300 times It's grappling with a very unfortunate crab here And you'll see in a moment the raptorial appendage deployed and it blows the crabs arm off um the video cuts now, but uh, I have it on authority that the Animal then picked up the claw and ate it in front of the crab. So they've got they've got a sort of Cruel charisma to them. They're they're really these um, very aggressive very mean animals and they're a lot of fun to work with Uh, they also have very for crustaceans quite complicated social interactions They do a complicated courtship displays where the male will males will show themselves off to the potential mates They have aggressive displays basically showing off their raptorial appendages They'll do this to you a lot. So even a human coming up to them. That's hundreds of times their size They'll they'll pop out of their burrow and say come at me. What do you got? They also I'm engaged in a strange ritualized combat So if they actually hit each other with these raptorial appendages, they can do some serious damage Um, so they've come up with this sort of dance They do where one individual will approach the other and put its heart and tail up in front of the other individual And then that one will hit that tail as hard as it can and then we'll switch around And hit the other one's tail as hard as they can and that way they can decide who's stronger without Smashing each other in the face and like damaging their eyes or antennae or anything else. That's really important um It's a good way of not wiping out your own species Uh, but the final thing that's really amazing about mana shrimps is their eyes. You can see them here Uh, they can rotate them three different axes independent independently of one another. They look in different directions at the same time Um, and for an invertebrate they they project a ton of inquisitiveness and curiosity You see him cleaning off his eyes there. I think keep to try this off of them But uh, I think that the way they look at things and they if there's something interest then they'll sort of snap to attention on it Is it's kind of a unique thing in invertebrates that they seem like to have have a lot going on behind the eyes Makes them very charismatic to work on visually To sort of explain to you, uh, how complicated their visual system is we can start by grounding you in a human visual system Um, this rainbow on top of the spectral plot tells you what these different wavelengths of uh, light Are um, corresponding to Uh in our color perception and to see these different colors. We have three cone photoreceptors a A blue a green and a red and we also have a rod for dim light vision Um, and then if we compare that then to a mantis shrimp photoreceptor of arsenal You can see that they have massively Expanded into the near infrared on one side and then to the deep uv on the other and then throughout the color space They but very much narrowed individual photoreceptors and bend them into these narrow bends all the way across the entire spectrum So really tremendous number of photoreceptors in a single eye for different colors and so to just orient you within a mantis shrimp eye Um, we break it down into three regions You could have noticed in the video earlier that when it looked at you the right way You can see the three pseudo pupils at the same time contributing to these three different parts of the eye There's the two hemispheres the dorsal and ventral hemisphere and then a specialized mid band region If we look at the dorsal and ventral hemispheres the actual structure of the underlying photoreceptors here and the omatidium Is very typical of crustaceans There's a cornea and a crystalline cone. These uh, lens segments Focus the light down into a raptom that is made by an r8 cell usually short wavelength sensitive First and then that goes past that raptom into a main raptom By what created by three other or seven other reticular cells And those are usually sensitive to blue green middle wavelength flight And if we look at the dorsal and ventral hemisphere from mantis shrimp it in many ways resembles a A typical crustacean eye system with a short wavelength r8 And then a longer wavelength blue green receptor. Well, that's quite broad However, if we look into the membrane the mid band things get a lot more complicated there they Um split some of these main radoms up into multiple tiers So light and rose one through four actually goes through the r8 uv receptor And then two other types of photoreceptors created by the other seven reticular cells So in all you get down to about 12 spectral types of photoreceptors in the room rose one to four of the mid band and we assume that this is A part of the eye that's very heavily special and is towards color vision and then on top of that uh beyond Luminance and color vision which were actually accustomed to mantis shrimps also can Discriminate polarized light a lot of invertebrates can see linear polarized light Mantis shrimps can see linear uv and also linear visible Polarized light but a unique thing that mantis shrimps can also do is they can see Circularly polarized light and they can tell whether a photon is corkscrewing toward you And a right-handed or a left-handed direction as far as we know They're the only animal in nature that's been conclusively proven to be able to do that so In general this eye has a tremendous amount of specialization and especially in the mid band where they're it's specialized for color and polarization vision and polarization vision is something that we have no actual Living concept of besides maybe polarized sunglasses So a lot of work has been done looking at what the physiology of the eye is how these different photoreceptor types are actually built and tuned um, and mantis shrimps have been shown in the past to use essentially every Possible theme and visual physiology to tune or structurally adapt their photoreceptors um They use filtering they use structural optics in the photoreceptors and also in the crystalline cones in the lenses they Yes, and just a tremendous amount of different physiological adaptations They use lots of different options in the photoreceptors We found that the photos the eye of one species expresses