Zika & Wolbachia I: Wolbach

   “‘It was just curiosity-based work, total serendipity’ Dr. O'Neill said.” (Carl Zimmer quoting Dr. Scott O'Neill in his article Bacteria-Infected Mosquitoes Could Slow Spread of Zika Virus published in the New York Times May 4, 2016)

   Can I quote a quote? I did, and hopefully I provided enough citations to make it legit. I know it is not wise to try and out-zimmer Carl Zimmer but there is so much to write about here I am going for it. This quote encompasses the mission of this blog (**although - see my commentary below) and is a great example of the return on our investment in curiosity. In this case, the return is slowing down the spread of Zika and other diseases transmitted by insects using Wolbachia, an insect bacterial parasite. The reason we know about Wolbachia, and its potential to reduce the spread of viruses like Zika, is because of public and institutional support for unbridled curiosity. The Wolbachia-Zika story is part of a decades long history of research on Wolbachia that goes back to 1924.

   A brief introduction. As with last week and Ebola, Wolbachia has been covered extensively. And while there is not as much known about Zika, there are many articles describing what has been discovered thus far. We will establish a basis for the underlying biology and go from there. Wolbachia is a genus of bacteria (unicellular organisms that have all of the machinery necessary to replicate themselves). While not harmful to humans, Wolbachia live within the cells of insect hosts. Zika, on the other hand, is a virus that infects humans and has been linked with microcephaly in infants. Like Ebola, and all other viruses, Zika does not have the cellular machinery to replicate itself and must co-opt the machinery from the cells of an infected host. How are Wolbachia and Zika linked? To understand that we need to take a closer look at decades of work by a long list of scientists, including Scott O'Neill, that began in 1924 when Hertig and Wolbach first discovered (and which Hertig later named) Wolbachia.

Image credit: Seth Bordenstein (from EOL). Image description: Insect testes showing sperm DNA (red) and Wolbachia endoysymbionts (green).

   If we start from the beginning, however, I think we will need to break this up into multiple posts, which is okay. There is plenty here to keep us all fascinated. Today we will start with Simeon Burt Wolbach, after whom Wolbachia was named, and based on what I have seen so far he is deserving of his own post. Here is an excerpt from a tribute published in the Harvard Medical School Alumni Bulletin:

“S. Burt Wolbach, one of Harvard Medical School's most beloved as well as one of its most distinguished professors, died on March 19, 1954, in his seventy-fourth year, after a relatively brief illness, of cancer of the prostate. In the minds of many, both his scientific achievements and his personality present a perfect synthesis of the best in the past and in the present. Sound training in morphology, guided by imaginative insight, made it possible for him to place new and fruitful interpretations upon cellular structural mechanisms. In his personality too, one was aware of that blend of conventional and liberal attitudes, an appreciation of the traditions of the past and the freedoms of the present. Thus his stature, [equaled] by few, resulted from that rare integration of the austerity and vision of the scientist with the humanity and warmth of the guide and teacher. His name will be remembered with a lift of the heart and a quickening of the imagination by student, colleague and friend.” (Dr. Charlotte L. Maddock and Dr. Arthur T. Hertig (1954) Harvard Medical School Alumni Bulletin 28: 41-45).  

Figure 1 from Hubbard (1987). Figure caption: "S. Burt Wolbach, circa 1938. Etching, 300 x 251 mm, by Arthur Heintzelman (1891-1965)."

   Simeon B. Wolbach was a polymath (much like my beloved Schrank) growing up riding horses on the plains of Nebraska “…ranging free with the cowboys…..” in the late 1800s, and graduating cum laude from Harvard Medical School in 1903. Wolbach subsequently held a variety of esteemed posts at various institutions on the east coast where he pursued research in two fields of study, infectious disease and vitamin deficiency. The diseases he worked on included both viral (i.e influenza and Rocky Mountain spotted fever) and bacterial (tuberculosis, leprosy, syphilis, and typhus) pathogens. In fact, it was his work on typhus that led to the discovery of Wolbachia. While Wolbach’s work on disease transmission is the most relevant to this blog post, some think “[h]is most brilliant work was done on those disorders associated with vitamin deficiency and excess.” Among other distinctions, the quality and breadth of Wolbach’s research granted him induction to the National Academy of Sciences in 1938.

