Data from: Three-dimensional analysis of the fast-start escape response of the least killifish, Heterandria formosa

Fish make C-starts to evade predator strikes. Double-bend (DB) C-starts consist of three stages: Stage 1, in which the fish rapidly bends into a C-shape; Stage 2, in which the fish bends in the opposite direction; and a variable Stage 3. In single-bend (SB) C-starts, the fish immediately straightens after Stage 1. Despite fish moving in 3D space, fast-start responses of adult fish have mainly been studied in a horizontal plane. Using automated 3D tracking of multi-camera high-speed video sequences, we show that both SB and DB fast-starts by adult female least killifish (Heterandria formosa) often contain a significant vertical velocity component, and large changes in pitch (DB: up to 43 deg) and roll (DB: up to 77 deg) angles. Upwards and downwards elevation changes are correlated with changes in pitch angle of the head; movement in the horizontal plane is correlated with changes in yaw angle of the head. With respect to the stimulus, escape heading correlates with the elevation of the fish at the onset of motion. Irrespective of the initial orientation, fish can escape in any horizontal direction. In many cases, the centre of mass barely accelerates during Stage 1. However, it does accelerate in the final direction of the escape in other instances, indicating that Stage 1 can serve a propulsive role in addition to its preparatory role for Stage 2. Our findings highlight the importance of large-scale 3D analyses of fast-start manoeuvres of adult fish in uncovering the versatility of fish escape repertoire.

鱼类通过C形逃逸（C-start）躲避捕食者的攻击。双弯（DB）型C形逃逸包含三个阶段：阶段1中，鱼类快速将身体弯曲为C形；阶段2中，鱼类向相反方向弯曲身体；以及可变的阶段3。在单弯（SB）型C形逃逸中，鱼类会在阶段1结束后立即伸直身体。尽管鱼类生活在三维空间中，但成鱼的快速逃逸反应此前多仅在水平面环境下开展研究。本研究通过多相机高速视频序列的自动化三维追踪技术，发现成年雌性最小花鳉（Heterandria formosa）的SB与DB型快速逃逸普遍存在显著的垂直速度分量，且俯仰角（DB型最大可达43°）、滚转角（DB型最大可达77°）均发生大幅变化。头部俯仰角的变化与垂直方向的抬升/下沉运动呈显著相关；水平面内的位移则与头部偏航角的变化高度关联。相对于刺激源而言，逃逸朝向与运动起始时刻鱼类的空间高度存在相关性。无论初始姿态如何，鱼类均可在水平面内朝任意方向逃逸。多数情况下，阶段1内鱼类的质心几乎不产生加速度；但在部分逃逸案例中，质心会沿逃逸最终方向加速，这表明阶段1除了为阶段2做好准备外，还可承担推进功能。本研究结果凸显了对成鱼快速逃逸机动开展大规模三维分析的重要性，这有助于揭示鱼类逃逸行为谱的多样性。