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Chernyshev AV, Kajihara H. Comparative muscular morphology in Archinemertea (Nemertea: Palaeonemertea). ZOOMORPHOLOGY 2019. [DOI: 10.1007/s00435-019-00440-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Turner AD, Fenwick D, Powell A, Dhanji-Rapkova M, Ford C, Hatfield RG, Santos A, Martinez-Urtaza J, Bean TP, Baker-Austin C, Stebbing P. New Invasive Nemertean Species ( Cephalothrix Simula) in England with High Levels of Tetrodotoxin and a Microbiome Linked to Toxin Metabolism. Mar Drugs 2018; 16:E452. [PMID: 30453540 PMCID: PMC6266807 DOI: 10.3390/md16110452] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Revised: 11/12/2018] [Accepted: 11/13/2018] [Indexed: 12/21/2022] Open
Abstract
The marine nemertean Cephalothrix simula originates from the Pacific Ocean but in recent years has been discovered in northern Europe. The species has been associated with high levels of the marine neurotoxin Tetrodotoxin, traditionally associated with Pufferfish Poisoning. This study reports the first discovery of two organisms of C. simula in the UK, showing the geographical extent of this species is wider than originally described. Species identification was initially conducted morphologically, with confirmation by Cox 1 DNA sequencing. 16S gene sequencing enabled the taxonomic assignment of the microbiome, showing the prevalence of a large number of bacterial genera previously associated with TTX production including Alteromonas, Vibrio and Pseudomonas. LC-MS/MS analysis of the nemertean tissue revealed the presence of multiple analogues of TTX, dominated by the parent TTX, with a total toxin concentration quantified at 54 µg TTX per g of tissue. Pseudomonas luteola isolated from C. simula, together with Vibrio alginolyticus from the native nemertean Tubulanus annulatus, were cultured at low temperature and both found to contain TTX. Overall, this paper confirms the high toxicity of a newly discovered invasive nemertean species with links to toxin-producing marine bacteria and the potential risk to human safety. Further work is required to assess the geographical extent and toxicity range of C. simula along the UK coast in order to properly gauge the potential impacts on the environment and human safety.
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Affiliation(s)
- Andrew D Turner
- Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, Weymouth, Dorset DT4 8UB, UK.
| | | | - Andy Powell
- Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, Weymouth, Dorset DT4 8UB, UK.
| | - Monika Dhanji-Rapkova
- Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, Weymouth, Dorset DT4 8UB, UK.
| | - Charlotte Ford
- Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, Weymouth, Dorset DT4 8UB, UK.
| | - Robert G Hatfield
- Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, Weymouth, Dorset DT4 8UB, UK.
| | - Andres Santos
- Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, Weymouth, Dorset DT4 8UB, UK.
- Laboratory of Applied and Molecular Biology, Avenida Alemania 0458, 4810296 Temuco, Chile.
- Scientific and Technological Bioresource Nucleus (BIOREN), Universidad de La Frontera, Avenida Francisco Salazar 01145, 4811230 Temuco, Chile.
| | - Jaime Martinez-Urtaza
- Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, Weymouth, Dorset DT4 8UB, UK.
| | - Tim P Bean
- Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, Weymouth, Dorset DT4 8UB, UK.
| | - Craig Baker-Austin
- Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, Weymouth, Dorset DT4 8UB, UK.
| | - Paul Stebbing
- Centre for Environment, Fisheries and Aquaculture Science (Cefas), Barrack Road, Weymouth, Dorset DT4 8UB, UK.
