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.

why we should eat insects

   I have not done it very much, but I am an advocate of eating insects. The first time was in my Entomology class in college, almost 20 years ago. My professor, Dr. Letourneau, sautéed some butter and garlic at the front of the classroom, dropped in a container of mealworms (which are actually beetle larvae, not worms at all), and served them with slices of baguette. It was good. Butter and garlic can make anything taste good. I also ate escamoles, an ant egg delicacy from Central Mexico.

Liometopum occidentale, one of two ant species whose eggs are harvested for escamoles (Image credit: Michael Branstetter 2007, AntWeb.org)

   
   During a work trip to Querétaro, Mexico my colleague introduced me to escamoles at a fancy Italian restaurant – they were not on the menu and I had no idea how much they cost. The ant eggs were cooked in spices and served alongside corn tortillas and guacamole and made into little tacos. Biting into the taco was superb, the texture worked and the flavor was unlike anything I had eaten before. There was a subtle popping with each chew, and the flavor of the eggs resembled that of buttery pine nuts. I have also had brownies with whole crickets embedded in the top. Is there more of a grossness factor when you can see and recognize the entire insect as it goes in your mouth? Yes, it made my stomach flutter. But the escamoles did not affect me at all, and the mealworms only a little.    

   Insects are traditional foods (and often delicacies) that are eaten regularly in Latin America, Africa, and Asia. The same cannot be said for the United States. Finding insects in the store or at a restaurant is rare. But it doesn't have to stay this way; Americans have overcome culturally-based food obstacles in the past. Let us consider the history of lobster in the United States. There was a time when New Englanders fertilized their gardens with lobsters, and eating them indicated things were not going well for you financially. So what are the barriers preventing this from happening with insects? I haven’t collected any data but I think it is safe to say that many Americans think it is just plain gross. How appealing does eating a whole cricket, or mealworm, sound to you? I don’t disagree. And I don’t think you and I are alone, which is why companies have started marketing insects in unrecognizable forms. Cricket flour, dry roasted crickets ground up into a fine powder; and mealworm tofu. We can also overcome this obstacle by thinking about eating insects and lobsters from an evolutionary perspective. Insects and lobsters are in the same evolutionary lineage called Arthropoda - they are very closely related. So much so that insects could be considered a terrestrial version of lobsters, crabs, and shrimp. So, biologically speaking, eating insects is no different than eating lobster.

   Why am I talking about eating insects? What does this have to do with scientific discoveries? Since I study insects I spend a lot of time thinking and reading about them in different contexts. One of those contexts is eating them, and it is impossible to overstate the benefits. As established by the United Nations Food and Agriculture Organization (FAO), consideration of insects as a critical food source is essential because they are 1) highly nutritious, 2) an important component of traditional diets in food insecure regions, and 3) environmentally sustainable relative to alternative protein sources such as beef. In addition, eating insect pests can reduce pesticide use with added economic incentives. Researchers in Mexico have developed a strategy to harvest a Mexican grasshopper pest from crops using mechanical methods (rather than pesticides) that would result in a gross income of US$350 million annually if the crickets are subsequently sold for human consumption.

   Because all of these factors can positively impact the health of our planet and its population for the long term, my plan is to come up with some good recipes and integrate insects into my diet. So I bought some cricket flour. I used it to make pizza dough. And as much as I want to tell you how successful my first try was, I can’t. Let me explain. I like to cook; and while I am no culinary genius, there is some culinary talent in my family. I have a basic understanding of flavors and flavor combinations.

Cricket flour (I am not sponsored by this company in any way and am not advocating for purchase of this particular flour)

    
   The cricket flour was brown and had an earthy, soil-like aroma. It tasted a lot like soil as well. I have read some articles describing cricket flour as nutty - I didn’t get nutty, just earthy. Since earthy falls in the savory category, I decided to make a savory dish rather than something sweet as many people suggest. I chose pizza dough.

Cricket flour pizza dough

    
   I followed the recipe of a simple pizza dough from my favorite food blog, Smitten Kitchen. It seemed small so I doubled it. Instead of adding three cups white flour I added two cups white flour, ¾ cup cricket flour, and ¼ cup whole-wheat pastry flour. To counteract the earthy, bitter flavor of the cricket flour I topped the pizza with caramelized onions. One half had olive oil, caramelized onions, and Trader Joe’s honey goat cheese; the other half had red pizza sauce, caramelized onions, and cheddar cheese. 

