There are species of shark that are bioluminescent and have evolved ocular structures designed to detect faint light patterns in the deep ocean produced by other bioluminescent sharks that live at depths from 600 to 3,000 feet in the mesopelagic zone where very little sunlight reaches.
These eyes as expected, have visual adaptations optimized for this environment. Julien Claes, the lead authors of a new study notes that “There are about 50 different shark species that are able to produce light”. Given that there are 50 separate bioluminescent species of shark, one might expect some visual system specializations and indeed there are. Everything from higher rod densities to descriptions of bioluminescent specializations used for communication and specialized transparencies in the upper socket of the eye to help adjust illumination. Continue reading “Glowing Sharks Have Unusual Eyes”