  The language used to describe Wolbach’s character is cryptic and intriguing. It outlines a person of genuine character that embodied both seriousness and a sound sense of humor. His lecture style was described as non-didactic, but his students clearly revered him as was demonstrated by two separate instances where they paid him tribute by coming to lecture with a red carnation in their lapel, something Wolbach did on a regular basis. While perhaps a tough nut to crack, it seems that upon cracking a plethora of goodness was exposed. He remained an avid outdoors-man through his academic pursuits and continued riding horses throughout his life. “It was there, along the banks of the Jeannotte River and Lac Castor, that his friends knew him best. There he became a boy again and would engage in an impromptu canoe race, or chase a moose in the lake until he could smack its rump with a paddle.” (All quotes from the previous two paragraphs are from the Maddock and Hertig tribute referenced above.)

   I could go on, and am surprised a more detailed biography of Wolbach has not been published. When I started looking for one I actually found that in addition to all of the accomplishments listed in the Harvard Medical School tribute, Wolbach appears to have written a biography of Hans Zissner, a physician, bacteriologist, and author of Rats, Lice, and History. !!. The more I find the more I am intrigued by these scientists, what amazing stories. I literally have about 20 tabs open in my web browser right now.

   I found an example of Wolbach’s non-didactic delivery method, combined with the foresight of a complex mind, in this passage from “The Glorious Past, the Doleful Present, and the Uncertain Future of Pathology”, a presentation he gave on Harvard Alumni Day in 1952 (his last public presentation) that was subsequently published in the Harvard Medical School Alumni Bulletin 28: 41-45:

“What do I mean by the Science of Pathology? Years ago, challenged by Theobald Smith, I defined Pathology as that branch of Biology which investigates the reactions of living things — unicellular to man — to injurious agents. Deleterious environments of all sorts are productive of pathological states and a super Darwin become pathologist would, I believe, have a grand time in attacking problems of phylogenesis from the viewpoint of a pathologist. The scientific use of the imagination is legitimate and I get satisfaction in believing that the adaptation of marine creatures to terrestrial conditions was the result of eons of responses in myriads of survivors of non-lethal injuries.”

I will give you, and myself, some time to ponder this and we will pick-up here next time.

PS **My issue with this quote, and this is my opinion only, is that the tone highlights an ongoing problem we all have of downplaying the importance of exploratory research. I do not know Dr. O'Neill and I want to make it clear that I am not slighting him; he and his colleagues have done amazing work, which we will look at next time. In all honesty, I think the quote reflects Dr. O'Neill’s humility while talking about his own research. But I am going to go all Sheryl Sandburg on this right now. I think we need to lean in to the immense impact of exploratory research. I think scientists, myself included, need to be careful about downplaying the importance of exploratory research. When I first read Dr. O'Neill’s quote I thought, bingo, perfect for the blog, and retweeted it. It wasn’t until I was typing it out for this post that I picked up on the tone, and thought about how much language can impact public perception. If we want curiosity driven research to be understood and funded by the public we need to be proud and put it on the pedestal it deserves. The same is true when we talk about taxonomy and natural history museums, which I have written about before. If we want our taxonomists to be rock stars and our museum collections respected, we cannot refer to them as a bunch of dead insects. Which happens, from places we should least expect it.

 

Again, I don't mean to diss anyone here, just highlighting the need to be more aware (and UConn got $500k, not $500).

