Variable vision in variable environments: the visual system of an invasive cichlid () in Lake Gatun, Panama.

An adaptive visual system is essential for organisms inhabiting new or changing light environments. The Panama Canal exhibits such variable environments owing to its anthropogenic origin and current human activities. Within the Panama Canal, Lake Gatun harbors several exotic fish species including the invasive peacock bass (), a predatory Amazonian cichlid. In this research, through spectral measurements and molecular and physiological experiments, we studied the visual system of and its adaptive capabilities. Our results suggest that (1) Lake Gatun is a highly variable environment, where light transmission changes throughout the canal waterway, and that (2) has several visual adaptations suited for this red-shifted light environment. filters short wavelengths (∼400 nm) from the environment through its ocular media and tunes its visual sensitivities to the available light through opsin gene expression. More importantly, based on shifts in spectral sensitivities of photoreceptors alone, and on transcriptome analysis, exhibits extreme intraspecific variation in the use of vitamin A/A chromophore in their photoreceptors. Fish living in turbid water had higher proportions of vitamin A, shifting sensitivities to longer wavelengths, than fish living in clear water. Furthermore, we also found variation in retinal transcriptomes, where fish from turbid and clear waters exhibited differentially expressed genes that vary greatly in their function. We suggest that this phenotypic plasticity has been key in the invasion success of .