Phylogenetic position of a whale-fall lancelet (Cephalochordata) inferred from whole mitochondrial genome sequences
Abstract Background The lancelet Asymmetron inferum (subphylum Cephalochordata) was recently discovered on the ocean floor off the southwest coast of Japan at a depth of 229 m, in an anaerobic and sulfide-rich environment caused by decomposing bodies of the sperm whale Physeter macrocephalus . This...
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ftbiomed:oai:biomedcentral.com:1471-2148-7-127 2023-05-15T17:59:28+02:00 Phylogenetic position of a whale-fall lancelet (Cephalochordata) inferred from whole mitochondrial genome sequences Kon, Takeshi Nohara, Masahiro Yamanoue, Yusuke Fujiwara, Yoshihiro Nishida, Mutsumi Nishikawa, Teruaki 2007-07-31 http://www.biomedcentral.com/1471-2148/7/127 en eng BioMed Central Ltd. http://www.biomedcentral.com/1471-2148/7/127 Copyright 2007 Kon et al; licensee BioMed Central Ltd. Research article 2007 ftbiomed 2007-11-11T15:23:32Z Abstract Background The lancelet Asymmetron inferum (subphylum Cephalochordata) was recently discovered on the ocean floor off the southwest coast of Japan at a depth of 229 m, in an anaerobic and sulfide-rich environment caused by decomposing bodies of the sperm whale Physeter macrocephalus . This deep sulfide-rich habitat of A. inferum is unique among the lancelets. The distinguishing adaptation of this species to such an extraordinary habitat can be considered in a phylogenetic framework. As the first step of reconstruction of the evolutionary processes in this species, we investigated its phylogenetic position based on 11 whole mitochondrial genome sequences including the newly determined ones of the whale-fall lancelet A. inferum and two coral-reef congeners. Results Our phylogenetic analyses showed that extant lancelets are clustered into two major clades, the Asymmetron clade and the Epigonichthys + Branchiostoma clade. A. inferum was in the former and placed in the sister group to A. lucayanum complex. The divergence time between A. inferum and A. lucayanum complex was estimated to be 115 Mya using the penalized likelihood (PL) method or 97 Mya using the nonparametric rate smoothing (NPRS) method (the middle Cretaceous). These are far older than the first appearance of large whales (the middle Eocene, 40 Mya). We also discovered that A. inferum mitogenome (mitochondrial genome) has been subjected to large-scale gene rearrangements, one feature of rearrangements being unique among the lancelets and two features shared with A. lucayanum complex. Conclusion Our study supports the monophyly of genus Asymmetron assumed on the basis of the morphological characters. Furthermore, the features of the A. inferum mitogenome expand our knowledge of variation within cephalochordate mitogenomes, adding a new case of transposition and inversion of the trnQ gene. Our divergence time estimation suggests that A. inferum remained a member of the Mesozoic and the early Cenozoic large vertebrate-fall communities before shifting to become a whale-fall specialist. Article in Journal/Newspaper Physeter macrocephalus Sperm whale BioMed Central |
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English |
description |
Abstract Background The lancelet Asymmetron inferum (subphylum Cephalochordata) was recently discovered on the ocean floor off the southwest coast of Japan at a depth of 229 m, in an anaerobic and sulfide-rich environment caused by decomposing bodies of the sperm whale Physeter macrocephalus . This deep sulfide-rich habitat of A. inferum is unique among the lancelets. The distinguishing adaptation of this species to such an extraordinary habitat can be considered in a phylogenetic framework. As the first step of reconstruction of the evolutionary processes in this species, we investigated its phylogenetic position based on 11 whole mitochondrial genome sequences including the newly determined ones of the whale-fall lancelet A. inferum and two coral-reef congeners. Results Our phylogenetic analyses showed that extant lancelets are clustered into two major clades, the Asymmetron clade and the Epigonichthys + Branchiostoma clade. A. inferum was in the former and placed in the sister group to A. lucayanum complex. The divergence time between A. inferum and A. lucayanum complex was estimated to be 115 Mya using the penalized likelihood (PL) method or 97 Mya using the nonparametric rate smoothing (NPRS) method (the middle Cretaceous). These are far older than the first appearance of large whales (the middle Eocene, 40 Mya). We also discovered that A. inferum mitogenome (mitochondrial genome) has been subjected to large-scale gene rearrangements, one feature of rearrangements being unique among the lancelets and two features shared with A. lucayanum complex. Conclusion Our study supports the monophyly of genus Asymmetron assumed on the basis of the morphological characters. Furthermore, the features of the A. inferum mitogenome expand our knowledge of variation within cephalochordate mitogenomes, adding a new case of transposition and inversion of the trnQ gene. Our divergence time estimation suggests that A. inferum remained a member of the Mesozoic and the early Cenozoic large vertebrate-fall communities before shifting to become a whale-fall specialist. |
format |
Article in Journal/Newspaper |
author |
Kon, Takeshi Nohara, Masahiro Yamanoue, Yusuke Fujiwara, Yoshihiro Nishida, Mutsumi Nishikawa, Teruaki |
spellingShingle |
Kon, Takeshi Nohara, Masahiro Yamanoue, Yusuke Fujiwara, Yoshihiro Nishida, Mutsumi Nishikawa, Teruaki Phylogenetic position of a whale-fall lancelet (Cephalochordata) inferred from whole mitochondrial genome sequences |
author_facet |
Kon, Takeshi Nohara, Masahiro Yamanoue, Yusuke Fujiwara, Yoshihiro Nishida, Mutsumi Nishikawa, Teruaki |
author_sort |
Kon, Takeshi |
title |
Phylogenetic position of a whale-fall lancelet (Cephalochordata) inferred from whole mitochondrial genome sequences |
title_short |
Phylogenetic position of a whale-fall lancelet (Cephalochordata) inferred from whole mitochondrial genome sequences |
title_full |
Phylogenetic position of a whale-fall lancelet (Cephalochordata) inferred from whole mitochondrial genome sequences |
title_fullStr |
Phylogenetic position of a whale-fall lancelet (Cephalochordata) inferred from whole mitochondrial genome sequences |
title_full_unstemmed |
Phylogenetic position of a whale-fall lancelet (Cephalochordata) inferred from whole mitochondrial genome sequences |
title_sort |
phylogenetic position of a whale-fall lancelet (cephalochordata) inferred from whole mitochondrial genome sequences |
publisher |
BioMed Central Ltd. |
publishDate |
2007 |
url |
http://www.biomedcentral.com/1471-2148/7/127 |
genre |
Physeter macrocephalus Sperm whale |
genre_facet |
Physeter macrocephalus Sperm whale |
op_relation |
http://www.biomedcentral.com/1471-2148/7/127 |
op_rights |
Copyright 2007 Kon et al; licensee BioMed Central Ltd. |
_version_ |
1766168281515819008 |