イカ墨による逃避行動の野外観察（C-change）
(47.3MB, 00:00:39)撮影場所：島根県隠岐郡隠岐の島町
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佐藤成祥
(Noriyosi Sato)
2020/02/18登録
種類:ヒメイカ, Idiosepius paradoxus
キーワード: Inking pseudomorph searching image secondary defence
動物界 >軟体動物門 >頭足綱 >ダンゴイカ目 >ヒメイカ科 >ヒメイカ属 >
伸縮アームにマウントしたアクションカメラの先にルアーを装着して、ヒメイカの逃避行動を誘発させ、墨を吐きながらどのように逃げるのか観察しました。ヒメイカは透明にも見えるほどの明るい体色を保ちつつ連続して墨を吐きながら、すばやく後方に直線的に泳いでいましたが、ある瞬間に突然、遊泳コースを変更して逃げていきました。
Below is the abstract from the article containing this video:
The characteristic inking behaviour of cephalopods is a secondary defence mechanism that helps them to escape predation. However, although it has been postulated that ink creates a decoy by disrupting the visual information received by the predator, the underlying mechanisms by which ink helps squid to escape from predators remain unknown. Therefore, we observed the inking behaviour of the Japanese pygmy squid (Idiosepius paradoxus). Field observations showed the squid intermittently and linearly ejected ink while rapidly swimming backwards in response to a predator and also changed their bodies to a light colour. This behaviour was then followed by a sudden and sharp change in swimming direction or sometimes a sudden break from swimming with a concurrent change in body colour to black. We also recorded the escape behaviour with inking under captive conditions in response to predatory sculpins, which allowed the successful escape from a predatory attack. Furthermore, the greater the number of ink ejections, the higher the probability that the sculpins would initiate a predatory attack on the ink rather than the squid. Together, these results suggest that squid inking behaviour exhibits a substantial decoy effect on predators and is associated with a series of complex, spatio-temporally regulated behaviours. Digital video images related to the article are available at http://www.momo-p.com/showdetail-e.php?movieid=momo200107ip01a, http://www.momo-p.com/showdetail-e.php?movieid=momo200107ip03a, and http://www.momo-p.com/showdetail-e.php?movieid=momo200107ip04a.
Yuto Hikidi, Noritaka Hirohashi, Takashi Kasugai, and Noriyosi Sato (2020).
An elaborate behavioural sequence reinforces the decoy effect of ink during predatory attacks on squid. J. Ethol. 10.1007/s10164-020-00640-8