at least 33 options And sometimes these options only a single one will be expressed in a certain photoreceptor But in many cases they actually co-express a number of options, especially it seems in the polarization receptor Which I'm not really sure what's going on there But a tremendous amount of complexity and option expression and also lots of filtering in the eyes I don't want to get into this too much now, but this was my phd topic You can read the papers there They actually for their uv receptors in order to tune them to these very narrow wavelengths of light in the uv They use these things called microspore and like amino acids They're biological sunscreen compounds that are used by a lot of animals to protect themselves from uv rays in the sunlight But they've uniquely sequestered very specific configurations of these microspore and like amino acids Into the lenses of some of their midband rows to tune out certain wavelengths of uv light And push the sensitivity of the photoreceptors behind them to shorter and longer wavelengths Another very unique thing that manuscripts are doing in their eyes but All of that all this is really cool. They do lots of neat things in their eyes very complicated They they have very complex visual and social interactions But why do they need to have 12 channels of color receptors in their eye? Why would why would you bother doing this when? most crustaceans are perfectly happy as dichromats And some species of manashrims have even scaled back on the spectral complexity of their photoreceptors down to a single monochromatic photoreceptor type these species of manashrims tend to live In uh in murky or dark or spectrally narrow environments And the molecular evidence we have suggests that they've actually pared down From a more complex eye to this simpler monochromatic eye But you know, why would you bother making of such a convoluted color vision system where you can use where sorry Where you could like a human we're able to see more than just three colors by comparing relative opponent stimulation of our different photoreceptor types Why would you bother Building a bit a color vision system like this that is just so much more seemingly needlessly complicated And some colleagues some uh colleagues of ours Did a experiment to see if this Increase in photoreceptor type in the eye actually conferred to better color discrimination behaviorally in manashrims And they published this pretty neat paper where they first modeled what the wavelength discrimination, which is on the y axis here Would be if their photoreceptors were actually performing in an opponent system where they were comparing relative stimulation of one another to each other and Modeling wise they should have had incredibly small wavelength discrimination thresholds Be able to tell very close colors together apart performing better across human visual wavelengths than most other animals But then they did an experiment when they trained them to associate a certain color of light with a food reward And then they Showed them two options of light and they moved those lights closer and closer and wavelength to one another until they couldn't tell them apart before anymore So they are able to create an actual A behavioral wavelength discrimination threshold and they found that it was much poorer than modeled and a lot poorer than a lot of these other visual systems So that that was kind of a surprising result Partially it could be the question they're asking but uh in the way they the behavioral experiments Were actually run But still the result is a much poorer spectral discrimination Threshold than was anticipated And so they came up with an alternate hypothesis for how their color vision system might be working They think that the mantis shrimp eye might be acting as a sort of spectral barcode scanner More like a spectrometer than an opponent color vision system like in a human In such a system as the eyes scan around the world and sweep these different photoreceptor types in the mid band across different colored objects They could create a a bit of a A temporal barcode as they run over different colors showing a subset of these very narrowly tuned photoreceptors being stimulated When pointing at these different parts of an object they're looking at And the advantage of this could be that it it it sort of pushes the processing of this color vision information Out of the out of the brain and into the eye So at the receptive level you're actually doing a lot of the processing And then that saves you having to do much more uh neural processing Further downstream in the brain and you can very quickly get a sort of a recognition of which color you're looking at without doing the opponent processing and comparing relative stimulation of different photoreceptors by just looking at which subset of photoreceptors were stimulated And that's that's quite an interesting idea and it's a very different path to a color vision system than The canonical system of color vision like ours and the opponent processing system where we see Much finer degrees gradations and wavelength by comparing relative stimulation They may their eye may function more just like a spectrometer but I Think that they might be able to do a little bit better even than those experiments Might have suggested but at the same time When you're trying to think about what a man's shrimps color vision system is being used for probably isn't being used To its fullest potential. I don't think to spot something floating in the water column and then go attack it If you look at man's shrimps, they're incredibly colorful and I think it's a quite obvious Hypothesis then that they might be using these This color vision system to look at it one another that that might be the primary importance of it For to facilitate these complex social interactions that they display So like I said earlier, they have these aggressive displays where they show off very specific parts of their body They're they're a raptorial appendages On the inside of the raptorial appendages is something called a meryl spot A lot of smasher species that live in overlapping Habitats with other smashers have different colored meryl spots. So we