Mantis shrimp are quite possibly the greatest adapted species in the animal kingdom, equipped with extraordinary eyes, claws capable of moving so fast they turn water to plasma, and shells so sturdy the U.S. military studies them when creating bullet proof vests. These unique reef residents are crustaceans resembling a crab and shrimp hybrid bursting with vibrant colors and audacious accessories. There are over 400 species of mantis shrimp, all possessing the same vision and powerful body build, however shell color varies from a dull brown and green to blue, red and yellow depending on where they live. Measuring only 4 inches long, the mantis shrimp is among the strongest animals in the world because their ability to strike at speeds of 50 miles per hour and a force of 330 pounds! In recent years mantis shrimp have become a hot topic for researchers as they attempt to understand this incredible species. New research reveals the complex and seemingly alien manner in which they communicate with each other – by sending light messages that only other mantis shrimp can interpret.
In order to understand how Mantis Shrimp communicate with light, a brief mantis shrimp vision 101 is required. Firstly, they are the only animal in the world with trinocular vision, meaning that they can produce a unique depth perception by focussing on one object with three separate regions of their eyes. In addition, their eyes are set slightly above their body on separate eye stalks that can move independently of each other. The most important facet of their vision is the ability to see multiple types of polarized light – a type of light energy that vibrates on a single plane which humans cannot see. Many other animals use polarized light for camouflage or navigation, however Mantis Shrimp are the only known animals to also decipher circular polarization (CP) patterns, which is a type of polarized light that takes the form of a spiralling helix that doesn’t exist on a flat plane. In fact, mantis shrimp are so in tune to CP that researcher, Justin Marshall from University of Queensland, has determined that they can tell the difference between clockwise and counterclockwise CP. The research group also determined that they possess CP patterns on their tail, legs, and head.
Marshall’s team, including post-doc student Yakir Gagnon, set out to test how mantis shrimp communicate. In order to test their hypothesis that communication relies on CP, the team designed an experiment in which mantis shrimp must choose between two burrows that had a filter, shaped like a mantis shrimp tail, covering the opening. Mantis shrimp are very territorial over their burrows, so the team planted an unpolarized filter over one burrow and a CP filter over the other. The results were astonishing, showing clear favoritism to the unpolarized burrow as 68% of mantis shrimp ran towards it. When the team further investigated this phenomenon by backlighting the burrows with either unpolarized or CP light, there was an even more predominant preference for unpolarized burrows as 88% of Mantis Shrimp ran to them. The results of the study told the researchers that the reflection of CP light off their shells translates to a “No Trespassing” or “Stay Out” sign to other mantis shrimp.
Other scientist around the globe praised Gagnon and Marshall for their success of unraveling (in part) the mystery of the mantis shrimp, though other uses for the CP communication is still being debated and researched. A researcher compliments the experiment by saying, “Trying to ascribe a function to CP is still difficult, but I think they’ve come closer than we have in the past”. Additional praise comes from Mike Bok of University of Laud who originally was in disbelief when reading the study, “However, Yakir has supported his results well, and I now believe that the high preference speaks to the great significance of CP signals to these animals”.
Marshall’s team has continued to investigate the importance of CP light to mantis shrimp vision and communication, including the possible significance of it to mating rituals. The culmination of this research has certainly further opened the field of Mantis Shrimp research; in addition to providing insight into effective methods and thinking when investigating animal behavior at large.