May 20, 2015 by cotesia1

Quorum Sensing On Capitol Hill

Last Fall I was selected to be a member of the inaugural class of the Entomological Society of America (ESA) Science Policy Fellows. Last week came our first big test – be advocates for entomology and entomological research on Capitol Hill. And guess what? We had a very productive time.

.@EntsocAmerica #SciPol Fellows prepping for 2morrow's visits to @uscapitol. W/ @EntoAriel @jamindreyer pic.twitter.com/BWwk1mGiIk

— Marianne Alleyne (@Cotesia1) May 13, 2015

I’ve wanted to write about our Congressional visits from before I even left on my trip, but was struggling to find a hook that would pull together government, politics and bioinspiration. I could go with a story about dominance hierarchies (=pecking order) in both human and animal societies, or one about gift giving and the influence it can buy, or an essay about insects that steal from other insects. Or was this finally going to be the blog post where I could discuss my favorite topic in all of biology: parasitism?

Actually, turns out that the Congressional visits were challenging, exciting, beneficial, fun, inspiring, etc. The most appropriate bioinspired analogy I can make is to quorum sensing seen in social insects.

“Now what? We better find the best new nest site quickly.”
Picture by Eran Finkle via Flickr.com

Honeybees, for instance, use quorum sensing to find a new nest site. A swarm comprised of 10,000+ bees decides on the best spot to start a new nest, not by letting just the queen decide, but by gathering information from different scout bees. A couple of hundred scout bees convey information to others in the swarm about the quality of about a dozen possible nest sites. Nest sites can be superb, mediocre or lousy, or somewhere in between. Based on the information about the possible site’s quality conveyed by the scout bees the swarm as a whole decides which site is most suitable. It is important that all information is freely shared, no bee’s opinion is stifled. Coalitions of scouts that have discovered a certain site will try their best to convince other scouts to go check out a potential site. The better the potential site, the more vigorous the bee will waggle-dance. A more vigorous dance will convince more uncommitted scouts to go check out the site. So there is competition between the coalitions, but what is important is that the uncommitted scout does not blindly follow the information. She will go check out the site but will decide for herself if she will advertise the site when she returns to the swarm. In other words, acceptance of a poor site (through cheating or through the creation of mass hysteria) is impossible. Through quorum sensing many opinions are heard and evaluated, yet this is done rather quickly so that the swarm is not vulnerable for long. Options are not debated “to death”.

Probably not the best nest site. Picture by By Nino Barbieri (Own work) [CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5)], via Wikimedia Commons

“Probably not the best nest site.”
Picture by Nino Barbieri (Own work) [CC BY-SA 2.5 via Wikimedia Commons]

Good group decisions, the bees show us, can be fostered by endowing a group with three key habits:
1. structuring each deliberation as an open competition of ideas,
2. promoting diversity of knowledge and interdependence of opinions among a group’s members
3. and aggregating the opinions in a way that meets time constraints yet wisely exploits the breadth of knowledge with the group.

Seeley, Visscher and Passino

American Scientist May-June 2006

What we can learn from honeybee democracies (yes, there is even a fantastic book on this topic) is that any democratic government can make the best decisions, within a reasonable time period, when it goes through phases of collective fact-finding, vigorous debate, and consensus building. Quorum sensing is a type of decision-making process in any decentralized system – one without a clear boss. Any decision-making group should rely on information of individuals with knowledge about the topic, shared interests (stakeholders) and mutual respect. Debate should be relied upon, diverse solutions should be sought, and the majority should be counted on for a dependable resolution. Sound familiar? Too idealistic?

Probably also not the best nest site. Picture by MSgt Todd E. Enderle, 309 AMU/MXACW, 13 Oct 2005, submitted by Wayne Fordham, HQ AFCESA/CESM, Tyndall AFB, FL.

Probably also not the best nest site.
Picture by MSgt Todd E. Enderle, Tyndall AFB, FL. via Flickr.com

I may seem a little idealistic here but while visiting the Senate’s and House of Representative’s offices I definitely had the feeling that constituents, experts, stakeholders and staffers were coming together to share information in an effort to help inform the legislators. All our meetings with staffers, and in my case in person with a Sen. Dick Durbin: D-IL and Rep. Rodney Davis: R-IL, were worthwhile. Staffers seemed interested, if not always knowledgeable about entomology (though many of them were). And it was clear to us that staffers were keen to have access to the best scientific information, preferably written/conveyed by experts using clear terminology and in a concise manner.

The leadership of the Entomological Society of America has put resources into the science policy fellowships, science policy committees and communication about science policy with the understanding that the pay-off may not become obvious until a few years from now. Even what this “pay-off” may be is not clear – it can vary from ESA name recognition, more familiarity with the field of entomology among legislators (beyond pesticide-spraying- or butterfly-net-waving-scientists), more expert entomological input into important policy decisions, job opportunities for entomologists with a science policy interest, more state and federal funding for entomology, etc.

