In any seemingly quiet pond the still waters actually team with tiny pond dwellers called&nbsp;Euglena gracilis.Unseen to the naked eye, the single-celled organism spirals through the water, pulled along a relatively straight path by a whiplike appendage in search of just the right level of light.But a new paper published Sept. 24 in <a href="http://dx.doi.org/10.1038/s41567-018-0277-7" target="_blank">Nature Physics</a> describes how, under some circumstances, Euglena halts its forward progress and begins tracing out elaborate counterclockwise polygons &mdash; triangles, squares, pentagons &mdash; in a mathematically defined effort to find a better environment.The discovery, led by <a href="https://profiles.stanford.edu/hans-riedel-kruse" target="_blank">Ingmar Riedel-Kruse</a>, assistant professor of bioengineering at Stanford University, could help scientists design tiny swimming robots of the future to be more efficient and effective at maneuvering through the bloodstream, for example, or navigating watery environments.&ldquo;We&rsquo;re trying to understand biological systems in a mathematical way,&rdquo; Riedel-Kruse said. &ldquo;Seemingly simple feedback loops in single cells can actually generate rather complex behaviors in order to accomplish various tasks.&rdquo;<h2>Well-studied organism</h2>Scientists in the 1800s once marveled at finding Euglena &mdash; a greenish oblong with a red eyespot and long, whiplike flagellum for swimming &mdash; under a microscope. Since then, the organism has been observed by countless generations of biology students. With such a history of being watched, it came as a surprise when postdoctoral fellow Alan Tsang first noticed Euglena&rsquo;s novel behavior in a computer model he&rsquo;d developed to study how it moves in relation to light. In his model, when he simulated increased light, the organism began tracing out polygons.Riedel-Kruse remembered being skeptical when Tsang first described what his model predicted.&ldquo;It was hard to believe that it&rsquo;s true,&rdquo; Riedel-Kruse said. &ldquo;I thought there was something wrong with the code.&rdquo; But when the pair checked under the microscope &mdash; increasing light levels as in the simulation &mdash; there were the polygons.The shapes are a result of how Euglena navigates the world. Because the organism normally rolls through the water on its long axis, the eyespot rotates to survey 360 degrees of light. In steady light conditions &mdash; which is normal under a microscope &mdash; it meanders along in a relatively straight path.However, Tsang said, if the eyespot detects increased light intensity, the Euglena makes a hard turn.&ldquo;Then they don&rsquo;t see the light and they swim straight again,&rdquo; Riedel-Kruse said. &ldquo;But since they keep rolling, then after a full cycle they see again the strong light so they make another strong side turn.&rdquo;Enough straight lines followed by sharp turns and a triangle is born.Tsang noticed that over the course of about 30 seconds, Euglena adapted to the stronger light and the turns became less sharp, creating ever-expanding polygons &mdash; squares, then pentagons &mdash; until, finally, the Euglena headed in a relatively straight line.As for why nobody had seen this before, Riedel-Kruse said people rarely alter light levels while observing Euglena under a microscope. But since Tsang was specifically trying to model how the organism moves in relation to light, he did something unusual and the behavior appeared.<h2>A novel behavior</h2>Riedel-Kruse argued that the behavior makes sense for a Euglena swimming along in a pond under a comfortable source of shade. When it suddenly encounters bright sunlight it can turn quickly to seek a patch of shade. By slowly spiraling outward if the first few turns didn&rsquo;t work, the Euglena ups its chances of eventually getting out of the sunlight.Riedel-Kruse&rsquo;s lab studies Euglena in part to better understand how microorganisms navigate their watery worlds. The researchers also integrate what they learn about Euglena into interactive biology setups for education. Euglena is an unusual organism that can both make its own food and eat what it finds in the water. It is related to plants, animals and fungi &mdash; all known as eukaryotes &mdash; but is a separate group with some unique characteristics.&ldquo;Because it is part of an outgroup to most eukaryotic life, you could learn something that is general, and you can also find out how diverse eukaryotic life can be,&rdquo; Riedel-Kruse said. &ldquo;That makes Euglena really interesting to me.&rdquo;What&rsquo;s more, Riedel-Kruse and Tsang said what they learn &mdash; and the mathematical models they developed &mdash; could be useful for microscale robotics.&ldquo;There is an emerging field where people are trying to engineer and program microscopic swarm robotics for things like microsurgery or drug delivery,&rdquo; Tsang said. &ldquo;I definitely see people looking for efficient control mechanisms at the microscale.&rdquo;<iframe src="https://www.youtube.com/embed/oxwP-waWJlQ?&wmode=opaque" frameborder="0" allowfullscreen="" class="fr-draggable" style="width: 1115px; height: 610px;"></iframe>

Euglena swim in polygons to avoid light which may help scientists understand biological systems in a mathematical way. | Video by Riedel-Kruse Lab

New insights about how euglena navigate their world could lead to advances in the way miniature robots of the future maneuver through the bloodstream or other watery environments.

