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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
Multiple cone visual pigments and the potential for trichromatic colour vision in two species of elasmobranch
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
* Author for correspondence (e-mail: n.hart{at}uq.edu.au)
Accepted 28 September 2004
Elasmobranchs (sharks, skates and rays) are the modern descendents of the
first jawed vertebrates and, as apex predators, often occupy the highest
trophic levels of aquatic (predominantly marine) ecosystems. However, despite
their crucial role in the structure of marine communities, their importance
both to commercial and to recreational fisheries, and the inherent interest in
their role in vertebrate evolution, very little is known about their visual
capabilities, especially with regard to whether or not they have the potential
for colour vision. Using microspectrophotometry, we show that the retinae of
the giant shovelnose ray (Rhinobatos typus) and the eastern
shovelnose ray (Aptychotrema rostrata) contain three spectrally
distinct cone visual pigments with wavelengths of maximum absorbance
(
max) at 477, 502 and 561 nm and at 459, 492 and 553 nm,
respectively. The retinae of R. typus and A. rostrata also
contain a single type of rod visual pigment with max at 504
and 498 nm, respectively. R. typus, living in the same estuarine
waters as A. rostrata, were found to have identical visual pigments
to R. typus inhabiting coral reef flats, despite a considerable
difference in habitat spectral radiance. This is the first time that multiple
cone visual pigments have been measured directly in an elasmobranch. The
finding raises the possibility that some species are able to discriminate
colour – a visual ability traditionally thought to be lacking in this
vertebrate class – and it is evident that the visual ecology of
elasmobranchs is far more complex than once thought.
Key words: elasmobranch, microspectrophotometry, shovelnose ray, visual pigment, Rhinobatos typus, Aptychotrema rostrata, shark, vision