Ebola, evolution, and the role of phylogenies

   As an evolutionary biologist I love phylogenies. Or, I love phylogenies so I became an evolutionary biologist. Except I did not always know what a phylogeny was. A phylogeny is similar to a family tree except we usually have to infer who the ancestors were. To do this, we collect and study present-day organisms and use the data to reconstruct what happened millions of years ago. In the end we are left with an illustration of relationships, a phylogeny, which gives us an idea of who is more closely related to whom. Are beetles more closely related to ants or cockroaches? Ants. Are pine trees more closely related to kelp or moss? Moss. In fact, there is a huge push to understand what is called the Tree of Life – a phylogeny that includes all the major extant (living) organismal lineages. An updated version was recently published and did a nice job of putting humans in our place. We are not as big of a deal as we like to think, evolutionarily speaking - we are merely a small nubbin on the twig of ‘Eukaryotes’.

Recently published phylogeny of the Tree of Life (Hug et al., 2016)

   Understanding phylogenetic relationships gives us a foundation to test hypotheses and tease out answers about how our world works. The information we retrieve tells us that birds are actually dinosaurs, neanderthals exchanged genes with humans, and that immune systems can evolve under pressure from viruses and other pathogens.

 

   That's where we are going today - using phylogenies to unpack the evolutionary dynamics of one-up-man-ship between a virus and the host immune system. The plan is to delve deep into stuff that will make you say, wow. First, a little background. I am not going into great detail about Ebola as this has been extensively covered. Briefly, Ebola is a filamentous virus, categorized as a filovirus, which infects humans (and other mammals) resulting in viral hemorrhagic fevers that can be fatal. In addition to researching treatment and vaccine options for Ebola, scientists are conducting research to understand how the virus ‘jumps’ from a non-human host to humans (a.k.a a spillover event). To do that, we first need to figure out what that non-human host is. Based on data showing remnants of filoviruses in fruit-eating bats and insect-eating bats, many researchers are focusing on bats as a likely reservoir. Of course there are many questions making this is an active area of research. One of those questions, investigated by Ng et al. (2015), is: how come bats do not seem susceptible to Ebola and other filoviruses? The short, brief, and tractable answer of the Ng et al. study is that some bats have a genetic mutation in the protein filoviruses use to bind to and infect the bat’s cells. It would be like playing a game of Pac-Man where the ghosts have gone wild and the only way Pac-Man can stay alive is by having a mutation that prevents the ghosts from recognizing him. Did I just date myself? Or, let’s try this analogy. Hackers recently found a way to generate ‘universal keys’ allowing them to break into cars with keyless entry systems. This would be our virus hacker, breaking into cars using sophisticated biochemical tactics. But, let’s say there is one type of car (the new Tesla Model 3?) that has changed its keyless entry system so it is no longer susceptible to hacking. The virus hacker tries its key against the lock but it doesn’t work. Now, of course, people with the resistant car are more likely to keep their cars in this hacking environment, and the desire to have this car spreads and they become more and more frequent. Tough luck for the hacker.

   And this is what Ng et al. (2015) found. The mutation that prevents Ebola virus from attaching to the bat’s cells is under positive selection, meaning that its frequency in the population increased rapidly relative to other genes. When researchers find evidence of positive selection it lends further support to the idea that something important is happening. Interestingly, Ng et al. found that not all bat species had the mutation.

   In walks the bat phylogeny. Bats are a diverse group of flying mammals with over 1200 species that live in many different habitats all over the world. 

Townsend's big-eared bat (Corynorhinus townsendii), a nice picture of a bat but not one included in the study by Ng et al. (Image Credit)