In principle the United States government encourages collective fact finding with an open sharing of ideas. Again, I felt that our message was welcomed, but we, ESA members, need to become more proactive in sharing our message. We need to continue to visit State and Federal government offices and explain to them why research on insects is important – why sustained funding is important. We need to be more proactive about sharing our entomological science and expertise. ESA needs to set the agenda, not react to it. If you, the scout bee, are not showing up, or do not have the credibility, then your opinion will not be considered. Over time, with name/research-field recognition, your expert science-based opinion may become more valued (of course, this does not happen in honeybee swarms, and neither does the importance of money in buying name recognition – this is where the bioinspiration model (or is it our current democracy model?) breaks down).
On paper a strong democracy should promote diversity of knowledge and vigorous debate among stakeholders. There is, however, a difference between scientific evidence and pseudo-science and the two should not receive equal consideration. Scientific evidence may also not line up with constituent (stakeholder) economic, social and cultural interests. And, again, money and power may outshine solid scientific evidence and stifle debate about the science. By asserting ourselves as the premier source of entomological science we should be able to be part of the debate.
The strength of quorum sensing in relation to honeybee swarm nest finding is that in a relatively short time period a consensus is reached. Currently consensus building in Congress on many issues is, let’s just say, difficult. But when it comes to a topic such as Pollinator Health then I am pretty hopeful. (On the issue of the importance of pollinator health we have generally strong bipartisan support.) One of the greatest weaknesses that I see is that even within the ESA itself consensus building is taking too long. For more than 6 months members have been working hard on position statement regarding Pollinator Health and Tick-borne diseases. Meanwhile Congressional hearings have been held, and White House “national strategies” have been set in motion – sometimes with little or no input from ESA. Again, we should help set the agenda, not just react to it!

Our message as entomological experts (7000+ ESA members) will be heard depending on if our information is backed up by good scientific evidence, is supplied in a timely manner and communicated properly. In addition, our representatives in government need to be open to receiving this information. Their willingness to incorporate our advice may depend on their committee assignments, ability to understand the topic, their home districts and states, their constituents, etc. ESA has to start somewhere in gaining more influence and securing sustained research funding for their members. I believe this month’s congressional visits by the science policy fellows was a great beginning.

Now we may be on to something. Picture by Ontheway2it via Flickr.com

Note: I want to thank Lewis-Burke Associates, the government relations firm that is working with ESA to train the Science Policy Fellows. We learn so much from them. Thank goodness for their collective sense of humor and endless patience!

The insect cuticle: (4) hydration

This post is part of a series on the insect cuticle as a biological material that can inspire novel engineered materials. The characteristics of the cuticle, setting it apart from most synthetic/engineered materials, will be discussed in this series. The introduction to the series can be found here.

Hydration: Slippery when wet-ish

Traditional manufacturing of engineered materials tries to avoid, at all cost, incorporating water. Yet, the properties of biological materials are determined to a large degree by the absence or presence of water molecules located within the extracellular spaces (=hydration level). The presence of water affects mechanical properties such as toughness or strength. It serves as a plasticizer, keeping a material flexible and resilient. Once an engineered material is manufactured we don’t really want to be able to manipulate these types of properties; materials are to remain static. But wouldn’t there be advantages to having bioinspired materials that are more adaptive depending on their surroundings? Certainly materials that are able to alter their function within a structure at different times will result in some very innovative applications.

Insects go through different life stages, most pronounced in holometabolous insects; egg, caterpillar, pupa, adult. All these life stages exhibit different cuticle characteristics, maybe even on the same body (e.g. tough thorax, soft abdomen).

Various Sphingid moth life stages and species – with different cuticle characteristics. Art by Rob Mitchell, used with permission.

It is not well understood how hydration influences one of the most impressive features of the insect cuticle: the ability to sclerotize (also called tanning or hardening). The chitin fibers that are a major component of the cuticle are hydrophylic and are thus surrounded by water molecules. Chitin becomes dehydrated when it becomes part of the protein matrix since the proteins within this matrix are generally hydrophobic. This dehydration contributes to cuticle stiffening and de-plasticization. The most commonly referenced mechanism that results in sclerotization is the cross-linking between proteins and phenols that are present in the cuticle. There is certainly some experimental evidence for covalent interactions between proteins and phenols that help stabilize the cuticle, but it is not clear if these interactions directly result in a stiffening of the cuticle. Now, all these interactions between chitin, proteins, phenols and water result in a type of hydrophobic coating of chitin fibrils that increases the mechanical load the proteins can carry. Softening of the cuticle also becomes less of an issue. Just which of these interactions have an hardening effect on the cuticle AND are actually resulting in sclerotization, has yet to be precisely determined

It has been shown that water content of the cuticle has an important role in determining cuticle mechanical properties. At the same time it also clear that sclerotization is not just simply dehydration. In other words, the cuticle minus water becomes hardened, no matter if the cuticle is sclerotized or not. Sclerotization is an irreversible pathway, the bonds cannot be broken. The presence or absence of water in an unsclerotized cuticle means that some fine-tuning of mechanical properties can still occur even after the cuticle has been fully formed.

