{"46266":{"#nid":"46266","#data":{"type":"news","title":"Study Reveals Sandfish Tucks Legs to Slither Like Snake Through Sand","body":[{"value":"\u003Cp\u003EA study published in the July 17 issue of the journal \u003Cem\u003EScience\u003C\/em\u003E details how sandfish -- small lizards with smooth scales -- move rapidly underground through desert sand. In this first thorough examination of subsurface sandfish locomotion, researchers from the Georgia Institute of Technology found that the animals place their limbs against their sides and create a wave motion with their bodies to propel themselves through granular media.\u003C\/p\u003E\n\u003Cp\u003E\u0022When started above the surface, the animals dive into the sand within a half second. Once below the surface, they no longer use their limbs for propulsion -- instead, they move forward by propagating a traveling wave down their bodies like a snake,\u0022 said study leader Daniel Goldman, an assistant professor in Georgia Tech\u0027s School of Physics.\n\u003C\/p\u003E\n\u003Cp\u003EWith funding from the National Science Foundation and the Burroughs Wellcome Fund, the research team used high-speed X-ray imaging to visualize sandfish -- formally called \u003Cem\u003EScincus scincus \u003C\/em\u003E-- burrowing into and through sand. The team used that information to develop a physics model of the lizard\u0027s locomotion.\n\u003C\/p\u003E\n\u003Cp\u003EThe sandfish used in this study inhabits the Sahara desert in Africa and is approximately four inches long. It uses its long, wedge-shaped snout and countersunk lower jaw to rapidly bury into and swim within sand. The sandfish\u0027s body has flattened sides and is covered with smooth shiny scales, its legs are short and sturdy with long and flattened fringed toes and its tail tapers to a fine point.\n\u003C\/p\u003E\n\u003Cul\u003E\u003Cstrong\u003E\u003Cem\u003E\n\u003Cli\u003EWatch a video of a sandfish using its limbs to run on the surface and rapidly bury into the interior of granular media \u003Ca href=\u0022http:\/\/www.gtresearchnews.gatech.edu\/movies\/1172490s1.mov\u0022\u003E here\u003C\/a\u003E. \u003C\/li\u003E\n\u003Cli\u003EWatch a video of a sandfish slither like a snake through granular media \u003Ca href=\u0022http:\/\/www.gtresearchnews.gatech.edu\/movies\/1172490s2.mov\u0022\u003E here\u003C\/a\u003E.\u003C\/li\u003E\n\u003Cli\u003EWatch a video of a sandfish swim through granular media with opaque markers on its body that clearly show that its limbs are held close to its body during swimming \u003Ca href=\u0022http:\/\/www.gtresearchnews.gatech.edu\/movies\/1172490s3.mov\u0022\u003E here\u003C\/a\u003E.\u003C\/li\u003E\n\u003Cp\u003E \u003C\/p\u003E\u003C\/em\u003E\u003C\/strong\u003E\u003C\/ul\u003E\n\n\u003Cp\u003ETo conduct controlled experiments with the sandfish, Goldman and graduate students Ryan Maladen, Yang Ding and Chen Li built a seven-inch by eight-inch by four-inch-deep glass bead-filled container with tiny holes in the bottom through which air could be blown. The air pulses elevated the beads and caused them to settle into a loosely packed solid state. Repeated pulses of air compacted the material, allowing the researchers to closely control the density of the material. \n\u003C\/p\u003E\n\u003Cp\u003ESince a sandfish might encounter and need to move through different densities of sand in the desert, the researchers tested whether sandfish locomotion changed when burrowing through media with volume fractions of 58 and 62 percent -- typical values for desert sand. \n\u003C\/p\u003E\n\u003Cp\u003E\u0022Since loosely packed media is easier to push through and closely packed is harder to push through, we thought there should be some difference in the sandfish\u0027s locomotion,\u0022 said Goldman. \u0022But the results surprised us because the density of the granular media did not affect how the sandfish traveled through the sand; it was always the same undulatory wavelike pattern.