title: Encephalic photoreception and phototactic response in the troglobiont Somalian blind cavefish Phreatichthys andruzzii.
abstract: Many physiological and behavioural responses to changes in environmental lighting conditions are mediated by extraocular photoreceptors. Here we investigate encephalic photoreception in Phreatichthys andruzzii, a typical cave-dwelling fish showing an extreme phenotype with complete anophthalmy and a reduction in size of associated brain structures. We firstly identified two P. andruzzii photopigments, orthologues of rod opsin and exo-rod opsin. In vitro, both opsins serve as light-absorbing photopigments with λ(max) around 500 nm when reconstituted with an A(1) chromophore. When corrected for the summed absorption from the skin and skull, the spectral sensitivity profiles shifted to longer wavelengths (rod opsin: 521 nm; exo-rod opsin: 520 nm). We next explored the involvement of both opsins in the negative phototaxis reported for this species. A comparison of the spectral sensitivity of the photophobic response with the putative A(2) absorbance spectra corrected for skin/skull absorbance indicates that the A(2) versions of either or both of these pigments could explain the observed behavioural spectral sensitivity.
authors: Faculty of Life Sciences, University of Manchester, Manchester M13 9PT,  UK.
authors: Emma E
authors: EE
authors: Tarttelin
authors: Elena
authors: E
authors: Frigato
authors: James
authors: J
authors: Bellingham
authors: Viviana
authors: V
authors: Di Rosa
authors: Roberto
authors: R
authors: Berti
authors: Nicholas S
authors: NS
authors: Foulkes
authors: Robert J
authors: RJ
authors: Lucas
authors: Cristiano
authors: C
authors: Bertolucci
mesh_terms: D000042:Absorption; D000595:Amino Acid Sequence; D000818:Animals; D001766:Blindness / Q000503:physiopathology*; D001921:Brain / Q000378:metabolism*; D059552:Caves; D003531:Cypriniformes / Q000502:physiology*; D057809:HEK293 Cells; D006801:Humans; D055537:Light Signal Transduction / Q000502:physiology*; D008969:Molecular Sequence Data; D038761:Photobleaching; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism*; D017299:Rod Opsins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D012998:Somalia; D013057:Spectrum Analysis; D013997:Time Factors
chemical_list: D017299:Rod Opsins