   If we want to understand disease dynamics, and how and why some bats have the mutation and others don’t, we can use the phylogeny as a forensic tool to reconstruct how resistance evolved. We can ask questions like: are bats with the mutation close relatives? Did they inherit it from an ancestor? Or, did the mutation evolve multiple times in different bat species? And, due to the innate curiosity of humans, there are phylogenies for lots of different animal groups, including bats. In 2007, Miller-Butterworth and colleagues put together an impressive genetic data set (over 11,000 base pairs of DNA) to essentially go back in time and figure out how different types of bats are related to each other. It is important to point out here that our estimates of phylogenetic relationships are just that, estimates. The reason is that any given phylogeny is a hypothesis, our best estimate given the data available. For a long time, biologists relied on morphological data to figure out who was most closely related to whom. Evidence of close relationship was inferred if two species shared a trait that was presumably inherited from a common ancestor. But you can imagine how this might lead to spurious relationships. Just because both bats and birds have wings, it doesn’t mean they are close relatives. We know from studying the morphology underlying bird and bat wings that these animals did not inherit wings from a common ancestor, they each evolved them independently; thus, it would be a mistake to infer they are close relatives because they both have wings. In the past few decades, researchers have been able to rely more heavily on genetic data to infer relationships. And while these data have their own set of problems, they provide an additional perspective to consider alongside morphological data. As new technologies are developed and our ability to accumulate more data improves, our phylogenies are continuously updated and remain dynamic. This may frustrate many students in introductory biology classes, but underscores the importance of understanding the process and history of scientific data collection and hypothesis testing.

  

   Back to bats. What Ng and colleagues found when they combined their data with the bat phylogeny was that the mutation preventing filovirus infection evolved once about 25 million years ago, and was passed down to descendant lineages. The researchers interpreted these results as evidence that bats have been evolving alongside filoviruses, and for much longer than previously thought. But what do we know about hackers that we should be thinking about here? They evolve too. Just because the Model 3 may be resistant to hackers now, the hackers are not going to sit idle and find another means of making a living. The hacker tactics will shift and evolve to overcome new car-locking technology. And Ng et al. found evidence of this happening between bats and Ebola too. What they see is multiple mutations with a signature of positive selection, which they suggest results from counter-attacks by the virus. In other words, the virus sees the bat mutation and raises it a mutation of its own. It is an arms race. Between the virus and its host. Between the hacker and the car company. It is known as the Red Queen Hypothesis (coined by Leigh Van Valen in 1973) and that is a story for another day.

“Now, HERE, you see, it takes all the running YOU can do, to keep in the same place.” (Lewis Carroll, Through the Looking Glass)

  P.S. There is a nice podcast on TWiEVO discussing the Ng et al. (2015) paper with some of the authors of the paper.

Schrank update

 

“Franz von Paula Schrank was a polymath in the true sense of the word.” (Edmund Launert)¹

   We first met Schrank back in February during our discussion of parasites and swellable microneedle adhesives. I promised to come back to Schrank, and I think about him often enough that I did not forget. Instead of going to the Stanford library, I submitted an interlibrary loan request for Annette Zimmerman’s biography on Schrank (Franz von Paula Schrank (1747-1835): Naturforscher zwischen Aufklärung und romantic) and got it over a month ago. 

 

Title page and table of contents of Zimmerman's biography on Schrank

And there it is, sitting on my kitchen table, filled with rich information on Schrank that I cannot read because I don’t speak German. It calls out to me on a daily basis (in English), taunting me to read it and learn about Schrank. I will have to return it soon, unread. (I am open to ideas for efficient translation to English if you have them.) Several of his publications have also been scanned by the Biodiversity Heritage Library and are available to read. But not only are these also in German, the intricate script makes it difficult to decipher the letters.

   I did track down a review of Zimmerman’s biography, written in English by Edmund Launert, by means of a second Interlibrary Loan (thank you UCSD library).¹ It is not a substitute by any means, but in combination with what is available from the Catholic Encyclopedia², it gives us a little information to fly with. Schrank was by all means a polymath, someone who is skilled and experienced in a variety of different subjects (not just math – the Greek translation of polymath is “having learned much”, derived from the Greek work ‘manthánein’). Schrank is on the list of Roman Catholic cleric-scientists and fulfilled the duties of priest, and professor of botany and zoology. While this may sound unusual to us given current perspectives of an oft-assumed divide between science and religion, this was very common historically, especially in 1774 when Schrank was ordained as a priest. Other notables on the list you may be familiar with are Nicolas Copernicus (mathematics and astronomy - a few hundred years before Schrank) and Gregor Mendel (genetics – a hundred years after Schrank). At age 15, Schrank became a Jesuit, a Catholic religious order well known for many things (good and bad) including its contributions to science. He was born into a well-respected family in Munich, Germany and started his studies at the Jesuit College of Passau when he was 9. 

