Figure 8.

Different species of Sinocyclocheilus demonstrate distinct wall-following behaviour associated with eye morphology. Our assay system recorded infrared video of swimming behaviour in a novel landscape with an aeration pump indicated by a black rectangle (a). The assayed tank region included an area (pale yellow) depicting the near-wall region. The orange-dotted region indicates the area of the tank in which a novel obstruction was placed. Representative swimming traces (red lines) are shown for 10 min of wall-following behaviour assay for an eyeless species (c,c′; S. tianeensis), a micro-eyed species (d,d′; S. microphthalmus) and a normal-eyed fish (e,e′; S. macrophthalmus). Plots were generated from EthoVision XT. Heatmaps generated from each trial represent the total time (min) a fish remained in one place where warmer colours denote a longer time, and cooler colours denote a shorter time (c′–e′). Histograms depict the relative differences in the amount of time spent for wall-following (f) and frequency of wall-following (g) tracking both left and right side for all trials. (Online version in colour.)