Research and design: how biologists draw inspiration from nature’s complexities

Written by Andrew Saintsing

Nature is full of awe-inspiring things, like a butterfly’s scaly wings diffracting light to produce brilliant color. For comparative physiologist Dr. Jon Harrison, wonder at the natural world sparked a lifelong passion in the rules of biological scaling. “I’ve always loved the stories about giraffes and their huge hearts and all the adaptations they have to be able to have such long necks and achieve those sizes.” But understanding how the forces of physics, chemistry and evolution shaped those adaptations is not easy. 

A deep understanding of biology requires consideration of many perspectives, ranging from biomaterials to physiology to ecology. Like Harrison, Dr. Emilie Snell-Rood is a biologist with a deep appreciation for nature, but she also strives to ensure everyone, not just biologists with doctoral degrees, can fully appreciate life in all of its multifaceted splendor. Bioinspired design is central to her goal.

Dr. Emilie Snell-Rood smiles and holds up her hand to show off a black and yellow butterfly with blue spots at the base of its wings.
Dr. Emilie Snell-Rood is an associate professor at the University of Minnesota, where she teaches an undergraduate course on bioinspired design. Here she is pictured with a Papilo glaucus butterfly. Structural coloration is responsible for the blue spots at the base of this butterfly’s wings. Photo credit: Jackson Eddy from A Frame Forward Photography

According to Snell-Rood, the process of bioinspired design is “problem-based, and you can take a problem, distill it to a function, come up with biological analogies, and then explore the space for ideas.” For example, clothing designers solving the problem of fading color could distill the function to color production, and then use, say, the structural coloration of butterflies as a solution. From textiles to robotics, bioinspired design could lead to breakthroughs, and it’s also a great tool to engage the public. “It makes all of this totally random-sounding biology immediately potentially relevant,” says Snell-Rood. Still, she worries that non-academic biologists may not appreciate the complicated realities of nature. She wants to caution people against letting their assumptions cloud their perceptions of the natural world. 

For example, Snell-Rood says designers interested in built environments, which account for how different human activities interrelate, often come to her “with an assumption that nature is harmonious and all the things in the forest are happily coexisting.” She tells them that specific cases of altruism could inspire a built environment but conflict is abundant and cooperation cannot be assumed. Snell-Rood wants to compile similar advice into a series of six modules (the first of which formed the basis of her talk at SICB this year). This series will equip engineers, designers, and others with the tools they need to draw informed inspiration from nature. 

Snell-Rood wants her modules to be comprehensive but approachable. An engineer designing a fast-running, cheetah-inspired robot needs to know that cheetahs complete many tasks to survive; the best version of the robot would not replicate features which, while vital to living cheetahs, compromise running speed. However, that engineer doesn’t need to know all the evolutionary drivers that shaped the modern cheetah. That work falls to biologists who, like Jon Harrison, have the necessary time and resources.

At this year’s conference, Harrison showed just how complicated and time-consuming the work of a biologist is. Driven to understand why insects are small relative to vertebrates, Harrison has spent over 20 years investigating whether an insect’s oxygen delivery system could limit its body size. “It’s just one of those patterns that we look around and accept, but to me it’s disturbing that we don’t understand why,” says Harrison. Over the years, various biologists have proposed explanations—from the material properties of insects’ exoskeletons to the effects of predation. But a hypothesis from the 1990s suggesting that prehistoric levels of atmospheric oxygen drove increased insect body size inspired Harrison to question how the insect’s respiratory system, the tracheal system, varies with body size. 

Differently sized cockroaches are arranged in a circle around an Oreo.
Relative to humans, all insects seem small. Only the biggest of the cockroaches pictured above approach the size of an Oreo. But the huge size variation within this group of cockroaches enables researchers like Dr. Jon Harrison to explore questions about the rules of biological scaling.

In the following decades, Harrison and colleagues collected multiple species of cockroaches and scarab beetles, which range from 50 mg to 35 g, and used X-ray and micro-CT imaging techniques to quantify the volume of each specimen’s tracheal system. For both types of insects, the researchers found that the proportion of the body volume devoted to the tracheal system was fairly consistent, regardless of body size. But if they only considered the insects’ legs, they found that the proportion of leg volume devoted to the tracheal system increased with insect body size.

A black-and-white micro-CT-generated image shows solid space broken up by irregular empty tubes. Arrows indicate tracheae and air sacs.
Harrison and colleagues used micro-CT to generate images like the one above that shows the interior of a scarab beetle. Here portions of both the thorax, which is the part of an insect’s body that connects to its legs and wings, and a leg of the specimen are shown. The researchers made tracheal measurements in different body regions, including the legs and the thorax.

To explain these observations, Harrison and his colleagues considered the function of the tracheal system, which delivers air from holes that line the sides of an insect’s body directly to all the cells that need oxygen. There aren’t any openings on the legs, so the tracheal system has to carry slow-moving oxygen from the side of the insect’s body down the length of its leg. Increased tracheal volume in the legs may compensate for a slow pace of oxygen delivery by increasing the amount of air going into and out of the legs. Harrison and his colleagues argue that the maximum body size of an insect occurs when any further increases in tracheal volume would crowd out other vital structures like muscles and nerves. Their compelling hypotheses could motivate new biological research. 

Both Harrison and Snell-Rood demonstrate how engaging and rewarding the work of a biologist can be—if one has the time, patience, and resources for it. Thankfully, Dr. Emilie Snell-Rood works to ensure designers and other inspiration seekers can also access that hard-won knowledge. Life is as messy as it is beautiful, but there’s always a biologist willing to help make sense of it. 


Author information: Andrew Saintsing is a PhD candidate in the Department of Integrative Biology at UC Berkeley. He studies how insects deal with challenges, like leg loss and uneven terrain, during walking and running.

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