Micro nikkor 60 mm f 2.8d lens

The experimental apparatus is similar to that used in previous studies (Stamper et al., 2012 (link); Biswas et al., 2018 (link); Uyanik et al., 2019b (link)). A refuge machined from a PVC pipe with a length of 15 cm and 5.08 cm diameter was placed in the experimental tank with the fish. The bottom face of the refuge was removed to allow video recording from below. Six windows, 0.625 cm in width and spaced within 2.5 cm intervals, were machined onto each side to provide visual and electrosensory cues. During experiments, we actuated the refuge using a linear stepper motor with 0.94 μm resolution (IntelLiDrives, Inc Philadelphia, PA, USA) driven via a Stepper motor controller (Copley Controls, Canton, MA, USA). MATLAB (MathWorks, Natick, MA, USA) scripts were used to control the movement of the refuge and to capture video. Video data were captured using a pco.1200s high speed camera (Cooke Corp., Romulus, MI, USA) with a Micro-Nikkor 60 mm f/2.8D lens (Nikon Inc, Melville, NY, USA). All videos used for data analysis were shot at 30 frames per second with 1280 × 1024 pixel resolution. Some videos of ribbon fin motion were shot at 100 frames per second.

The experimental setup (Figure 1A) was similar to that used in previous reports (Cowan and Fortune, 2007 (link); Roth et al., 2011 (link); Stamper et al., 2012 (link)). Eight different refuges were used for the experiments. Refuges were machined from 2” × 2” gray rectangular PVC tube at four different lengths; 7.5, 12.5, 15, and 22.5 cm. We had two refuges at each of these lengths. Refuges with “windows” had rectangular holes, 0.625 cm width, 2.0 cm spacing machined into each side. Windows provide additional visual and electrosensory cues than refuges with solid sides, “no windows.”
The bottom faces of the refuges were removed to allow video recording from below. Video was captured at 30frames·s⁻¹ with 1280 × 1024 resolution using a high-speed camera (pco.1200s, Cooke Corp, Romulus, MI) with a Micro-Nikkor 60mm f/2.8D lens (Nikon Inc., Melville, NY) and Camware software (Cooke Corp, Romulus, MI). For each trial, the refuge was moved back and forth according to predefined sinusoidal trajectories by a linear stepper motor (IntelliDrives, Inc, Philadelphia, PA) driven by a Stepnet motor controller (Copley Controls, Canton, MA). The actuator trajectories and camera triggering were synchronized using a Multifunction DAQ (USB-6221, National Instruments, Austin, TX) and controlled with custom Matlab scripts (MathWorks, Natick, MA).