Strong but Flexible: the Seahorse Tail and Modern Engineering
By: Ashley Gustafson
Seahorse tails may not be the first thought that goes through your head when you imagine amazing seahorse adaptations and abilities. Many of you probably think of their elusive camouflage or perhaps their extraordinary way of reproduction (primarily paternal care is almost unheard of in many animal species)! The seahorse tail may seem pale in comparison to such evolutionary feats but not according to a new team of engineers and biologists. Recently reported by the Federation of American Societies for Experimental Biology (FASEB), a team of engineers and biologists are working together using computer based technology and 3D shape analysis to gain more insight into the unique mechanism and structure of the grasping tails of seahorses.
Seahorses use their flexible yet strong tails to grasp their surroundings. This grounds them and allows them to hide from predators. Seahorse trails are prehensile meaning they have the capacity to grasp which is seen primarily in animal tails and limbs. The word prehensile comes from the Latin “prae” meaning before and “hendere” meaning to grasp. While seahorse tails have the ability to grasp (meaning they need flexibility), their tails are also contradictorily rigid, built with armor like bone to protect them. Discovering how the seahorse has evolved such a useful contradiction of flexibility and rigidity could prove quite helpful to engineers who have been struggling with this same feat for centuries. Being able to tackle this problem when engineering new devices could open up new doors for engineers to create devices that are both flexible and strong and the seahorse is the perfect subject.
As expected, this project “brought together engineers who know computer modeling and biologists who can provide the evolutionary questions,” as said by the team leader, evolutionary biologist Dominque Adriaens who is a Ph.D. professor at Ghent University. Adriaens is a member of the American Association of Anatomists (AAA) and will go on to present this revolutionary research at the AAA Annual Meeting during Experimental Biology 2015. He goes on to explain that from a biological perspective, the team is looking to understand how natural selection selected for this tail model over others that may have previously dominated seahorse populations. Historical seahorse tails were much more rigid in comparison to the modern seahorse and covered with bony plates of armor. Somehow the seahorse has been able to maintain a tail covered with bony plates of armor but evolve a much more flexible version that can grip the environment around them but remain strong.
Adriaens and his team were able to use real seahorse specimens to create a computer model of the muscles and bones of the seahorse tail so that they could analyze the seahorse’s incredible tail sustainably and uncover the manner of which it evolved these traits. One way the computer model allowed them to look at a seahorse tail was by letting researchers test small, specific areas of muscle and skeletal structure to see how they contributed to the tail’s grasping movement and the affect the angle of bending. This is something that researchers would not be able to do with a living seahorse. By using this technology, the team can use 3D animations to visualize the tail and from that can estimate the approximate energy needed to bend the tail in such a way. In order to map the seahorse’s armor, muscular, and skeletal system, the researchers applied thousands of 3D points from the computer model. They also linked the anatomy of the tails of other fish species within the seahorse family, even if those members did not have tails that bend. According to Adriaens, “We hypothesized that the variation in the grasping species would be much less than non-grasping fish because it would require certain building blocks to construct a tail that is flexible and rigid at the same time.” Adriaens and the team were surprised to find differences in the methods a grasping tail was made. They found that even though a grasping tail is highly extraordinary in a fish, it has evolved many times self-sufficiently within the seahorse family, quite an achievement for such an exceptional adaptation.
These findings have the potential to be an evolutionary stepping stone in modern engineering of body armor. After collecting his findings, Adriaens will be collaborating with Michael Porter Ph.D. assistant professor in the Department of Mechanical Engineering at Clemson University. Together they plan to use this new research to develop a strong, protective armor that is also flexible or possibly create a grasping robot that is long and slender. According to Porter, “Understanding the mechanisms involved in the evolution of the seahorse tail, lets us eliminate engineering optimization and instead use biology as our optimization model.” Thus, by using this new map of the seahorse tail throughout time and evolution, engineers can tweak their methodologies by looking at the biology of the seahorse tail to achieve a combination of flexibility and strength in new inventions and devices.
It will be very interesting to see if Adriaens, Porter, and the rest of the team will be able to achieve the perfect balance of strength and flexibility in a new breed of body armor. Their goal of strong and flexible armor that allows a large range of motion and multiple degrees of freedom may have been laughed at five, ten, twenty years ago but today is completely plausible thanks to a modern cocktail of biology and engineering technology.