Left: goat cheese and caramelized onions. Right: red sauce, caramelized onions and cheddar cheese.

   
   My husband (J) and I were the judges of the cricket flour pizza dough experiment. I am not a picky eater, the only thing I will not eat is raw celery. J is even less of a picky eater and will ravenously eat almost anything.

  After my whole introduction about how healthy and sustainable it is to eat insects, you can imagine my disappointment when I did not like the cricket flour pizza dough. My initial optimism was very high. For the first couple of chews I didn’t notice a difference, especially for the half with red sauce and cheddar cheese. But as I kept chewing and swallowing, the aftertaste set it in. So earthy, too earthy. The honey goat cheese side was even more difficult, it didn’t have any sauce to overwhelm the earthy flavor. I kept trying to clear my mind and have another bite. I really wanted to love it. I wanted to be able to sit down and write about how great it was and advocate for it like nobody’s business, but my disappointment was real.

I couldn't bring myself to eat the crusts

   
   J liked it and helped himself to seconds. Maybe his disconnection with the preparation process made it easier for him? The other upside was the nutritional improvement. In one slice of pizza, the cricket flour pizza dough had 8.4 grams of protein compared to 1.6 if I had made it with all white flour. It also had 60% of the suggested daily amount of vitamin B₁₂, of which white flour has none.

   Don’t worry, I am not giving up. In the spirit of George de Mestral, and all of the other curious experimenters out there, I will keep trying. I will compare different cricket flours, and I have more recipe ideas. I will also experiment with other insect food products, like the mealworm tofu. This is not the end of insect eating for me - I have only just begun - and I will continue to be an entomophagy advocate.

commentary: evolution, bioinspiration, and biomimicry

   I am doing something a little different this week. Instead of investigating the foundational work underlying a biological discovery, I am going to talk about the difference between bioinspiration and biomimicry in the context of evolution. These are terms that have come up in previous blogs, and understanding the implications of each is both interesting and important.

Spiny-headed worms inspire. Roohi & Sattari (2015) Image caption: Fig. 2. P. laevis recovered from S. cephalus intestine stained with acetocarmine.

    Last week I engaged in some enlightening intellectual banter with one of my dear friends from college. She is a social scientist and I am an evolutionary biologist, and so it goes without saying that we are exposed to different literature, experiences, and applications of our research. One thing that came up during our conversation was whether there was directionality to evolution. We were talking about human evolution specifically but I, of course, was drawing on my own work studying evolution in beetles. Evolution by way of natural selection, as posited by Darwin and Wallace, can only operate on the variation present in a population at any given time. If we put this in terms of my favorite reality TV show, So You Think You Can Dance, it would go something like this. During the tryouts, the only option the judges have is to move someone to the next round or eliminate them. The judges cannot pick the feet of one contestant, add them to the legs of a second contestant, and then move the chimera to the next round. They must work with the variation at hand and either send a contestant to Vegas or send them home. Evolution is also much more dynamic, mostly due to the constantly changing environment organisms live in. Trait A, which may be favored most of the time, gives way to trait B during drought conditions.

Darwin, Charles (1845) Journal of Researches into the Natural History and Geology ofthe Countries Visited During the Voyage of H.M.S. Beagle Round the World (from1832-6). Under the Command of Capt. Fitz Roy.

   In other words, just because a bird beak has been evolving for millions of years, it doesn’t mean it is optimized. There is no optimum in evolution. What was optimal 100 million years ago may no longer be optimal now, but it may be 100 million years in the future. Just like bell-bottoms were high fashion in the 70’s, but definitely not in the 80’s. Then they made a comeback in the 2000’s, went out in the 2010’s, and may be coming back now (maybe, mom?) [2/23/16 update from my mom - they are now called flares].

