The blue-green world of deep-sea fish












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            * The blue-green world of deep-sea fish
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            An international team of scientists, including lead co-author Zuzana Musilová from the CU 

            Science, recently discovered that some deep-sea fish possess a unique set of photosensitiv
            probably enable some form of colour vision, even at great depths. The article was publishe
            story of the most recent issue of the world's most prestigious scientific magazine, Scienc

            There are few places on the Earth subject to such extreme conditions as the ocean depths. 
            organisms must cope with enormous pressure, low light and the absence of landmarks to orie
            in the “endless” space of the deep sea and find prey or potential partners. The dominant p

            this environment are deep-sea fish, which have evolved in various ways to deal with the la
            our research we analysed individual photoreceptor cells, i.e. the rods and cones in the re

            photosensitive pigments,” said Zuzana Musilová from the CU FS Zoology Department, the lead
            article published in the most recent issue of Science.
            “We focused on complete genome data from a total of 101 species throughout groups of bony 

            (Teleostei). Then we specifically focused on the genomes of the deep-sea fishes and looked
            indicating that these fish live in such specific conditions,” said Musilová. The deep sea 
            environment, not only due to the reduced light intensity, i.e. the number of photons that 

            water column, but the colour spectrum is also narrower – basically only the middle blue-gr
            light spectrum penetrates into the depths.
            Genome research first revealed that fish living at great depths often lack the genes respo

            seeing colours at the edges of the visible spectrum, meaning these fish have lost the gene
            and red light. That corresponds to the light conditions present at this depth. Contrary to
            further genome analysis also showed that certain genes in deep-sea fishes have multiplied 

            Genes for rod opsin, the photosensitive pigment found in rods usually responsible for blac
            vision in dim light, have multiplied in certain groups of deep-sea fish. This has even bee
            independent evolutionary lineages! In the silver spinyfin (Diretmus argenteus), scientists

            of this gene, a phenomenon that is absolutely unique among vertebrates.
            The question remains how deep-sea fish utilize this complicated structure of changes. “We 
            be some form of colour vision that functions in an entirely differently way than what we a

            in other animals,” mused Zuzana Musilová. Colour vision in vertebrates always involves the
            however, is a fish that only has rods and yet can see colours thanks to various changes in
            opsin genes. It is not yet fully understood how vision takes place at a higher physiologic

            how visual perception is transmitted through the nervous system.
            “The silver spinyfin, which we mainly studied because of the high number of copies of rod 
            feeds on crustaceans that produce coloured bioluminescent signals and can therefore be rec

            easily by this adaptation – the fish can then specifically focus on the tastiest prey,” Mu
            The mystery remains, however, why these fish have so many types of rhodopsin since, accord
            modelling, two or even one type should be sufficient. The answer to this question will req

            research.
            By Michal Anderle
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            References:
            Musilova, Z., Cortesi, F., Matschiner, M., Davies, W. I., Patel, J. S., Stieb, S. M., ... 
            Vision using multiple distinct rod opsins in deep-sea fishes. Science. (Accepted)

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            Zuzana Musilová began this study on deep-sea fish during her post-doctoral stay at the Uni
            in Switzerland. She shares the lead authorship with her former colleague from the same ins

            Cortesi, currently based at the University of Queensland in Brisbane, Australia. The core 
            was carried out at the University of Basel and Charles University, although specific quest
            answered through collaboration with colleagues at various laboratories all over the world,

            University of Oslo, University of Zurich, University of Western Australia in Perth, Univer
            and University of Idaho in the USA and several others.