Stanford Earth Undergraduate Research Symposium
Summer research projects from the 2020 SESUR cohort
Christopher Noll: The Correlation Between Paleopteran Wing Vein Density and Body Size
Authors: Christopher Noll, Sandra R Schachat, Dr. Kevin Boyce, and Dr. Jonathan Payne
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Abstract:
Prior research on plant physiology has suggested that high leaf vein density, highly hierarchical vein networks, and other leaf structures allow for more efficient water transportation and higher productivity in angiosperms (Boyce & Zwieniecki, 2019). In a similar vein, winged paleopteran insects must also rely on their wing vein network to perform similar functions. Paleopteran insect wing veins allow for the transmission of hemolymph, oxygen, and sensory information to and from their wings (Wootton, 1992). Moreover, winged insects rely on their wing veins for much more than just nutritional and sensory information transport: wing veins may also provide a mechanical skeleton that both stiffens the wing (Wootton, 1992; Jongerius & Lentink, 2010; Rees, 1975) and hampers the propagation of wing fractures (Dirks & Taylor, 2012; Rajabi et al., 2015). The wing-stiffening and fracture-preventative functions of wing veins are especially crucial for longer-lived, predacious paleopteran insects like odonates that need to be mobile to catch their prey while preventing wing failure. Despite the beneficial aspects of prolific wing venation, wings with dense venation can become less flexible (Combes & Daniel, 2003) and may become heavier than their counterparts. As such, insect wing vein density (a measurement of how densely an insect’s wings are covered with veins) and its correlation with the insect’s wing length have important implications. The wing vein density of meganeurids is especially insightful in understanding how large paleopteran winged insects evolutionarily handled wing vein density trade-offs. Wing vein density correlations may also be able to provide additional insight into the lifestyles and wing use of Paleopteran insects (e.g., the difference in lifestyle and predatory behavior indicated by the wing vein density of odonates and ephemeropterids). Finally, wing vein density optimization is especially pertinent to the creation of larger micro-air vehicles with wings that are durable and long lasting.
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References:
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Hi Christopher — very impressive presentation, great work! I was fascinated by the scientific approach and I learned a lot!
Hello, Tyler!
Thank you for your kind words!
Cheers!
Hi Christopher, Congratulations! Very interesting. Can you tell me more about how you measured the wing density? Was this both living and fossil species that you looked at?
Your description of the comparison of different life styles of flying – mating or feeding – was interesting. How might you think about representing the relationship between vein density and life style?
– Jenny
Hello, Jenny!
I’d be happy to tell you more!
Specifically, in our research, wing vein density is measured by simply dividing a wing’s total vein length (in cm) by its wing surface area (in cm2). These two variables that make up our wing vein density value were obtained by using the image analyses software MIPAR on “processed” line drawings of insect wings. A “processed” image is one where I have used the Affinity Designer graphics software to add two bars and one shape to a line-drawn image of an insect wing. The first bar provides MIPAR with a 1 cm scale bar for reference, the second bar provides MIPAR the length of the wing, and the shape provides MIPAR with the surface area of the wing.
Indeed! Both fossil and living specimens were looked at in this study.
Unfortunately, although initially I had thought that lifestyle and wing vein density could be somehow correlated, this does not seem to be the case. Namely, despite insects of various lifestyles having various wing vein densities, the flying insects we have studied are heavily dependent on their wings. Whether we are referring to the shortlived Ephemeroptera, the predacious Odonata, or some other flying insect, if the insect relies on flight for an important purpose (e.g., reproduction, predation, etc.) they will likely evolve to have their wings be as structurally sound and efficient as possible. Thus, we are unlikely to be able to correlate lifestyle to wing vein density FOR OUR CURRENT SPECIMENTS. We MAY be able to do some wing vein density analyses on insects with vestigial wings, which may provide a better sense of how insects that do not use their wings at all have altered their wing vein density. This research is a little further out, as we are currently focusing on including neopteran specimens in our analyses.
Thank you for your question!
Hi Christopher! Wow, I had never heard of any of this.. super cool! What do you see as avenues for future research? Do you plan to explore something else?
Hello Isabelle!
Thank you for your compliment!
I’m currently delving into the wing vein density of neopterans.
The neopterans are what we typically think of as flying insects! From mosquitos to the mighty Atlas beetle, all neopterans can fold their wings, which separates them from the palaeopterans (the flying insects that cannot fold their wings akin to dragonflies).
If our research group continues to find a large swath of neopterans displaying the same negative wing vein density/wing length trend, this may indicate a more general restriction in wing vein density and its optimization in flying insects.
For example, if Diptera (the order encompassing true flies like houseflies) and Ephemeroptera (the mayflies) specimens both lie on the same trend line, this may indicate a more general rule that, if a flying insect with a short wing wants to fly well, it must adhere to this trend. If this outcome would occur, it would significantly reinforce my general restriction assertion because Diptera and Ephemeroptera are VERY distantly related (the former a neopteran and the latter a palaeopteran).
If you are interested in the phylogeny of modern insects, you can find a lovely, relatively-recent diagram here: http://www.sci-news.com/biology/science-family-tree-insects-02264.html
Thank you for your question!
Hey Christopher! Nice work! I’m curious if had any ideas as to why the wing density of Ephemeroptera varied so greatly, especially compared to the other orders?
Hello, Patrick!
Indeed, that is the question of the hour!
My current hypothesis is that wing vein density is something to optimize. As such, when wings grow longer, the winged insects need to be more efficient and avoid the potential pitfalls of highly veined wings. Thus, I believe that these drawbacks likely are the potential reasons why wing vein density for ephemeropterids takes a sudden nosedive.
If the dipterans, who also sport extremely short wings, display a vastly different trend, the variation you speak of may solely be an Ephemeroptera-only occurrence to look into and perform further research on. The similar wing vein density research I am currently conducting on Diptera may be able to more concretely point to the cause of this drastic wing vein density shift.
Thank you for your question!
Hi Chris!
I learned a lot from your presentation! I’m interested to know if and how differences in wing vein density may affect the flight of these Palopteran insects. Do you know if higher wing density and thus smaller wing length inhibits their flight performance?
Hello!
My name is Chris.
These differences in wing vein density likely mirror what these flying insects need to fly most efficiently. If you think of the difference between a small hand fan (which needs more support to meaningfully move air) and a longer piece of cardboard (which is able to more easily move air due to its larger surface area), these short wing length flying insects likely need this higher wing density to be able to fly and do so well.
Thank you for your question!
Hi Christopher! Great work. I was wondering: if you could design your own micro-air vehicle imitating a paleopteran, would you choose short wings with high vein density or longer wings with a lower vein density — and why?
Hello, Colette!
Personally, I would choose the latter!
This is because these flying insects largely are odonates (the order encompassing dragonflies), who can do incredible things when flying! Odonates can hover, fly backwards, and perform other amazing flight manoeuvres! Their wing vein density and the way they have placed them on their wings likely allow them to preserve their efficiency and prevent fractures when pursuing their prey.
If you would like to learn more about dragonflies, a link to an extremely informative yet short article on dragonfly fight can found here: https://bit.ly/3drBWSc
Thank you for your question!