   What does this have to do with bioinspiration and biomimicry? Many biologists, engineers, and bioengineers prefer the term bioinspiration over biomimicry because they feel it more accurately portrays the process of evolution. Biomimicry implies that we can mimic an optimal biological solution to a societal problem. But if we do that we are selling ourselves short because, from an evolutionary perspective, there is no optimal solution. As an engineer, you can take feet from one contestant and add them to the legs of another and generate a product that was inspired by nature, but not an exact mimic. Is this a matter of semantics? Maybe, but I think the distinction is important. Not just to have something to blog about, but to really try and understand the evolutionary process. And, to use that understanding to the benefit of our society by developing solutions to hard problems. Some organisms have already evolved adaptations to some of our problems, so why not take their millions of years of experience and break free from the constraints of natural selection? We are not limited by the variation currently at hand, and we shouldn’t let our curiosity be either.

spiny-headed worms: interesting enough for round two

   To delve deeper into the spiny-headed worm story we must first understand the proboscis. The proboscis is a tubular body part that sucks. A butterfly’s tongue that sucks nectar out of flowers is a proboscis. An elephant’s trunk is often called a proboscis. And the spiny sucking apparatus of acanthocephalan worms is a proboscis. 

Close-up of butterfly proboscis (image credit)

   The proboscis in parasitic worms has two functions, to attach to the host and extract nutrients from the intestinal lining. The crazy thing about the proboscis in this particular group of worms is that it is biphasic; it can be tube-like and erect, or it can be flaccid and turn itself outside-in and retract within a compartment of the worm body. When R. A. Hammond started working on Acanthocephalus ranae, our spiny-headed worm friend from last week’s post, it was known that the proboscis could retract, or invaginate. What wasn’t known was how it actually happened. Thus, the goal of R. A. Hammond’s study was to identify the in-and-out mechanism of the proboscis. Let me just say here that up until this point I have tried not to use words suggestive of a penile erection. It is a little difficult because I am talking about a tube-like structure that swells and becomes erect to function, only to return to a flaccid state when not being used. But, it is important to understand that I am not avoiding this comparison because I am afraid to talk about genitalia; on the contrary, I talk about genitalia on a daily basis. I am avoiding this comparison because it is misleading. The main difference is that when a human (or mammalian) penis becomes flaccid it does not invaginate, it just goes limp. To invaginate, the tip would have to retract in on itself and rest within an internal receptacle. Interesting idea, right? This is how many animal penises operate, from insects to reptiles. Evagination for operation, invagination for daily life. Now that we have this out of the way, let’s move on.

   To figure out how the proboscis worked, Hammond used a technique first described by Pflugfelder in 1949. Pflugfelder! I am not going to go on a tirade about him, I want to focus on Hammond, but what a name. The technique involved feeding the parasite host, in this case the common toad (Bufo bufo), pork fat with a red stain dissolved in it. Once the fat/red stain solution was in the toad’s digestive system the parasites fed on it too. The stain was sequestered in particular structures of the worm called lemnisci, which were hypothesized to be involved with the evaginate – invaginate process. I know, lemnisci is not a term I use on a regular basis either, I’ll try not to let it contribute to confusion. To summarize, Hammond fed toads a fat/red stain mixture, dissected the intestines out of the toad, pulled out the worms, imaged the stained lemnisci under the microscope using still pictures and video, and traced the morphological changes from beginning to end. All of this to find out how the worm proboscis worked. Not to invent microneedles, not to develop a surgical adhesive, he wanted to know how it worked.

   What Hammond discovered was that the invagination and evagination mechanism was controlled by a set of muscles that pulled and pushed the proboscis into and out of the receptacle by changing the hydrostatic (fluid) pressure of various morphological components. Interestingly, once the proboscis was fully extended, a set of collar muscles around the base contracted and pushed fluid up into the proboscis wall causing the skin to swell. It was this swelling mechanism of the worm that inspired the microneedle adhesive.

Figure 1a from Yun Yang et al. (2013). Image caption: "Illustration showing mechanical interlocking of a water responsive shape-changeable microneedle following penetration into tissue."

I want to point out that the microneedle adhesives were inspired by the proboscis (bioinspiration) as opposed to mimicking the proboscis (biomimicry). The reason is that the swelling mechanism of the worm proboscis relies on muscular contraction whereas swelling of the microneedles occurs with the addition of water. What is similar is that they are biphasic, and have a tip that swells relative to a base that does not. A patent application for this discovery was filed on Nov. 26, 2015. Since the original publication describing swellable microneedles, there have been several other useful applications including designs to deliver drugs, vaccines, and insulin directly through the skin.

A side note: In light of what is going on with the water supply in Flint, Michigan, I wanted to also mention how P. laevis and its relatives can be used as bioindicators in freshwater ecosystems. Because P. laevis parasitizes freshwater fish, it has been shown they accumulate heavy metals, such as lead, from the aquatic environment and can be used to monitor heavy metal concentrations. Maybe we should send some to Flint.