title: The lantern shark's light switch: turning shallow water crypsis into midwater camouflage.
abstract: Bioluminescence is a common feature in the permanent darkness of the deep-sea. In fishes, light is emitted by organs containing either photogenic cells (intrinsic photophores), which are under direct nervous control, or symbiotic luminous bacteria (symbiotic photophores), whose light is controlled by secondary means such as mechanical occlusion or physiological suppression. The intrinsic photophores of the lantern shark Etmopterus spinax were recently shown as an exception to this rule since they appear to be under hormonal control. Here, we show that hormones operate what amounts to a unique light switch, by acting on a chromatophore iris, which regulates light emission by pigment translocation. This result strongly suggests that this shark's luminescence control originates from the mechanism for physiological colour change found in shallow water sharks that also involves hormonally controlled chromatophores: the lantern shark would have turned the initial shallow water crypsis mechanism into a midwater luminous camouflage, more efficient in the deep-sea environment.
authors.affiliation: Laboratory of Marine Biology, Earth and Life Institute, Université catholique de Louvain, 3 Place Croix du Sud, 1348 Louvain-la-Neuve, Belgium. julien.m.claes@uclouvain.be
authors.forename: Julien M
authors.initials: JM
authors.lastname: Claes
authors.forename: Jérôme
authors.initials: J
authors.lastname: Mallefet
mesh_terms: D000818:Animals; D049449:Luminescence; D012754:Sharks / Q000502:physiology*
references.citation: Symp Soc Exp Biol. 1985;39:323-50
references.pmid: 3914720
references.citation: Nature. 2005 Oct 27;437(7063):1349-52
references.pmid: 16251963
references.citation: J Exp Biol. 2009 Nov;212(Pt 22):3684-92
references.pmid: 19880730
references.citation: Zoology (Jena). 2009;112(6):433-41
references.pmid: 19674879
references.citation: Crit Rev Microbiol. 1993;19(4):191-216
references.pmid: 8305135
references.citation: Ann Rev Mar Sci. 2010;2:443-93
references.pmid: 21141672
references.citation: Science. 1979 Mar 16;203(4385):1109-10
references.pmid: 17776046
references.citation: J Exp Zool. 1999 Oct 1;284(5):485-91
references.pmid: 10469985