Tiny pond dwellers could help scientists design swimming robots

Robots perform many tasks that humans can&rsquo;t or don&#39;t want to perform, getting around on intricately designed wheels and limbs. If they tip over, however, they are rendered almost useless. A team of University of Illinois mechanical engineers and entomologists are looking to click beetles, who can right themselves without the use of their legs, to solve this robotics challenge.The researchers presented their findings at Living Machines 2017: The 6th International Conference on Biomimetic and Biohybrid Systems at Stanford University, and later won second place in a student and faculty research competition at the international BIOMinnovate Challenge, in Paris, France &ndash; a research expo that showcases biologically-inspired design in engineering, medicine and architecture.<iframe src="https://www.youtube.com/embed/9ozz2jRfBUk?&wmode=opaque" allowfullscreen="" class="fr-draggable" style="width: 766px; height: 406px;" frameborder="0"></iframe> &ldquo;This idea came to life when a group of insect physiology students decided to take a closer look at what makes click beetles jump as part of a class project,&rdquo; said <a href="https://www.life.illinois.edu/entomology/index.html" target="_blank">department of entomology</a> research scientist and study co-author <a href="https://www.life.illinois.edu/entomology/faculty/alleyne.html" target="_blank">Marianne Alleyne.</a>The beetles have a unique hinge-like mechanism between their heads and abdomens that makes a clicking sound when initiated and allows them to flip into the air and back onto their feet when they are knocked over, Alleyne said.&ldquo;Very little research had been performed on these beetles, and I thought this legless jumping mechanism would be a perfect candidate for further exploration in the field of bioinspiration,&rdquo; said Alleyne, who teaches a bioinspiration design course with <a href="https://mechanical.illinois.edu/" target="_blank">mechanical science and engineering</a> professor, co-author and lead investigator <a href="https://mechanical.illinois.edu/directory/faculty/awissa" target="_blank">Aimy Wissa</a>.The researchers looked at several species of click beetles, ranging in size from a few just few millimeters to several centimeters in length.&ldquo;Each insect goes through an assembly line of analyses that involve basic characterization, high-speed filming to observe the jump and measurements in the <a href="https://publish.illinois.edu/tribology/" target="_blank">Materials Tribiology Lab</a> with co-author and mechanical science and engineering professor <a href="http://mechanical.illinois.edu/directory/profile/acd" target="_blank">Alison Dunn</a>, to determine how much force it takes to overcome the friction of the hinge within an individual beetles jumping mechanism,&rdquo; Wissa said. &ldquo;We observe, model and validate each stage of the jump with the hopes that we can later integrate them into a self-righting robot.&rdquo;<img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1568998642025-118939.jpg" style="width: 766px;" class="fr-fic fr-dib">The University of Illinois click beetle robotics team. Front row, from left: Professor Aimy Wissa, Aidan Garrett, Luis Urrutia, Ophelia Bolmin and professor Alison Dunn. Back row, from left: Isandro Malik, Xander Hazel, Robert Chapa, Harmen Alleyne, Chengfang Duan and research scientist Marianne Alleyne. Garrett, Malik and H. Alleyne are University of Illinois Laboratory High School students. Photo by L. Brian StaufferThe group has already built several prototypes of a hinge-like, spring-loaded device that will eventually be incorporated into a robot, the researchers said.&ldquo;This study is a two-way street &ndash; engineers are informing the biologists and vice versa,&rdquo; Wissa said. &ldquo;We look forward to seeing where this research will take us and are very proud of the attention it received at the BIOMinnovate Challenge expo.&rdquo;

Click beetles can jump without the aid of their limbs when they are tipped onto their backsides. A team of University of Illinois researchers are examining this mechanism to engineer self-righting robots.  Photo by L. Brian Stauffer

Robots perform many tasks that humans can’t or don't want to perform, getting around on intricately designed wheels and limbs. If they tip over, however, they are rendered almost useless.

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Tiny pond dwellers could help scientists design swimming robots

Click beetles inspire design of self-righting robots