Journal of Fish Biology (2013) 83, 1468–1473 doi:10.1111/jfb.12253, available online at wileyonlinelibrary.com Calcium-activated chloride channels do not contribute to the odorant transduction current in the marine teleost Isacia conceptionis R. Osorio and O. Schmachtenberg* Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Avda. Gran Breta˜ na 1111, 2360102, Valparaíso, Chile (Received 6 April 2013, Accepted 11 September 2013) This study compared the contribution of the Ca 2+ -activated Cl − conductance to the electro- olfactogram (EOG) evoked by different odorant classes between the marine Cabinza grunt Isacia conceptionis and rainbow trout Oncorhynchus mykiss . The Ca 2+ -activated Cl − channel blocker niflumic acid significantly diminished odorant responses in O. mykiss , but had no effect on the EOG in I. conceptionis , supporting the notion that Ca 2+ -activated Cl − channels may not operate as odorant transduction current amplifiers in this marine teleost. © 2013 The Fisheries Society of the British Isles Key words: fish; olfaction; olfactory receptor neuron; rainbow trout. Twenty years ago, two independent publications in the journal Nature reported the contribution of a Ca 2+ -activated Cl − conductance to the odorant transduction cas- cade in vertebrate olfactory receptor neurons (Kurahashi & Yau, 1993; Lowe & Gold, 1993). This conductance, which had first been described in olfactory cilia from the northern grass frog Rana pipiens (Kleene & Gesteland, 1991), has now been established to contribute a significant portion to the odorant transduction current in all terrestrial and freshwater mammals and amphibians tested (Schild & Restrepo, 1998; Kleene, 2008). Recently, the molecular identity of the olfactory Ca 2+ -activated Cl − channel has been tentatively identified as anoctamin2 (Ano2) in mammals, also known as TMEM16B (Stephan et al., 2009; Pifferi et al., 2012). In fishes, the largest group of vertebrates, evidence remains limited to one patch-clamp study in dissoci- ated olfactory receptor neurons from the rainbow trout Oncorhynchus mykiss (Wal- baum 1792), that demonstrated the presence of a Ca 2+ -activated Cl − conductance in these cells and its participation in odorant transduction (Sato & Suzuki, 2000). To date, however, no study has addressed the possible role of Ca 2+ -activated Cl − chan- nels in the olfactory transduction cascade of marine or saltwater-adapted euryhaline teleosts. Owing to the elevated chloride concentration in the marine environment, c . 500 mM, the chloride reversal potential is shifted to negative values compared to *Author to whom correspondence should be addressed. Tel.: +56-32-2995505; email: oliver. schmachtenberg@uv.cl 1468 © 2013 The Fisheries Society of the British Isles