Fovea-like photoreceptor specialisations underlie single UV-cone driven prey capture behaviour in zebrafish

In the eye, the function of same-type photoreceptors must be regionally
adjusted to process a highly asymmetrical natural visual world. Here we
show that UV-cones in the larval zebrafish area temporalis are
specifically tuned for UV-bright prey capture in their upper frontal
visual field, which uses the signal from a single cone at a time. For
this, UV-detection efficiency is regionally boosted 42-fold. Next, in vivo
2-photon imaging, transcriptomics and computational modelling reveal that
these cones use an elevated baseline of synaptic calcium to facilitate the
encoding of bright objects, which in turn results from expressional tuning
of phototransduction genes. Finally, this signal is further accentuated at
the level of glutamate release driving retinal networks. These regional
differences tally with variations between peripheral and foveal cones in
primates and hint at a common mechanistic origin. Together, our results
highlight a rich mechanistic toolkit for the tuning of neurons.