To me this seems like a feature that we might want to consider using in engineered materials. Fabricating materials using chemistry in water is a different approach, but this is how biological materials are synthesized in nature. To be able to create materials that can adapt to their environment, or are multifunctional, just by varying the degrees of adsorption and absorption of water, could lead to exciting innovations.

Various beetle life stages and species (plus some of their natural enemies) – all with different cuticle characteristics. Art by Rob Mitchell, used with permission.

May 6, 2015 by cotesia1

The insect cuticle: (3) self-assembly

Self-assembly: manufacturing the future

The materials and structures that we humans create for ourselves generally involve large factory manufacturing systems where we “Heat, Beat and Treat” materials into the structure we require.

“Motor Manufacturing” By Clive Gardiner for the Empire Marketing Board. c1930 National Archives UK

In contrast to most engineered materials, biological materials are assembled from the bottom up, rather than from the top down. The formation of materials like chitin, which is the main component of the insect cuticle, is the result of self-assembly and well ordered biosynthesis.

In engineering the material used is relatively cheap but the shape of the structure is expensive, since it results of very energy-intensive processing (the heating, beating and treating parts).

“A Blast Furnace” By Clive Gardiner for the Empire Marketing Board. c1930 National Archives UK

In biology it is actually the other way around. The instructions for manufacturing processes are stored in the genes of all living things. The information contained in an organism’s DNA determines the sequence of molecules that will be expressed by the organism’s cells. It is the characteristics of these molecules that will determine how they interact and ultimately determine the shape of the final material and resulting structure (=self-assembly). In other words, energy is replaced by information, which is cheap. In biology it is the building blocks that make the structure that are relatively expensive to obtain (through capture, consumption, assimilation, etc.) and organisms cannot afford to waste these building blocks.

The biological manufacturing process is constrained by a range of external factors, which then may result in different structures under different circumstances. These external factors are, for instance, temperature (variable on different time-scales), mechanical loading (variable at different life stages and during different seasons) and the presence or absence of water, light and appropriate nutrition (which all three vary over the lifetime of an organism).

“Kreeping It Real” (Graffiti art on boxcar). Picture by Rob Swatski. Flickr.com.

A characteristic of biological materials is that they grow relatively slowly. At first this may seem like a disadvantage, but since these materials as they grow are exposed to a range of forces they can adapt to situations that may alter over the course of the structure’s lifetime. Engineers, using traditional manufacturing techniques, do not have this luxury, they have to preempt and anticipate changing conditions – or ignore them resulting in a reduced effective lifetime.

Self-assembly happens at all scales in nature – it starts at the molecular scale at which molecules are formed into globs which are formed into fibers. Manufacturing at the nano- or micro-scale may still be in its infancy but great strides are being made. And in the meantime we can apply nature’s lessons regarding biosynthesis and self-assembly at a larger scale – creating hybrids of multiple materials with the functional variety that is required of the material.

As Carl Hastrich points out on his Bouncing Ideas blog:

[the] future is fibre. Everything in nature is a fibre. From beetle exoskeletons, to the incredible structures found in the botanical world, they are all fibres. The results are complex, malleable, repairable materials that integrate a vast array of functions. Have a look at a cross section of human muscle and you’ll see what I mean. Humans on the other hand build with large brittle mono-materials and achieve complex function by mechanically integrating multiple components.

Over the past few decades we have tried to incorporate more manufacturing techniques that are non-toxic, water-based, and do not require high-energy inputs – life-friendly chemistry. 3-D printing techniques open up such an avenue since it is by definition builds from the bottom-up, rather than top-down, thus already mimicking nature in that regard, and new non-toxic base materials for these printers are being developed.

The future of manufacturing. (Art based on pictures by M. Alleyne, Yogendra Joshi and MKZero)

The future of manufacturing biological materials. (Art based on pictures by M. Alleyne, Yogendra Joshi and MKZero)

How insects bioinspire us to innovate

Month: May 2015

The insect cuticle: (4) hydration

Hydration: Slippery when wet-ish

The insect cuticle: (3) self-assembly

Self-assembly: manufacturing the future

Further Reading

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Hydration: Slippery when wet-ish

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Self-assembly: manufacturing the future

Further Reading

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