   His interest in the natural world was inspired by Father Sluha (Szluha is the native spelling) when Schrank was a budding Jesuit student at Oedenburg collegium in Hungary. Father Sluha had been a Jesuit missionary in Brazil until he was put in a Portuguese jail when the Jesuits were expunged from Brazil in 1759.² There is very little known about Sluha, and another source (McKinley³) (who, unlike me, could read German) reported that Zimmerman was not able to find much out about Sluha when she was working on her biography of Schrank. Presumably, the idea is that as a missionary in Amazonian Brazil (1753-1760) Sluha acquired or refined his skills as a naturalist (probably focusing on botany), and opened the door of natural history to the young Schrank. Just to be clear, I am speculating on this, but the idea is not that far-fetched.

   Schrank was a Jesuit teacher until 1773 when the Jesuit religious order was repressed and abolished by Pope Clement XIV, the year before Schrank was ordained and received his doctorate in Theology. He started his academic career as a professor of mathematics and physics in 1776 at Amberg, and was a professor of botany, agriculture, mining, forestry, and zoology at the University of Ingolstadt starting in 1784 (with a subsequent move to Landshut). Schrank published his first scientific study (of over 40) during this time (Beiträge zur Naturgeschichte - Contributions to Natural History - in 1776). While many of Schrank’s publications were focused on natural history (botanical, zoological, and entomological), he also published papers in the fields of physics, chemistry, agriculture, travel, geology, mineralogy, theology, and poetry. Are you kidding me? And, all of this is inaccessible to me because it is written in German. An unfortunate outcome of growing up monolingual.

   In 1809, Schrank was appointed to be the first Director of the München Botanical Garden. His influence there was described by Stafleu & Cowan⁴ as follows: “The present state of the garden bears out Schrank’s early and wise judgment” (p. 325). In the same text, he was attributed with the quote: “Man würde weniger deräsonniren, wenn mann über nichts räsonnirete, was man nicht versteht.” When I type this into Google translate I get “One would less deräsonniren when man räsonnirete about anything you do not understand”, which is not super helpful. So I asked a German colleague of mine for help and he responded: “Hehe, ‘deräsonieren’ appears to be a word creation by the author. It means: the opposite of ‘reasoning’, maybe unreasoning, or reasoning in an unreasonable way.” I love this, he made up a word for something I can barely wrap my head around. But, essentially, he seems to be saying: One would have fewer mental issues if one did not speculate on things one does not know about. Seems like a good idea. My German colleague referred me to a similar quote from a German comedian, Dieter Nuhr: "Wenn man keine Ahnung hat, einfach mal die Fresse halten". Consider to shut up if you don’t know what’s going on. I don't think there is a moral here but thought it was interesting.......

München Botanical Garden (Image credit: Diego Delso)

¹E.E. Launert (1983) Natruforscher zwischen Aufklarun und romantic. Archives of Natural History 11: 362-363.

³ J. Stein (1912) Franz Paula von Schrank. In The Catholic Encyclopedia. New York: Appleton Company. Retrieved April 7, 2016 from New Advent:

² D. McKinley (1992) Adrien Lebreton, S.J. (1662-1736): A search for the identity of a neglected botanist in early Martinique. Huntia 8: 155-162.

