Most vertebrates have one layer of the dim-light active rod photoreceptors. However, multiple rod layers, known as a multibank retina, can be found in over 100 species of fish, including several deep-sea species and one family of nocturnally active reef fish, the Holocentridae. Although seemingly associated with increased photon catch, the function of multibank retinas remained unknown. We used an integrative approach, combining histology, electrophysiology, and amino acid sequence analysis, applied to three species of nocturnal reef fishes, two holocentrids with a multibank retina (Neoniphon sammara and Myripristis violacea) and an apogonid with a single rod bank (Ostorhinchus compressus), to determine the sensory advantage of multiple rod layers. Our results showed that fish with multibank retinas have both faster vision and enhanced sensitivity to bright and dim light intensities. Faster vision was indicated by higher flicker fusion frequencies during temporal resolution electroretinography as well as faster retinal release kinetics estimated from their rhodopsin proteins. Enhanced sensitivity was demonstrated by broadened intensity-response curves derived from luminous sensitivity electroretinography. Overall, our findings provide the first functional evidence for enhanced dim-light sensitivity using a multibank retina while also suggesting novel roles for the adaptation in enhancing bright-light sensitivity and the speed of vision.

Data are derived from electroretinograms recorded from individual nocturnal coral reef fish as described in the associated preprint. 

Data are either normalised to the maximal response (Vmax) or to both the maximal response and eye size.

Eye diameter (in millimetres) is given in an additional file.

Files are given in tsv format. No proprietary software is required to open the files or manipulate the data.