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To See in the Deep Dark Sea

Deep sea-dwelling fish may be able to see in color, the Los Angeles Times reports. It adds that an international team of researchers may have uncovered a new type of visual system among vertebrates.

"We didn't expect this at all," study co-first author Fabio Cortesi from the University of Queensland tells the LA Times. "We were like, 'Whoa, what's happening?'"

He and his colleagues report in Science that they examined the genomes of more than 100 fish to find three fish lineages that live in the deep ocean, each of which have expanded rhodopsin 1 gene repertoires. Vertebrates, they note, typically harbor multiple cone opsins, which allow color vision in the light, but have just one rod opsin that enables monochrome vision in the dark.

But these three lineages harbored many more RH1 genes. The silver spinyfin (Diretmus argenteus) fish has, for instance, two cone opsins and 38 rod opsins and expresses up to 14 RH1 genes, the researchers report. "They very likely are able to see color purely by rods, which is unique among vertebrates," co-first author Zuzana Musilova from Charles University adds at Reuters.