Hypothesize that there's some role in species identification in these spots They also do a display called a hammer block where they push their hammers to the entrance of their burrow As if to say there's a there's a man's shrimp in here So these became very obvious parts of the anatomy that might have some sort of color cue that they're showing one another that's important For facilitating their combat. So we did a very simple Analysis of this where we looked at what the sensitivities of their different photoreceptors were And then we measured the reflectances of lots of different parts of man's shrimp anatomy and focused mainly on the Meryl spot and the club which they show off very predominantly in their aggressive displays to one another And one thing we noticed Immediately was that this very special uvb photoreceptor that they have that sensitive to very very short wavelengths of light Overlaps really nicely with a short uvb reflectance that is very specifically on the club but we could go beyond this and then Sort of model if a man's shrimp I scanned over this on this a raptorial appendage of another animal And made it a simple color recognition comparison between the Meryl spot and the club You can create this simple little chart where each of these bars is associated with one of their color photoreceptors and And if you looked at how much the raptorial appended the club versus the Meryl spot stimulates each individual photoreceptor you get this sort of wavy graph of bars saying This simple scan pattern is what's attributed with this species of man's shrimp And then if we look at lots and lots of different species of man's shrimps and create these graphs from their reflectances of their Meryl spots and their clubs We can see that amongst these large Smasher species that live in overlapping habitats There's a tremendous amount of comparative information you can get by doing this scanning method Much less so for many of the spear species The spears are typically more sedentary and their habitats. They don't they don't meet each other as they're out roaming So this visual system this color vision system could be a really quick Snapshot way of doing species identification based on color profiles of various parts of the body It might also be used for sexual discrimination Uh many species the male and the female if you look at these parts of the aggressive display the Meryl spot in the club There's no difference in the There's very little difference in the reflective patterns between the males and the females But then if you look at other spots that they show one another when they're doing courtship displays such as the the uropods on their tail and the Colors on their back which they will sort of walk around past each other and show off You can see some some severe departures, especially in the uv For males versus females males are more reflective of certain uv wavelengths And you can actually extrapolate this idea of a snapshot system to that as well of color recognition So what is the managed from color vision system being used for? We don't really know yet, but it seems like a really good hypothesis that This really really elaborate color vision array Is used being used for a sort of color recognition that's different than color vision? That quickly allows managed shrimps to make assessments about whether it's a spear or smash if they're looking at What species they're looking at what gender they're looking at how vital How how well pigmented and healthy the animal looks So I think that's that's quite a Interesting thing we're going to follow up in the future to look at what they're actually using their color vision for The high I really like that this idea Very early on in Manchester evolution. This is a species from the Devonian And you can see even very on 350 million years ago. They already have a well-developed rectorial appendages And I like I like the hypothesis that once they had this weapon that they could literally obliterate each other with There was a tremendous amount of evolutionary pressure to Uh Make the a visual system that could quickly communicate visually to one another And be able to diffuse and talk things out and assess one another quickly before coming to blows and Killing each other Roy Caldwell a great mantis shrimp ecologist called this living with the bomb Which once you have a atomic weapon on your arm, you have to rethink about how you do everything and the evolutionary process of Have apparently we thought how color vision works in the mantis shrimp by in order to give them this system a really quick color recognition and That I think that's a really fun hypothesis and I really want to follow that further in the future and I hope Now both of these examples have shown you Uh, some things I'm interested in with animal vision and how uh creative evolutionary processes can be to creating eyes Um To solve very very specific behavioral problems in the fan worms. We see that they Have come up with all these different photo receptor design and optic solutions to doing the same exact tasks and in mantis shrimps Uh, you can see this really interesting departure of a color vision system in order to do a very specific job of but perhaps visually communicating with one another And with that, I'd like to thank uh, many of the people that have contributed to this work over the years um, especially my uh PhD supervisor tom cronin and my postdoc supervisor dan eric nilson and uh, Megan porter who I've been collaborating with since I first started my phd Um, also all of these uh, nice funding institutions that give me money to do this really really fun and exciting work And I'd like to thank you all for listening and with that, uh, unlike this fan worm. I'd be happy to take any questions Thank you Thanks a lot michael that was very very interesting Um, we have lots of questions If you have to ask But before we start I'd like to remind our hodjens that uh, is I want to ask the questions themselves Or if you want to join us to further continue this topic this discussion They're welcome to join us. Uh, I've just shared the the link for the current zoom room. We're sitting in so, uh Let's try to organize everything. Uh, first can we