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Ostrovsky AN, Lidgard S, Gordon DP, Schwaha T, Genikhovich G, Ereskovsky AV. Matrotrophy and placentation in invertebrates: a new paradigm. Biol Rev Camb Philos Soc 2016; 91:673-711. [PMID: 25925633 PMCID: PMC5098176 DOI: 10.1111/brv.12189] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Revised: 03/18/2015] [Accepted: 03/24/2015] [Indexed: 12/29/2022]
Abstract
Matrotrophy, the continuous extra-vitelline supply of nutrients from the parent to the progeny during gestation, is one of the masterpieces of nature, contributing to offspring fitness and often correlated with evolutionary diversification. The most elaborate form of matrotrophy-placentotrophy-is well known for its broad occurrence among vertebrates, but the comparative distribution and structural diversity of matrotrophic expression among invertebrates is wanting. In the first comprehensive analysis of matrotrophy across the animal kingdom, we report that regardless of the degree of expression, it is established or inferred in at least 21 of 34 animal phyla, significantly exceeding previous accounts and changing the old paradigm that these phenomena are infrequent among invertebrates. In 10 phyla, matrotrophy is represented by only one or a few species, whereas in 11 it is either not uncommon or widespread and even pervasive. Among invertebrate phyla, Platyhelminthes, Arthropoda and Bryozoa dominate, with 162, 83 and 53 partly or wholly matrotrophic families, respectively. In comparison, Chordata has more than 220 families that include or consist entirely of matrotrophic species. We analysed the distribution of reproductive patterns among and within invertebrate phyla using recently published molecular phylogenies: matrotrophy has seemingly evolved at least 140 times in all major superclades: Parazoa and Eumetazoa, Radiata and Bilateria, Protostomia and Deuterostomia, Lophotrochozoa and Ecdysozoa. In Cycliophora and some Digenea, it may have evolved twice in the same life cycle. The provisioning of developing young is associated with almost all known types of incubation chambers, with matrotrophic viviparity more widespread (20 phyla) than brooding (10 phyla). In nine phyla, both matrotrophic incubation types are present. Matrotrophy is expressed in five nutritive modes, of which histotrophy and placentotrophy are most prevalent. Oophagy, embryophagy and histophagy are rarer, plausibly evolving through heterochronous development of the embryonic mouthparts and digestive system. During gestation, matrotrophic modes can shift, intergrade, and be performed simultaneously. Invertebrate matrotrophic adaptations are less complex structurally than in chordates, but they are more diverse, being formed either by a parent, embryo, or both. In a broad and still preliminary sense, there are indications of trends or grades of evolutionarily increasing complexity of nutritive structures: formation of (i) local zones of enhanced nutritional transport (placental analogues), including specialized parent-offspring cell complexes and various appendages increasing the entire secreting and absorbing surfaces as well as the contact surface between embryo and parent, (ii) compartmentalization of the common incubatory space into more compact and 'isolated' chambers with presumably more effective nutritional relationships, and (iii) internal secretory ('milk') glands. Some placental analogues in onychophorans and arthropods mimic the simplest placental variants in vertebrates, comprising striking examples of convergent evolution acting at all levels-positional, structural and physiological.
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Affiliation(s)
- Andrew N Ostrovsky
- Department of Invertebrate Zoology, Faculty of Biology, Saint Petersburg State University, Universitetskaja nab. 7/9, 199034, Saint Petersburg, Russia
- Department of Palaeontology, Faculty of Earth Sciences, Geography and Astronomy, Geozentrum, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria
| | - Scott Lidgard
- Integrative Research Center, Field Museum of Natural History, 1400 S. Lake Shore Dr., Chicago, IL, 60605, U.S.A
| | - Dennis P Gordon
- National Institute of Water and Atmospheric Research, Private Bag 14901, Kilbirnie, Wellington, New Zealand
| | - Thomas Schwaha
- Department of Integrative Zoology, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria
| | - Grigory Genikhovich
- Department for Molecular Evolution and Development, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria
| | - Alexander V Ereskovsky
- Department of Embryology, Faculty of Biology, Saint Petersburg State University, Universitetskaja nab. 7/9, 199034, Saint Petersburg, Russia
- Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale, Aix Marseille Université, CNRS, IRD, Avignon Université, Station marine d'Endoume, Chemin de la Batterie des Lions, 13007, Marseille, France
