Deep-sea fish with enhanced vision: silver spinyfin (top), tube-eye (bottom) and lantern fish (middle). Illustration: Pavel Riha, University of South Bohemia, Ceske Budejovice, Czech Republic

How Fish See in the Deep Dark Sea

You can’t ask fish what they see. But you can study their genomes to get clues about how their eyes work. When scientists did that with some freaky deep-sea fish, they saw something surprising: Four species seem to have evolved four distinct and previously unknown systems for spotting color amid utter darkness more than a mile down.