\u0022 \n\u003C\/p\u003E\n\u003Cp\u003EFor a given wave frequency, the swimming speed depended only on the frequency of the wave and not on the density. Unexpectedly though, the animals could swim a bit faster in closely packed material by using a higher frequency range. The team also varied the diameter of the glass beads, but still observed similar wavelike motion. \n\u003C\/p\u003E\n\u003Cp\u003EBy tracking the sandfish in the X-ray images as it swam through the glass beads, Goldman was able to characterize the sandfish\u0027s motion -- called its kinematics -- as the form of a single-period sinusoidal wave that traveled from the head to the tail. \n\u003C\/p\u003E\n\u003Cp\u003E\u0022The large amplitude waves over the entire body are unlike the kinematics of other undulatory swimming organisms that are the same size as the sandfish, like eels, which propagate waves that start with a small amplitude that gets larger toward the tail,\u0022 explained Goldman. \n\u003C\/p\u003E\n\u003Cp\u003EAfter collecting the experimental data, Goldman\u0027s team developed a physics model to predict the speed at which sandfish swim through sand. The model was inspired by the resistive force theory, which allowed the researchers to partition the body of the sandfish into segments, each of which generated thrust and experienced drag when moving through the granular environment. \u003C\/p\u003E\n\u003Cp\u003E\u0022When you balance the thrust and drag, you get motion at some velocity, but we needed to determine the forces on the animal segments because we don\u0027t have the appropriate equations for drag force during movement through granular media,\u0022 explained Goldman.\n\u003C\/p\u003E\n\u003Cp\u003ETo establish these equations, the researchers measured the granular thrust and drag forces on a small stainless steel cylindrical rod, thus allowing them to predict the wave efficiency and optimal kinematics. They found that the faster the sandfish propagate the wave, the faster they move forward through granular media -- up to speeds of six inches per second. This speed allows the animal to escape predators, the heat of the desert surface and quickly swim to ambush surface prey they detect from vibrations. \n\u003C\/p\u003E\n\u003Cp\u003E\u0022The results demonstrate that burrowing and swimming in complex media like sand can have intricacy similar to that of movement in air or water, and that organisms can exploit the solid and fluid-like properties of these media to move effectively within them,\u0022 noted Goldman.\n\u003C\/p\u003E\n\u003Cp\u003EIn addition to having a biological impact, this study\u0027s results also have ecological significance, according to Goldman. Understanding the mechanics of subsurface movement could reveal how the actions of small burrowing organisms like worms, scorpions, snakes and lizards can transform landscapes by their burrowing actions. This research may also help engineers build sandfish-like robots that can travel through complex environments.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022If something nasty was buried in unconsolidated material, such as rubble, debris or sand, and you wanted to find it, you would need a device that could scamper on the surface, but also swim underneath the surface,\u0022 Goldman said. \u0022Since our work aims to fundamentally understand how the best animals in nature move in these complex unstructured environments, it could be very valuable information for this type of research.\u0022\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cem\u003EThis material is based upon work supported by the National Science Foundation (NSF) under Award No. PHY-0749991 and the Burroughs Wellcome Fund. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the researcher and do not necessarily reflect the views of the NSF.