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

Bailes HJ, Davies WL, Trezise AE, Collin SP - BMC Evol. Biol. (2007)

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, QLD 4072, Australia. helena.bailes@manchester.ac.uk

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.

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A phylogenetic tree of the five photoreceptor opsins of Neoceratodus forsteri and selected full-length nucleotide coding sequences of related species. The tree was constructed using the Neighbour-joining method with 1000 bootstrap replications [39]. Sarcopterygian fish (coelacanth and lungfish) are in red, agnathan fish (lamprey) are in light blue, teleost fish are in dark blue, amphibians are in green and reptiles are in purple. Genbank accession numbers are listed in Table 1. Bootstrap confidence values are at the base of each node. The rh4 opsin of Drosophila melanogaster (Table 1) was used as an outgroup. Scale bar indicates nucleotide substitutions per site.
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Figure 3: A phylogenetic tree of the five photoreceptor opsins of Neoceratodus forsteri and selected full-length nucleotide coding sequences of related species. The tree was constructed using the Neighbour-joining method with 1000 bootstrap replications [39]. Sarcopterygian fish (coelacanth and lungfish) are in red, agnathan fish (lamprey) are in light blue, teleost fish are in dark blue, amphibians are in green and reptiles are in purple. Genbank accession numbers are listed in Table 1. Bootstrap confidence values are at the base of each node. The rh4 opsin of Drosophila melanogaster (Table 1) was used as an outgroup. Scale bar indicates nucleotide substitutions per site.

Mentions: Phylogenetic comparison of codon-matched alignments of both nucleotide and deduced amino acid sequences of rh1, rh2, lws1, sws1 and sws2 with other vertebrate opsins (Genbank accession numbers listed in Table 1) using two fundamentally different methods of phylogenetic inference (both the Neighbour-joining (NJ) method and Bayesian inference via a Metropolis Markov chain Monte Carlo simulation) reveals that lungfish opsins share more similarity with tetrapod opsins than those of other fishes (Figs. 3 and 4 and Additional file 1). Lungfish opsins form a clade with tetrapod opsins rather than teleost fish in four out of the five opsin families in each analysis, but different topology is obtained between tree branches with low bootstrap values or low posterior probability, in particular within the rh1 and lws groups.


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

Bailes HJ, Davies WL, Trezise AE, Collin SP - BMC Evol. Biol. (2007)

A phylogenetic tree of the five photoreceptor opsins of Neoceratodus forsteri and selected full-length nucleotide coding sequences of related species. The tree was constructed using the Neighbour-joining method with 1000 bootstrap replications [39]. Sarcopterygian fish (coelacanth and lungfish) are in red, agnathan fish (lamprey) are in light blue, teleost fish are in dark blue, amphibians are in green and reptiles are in purple. Genbank accession numbers are listed in Table 1. Bootstrap confidence values are at the base of each node. The rh4 opsin of Drosophila melanogaster (Table 1) was used as an outgroup. Scale bar indicates nucleotide substitutions per site.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2194722&req=5

Figure 3: A phylogenetic tree of the five photoreceptor opsins of Neoceratodus forsteri and selected full-length nucleotide coding sequences of related species. The tree was constructed using the Neighbour-joining method with 1000 bootstrap replications [39]. Sarcopterygian fish (coelacanth and lungfish) are in red, agnathan fish (lamprey) are in light blue, teleost fish are in dark blue, amphibians are in green and reptiles are in purple. Genbank accession numbers are listed in Table 1. Bootstrap confidence values are at the base of each node. The rh4 opsin of Drosophila melanogaster (Table 1) was used as an outgroup. Scale bar indicates nucleotide substitutions per site.
Mentions: Phylogenetic comparison of codon-matched alignments of both nucleotide and deduced amino acid sequences of rh1, rh2, lws1, sws1 and sws2 with other vertebrate opsins (Genbank accession numbers listed in Table 1) using two fundamentally different methods of phylogenetic inference (both the Neighbour-joining (NJ) method and Bayesian inference via a Metropolis Markov chain Monte Carlo simulation) reveals that lungfish opsins share more similarity with tetrapod opsins than those of other fishes (Figs. 3 and 4 and Additional file 1). Lungfish opsins form a clade with tetrapod opsins rather than teleost fish in four out of the five opsin families in each analysis, but different topology is obtained between tree branches with low bootstrap values or low posterior probability, in particular within the rh1 and lws groups.

Bottom Line: 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.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, QLD 4072, Australia. helena.bailes@manchester.ac.uk

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.

Show MeSH