Spectral sensitivity of mollies: comparing surface- and cave-dwelling Atlantic mollies, Poecilia mexicana K. E. KO ¨ RNER*, I. SCHLUPP*†, M. PLATH*‡ AND E. R. LOEW§ *Universita¨t Hamburg, Biozentrum Grindel, Abteilung fu¨r Verhaltensbiologie, Martin- Luther-King Platz 3, 20146 Hamburg, Germany and §Department of Biomedical Science, Cornell University, Ithaca, NY 14853, U.S.A. (Received 21 June 2004, Accepted 19 December 2005) The visual pigments of cones and rods in three species of mollies, Poecilia mexicana, Poecilia latipinna and their asexual hybrid Poecilia formosa, were examined using microspectrophotom- etry. In P. mexicana, populations from extreme photic habitats were used: one population originated from a clear water habitat, one from a milky water habitat and another from a completely dark cave. Ultraviolet-sensitive cones were found in all species. Differences in the l max values of the visual pigments were small between species and among the three P. mexicana populations, but dark-reared cave fishes showed appreciably higher variance. The hybrid species P. formosa showed a highly variable long wavelength cone absorbance, ranging from 5289 to 5985 nm, suggesting multiple opsin expression or chromophore mixing. # 2006 The Authors Journal compilation # 2006 The Fisheries Society of the British Isles Key words: Amazon molly; cave fishes; colour vision; microspectrophotometry; UV; video playback. INTRODUCTION Visual information is widely used in decision making (Bradbury & Vehren- camp, 1998). Body colour patterns in fishes can play an important role in pred- ator avoidance (Smith, 1997), food selection (Rodd et al., 2002), mate choice (Andersson, 1994) or any combination of these factors. For example, female mating preferences can be based on male ornamentation such as the intensity of certain colour patterns, e.g. guppies Poecilia reticulata (Peters) (Long & Houde, 1989; Kodric-Brown, 1993; Endler & Houde, 1995; McKinnon, 1995; Houde, 1997), cichlids (Hert, 1989), pipefishes (Berglund et al., 1986) and three-spined stickleback Gasterosteus aculeatus L. (McLennan & McPhail, 1990; Milinski & Bakker, 1990; Rowe et al., 2004). †Author to whom correspondence should be addressed at present address: Department of Zoology, University of Oklahoma, 703 Van Vleet Oval, Norman, OK 73019, U.S.A. Tel.: þ1 405 3254908; fax: þ1 405 3256202; email: schlupp@ou.edu ‡Present address: Unit of Evolutionary Biology and Systematic Zoology, Department of Biochemistry and Biology, University of Potsdam, Karl-Liebknecht-Str. 24–25, 14476 Potsdam, Germany. Journal of Fish Biology (2006) 69, 54–65 doi:10.1111/j.1095-8649.2006.01056.x, available online at http://www.blackwell-synergy.com 54 # 2006 The Authors Journal compilation # 2006 The Fisheries Society of the British Isles