Tobias Gerlach; Jennifer Theobald; Nathan S. Hart; Shaun P. Collin; Nico K. Michiels

“ Inspection of individual scans from single cone outer segments and also the mean spectrum constructed from all acceptable single cone records suggest the possibility that single cones express more than one visual pigment: the absorbance spectrum deviates markedly from the template on the short-wavelength limb, i.e. has a greater spectral bandwidth, and the running average of the peak of the spectrum (507 nm) is different to the estimate of λmax obtained by fitting a regression line to the long wavelength limb (516 nm) . ”

“ Indeed, recent behavioural experiments have shown that the pseudocheilinid fairy wrasse Cirrhilabrus solorensis [26] can perceive its own red fluorescent body colouration and that this fluorescent colour affects agonistic male-male interactions [27] .
This work aims to characterise the visual system of the pseudocheilinid wrasse C. solorensis by reporting microspectrophotometric measurements of the spectral absorbances of each of the retinal photoreceptor types as well as the spectral transmittance data on the ocular media. ”

“ The photoreceptor visual pigment λmax values of absorbance values of C. solorensis presented here are similar to existing data on other reef fish families [20] and generally match the blue dominated light environment, but lack a distinct UV cone receptor found in some shallow water species [20] , [42] . This indicates that the visual system of fairy wrasses is well adapted to their stenospectral habitat, as predicted by the sensitivity hypothesis [18] , [43] . ”

“ Fluorescence is characterised by wavelength of maximum emission and fluorescent brightness in Fig. 2.
Wavelength of maximum fluorescent emission across species. Size of circles depicts relative fluorescent brightness Microspectrophotometry
Microspectrophotometric data for all photoreceptor classes found in the fairy wrasse Cirrhilabrus solorensis are summarised in Table 1 and displayed in Figs. 3 and 4. All visual pigment absorbance spectra are considered to represent vitamin A1-based visual pigments (i.e. rhodopsins) , according to the fit of the data to A1 visual pigment templates [31] . ”

“ Every animal was measured repeatedly on several predefined locations: the eye, dorsal part of the head, the operculum, both ventral and dorsal parts of the lateral body as well as each fin. Within all individuals, peak fluorescent emission was highly consistent across these body parts. ”

“ Competing interestsThe authors declare that they have no competing interests,Authors’ contributionsTG and NKM designed the research. JT established the setup for fluorescence characterisation, collected emission measurements and processed fluorescence data. TG gathered data on microspectrophotometry, NSH provided microspectrophotometric setup, analysed and processed data on photoreceptor absorbance and collected spectra for ocular media transmittance. ”

“ Wrasses represent the second largest family of marine fishes and display a high diversity of complex colours linked to ecological functions. Recently, red autofluorescent body colouration has been reported in some of these fishes. ”

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“ Naturwissenschaften. 2011;98:193–201.10.1007/s00114-010-0758-821212930↑ Boehlert GW. Intraspecific evidence for the function of single and double cones in the teleost retina. Science. 1978;202:309–11.10.1126/science.694534694534↑ Hawryshyn C, Moyer H, Allison W, Haimberger T, McFarland W. Multidimensional polarization sensitivity in damselfishes. J Comp Physiol A. 2003;189:213–20.1 2 Pignatelli V, Champ C, Marshall J, Vorobyev M. Double cones are used for colour discrimination in the reef fish, Rhinecanthus aculeatus. Biol Lett. ”

“ Proc R Soc Lond B Biol Sci. 2010;277:2607–15.10.1098/rspb.2010.0345↑ Bleeker P. Bijdrage tot de kennis der ichthyologische fauna van Singapore. 1851. ↑ Allen G, Kuiter R. Descriptions of two new wrasses of the genus Cirrhilabrus (Labridae) from Indonesia. Aqua J Ichthyol Aquat Biol. 1999;3:133–40.↑ Wucherer MF, Michiels NK. A Fluorescent Chromatophore Changes the Level of Fluorescence in a Reef Fish. PLoS One. 2012;710.1371/journal.pone.003791322701587↑ Wucherer MF, Michiels NK. Regulation of red fluorescent light emission in a cryptic marine fish. Front. Zool. ”