⁴ F.A. Stafleu & Cowan, R.S. (1985) Taxonomic literature, a selective guide to botanical publications and collections, with dates, commentaries and types. 2ed. Vol. 5 (Sal-Ste) p. 323-325.

why diversity is important to me

   Diversity is the reason I pursued a career in science. And several events over the past few months have prompted me to think about diversity more than I usually do. The esteemed entomologist and science writer Edward O. Wilson published his 32^nd book “Half Earth: Our Planet’s Fight for Life”, asserting we dedicate one half of earth to maintain current biodiversity levels. A few weeks later, the US National Science Foundation announced a funding “hiatus” for natural history and living collections; the places where species diversity is stored, studied, and documented. But it’s not just biological diversity I have been thinking about. Diversity in general has been on the chopping block, even more so than usual. Generally speaking, diversity is valuable. Not just for ecosystems, but for our own society as well. A variety of perspectives, ideas, and experiences can generate more opportunity than uniform societies. From financial portfolios to biological systems, diversity improves buffering capacity and increases stability. Uniformity is vulnerable to even the smallest disturbance.

Figure 2 from Schilthuizen (2003). Figure caption: "Diversity of shell ornamentation in Bornean species of the subgenus Plectostoma of the genus Opisthostoma. Top row, from left to right: O. everettii, O. goniostoma, O. grandispinosum. Middle row, from left to right: O. hosei, O. mirabile, O. pulchellum. Bottom row, from left to right: O. lituus, O. shelfordi, O. stellasubis. All drawings by J.J. Vermeulen."

 

   Biodiversity refers to variation within species, among species, and among ecosystems. It was first put into print by E.O. Wilson in the late 1980s (with a likely influence from W.G. Rosen) and was a contraction of the words biological diversity, a phrase coined by Thomas Lovejoy in 1980. Both of these men have been instrumental to the study of biodiversity, and have made a large impact raising awareness of the risks associated with large-scale extinction. Both have been doing this work for most of their lives, E.O. Wilson is 86 and Thomas Lovejoy is 74. And, remarkably, based on recent published interviews, it is clear that both Lovejoy and Wilson remain refreshingly optimistic about our ability to protect and maintain biodiversity.

   In previous discussions outlining the role of taxonomy, we have touched on particular aspects of diversity science and its importance for describing and documenting new species. If I go out collecting, it is possible I will collect a beetle specimen that is new to science. In order to test this hypothesis, I need to compare my newly collected specimen to specimens maintained in collections and verify similarities and differences. Without such reference material it would be very difficult, if not impossible, to continue the process of documenting earth’s species. An essential task for many reasons, including the reasons I started this blog. There are of course many other important roles collections play, and I will refer you to one of many articles published in the media when funding agencies threaten to pull support.

   One of the reasons I pursued a graduate degree in entomology was to help study and document biodiversity. Some of the motivating factors behind this decision were books (some of which were written by E.O. Wilson), journal articles, and other literature that lamented how much more work there was to do. Sign me up, I thought, I wanted to contribute. What I didn’t realize at the time was how low of a priority it was to granting agencies and many institutions. And this reflects the priorities of our society. It is safe to say that studying diversity, taxonomy, and systematics is not a moneymaker, either for the individual doing it or for the institution they are working for. We can change that. I am imagining a society where collections are revered, put on pedestals, and the curators are rock stars. Why not? Let's carry the torch of optimism. Natural history collections started out as privately owned cabinets of curiosity (mostly by people wealthy enough to purchase and maintain the specimens) and proudly displayed to visitors. It was actually cool and distinguished to have a collection. While we have come a long way in prioritizing scientific study of collected specimens, dwindling public admiration for our collections is putting them at risk. 

 

A curiosity cabinet of corals that is referred to as an "An early eighteenth-century German Schrank with a traditional display of corals (Naturkundenmuseum Berlin)." But I am wondering if there was a translation issue and this was a cabinet from our friend Schrank. I will look into this and provide details in the upcoming Schrank update I am planning (Image credit)

   So let’s think about collections in a different way. Museum collections fall into the category of biological infrastructure. They are the foundation from which other types of science can progress. Infrastructure in general is not categorically sexy, and competitive funding environments like the one we are in right now tend not to favor investment. For example, collections are like transportation infrastructure. We rely on roads, bridges, and railways to travel and don’t realize how important continued investment is until something tragic happens. But investment in maintenance is boring; it does not result in anything new. It is not sexy. But it is necessary if we want to get from point A to B. The same is true for biological infrastructure; collections are an essential aspect of scientific study. It may not seem sexy but without it, the sexy science will eventually get held up by a collapsed bridge.

