Fig. 2

Time-course of nearby interaction changes during 9 weeks of control diet (CD) or ketogenic diet (KD) feeding. A Experimental procedure. After rearing fish for 3–4 months on a brine shrimp larva diet, the pre-treatment recording was performed, followed by CD or KD feeding for 5 weeks. Nearby interactions were recorded every week until week 5 of feeding. Subsequently, all groups, including KD-fed fish, were given the CD until week 9. B Example of nearby interaction events among surface fish (SF). The left panel presents an example frame of the video, with colored lines indicating the trajectories of individual fish. A red-labeled fish was followed by a blue-labeled fish. Each nearby event that met the detection criteria, namely a distance of ≤ 5 cm between two fish that was maintained for more than 4 s, was counted as a nearby interaction event. The right panel presents an example of the detected events in a raster plot, where each yellow bar indicates a nearby interaction event. Each pair of fish (six pairs among four fish) is presented in the rows. C Duration of nearby interactions. Although SF did not exhibit any differences in the duration of nearby interactions (s) between CD (green) and KD (blue) feeding, differences were detected among cavefish (CF) in week 5. However, the nearby interaction duration was indistinguishable from that of the CD group starting in week 6 when the KD was withdrawn from the experimental group. Data are shown in boxplots indicating the 25th, 50th, and 75th percentiles in the boxes. The linear mixed-effect model followed by post hoc Holm’s correction was applied for the statistical tests. D Number of nearby interactions. Whereas SF exhibited no differences between CD and KD feeding, differences were observed in CF in weeks 4–6. After the KD was withdrawn in week 6, the number of events decreased to the level observed with CD feeding. Data are presented as boxplots indicating the 25th, 50th, and 75th percentiles. The generalized linear model (family = Poisson) followed by post hoc Holm’s correction was applied for the statistical tests. Dots indicate individual data. N = 20 for each group. *: P < 0.05, **: P < 0.01, ***: P < 0.001. All detailed statistical data are available in Additional file 3