Notomi Yusuke, Dobata Shigeto, Kazawa Tomoki, Maezawa So, Namiki Shigehiro, Kanzaki Ryohei, Haupt Stephan Shuichi
Department of General Systems Studies, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1, Komaba, Meguro-ku, Tokyo 153-8902, Japan.
Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan.
J Exp Biol. 2025 Jul 1;228(13). doi: 10.1242/jeb.250278. Epub 2025 Jul 8.
Many animals exhibit an innate attraction to dark areas or objects, driving orientation behaviours such as beacon aiming. In ants, some species do not appear to display beacon aiming. Here, we show that in one such species, Camponotus japonicus, the behaviour is triggered when crossing liquid-covered surfaces, regardless of locomotor pattern and the presence of water in the liquid. Once initiated, beacon aiming persisted even after the ants transitioned from water to dry substrates, as evidenced by their reorientation towards a displaced beacon. Beacon aiming could be observed before the ants fully transitioned from a dry substrate to a liquid-covered surface: when the ants were isolated on a water-surrounded platform, attraction to a beacon emerged while they were contacting the water, before finally deciding to swim towards the beacon. Adverse substrate conditions in general appear to be a factor triggering beacon aiming as we also identified one condition (so far) in which even liquid immersion was not required for beacon aiming, namely upside-down walking. These results indicate that beacon aiming in C. japonicus is performed before, during and after escape from adverse substrates. Evidence that substrate conditions can alter seemingly hardwired responses suggests that insects may adjust even simple behaviours in response to environmental conditions in a more sensitive way than commonly assumed.
许多动物对黑暗区域或物体表现出天生的吸引力，从而驱动诸如信标瞄准等定向行为。在蚂蚁中，有些物种似乎不表现出信标瞄准行为。在此，我们表明，在一种这样的物种——日本弓背蚁中，当蚂蚁穿过液体覆盖的表面时，无论其运动模式以及液体中是否有水，都会触发这种行为。一旦启动，即使蚂蚁从水面转移到干燥的基质上，信标瞄准行为仍会持续，这一点从它们重新定向朝向一个移位的信标得到证明。在蚂蚁完全从干燥基质转移到液体覆盖的表面之前就能观察到信标瞄准行为：当蚂蚁被隔离在一个被水环绕的平台上时，在它们接触水的时候，对信标的吸引力就会出现，最终才决定朝着信标游去。一般来说，不利的基质条件似乎是触发信标瞄准行为的一个因素，因为我们还确定了一种（目前为止）即使不需要液体浸没也能触发信标瞄准行为的情况，即倒挂行走。这些结果表明，日本弓背蚁的信标瞄准行为在逃离不利基质之前、期间和之后都会发生。有证据表明基质条件可以改变看似固定的反应，这表明昆虫可能比通常认为的更敏感地根据环境条件调整甚至简单的行为。
