2026-10-26 東京大学
図1：ヤリイカの縄張り雄による墨吐き
＜関連情報＞
- https://www.aori.u-tokyo.ac.jp/research/news/2026/20261026.html
- https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.70576
沿岸性イカHeterololigo bleekeri の縄張りを持つ雄による墨の新たな利用法
Novel use of ink by territorial males in the coastal squid Heterololigo bleekeri
Shota Hosono, Shun Tokioka, Jun Yamamoto, Yoshio Masuda, Yuka Koike, Yoko Iwata
Ecology Published: 22 October 2026
DOI:https://doi.org/10.1002/ecy.70576
Ink is a fascinating feature of cephalopods, primarily used for secondary defense in various forms. For instance, diffusive ink is used as a smokescreen that obscures a predator’s view (Derby, 2014), or ink blobs suspended in the water are used as pseudomorphs that confuse predators (Hikidi et al., 2020). In addition to visual effects, chemical cues from ink have been suggested to deter predators from attack (Derby et al., 2013). Ink has also been proposed to serve as an alarm cue for conspecifics, both through visual (Wood et al., 2008) and chemical cues (Gilly & Lucero, 1992). Additionally, recent studies have revealed that ink is also used in contexts other than defense, such as predation (Sato et al., 2016), male–male competition (Allen et al., 2017), courtship (Nakayama et al., 2024), copulation (Sato et al., 2025), and spawning (Wada et al., 2006). Here, we report a novel use of ink by territorial males of the Japanese spear squid Heterololigo bleekeri, which was observed during captive observations of reproductive behaviors (Figure 1; Video S1). Our observations suggested that the released ink may be involved in territory maintenance against rival males and/or in attracting females to territories centered on a spawning substrate. As territoriality has been reported only in this species among squid (Tokioka et al., 2025), inking associated with territorial behavior is highly novel.
