spinax failed to identify the reactive compounds underlying the emission of light (i.e., luciferin/luciferase or photoprotein) ( Renwart and Mallefet, 2013). Recently, studies of the luminous system of E. Photophores also display an iris-like structure (ILS), composed mainly of chromatophores, between the photocytes and the lens cells ( Renwart et al., 2014 Duchatelet et al., 2020b). spinax, a guanine crystal reflector structure is located between the cup-shaped pigmented layer and the photocyte ( Renwart et al., 2014, 2015). Each photophore is composed of a cup-shaped layer of pigmented cells encapsulating one to more than twelve photogenic cells (i.e., photocytes) and topped by one or more lens cells. Luminescence is achieved via thousands of photophores located within the epidermis. Luminous sharks appear to produce blue-green light (between 455 and 486 nm Claes et al., 2014a) for multiple purposes, such as counterillumination ( Claes et al., 2010a), aposematism ( Claes et al., 2013 Duchatelet et al., 2019b), and conspecific recognition ( Claes et al., 2014a, 2015). These studies investigated bioluminescence in three etmopterids, Etmopterus spinax (Linnaeus, 1758), Etmopterus molleri (Whitley, 1939), Etmopterus splendidus (Yano, 1988), and one dalatiid, Squaliolus aliae (Teng, 1959) (e.g., Claes and Mallefet, 2009b, c, 2015 Claes et al., 2010a, 2011b, 2012 Renwart et al., 2014, 2015 Duchatelet et al., 2019b, 2020b). The first mentions of shark light emission date back to the nineteenth century ( Bennett, 1840 Johann, 1899), but it is only recently that bioluminescence studies, focusing on physiological control, and photophore morphology and function, have been developed. squamulosus being a luminous species ( Duchatelet et al., 2021). A third family, Somniosidae was recently suggested to also contain a luminous species, Zameus squamulosus (Günther, 1877), based on density and upper view of putative light organs (i.e., photophores) ( Straube et al., 2015), new results brought clear evidence Z. Among Squaliformes, bioluminescence is documented for two deep-sea families: Dalatiidae and Etmopteridae ( Claes and Mallefet, 2009b Straube et al., 2015). This living light, also called cold light, occurs through a biochemical reaction the oxidation of a substrate, a luciferin, by an enzyme, the luciferase, or through a stabilized complex called photoprotein ( Shimomura, 2006). This first experimental study of three luminous shark species from New Zealand provides an insight into the diversity of shark bioluminescence and highlights the need for more research to help understand these unusual deep-sea inhabitants: the glowing sharks.īioluminescence, defined as the production of visible light by living organisms, is a widespread phenomenon mainly encountered among various marine taxa ( Widder, 1999 Haddock et al., 2010). licha, the largest known luminous vertebrate. A special emphasis is placed on the luminescence of D. Comparison of glowing shark pictures, combined with histological description of light organs and hormonal control analysis, highlight the evolutive conservation of the bioluminescence process within Dalatiidae and Etmopteridae. Three species of deepwater sharks ( Dalatias licha, Etmopterus lucifer, and Etmopterus granulosus) were collected from the Chatham Rise, off New Zealand, and for the first time, we documented their luminescence. ![]() 2National Institute of Water and Atmospheric Research (NIWA), Wellington, New Zealandīioluminescence has often been seen as a spectacular yet uncommon event at sea but considering the vastness of the deep sea and the occurrence of luminous organisms in this zone, it is now more and more obvious that producing light at depth must play an important role structuring the biggest ecosystem on our planet. ![]() ![]() 1Marine Biology Laboratory, Earth and Life Institute, Université catholique de Louvain – UCLouvain, Louvain-la-Neuve, Belgium.
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