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First published online December 3, 2004
Journal of Experimental Biology 207, 4587-4594 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01314

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Multiple cone visual pigments and the potential for trichromatic colour vision in two species of elasmobranch

Nathan S. Hart^1,*, Thomas J. Lisney², N. Justin Marshall¹ and Shaun P. Collin²

¹ Vision, Touch and Hearing Research Centre (Queensland Brain Institute), University of Queensland, Brisbane, Queensland 4072, Australia
² Department of Anatomy and Developmental Biology School of Biomedical Sciences, University of Queensland, Brisbane, Queensland 4072, Australia

View larger version (131K): [in a new window]   Fig. 1. Dorsal (A) and lateral (B) views of the giant shovelnose ray, Rhinobatos typus, showing the raised eyes and crescent-shaped pupil in the light-adapted state. (C) Light micrograph of the retina of R. typus showing the duplex nature of the photoreceptor layer (smaller receptors are cones). gc, ganglion cell layer; h, horizontal cell layer; ipl, inner plexiform layer; p, photoreceptor layer. Scale bars: (A) 50 mm; (B) 80 mm; and (C) 100 µm.

View larger version (214K): [in a new window]   Fig. 2. Ultrastructure of rods and cones in Rhinobatos typus. (A) Typical rod (r) and cone (c) morphology. (B,C) Different types of cone photoreceptors can be distinguished based on minor differences in receptor size, mitochondrial alignment and the location of the nucleus in the outer nuclear layer. (D) High-power micrograph of the outer segment (os) of a cone photoreceptor showing the lack of a plasma membrane surrounding the discs. c, cone; cn, cone nucleus; m, mitochondria; my, myoid; r, rod. Scale bars: (A–C) 5 µm; and (D) 0.5 µm.

View larger version (35K): [in a new window]   Fig. 3. Normalized absorbance spectra of rod and cone visual pigments in (A) the giant shovelnose ray Rhinobatos typus, and (B) the eastern shovelnose ray Aptychotrema rostrata. Prebleach spectra (circles) are best-fitted with a rhodospin visual pigment template of the appropriate max; postbleach spectra (squares) are fitted with an unweighted running average. SWS, MWS and LWS refer to short-, medium- and long-wavelength-sensitive visual pigments, respectively.

View larger version (28K): [in a new window]   Fig. 4. Spectral radiance along different lines of sight at different depths in Australian reef and coastal waters. (A) Reef water 1 m depth; (B) coastal water 1 m depth; (C) reef water 5 m depth; (D) coastal water 3–5 m depth. Solid line, down-welling radiance; broken line, horizontal radiance; dotted line, up-welling radiance.