\u003C\/em\u003E\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\nGeorgia Institute of Technology\u003Cbr \/\u003E\n75 Fifth Street, N.W., Suite 100\u003Cbr \/\u003E\nAtlanta, Georgia  30308  USA\n\u003C\/strong\u003E\u003C\/p\u003E\n\u003Cp\u003EMedia Relations Contacts: Abby Vogel (404-385-3364); E-mail: (\u003Ca href=\u0022mailto:avogel@gatech.edu\u0022\u003Eavogel@gatech.edu\u003C\/a\u003E) or John Toon (404-894-6986); E-mail: (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E)\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003ETechnical Contact:\u003C\/strong\u003E Daniel Goldman (404-894-0993); E-mail: (\u003Ca href=\u0022mailto:daniel.goldman@physics.gatech.edu\u0022\u003Edaniel.goldman@physics.gatech.edu\u003C\/a\u003E) \n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EWriter:\u003C\/strong\u003E Abby Vogel\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"In the first thorough examination of subsurface sandfish locomotion, researchers found that the small lizards place their limbs against their sides and create a wave motion like snakes to propel themselves through granular media.","format":"limited_html"}],"field_summary_sentence":[{"value":"Study shows how small lizards move rapidly underground through s"}],"uid":"27206","created_gmt":"2009-07-16 00:00:00","changed_gmt":"2016-10-08 03:03:14","author":"Abby Vogel Robinson","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2009-07-16T00:00:00-04:00","iso_date":"2009-07-16T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"46267":{"id":"46267","type":"image","title":"Sandfish lizard","body":null,"created":"1449174375","gmt_created":"2015-12-03 20:26:15","changed":"1475894414","gmt_changed":"2016-10-08 02:40:14","alt":"Sandfish lizard","file":{"fid":"101056","name":"tjw66159.jpg","image_path":"\/sites\/default\/files\/images\/tjw66159_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/tjw66159_0.jpg","mime":"image\/jpeg","size":633936,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/tjw66159_0.jpg?itok=98LitytK"}},"46268":{"id":"46268","type":"image","title":"Dan Goldman scincus scincus","body":null,"created":"1449174375","gmt_created":"2015-12-03 20:26:15","changed":"1475894414","gmt_changed":"2016-10-08 02:40:14","alt":"Dan Goldman scincus scincus","file":{"fid":"101057","name":"tpd66160.jpg","image_path":"\/sites\/default\/files\/images\/tpd66160_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/tpd66160_0.jpg","mime":"image\/jpeg","size":1373316,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/tpd66160_0.jpg?itok=yHS8UAZS"}},"46269":{"id":"46269","type":"image","title":"Dan Goldman sandfish","body":null,"created":"1449174375","gmt_created":"2015-12-03 20:26:15","changed":"1475894414","gmt_changed":"2016-10-08 02:40:14","alt":"Dan Goldman sandfish","file":{"fid":"101058","name":"tbc66160.jpg","image_path":"\/sites\/default\/files\/images\/tbc66160_0.jpg","image_full_path":"http:\/\/www.tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/tbc66160_0.jpg","mime":"image\/jpeg","size":682990,"path_740":"http:\/\/www.tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/tbc66160_0.jpg?itok=HNynnYb3"}}},"media_ids":["46267","46268","46269"],"related_links":[{"url":"http:\/\/www.physics.gatech.edu\/research\/goldman\/","title":"Daniel Goldman"},{"url":"http:\/\/www.physics.gatech.edu\/","title":"Georgia Tech School of Physics"},{"url":"http:\/\/dx.doi.org\/10.1126\/science.1172490","title":"Science article"}],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"146","name":"Life Sciences and Biology"},{"id":"135","name":"Research"},{"id":"150","name":"Physics and Physical Sciences"},{"id":"152","name":"Robotics"}],"keywords":[{"id":"7118","name":"desert"},{"id":"7123","name":"drag"},{"id":"987","name":"imaging"},{"id":"7121","name":"kinematics"},{"id":"7116","name":"lizard"},{"id":"377","name":"locomotion"},{"id":"1383","name":"model"},{"id":"960","name":"physics"},{"id":"169242","name":"sand"},{"id":"169581","name":"sandfish"},{"id":"170845","name":"scincus"},{"id":"170846","name":"skink"},{"id":"170847","name":"slither"},{"id":"169001","name":"Snake"},{"id":"7122","name":"thrust"},{"id":"7119","name":"undulation"},{"id":"7120","name":"wave"},{"id":"1448","name":"x-ray"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cstrong\u003EAbby Vogel\u003C\/strong\u003E\u003Cbr \/\u003EResearch News and Publications\u003Cbr \/\u003E\u003Ca href=\u0022http:\/\/www.gatech.edu\/contact\/index.html?id=avogel6\u0022\u003EContact Abby Vogel\u003C\/a\u003E\u003Cbr \/\u003E\u003Cstrong\u003E404-385-3364\u003C\/strong\u003E","format":"limited_html"}],"email":["avogel@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}