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Herrera-Bachiller A, Fernández-Álvarez FÁ, Junoy J. A Taxonomic Catalogue of the Nemerteans (Phylum Nemertea) of Spain and Portugal. Zoolog Sci 2015; 32:507-22. [DOI: 10.2108/zs140242] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Whelan NV, Kocot KM, Santos SR, Halanych KM. Nemertean toxin genes revealed through transcriptome sequencing. Genome Biol Evol 2014; 6:3314-25. [PMID: 25432940 PMCID: PMC4986456 DOI: 10.1093/gbe/evu258] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Nemerteans are one of few animal groups that have evolved the ability to utilize toxins for both defense and subduing prey, but little is known about specific nemertean toxins. In particular, no study has identified specific toxin genes even though peptide toxins are known from some nemertean species. Information about toxin genes is needed to better understand evolution of toxins across animals and possibly provide novel targets for pharmaceutical and industrial applications. We sequenced and annotated transcriptomes of two free-living and one commensal nemertean and annotated an additional six publicly available nemertean transcriptomes to identify putative toxin genes. Approximately 63–74% of predicted open reading frames in each transcriptome were annotated with gene names, and all species had similar percentages of transcripts annotated with each higher-level GO term. Every nemertean analyzed possessed genes with high sequence similarities to known animal toxins including those from stonefish, cephalopods, and sea anemones. One toxin-like gene found in all nemerteans analyzed had high sequence similarity to Plancitoxin-1, a DNase II hepatotoxin that may function well at low pH, which suggests that the acidic body walls of some nemerteans could work to enhance the efficacy of protein toxins. The highest number of toxin-like genes found in any one species was seven and the lowest was three. The diversity of toxin-like nemertean genes found here is greater than previously documented, and these animals are likely an ideal system for exploring toxin evolution and industrial applications of toxins.
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Affiliation(s)
- Nathan V Whelan
- Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, Alabama
| | - Kevin M Kocot
- Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, Alabama Present address: School of Biological Sciences, University of Queensland, Brisbane, QLD, Australia
| | - Scott R Santos
- Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, Alabama
| | - Kenneth M Halanych
- Department of Biological Sciences, Molette Biology Laboratory for Environmental and Climate Change Studies, Auburn University, Auburn, Alabama
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Andrade SCS, Montenegro H, Strand M, Schwartz ML, Kajihara H, Norenburg JL, Turbeville JM, Sundberg P, Giribet G. A Transcriptomic Approach to Ribbon Worm Systematics (Nemertea): Resolving the Pilidiophora Problem. Mol Biol Evol 2014; 31:3206-15. [DOI: 10.1093/molbev/msu253] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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Sun WY, Xu DL, Chen HX, Shi W, Sundberg P, Strand M, Sun SC. Complete mitochondrial genome sequences of two parasitic/commensal nemerteans, Gononemertes parasita and Nemertopsis tetraclitophila (Nemertea: Hoplonemertea). Parasit Vectors 2014; 7:273. [PMID: 24946714 PMCID: PMC4081467 DOI: 10.1186/1756-3305-7-273] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2014] [Accepted: 06/14/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Most nemerteans (phylum Nemertea) are free-living, but about 50 species are known to be firmly associated with other marine invertebrates. For example, Gononemertes parasita is associated with ascidians, and Nemertopsis tetraclitophila with barnacles. There are 12 complete or near-complete mitochondrial genome (mitogenome) sequences of nemerteans available in GenBank, but no mitogenomes of none free-living nemerteans have been determined so far. In the present paper complete mitogenomes of the above two parasitic/commensal nemerteans are reported. METHODS The complete mitochondrial genomes (mitogenome) of G. parasita and N. tetraclitophila were amplified by conventional and long PCR. Phylogenetic analyses of maximum likelihood (ML) and Bayesian inference (BI) were performed with both concatenated nucleotide and amino acid sequences. RESULTS Complete mitogenomes of G. parasita and N. tetraclitophila are 14742 bp and 14597 bp in size, respectively, which are within the range of published Hoplonemertea mitogenomes. Their gene orders are identical to that of published Hoplonemertea mitogenomes, but different from those of Palaeo- and Heteronemertea species. All the coding genes, as well as major non-coding regions (mNCRs), are AT rich, which is especially pronounced at the third codon position. The AT/GC skew pattern of the coding strand is the same among nemertean mitogenomes, but is variable in the mNCRs. Some slight differences are found between mitogenomes of the present species and other hoplonemerteans: in G. parasita the mNCR is biased toward T and C (contrary to other hoplonemerteans) and the rrnS gene has a unique 58-bp insertion at the 5' end; in N. tetraclitophila the nad3 gene starts with the ATT codon (ATG in other hoplonemerteans). Phylogenetic analyses of the nucleotide and amino acid datasets show early divergent positions of G. parasita and N. tetraclitophila within the analyzed Distromatonemertea species, and provide strong support for the close relationship between Hoplonemertea and Heteronemertea. CONCLUSION Gene order is highly conserved within the order Monostilifera, particularly within the Distromatonemertea, and the special lifestyle of G. parasita and N. tetraclitophila does not bring significant variations to the overall structures of their mitogenomes in comparison with free-living hoplonemerteans.