go back to the fun worms and talk about the species diversity? Uh, so we have a question from uh, tom badon Who's asking why are christmas tree worms colorful? What do you think can you speculate what the color is for? For whom? The color is um, it's not for the fan worms I don't think um, I've actually really wanted to write up a grant or project working on that exact question Is it's really amazing how colorful they are and it's not just the the primary colors they use It's the they get all these different patterns and uh, it doesn't seem to work great for camouflage It's quite obvious to see them on on the reef um, and you could assume maybe it has something to do with a epistematic signal of Warning them that they're warning trying to warn predators that they're poisonous But uh, then some species are have very well camouflaged I mean some individuals have very well camouflaged fans Yeah, it's a really interesting question. Uh, it does not We've looked at their photoreceptors. They have one photoreceptor type. They can see blue green light I've looked at their opsons. They have one opson And where where their eyes are tough, they would never see one another and they don't have much of a behavioral reason to see one another They they do broadcasts falling where they all eject their gametes the waterfall Um, but it's a really interesting question of what they're doing with those different colors How they're building those different colors have those different pigments But I really like to try to drill down on that what the genetic reasons that are causing those differences and maybe do some modeling of What these different colors could mean to various animals on the reef? But yeah, we don't know. Sorry, Tom Sorry, I tried to convince myself So still relating to diversity. I have a question from greg schwarz Are the sea opsins in farm worlds related to Opsin three and up in five in memos Opsin five I'm talking about a genus that doesn't work on mammals. I don't know the numberings off the top of my head. Are those uh Is that is that um, like a a pine opsin or a para pine opsin or Well, the point is though is that uh, there is a um So they're they're as related to our cone and rod opsins as they are to Um, the rest of our sea opsin. So these uh invertebrate Sea opsins I call them are on a a sister clade to all other Sea opsins so at the very base of the sea opsins clade these guys come off So they're they're more related to Um opsin three and opsin four and humans I get or unless it's neuropsy. He's talking about or melanopsin. No, no He's opsin three. Yeah, I don't think so Sorry, phyllis. I know what was watching and I'm sorry. I don't remember which one of the uh The human opsins is melanopsin. I'm sorry. Yeah, I don't I don't know which the uh, Sure, but but not they're they're not they're not closely related to any Our human opsins more so than any other sea opsin I have another one uh from Karola Yovanovich So how much phylogenetic phylogenetic diversity exists for signal transaction machinery downstream of obscene across phyla Do you know if your fun worms proteins seed closer to vertebrates as happens with opsins? So I I didn't hear part of this looking at the comment. Hi, Karola. Um Do do you see the question? Yeah, I'm looking at it now Yeah, and melanopsin is opium four Oh, it's opsin four. Okay. Wait, it's it's closer to our sea opsins than it is to melanopsin, which is a microvillar opsin a gq opsin But I'm not sure if I understand Karola's question Yeah, to be honest. Oh, oh the signal transaction machinery. I didn't read the very first Yeah, so we know that they express in these eyes gi and go type G protein beta subunits But it's see it's not we don't have a clear picture yet Which one they're exactly using for their phototransduction cascade We're doing some more work that hasn't been published yet on on that that we were in but it's not very clear yet, unfortunately but they do seem to have some Some interesting things happening with the phototransduction cascade that is unusual for most visual opsins I can talk more about that in the chat if you come over to that later Yeah, so it's so I guess join us later Karola if you want to continue this interaction. Uh, sorry. We're on time. So I'll continue moving on If we know talk about the eye organization I have a question from top button who's asking if In the fan worms is the mitochondrial density observing these highs are related to anything obvious The mitochondrial density in the fan worms um Well, I mean of of course a photoreceptor wants to have mitochondria because a photoreception requires a lot of energy to Be constantly being responding to late um, so naturally there's going to be mitochondria stuffed into these photoreceptors and I think it just so happened that in certain um certain species Uh, they started consolidating on these mito mitochondria into these masses that happen to be in front of the photo photoreceptive cilia and the lamellae sheets where the actual photoreceptors are and As we could see in other animals like birds which have masses of mitochondria some of their photoreceptors And on a lipsoid type situation um Eventually you can use that to have enough of a refractive index change against the cytoplasm around all the the packed mitochondria that you get some optical benefit um And that seems to have happened in a couple groups and some of these moda these mitochondria might be modified in certain ways to make them more refractive They don't look like typical mitochondria in most cases Some of the simpler photoreceptors look like they are just normal mitochondria packed in Lots of lots of diversity Okay, shall we move to some processing question? Um, so actually I had a similar question to that one. We're just going to ask another one from tombadon Was asking in the case of consolidated highs for the farm worms What does the post receptor wiring look like in terms of synaptic layers projection neurons long photoreceptors, etc? Yeah, uh, we don't we don't know yet. Unfortunately. Well, that is something I am very specifically working on right now um trying to sort out the What the actual substrate of that region where these photoreceptors all project to in