23-08-26 Raw data for 4 taxa of melanopsids - distance travelled by shell - rod - magnet assembly

The aperture of the shell was sealed with a thin film of general-purpose waterproof glue and the shell was then attached by a hot-glue gun to the end of a fibre-glass rod (2 mm diameter) with the main whorl pointing upstream (‘head-upstream’). The resistance to water flow offered by the shell caused this assembly of shell, rod and magnet to be pushed towards a larger fixed magnet which resisted the deflection of the rod assembly. The shell was held in a tube 0.03m internal diameter and 30mm from the point at which the tube discharged into a test chamber. We focussed on empty shells to avoid the influence of biological behaviour, and we did not attempt to position the shell close to a surface. the shell assembly was in place, the gate valve was opened in steps. At each step, a measurement was made when the shell had stopped moving and was in a stable position. The water velocity was calculated by measuring the volume of the discharge from the pipe over a known period. All results were analysed after subtracting the response of the rod alone. For each shell measured in flowing water in the apparatus, a mean deflection from three replicated readings was obtained. When flow rates were reduced, the assembly moved firmly back to its original position; there was no indication that there was an issue of friction of the rod in its holding tube.

壳体的开口采用通用防水胶薄膜密封，随后通过热熔胶枪将壳体固定于一根直径2毫米的玻璃钢杆末端，使壳体的主螺层朝向上游（即“头朝上流”）。壳体所受到的水流阻力，会带动该壳体、杆与磁体的组件向一块更大的固定磁体移动，而固定磁体则会阻碍杆组件的偏转。该壳体被置于内径为0.03米的管道内，且该管道的排水口距离试验舱的入口处30毫米。为规避生物行为带来的干扰，我们仅采用空壳体开展实验，且未尝试将壳体贴近管壁表面。当壳体组件就位后，分阶段开启闸阀。每完成一次阶段开启，待壳体停止移动并处于稳定位置时，便开展一次测量。水流流速通过计量已知时长内管道排水量的体积计算得到。所有实验结果均在扣除单独杆体的响应信号后进行分析。针对装置中于流水中被测试的每个壳体，我们均获取三次重复读数的平均偏转量。当流速降低时，该组件会稳固地回到初始位置，未观察到杆在支撑管内存在摩擦异常的情况。