Seeing in the swamp: hydrogen sulfide inhibits eye metabolism and visual acuity in a sulfide-tolerant fish

In fish, vision may be impaired when eye tissue is in direct contact with environmental conditions that limit aerobic ATP production. We hypothesized that the visual acuity of fishes exposed to hydrogen sulfide (H₂S)-rich water would be altered owing to changes in cytochrome c oxidase (COX) activity. Using the H₂S-tolerant mangrove rivulus (Kryptolebias marmoratus), we showed that a 10 min exposure to greater than or equal to 200 µM of H₂S impaired visual acuity and COX activity in the eye. Visual acuity and COX activity were restored in fish allowed to recover in H₂S-free water for up to 1 h. Since K. marmoratus are found in mangrove pools with H₂S concentrations exceeding 1000 µM, visual impairment may impact predator avoidance, navigation and foraging behaviour in the wild.