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Fig. 4 | BMC Evolutionary Biology

Fig. 4

From: A pleiotropic interaction between vision loss and hypermelanism in Astyanax mexicanus cave x surface hybrids

Fig. 4

Hypermelanic fish behave similar to cavefish in a visually-mediated behavioral assay. A ‘half-moon’ arena, separated into equal white and black background halves, was used to test visual function based on predicted surface fish behavior. Representative screenshots from 1-min video trials illustrate behavior (red trace line) for individual surface fish (a), eyeless Pachón cavefish (b) and hypermelanic fish (c). The number of midline crosses was recorded for the total number of crosses, as well as the number of crosses into the white and black halves of the arena (d). Both cavefish and hypermelanic fish showed no preference to the light and dark sides of the arena, while the surface fish rarely crossed the midline. The amount of time (seconds) each fish spent on each side of the arena was also recorded (e). Surface fish showed a clear preference for the dark side of the arena, spending almost the entire 60 s trial in the dark, while cavefish and hypermelanic fish spent relatively equal time on both sides of the tank. For both metrics, there was no difference between hypermelanic fish and cavefish behavior, however both differed significantly from surface fish (***p < 0.0001)

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