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Affiliation(s)
- Wen-Yan Sun
- Institute of Evolution & Marine Biodiversity, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
| | - Dong-Li Xu
- Institute of Evolution & Marine Biodiversity, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
| | - Hai-Xia Chen
- Institute of Evolution & Marine Biodiversity, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, SE-405 30 Gothenburg, Sweden
| | - Wei Shi
- Key Laboratory of Marine Bio-resource Sustainable Utilization (LMB), South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China
| | - Per Sundberg
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, SE-405 30 Gothenburg, Sweden
| | - Malin Strand
- Swedish Species Information Centre, Swedish University of Agricultural Sciences, Box 7007, SE 75007 Uppsala, Sweden
| | - Shi-Chun Sun
- Institute of Evolution & Marine Biodiversity, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
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Kvist S, Laumer CE, Junoy J, Giribet G. New insights into the phylogeny, systematics and DNA barcoding of Nemertea. INVERTEBR SYST 2014. [DOI: 10.1071/is13061] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Although some clades of ribbon worms (phylum Nemertea) are consistently recovered with high support in molecular phylogenies, the placement and inter-relationships of some taxa have proven problematic. Herein, we performed molecular phylogenetic analyses aimed at resolving these recalcitrant splits, using six loci (nuclear 18S rRNA, 28S rRNA, histones H3 and H4, and mitochondrial 16S rRNA and COI) for 133 terminals, with particular emphasis on the problematic families Hubrechtidae and Plectonemertidae. Three different datasets were used for phylogenetic analyses and both maximum likelihood and maximum parsimony methodologies were applied. All but one of the resulting tree topologies agree on the paraphyly of the class Palaeonemertea, whereas Heteronemertea, Hoplonemertea, Polystilifera, Monostilifera and Hubrechtidae are always recovered as reciprocally monophyletic. Hubrechtidae is sister group to Heteronemertea (the Pilidiophora hypothesis) only when length variable regions of 18S rRNA and 28S rRNA are excluded. Moreover, the terrestrial and freshwater family Plectonemertidae is recovered with high support and the implications of this finding are further discussed. Finally, we evaluate the utility of DNA barcoding for specimen identification within Nemertea using an extended dataset containing 394 COI sequences. Results suggest that DNA barcoding may work for Nemertea, insofar as a distinct barcoding gap (the gap between the maximum intraspecific variation and the minimum interspecific divergence) may exist, but its recognition is regularly hampered by low accuracy in species level identifications.
