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Open Access Highly Accessed Research article

Visual pigments in a living fossil, the Australian lungfish Neoceratodus forsteri

Helena J Bailes12*, Wayne L Davies13, Ann EO Trezise1 and Shaun P Collin1

Author Affiliations

1 School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, QLD 4072, Australia

2 Faculty of Life Sciences, Manchester University, Oxford Road, Manchester, M13 9PL, UK

3 UCL Institute of Ophthalmology, 11-43 Bath Street, London, EC1V 9EL, UK

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BMC Evolutionary Biology 2007, 7:200  doi:10.1186/1471-2148-7-200

Published: 25 October 2007

Abstract

Background

One of the greatest challenges facing the early land vertebrates was the need to effectively interpret a terrestrial environment. Interpretation was based on ocular adaptations evolved for an aquatic environment millions of years earlier. The Australian lungfish Neoceratodus forsteri is thought to be the closest living relative to the first terrestrial vertebrate, and yet nothing is known about the visual pigments present in lungfish or the early tetrapods.

Results

Here we identify and characterise five visual pigments (rh1, rh2, lws, sws1 and sws2) expressed in the retina of N. forsteri. Phylogenetic analysis of the molecular evolution of lungfish and other vertebrate visual pigment genes indicates a closer relationship between lungfish and amphibian pigments than to pigments in teleost fishes. However, the relationship between lungfish, the coelacanth and tetrapods could not be absolutely determined from opsin phylogeny, supporting an unresolved trichotomy between the three groups.

Conclusion

The presence of four cone pigments in Australian lungfish suggests that the earliest tetrapods would have had a colorful view of their terrestrial environment.