Image credit

insect eyes at the nanoscale

  The prefix nano- is a unit of measurement that denotes one billionth; it is used to talk about very small things. If you were a billionaire, one dollar would represent your nano-wealth. If we go with the more traditional Wiki definition, a nanometer is one billionth of a meter, or the amount your fingernail grows in one second. Bottom line is nano- is small, very small. So much smaller than today’s subject, insect eyes, which we think of as being pretty small.

   Different insect groups (beetles, flies, cicadas, etc.) have different eye shapes that cover varying degrees of the insect head. This variation often reflects what is adaptive for a particular insect group; for instance, the eyes of dragonflies cover nearly 270º of their head, while those of june beetles cover less surface area.

Left: head of a dragonfly (Image credit: James Douch). Right head of a june beetle (Image credit)

   A dragonfly relies on their compound eyes to find and catch prey while flying, while the june beetle, a vegetarian, has a simpler task of locating a stationary deciduous tree for dinner. From an evolutionary perspective, the diversity of eye shapes across insect groups is not very difficult to modify because insects have compound eyes; meaning that the structure we recognize as an eye is actually comprised of many repeated units called ommatidia. Thus, to change the size of the eye evolution acts on the number of ommatidia, rather than on the size of a single organ.

A detailed illustration of a single ommatidium from Snodgrass (1935).

  

For details regarding the structure of the ommatidia I defer to the father of insect morphology, Robert Evans Snodgrass, and his Principles of Insect Morphology published in 1935. An interesting man with an inspiring career that would be worthy of revisiting in a later blog post. 

R. E. Snodgrass (Image credit)

 

   The outer layer of each ommatidium (singular) has a corneal lens, which is hypothesized to have self-cleaning, anti-fogging, and anti-reflective properties¹. Lucrative properties for humans trying to keep fog from freezing on power lines, or prevent condensation from accumulating on scuba diving and skiing masks. In order to put insect eye structure to work for us we first need to determine what the corneal lens structure looks like in insects, and then we may want to know how it has evolved along the insect phylogeny. The framework necessary for these investigations is an understanding of the anatomy of insect eyes, which we have thanks to Snodgrass and other curious-minded insect anatomists. And then we need a phylogeny, or historical perspective of insect relationships, to understand how these structures change through time. 

   In 2014, Sun and colleagues published a paper in the journal Small (not because the journal is small or publishes small science, but because it publishes science focused at the nano- and microscales) describing the development of an anti-fogging polymer inspired by the nanostructures on the corneal lens of a green bottle fly (Lucilia sericata, described by Meigen in 1826 - although there appears to be some conflict regarding whether this fly should be in the genus Lucilia or the genus Phaenicia. A fascinating story I’m sure but we will let that one go for now.). You have probably seen a green bottle fly, they look like house flies but are larger and metallic green. They coalesce around poop; horse poop, dog poop, etc., which is one of the reasons scientists chose this fly. They wanted to know how the eye remained pristine in “…dusty, miry, and moist environments” (p. 3001). The scientists put their study subjects in front of a fog machine and found that the eye was superhydrophobic and stayed dry while the rest of the body was covered in water droplets.