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Protonephridia in the larvae of the paleonemertean species Carinoma mutabilis (Carinomidae, Nemertea) and Cephalothrix (Procephalothrix) filiformis (Cephalothricidae, Nemertea). ZOOMORPHOLOGY 2013. [DOI: 10.1007/s00435-013-0206-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Taboada S, Junoy J, Andrade SCS, Giribet G, Cristobo J, Avila C. On the identity of two Antarctic brooding nemerteans: redescription of Antarctonemertes valida (Bürger, 1893) and description of a new species in the genus Antarctonemertes Friedrich, 1955 (Nemertea, Hoplonemertea). Polar Biol 2013. [DOI: 10.1007/s00300-013-1360-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Beckers P, Loesel R, Bartolomaeus T. The nervous systems of basally branching nemertea (palaeonemertea). PLoS One 2013; 8:e66137. [PMID: 23785478 PMCID: PMC3681988 DOI: 10.1371/journal.pone.0066137] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 05/01/2013] [Indexed: 11/18/2022] Open
Abstract
In recent years, a lot of studies have been published dealing with the anatomy of the nervous system in different spiralian species. The only nemertean species investigated in this context probably shows derived characters and thus the conditions found there are not useful in inferring the relationship between nemerteans and other spiralian taxa. Ingroup relationships within Nemertea are still unclear, but there is some agreement that the palaeonemerteans form a basal, paraphyletic grade. Thus, palaeonemertean species are likely the most informative when comparing with other invertebrate groups. We therefore analyzed the nervous system of several palaeonemertean species by combining histology and immunostaining. 3D reconstructions based on the aligned slices were performed to get an overall impression of the central nervous system, and immunohistochemistry was chosen to reveal fine structures and to be able to compare the data with recently published results. The insights presented here permit a first attempt to reconstruct the primary organization of the nemertean nervous system. This comparative analysis allows substantiating homology hypotheses for nerves of the peripheral nervous system. This study also provides evidence that the nemertean brain primarily consists of two lobes connected by a strong ventral commissure and one to several dorsal commissures. During nemertean evolution, the brain underwent continuous compartmentalization into a pair of dorsal and ventral lobes interconnected by commissures and lateral tracts. Given that this conclusion can be corroborated by cladistic analyses, nemerteans should share a common ancestor with spiralians that primarily have a simple brain consisting of paired medullary, frontally commissurized and reinforced cords. Such an organization resembles the situation found in presumably basally branching annelids or mollusks.
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Affiliation(s)
- Patrick Beckers
- Institute for Evolutionary Biology and Ecology, Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany.
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Chen HX, Sun SC, Sundberg P, Ren WC, Norenburg JL. A comparative study of nemertean complete mitochondrial genomes, including two new ones for Nectonemertes cf. mirabilis and Zygeupolia rubens, may elucidate the fundamental pattern for the phylum Nemertea. BMC Genomics 2012; 13:139. [PMID: 22507536 PMCID: PMC3368773 DOI: 10.1186/1471-2164-13-139] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2011] [Accepted: 04/17/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The mitochondrial genome is important for studying genome evolution as well as reconstructing the phylogeny of organisms. Complete mitochondrial genome sequences have been reported for more than 2200 metazoans, mainly vertebrates and arthropods. To date, from a total of about 1275 described nemertean species, only three complete and two partial mitochondrial DNA sequences from nemerteans have been published. Here, we report the entire mitochondrial genomes for two more nemertean species: Nectonemertes cf. mirabilis and Zygeupolia rubens. RESULTS The sizes of the entire mitochondrial genomes are 15365 bp for N. cf. mirabilis and 15513 bp for Z. rubens. Each circular genome contains 37 genes and an AT-rich non-coding region, and overall nucleotide composition is AT-rich. In both species, there is significant strand asymmetry in the distribution of nucleotides, with the coding strand being richer in T than A and in G than C. The AT-rich non-coding regions of the two genomes have some repeat sequences and stem-loop structures, both of which may be associated with the initiation of replication or transcription. The 22 tRNAs show variable substitution patterns in nemerteans, with higher sequence conservation in genes located on the H strand. Gene arrangement of N. cf. mirabilis is identical to that of Paranemertes cf. peregrina, both of which are Hoplonemertea, while that of Z. rubens is the same as in Lineus viridis, both of which are Heteronemertea. Comparison of the gene arrangements and phylogenomic analysis based on concatenated nucleotide sequences of the 12 mitochondrial protein-coding genes revealed that species with closer relationships share more identical gene blocks. CONCLUSION The two new mitochondrial genomes share many features, including gene contents, with other known nemertean mitochondrial genomes. The tRNA families display a composite substitution pathway. Gene order comparison to the proposed ground pattern of Bilateria and some lophotrochozoans suggests that the nemertean ancestral mitochondrial gene order most closely resembles the heteronemertean type. Phylogenetic analysis proposes a sister-group relationship between Hetero- and Hoplonemertea, which supports one of two recent alternative hypotheses of nemertean phylogeny.
