2026-05-15 東京大学,東京理科大学,青森県営浅虫水族館
図2：左：エゾハリイカの求愛ディスプレイ。装飾腕を光が透過することによって、光の偏光の向き（黒両矢印）が回転する。右上：腕の太さが大きくなると、偏光方向の回転量も増加する。右下：腕の太さの成長は、偏光を90°回転させる値に収束する。
＜関連情報＞
- https://www.aori.u-tokyo.ac.jp/research/news/2026/20260515.html
- https://journals.biologists.com/jeb/article-abstract/229/9/jeb252261/371664/Optical-constraints-shape-a-polarized-sexual
光学的制約がコウイカの偏光した性的装飾を形成する Optical constraints shape a polarized sexual ornament in cuttlefish
Arata Nakayama,Ryosuke Ohnuki,Shota Hosono,Tatsuya Toda,Shinya Yoshioka,Toshihiko Kushihiki,Yoko Iwata
Journal of Experimental Biology Published:15 May 2026
DOI:https://doi.org/10.1242/jeb.252261
ABSTRACT
Ornamented traits involved in sexual signaling are shaped by trade-offs between reproductive benefits and survival costs, yet their evolution may be constrained by physical mechanisms that generate signals. Here, we show that optical constraints shape the morphology and development of sexually ornamented arms in the cuttlefish Doratosepion andreanum, which produces conspicuous polarization signals. Their polarization patterns arise from light transmission through circularly birefringent muscle tissue, which rotates the light’s angle of linear polarization (AoLP). Optical experiments showed that AoLP rotation increases linearly with arm width, reaching 90 deg shift at a width of 3.91 mm, which maximizes polarization contrast against underwater background for cephalopod polarization vision. Morphological analyses revealed that growth of the ornamented arm converges on this width, with development deviating from the typical conical shape into a uniform cylindrical shape. These results suggest that optical mechanisms of signaling define a narrow morphological design space for polarized ornaments.