Figure 1 from Sun et al. (2014). Figure caption: "Microstructures of the fly compound eye and bio-inspired nanostructures. (a) optical image of a green bottle fly, Lucilia sericata, in a fogging test chamber showing the superhydrophobic and clean surface of the compound eyes, even with drops nucleated in the surrounding hairs, (b) schematic illustration of the anatomic structure of the fly compound eye, (c) low magnification SEM image of one fly compound eye, (d) high magnification SEM image of the compound eye showing the close packed ommatidium lens surface, (e) bubble-like protuberances with diameters of ∼100 nm on the surface of the ommatidium, (f) microstructure of the fly-eye bio-inspired ZnO nanostructures consisting of ommatidium-lens-like structures, and (g) a cross-sectional view of the bio-inspired nanostructures, showing similar structures to the anatomic structure of natural fly eyes."

   The key to keeping water droplets off of a surface is getting it to bead up to prevent the droplet from sticking, which facilitates motion in accordance with gravity. I think about this in relation to water droplets forming on the windshield of the fancy car of an unnamed family member versus the windshield of my 2006 Honda Civic. On fancy cars, water droplets bead up and slide off the windshield. On my car they spread out like an amoeba and the added surface area prevents them from sliding down. Same idea with the insect eye – the nanostructures on the surface of the corneal lens make it as hydrophobic as the windshield of a Tesla. When scientists looked at insect eyes at very high magnification, they found the surface is uneven and rough due to multiple layers of overlapping hexagonal nanostructures. 

 With this information in hand, Sun and colleagues used trial and error to establish a protocol to synthesize a polymer resembling the nanostructure of the fly-eye corneal lens. And, results from subsequent experimental tests using treated and untreated surfaces in a foggy room were very clear, the polymer was a success.

Figure 4d from Sun et al. (2014). Figure caption: "Dynamic anti-fogging properties of the bio-inspired nanostructures….. (d) Fogging of the samples placed at a tilting angle of 10^o, clearly showing the fog sliding off of the bio-inspired nanostructured coating, but strongly sticking onto the bare glass surface."

  But the question remains, what do these nanostructures look like in other insects? Does the corneal lens surface of cockroaches look the same as the green bottle fly? Based on some work done in the 1970’s, using the best technology at that time, Bernhard and colleagues² revealed significant variation of corneal lens structures in different insect groups. A recent follow-up analysis using newer technology supported the original finding and uncovered a shocking diversity of nanostructures. 

Figure 4 from Blagodatski et al. (2015). Figure caption: "Transformations of corneal nanopatterns. The morphogramme depicts the likely interconversions among the nanostructural patterns found in the insect class rather than phylogenetic relationships of the patterns. Primordial dimpled nanopatterns (1, here from a Forficula earwig) can transform into various maze-type nanostructures (2–4; 2 from a Pyrrhocoris firebug, 3 from a Tabanidae fly, and 4 from the butterfly Protographium asius). The latter can further transform into disordered nipples (6, here from the fruit fly Drosophila melanogaster), which can further become orderly packed (7, here from a Pterophoridae moth). Alternatively, parallel ridges (5, here from a Tipulidae fly) can evolve either from mazes or nipples. The figure is made of reconstructed 3D AFM images fused, for the sake of visualization not in exact scale, using MATLAB."

  Using a technique called atomic force microscopy, Blagodatski and colleagues (2015) documented how nanostructure diversity changes through time. So now, not only are we interested in how fly-eyes inspire anti-fogging polymer treatments, we are thinking about the evolution of the corneal lens and what it mean for insects carrying out their lives in miry environments. From the perspective of the insects, what I find interesting is that closely related groups do not necessarily have similar nanostructures. This is unusual because we typically think of close relatives resembling each other more than they resemble distant relatives – me and my dad look more alike than me and my friend’s dad, hopefully. Scientists often hypothesize that such a pattern is indicative of adaptation, rather than just inheriting what your ancestors had. It is too early to tell whether this is the case in insects. But the images are beautiful.

¹Bernhard, Miller, and MØller (1962) Function of the corneal nipplein compound eyes of insects. Acta Physiologica 58: 381-381

²Bernhard, Gemne, Sälstrom (1970)Comparative ultrastructure of corneal surface topography in insects withaspects on phylogenesis and function. Journal of Comparative Physiology A 67:1-25.