"Be my squidmate?" A cuttlefish that woos with polarized light

At first glance, it is hard to tell exactly what kind of creature this is. This is a photo of a male cuttlefish Doratosepion andreanum, a species found in the seas from southern Hokkaido and further south, taken from in front of its arms (which people often call "legs"). The way he curls his arms into a spiral is quite cute. A research group led by the University of Tokyo discovered that these cuttlefish use a hidden trick in their arms to control light and grab the attention of females.

Male peacocks spread their beautiful tail feathers in courtship. While cephalopods like squid and octopuses cannot distinguish between colors, they can recognize "light polarization," a property of light that differs from color and brightness. Light polarization refers to the orientation of light wave oscillation. The study found that the males stretch out their long arms and use a clever trick: they reflect light off special cells in their skin and pass it through their transparent muscles. This creates flashy, polarized patterns to impress females. The world of animal communication is truly amazing.

Note that in this photo, the parts that look like they are glowing yellow-green are where the polarized reflection happens. However, the glowing look itself is not caused by polarization.

The research group consists of the University of Tokyo, Tokyo University of Science, Tokai University, and Aomori Prefectural Aquarium Asamushi. The results were published in the Proceedings of the National Academy of Sciences of the United States on January 26 and announced by the University of Tokyo and others on January 27. The research was supported by Grant-in-Aid for Scientific Research, Support for Pioneering Research Initiated by the Next Generation of the Japan Science and Technology Agency (JST), Fujiwara Natural History Foundation, and others.