How does a zebrafish see the world?

A zebrafish carries four cone classes—ultraviolet, blue, green and red—in a retina built for bright shallow water. Its side-set eyes survey 339 degrees around the body, while adult behavioural tests place spatial acuity at only 0.56 to 0.58 cycles per degree. Fine detail blurs, but colour and near-panoramic coverage remain central. Four cone classes feed colour-opponent retinal circuits. The ultraviolet channel is especially specialized in the upper frontal field for detecting UV-bright prey in larvae.

Four cone classes feed colour-opponent retinal circuits. The ultraviolet channel is especially specialized in the upper frontal field for detecting UV-bright prey in larvae. Tetrachromat (UV, blue, green and red cones)

Its eyes resolve about 0.57 cycles per degree (No direct Snellen equivalent; 0.56–0.58 cpd behavioural OKR), while a human reaches around 60 cpd (20/20). Its field of view spans about 339°.

Its eyes resolve about 0.57 cycles per degree against your 60, so a face has to be roughly 105 times closer for it to pick out the detail you do. Your outline and your movement read clearly; your expression does not.

A duplex retina contains rods and cones; rod responses are roughly 40–220 times more photosensitive than cone responses, while colour is a bright-light function.

Four cone classes including ultraviolet. 339° adult visual coverage with only a 21° rear blind sector. Fronto-dorsal acute zone; larval UV cones specialize for prey capture. In larvae, ultraviolet cones in the upper frontal retina capture more than ten times as many ultraviolet photons as other ultraviolet cones, helping the fish find tiny ultraviolet-bright prey. This specialization is life-stage specific.

Humans use three cone classes and do not see ultraviolet; zebrafish use four and cover 339 degrees rather than roughly 200. An RGB screen can only use false colour and measured blur to communicate that difference, never reproduce it literally.