Melanopsin has been proposed to be the photopigment of the intrinsically photosensitive retinal ganglion cells (ipRGCs); these photoreceptors of the mammalian eye drive circadian and pupillary adjustments through direct projections to the brain. Their action spectrum (lambda(max) approximately 480 nm) implicates an opsin and melanopsin is the only opsin known to exist in these cells. Melanopsin is required for ipRGC photosensitivity and for behavioural photoresponses that survive disrupted rod and cone function. Heterologously expressed melanopsin apparently binds retinaldehyde and mediates photic activation of G proteins. However, its amino-acid sequence differs from vertebrate photosensory opsins and some have suggested that melanopsin may be a photoisomerase, providing retinoid chromophore to an unidentified opsin. To determine whether melanopsin is a functional sensory photopigment, here we transiently expressed it in HEK293 cells that stably expressed TRPC3 channels. Light triggered a membrane depolarization in these cells and increased intracellular calcium. The light response resembled that of ipRGCs, with almost identical spectral sensitivity (lambda(max) approximately 479 nm). The phototransduction pathway included Gq or a related G protein, phospholipase C and TRPC3 channels. We conclude that mammalian melanopsin is a functional sensory photopigment, that it is the photopigment of ganglion-cell photoreceptors, and that these photoreceptors may use an invertebrate-like phototransduction cascade.

The eyes of the female small white butterfly, Pieris rapae crucivora, are furnished with three classes of short-wavelength photoreceptors, with sensitivity peaks in the ultraviolet (UV) ( max ϭ 360 nm), violet (V) ( max ϭ 425 nm), and blue (B) ( max ϭ 453 nm) wavelength range. Analyzing the spectral origin of the photoreceptors, we isolated three novel mRNAs encoding opsins corresponding to shortwavelength-absorbing visual pigments. We localized the opsin mRNAs in the retinal tissue and found that each of the short-wavelengthsensitive photoreceptor classes exclusively expresses one of the opsin mRNAs. We, accordingly, termed the visual pigments PrUV, PrV, and PrB, respectively. The eyes of the male small white butterfly also use three classes of short-wavelength photoreceptors that equally uniquely express PrUV, PrV, and PrB. However, whereas the spectral sensitivities of the male photoreceptors with PrUV and PrB closely correspond to those of the female, the male photoreceptor expressing PrV has a double-peaked blue (dB) spectral sensitivity, strongly deviating from the spectral sensitivity of the female V photoreceptor. The male eyes contain a pigment that distinctly fluoresces under blue-violet as well as UV excitation light. It coexists with the dB photoreceptors and presumably acts as a spectral filter with an absorbance spectrum peaking at 416 nm. The narrow-band spectral sensitivity of the male dB photoreceptors probably evolved to improve the discrimination of the different wing colors of male and female P. rapae crucivora in the short-wavelength region of the spectrum.

Ommatidial heterogeneity in the compound eye of the male small white butterfly, Pieris rapae crucivora Qiu, XD; Vanhoutte, KAJ; Stavenga, Doekele; Arikawa, K; Qiu, Xudong Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date: 11-05-2018Abstract The ommatidia in the ventral two-thirds of the compound eye of male Pieris rapae crucivora are not uniform. Each ommatidium contains nine photoreceptor cells. Four cells (R1-4) form the distal two-thirds of the rhabdom, four cells (R5-8) approximately occupy the proximal one-third of the rhabdom, and the ninth cell (R9) takes up a minor basal part of the rhabdom. The R5-8 photoreceptor cells contain clusters of reddish pigment adjacent to the rhabdom. From the position of the pigment clusters, three types of ommatidia can be identified: the trapezoidal (type I), square (type II), and rectangular type (type III). Microspectrophotometry with an epi-illumination microscope has revealed that the reflectance spectra of type I and type III ommatidia peak at 635 nm and those of type II ommatidia peak at 675 nm. The bandwith of the reflectance spectra is 40-50 nm. Type II ommatidia strongly fluoresce under ultra-violet and violet epi-illumination. The three types of ommatidia are randomly distributed. The ommatidial heterogeneity is presumably crucial for color discrimination.

The compound eyes of insects consist of a number of units called ommatidia. The ommatidial lattice is strikingly regular, and the ommatidia are identical in terms of the basic structure. However, recent studies have demonstrated that in many insect species, including flies (Franceschini et al., 1981;Hardie, 1986), moth (Meinecke and Langer, 1984), backswimmer (Schwind and Langer, 1984) and butterflies (Bernard and Miller, 1970;Ribi, 1978a;Arikawa and Stavenga, 1997; Arikawa et al., 1999a,b;Stavenga et al., 2001; Stavenga, 2002a,b), the ommatidia are in fact not identical to each other, but heterogeneous.The white butterfly, Pieris, is a cosmopolitan genus that has long been used for vision research. Early anatomical work revealed that the ommatidia contain nine photoreceptor cells, numbered R1-9, and bear red pigmentation in the ventral half of the compound eye (Kolb, 1978;Ribi, 1978b). The photoreceptors were also shown to be strongly diverse in terms of their sensitivity spectra, with peak sensitivities ranging from the ultraviolet to the red wavelengths (Shimohigashi and Tominaga, 1991). The different spectral receptor types participate in various behavioral tasks such as egg laying and feeding (Kolb and Scherer, 1982). Behavioral aspects related to color vision of Pieris have also been studied (Goulson and Cory, 1993; Ohsaki, 1996, 1998), and some behavioral experiments (Scherer and Kolb, 1987) and associated model calculations (Kelber, 2001) have together demonstrated that Pieris rapae has true color vision, as in Papilionid species (Kinoshita et al., 1999;Kelber and Pfaff, 1999).Our research on the yellow swallowtail Papilio xuthus has revealed that the eyes contain three types of ommatidia, each with a distinct set of photoreceptors, with sensitivity spectra shaped by the rhodopsin absorption spectra of both visual and filtering pigments (Arikawa and Stavenga, 1997; Arikawa et al., 1999a,b). The accumulated information about the retinal anatomy and the photoreceptor spectra of the Pieris compound eye inspired us to investigate whether this butterfly has a similar ommatidial heterogeneity. As expected, we identified three types of anatomically distinct ommatidia in the compound eye of Pieris rapae crucivora (Qiu et al., 2002). All ommatidia of a Pieris eye are tiered, containing four distal (R1-4) and four proximal (R5-8) photoreceptor cells, the rhabdomeres, of which together form the fused rhabdom, a cylindrical structure along the central axis of the ommatidium. The R9 cell contributes to the rhabdom at the very base (i.e. is most proximal) (Fig.·1). Except for the dorsal part of the eye, all ommatidia are prominently pigmented (Ribi, 1978b). The proximal photoreceptors, R5-8, bear a dense pigmentation The compound eye of the small white butterfly Pieris rapae crucivora contains three anatomically distinct types of ommatidia. They differ in pigmentation around the rhabdom, colour of tapetal reflection and violet lightinduced autofluorescence, indicating physiological differences between them. We rece...

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