the brain looks like? Uh, looks like there might be some layering that looks like there There's there's some sort of um Organizations that region that it's just not a massive photoreceptor termini There's there might there we have a little bit of uh evidence that there's some retinotopic mapping Of photoreceptors from different part of the eyes to very specific parts of those mushroom shaped structures But yeah, that's a really interesting Future goal is to figure out what the circuitry actually looks like in that region, but we don't know yet That would be instructing did it Uh, still unprocessing motion processing. I have one from I lost you a great Schwartz Uh for the farm worms. What about the direction of the object? Do consolidated highs help for that? distributed Distributed highs could work too if which high activity into tells animal about their approach direction Yeah, no, certainly certainly you could imagine a system where The distributed eyes are covering the same space In a more overlapping convoluted way. I think that makes the processing actually in some ways more complicated Because you have to filter out a lot of overlap and noise and and in a situation like that you would probably think they're not creating a In general in the fan words, we don't think they're creating a mental representation of the state the world around Yeah, but it still creates a convoluted problem for processing out motion and wave flickering and things like that But does that answer the question? I'm not uh, yeah I might have lost track of myself answering that one I've been talking too long and my brain is scrambled now That's fine. I mean, I got the idea. I actually have a following up question on that if you consider for non-conciliate highs Where was it? I had a question from Phyllis Robinson. Phyllis, sorry Do fun worms high regenerate because you were seeing at some point that if you lose part of it You will lose half of your visual world Therefore intercondition of eye movement. I mean object motion You can actually lost part of the movement. So do they regenerate? Yes, and this is another really cool thing about them I didn't have time to get to is the eyes do regenerate You can cut off the eyes and they'll rebuild them. You can cut off the crown The whole crown will be rebuilt including the eyes You can cut off the head and most of the word besides the last few segments and they'll regrow a brain a crown in the eyes So this gives us a really huge level of manipulation of this visual system that we can do in the lab and I've done some experiments where we remove Some of the eyes and test how good their visual system They're how good their spatial resolution and motion detection Is and how long it takes them to regain it as they regenerate the eyes and rebuild these neural prostheses But this is this is something that I'm working on right now I just got a grant for and I think it's a And also from the developmental angle of how they tell an eye to become more or less complicated As they're regenerating them is really interesting We can look at that in the species with the complicated versus simple eyes and look at what factors are telling them to make a big eye versus a small eye and if way down the line you can find a way to Force the species with a simpler eyes to make a bigger eye And to see how flexible the nervous system is to be able to integrate integrate more information and they're able to gain some Some visual sophistication that way. It's gonna be a lot of fun to play with I think it would be interesting to see indeed So before we move to mantis shrimp's question I would like to remind our audience that we're going to answer stream soon So if you want to continue this question, please join us now I had a question from You did have on sale. Sorry if I say that wrong Hey, Michael, uh, thanks for the great talk I was wondering why the mantis shrimps are so colorful Two different parts of the bodies, you know Different things and I will go even further at the beginning. You said that it was a social animal I guess you mean more than just courting and avoid killing each other Well, not not much more than courting courting and avoiding killing each other Some species a lot of the spears actually form Long-term monogamous pairs and uh, yeah, the females will yeah The females will live below them in the the male in the burrow and the males will have much larger eyes and much bigger reptorial appendages for hunting and they catch fish and nor squid and they pass them down to the The female and she eats most of it and gives him the scraps And she she and if the male's ever lost then she advertises for a new male to come or she goes to look for a new male Um, but uh, yeah, I think they are quite For a crustacean and for an invertebrate. I think they have quite sophisticated social interactions The courtship and especially that the ritualized comet these days Uh obliterating each other. It's like like um, like sparring with horton shields. It's a really cool dynamic, but yeah, I think I mentioned that I may have been going through it very quickly in the talk. I think That there are there are specialized regions on the body for these different sorts of Communications that they're doing so the aggressive display is very much focused on the reptorial appendages When they do a courtship display, they are Sometimes they'll be sort of walking pack and forth showing different parts showing off these antenna scales Which are these little flappers on the side of it and also the these feather-like things on their tails and that they seem to use those in courtship. Um, and then The ritualized combat that usually comes from an aggressive display initially But yeah, I think it's very uh anatomically distinct regions have important color information for different behaviors that they're doing So That's a large topic indeed Thank you, Michael. That was very interesting Um, I will no hands, uh, the youtube live if you want to join us You have 30 seconds to do so and I would like to remind our guests that we have another talk next week and I hope to see you there. So thanks again, Michael and see you on this on site. Thank you very much. Thanks everyone for listening