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Affiliation(s)
- Hai-Xia Chen
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, SE-405 30 Gothenburg, Sweden
- Institute of Evolution & Marine Biodiversity, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
| | - Shi-Chun Sun
- Institute of Evolution & Marine Biodiversity, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
| | - Per Sundberg
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, SE-405 30 Gothenburg, Sweden
| | - Wei-Cheng Ren
- Department of Rheumatology and Inflammation Research, Sahlgrenska Academy, University of Gothenburg, PO Box 480, SE-405 30, Sweden
| | - Jon L Norenburg
- Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560-0163, USA
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Andrade SCS, Strand M, Schwartz M, Chen H, Kajihara H, von Döhren J, Sun S, Junoy J, Thiel M, Norenburg JL, Turbeville JM, Giribet G, Sundberg P. Disentangling ribbon worm relationships: multi-locus analysis supports traditional classification of the phylum Nemertea. Cladistics 2011; 28:141-159. [DOI: 10.1111/j.1096-0031.2011.00376.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
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KAJIHARA HIROSHI, OLYMPIA MINERVA, KOBAYASHI NORIO, KATOH TORU, CHEN HAIXIA, STRAND MALIN, SUNDBERG PER. Systematics and phylogeny of the hoplonemertean genus Diplomma (Nemertea) based on molecular and morphological evidence. Zool J Linn Soc 2011. [DOI: 10.1111/j.1096-3642.2010.00650.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Sundberg P, Gibson R, Strand M. Swedish nemerteans (phylum Nemertea), with description of a new hoplonemertean genus and species. J NAT HIST 2010. [DOI: 10.1080/00222930701589939] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Bartolomaeus T, von Döhren J. Comparative morphology and evolution of the nephridia in Nemertea. J NAT HIST 2010. [DOI: 10.1080/00222933.2010.503941] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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von Döhren J, Beckers P, Vogeler R, Bartolomaeus T. Comparative sperm ultrastructure in Nemertea. J Morphol 2010; 271:793-813. [DOI: 10.1002/jmor.10834] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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SUNDBERG PER, CHERNYSHEV ALEXEYV, KAJIHARA HIROSHI, KÅNNEBY TOBIAS, STRAND MALIN. Character-matrix based descriptions of two new nemertean (Nemertea) species. Zool J Linn Soc 2009. [DOI: 10.1111/j.1096-3642.2008.00514.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Mahon AR, Thornhill DJ, Norenburg JL, Halanych KM. DNA uncovers Antarctic nemertean biodiversity and exposes a decades-old cold case of asymmetric inventory. Polar Biol 2009. [DOI: 10.1007/s00300-009-0696-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Altaba CR. Universal artifacts affect the branching of phylogenetic trees, not universal scaling laws. PLoS One 2009; 4:e4611. [PMID: 19242549 PMCID: PMC2644784 DOI: 10.1371/journal.pone.0004611] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Accepted: 01/21/2009] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND The superficial resemblance of phylogenetic trees to other branching structures allows searching for macroevolutionary patterns. However, such trees are just statistical inferences of particular historical events. Recent meta-analyses report finding regularities in the branching pattern of phylogenetic trees. But is this supported by evidence, or are such regularities just methodological artifacts? If so, is there any signal in a phylogeny? METHODOLOGY In order to evaluate the impact of polytomies and imbalance on tree shape, the distribution of all binary and polytomic trees of up to 7 taxa was assessed in tree-shape space. The relationship between the proportion of outgroups and the amount of imbalance introduced with them was assessed applying four different tree-building methods to 100 combinations from a set of 10 ingroup and 9 outgroup species, and performing covariance analyses. The relevance of this analysis was explored taking 61 published phylogenies, based on nucleic acid sequences and involving various taxa, taxonomic levels, and tree-building methods. PRINCIPAL FINDINGS All methods of phylogenetic inference are quite sensitive to the artifacts introduced by outgroups. However, published phylogenies appear to be subject to a rather effective, albeit rather intuitive control against such artifacts. The data and methods used to build phylogenetic trees are varied, so any meta-analysis is subject to pitfalls due to their uneven intrinsic merits, which translate into artifacts in tree shape. The binary branching pattern is an imposition of methods, and seldom reflects true relationships in intraspecific analyses, yielding artifactual polytomies in short trees. Above the species level, the departure of real trees from simplistic random models is caused at least by two natural factors--uneven speciation and extinction rates; and artifacts such as choice of taxa included in the analysis, and imbalance introduced by outgroups and basal paraphyletic taxa. This artifactual imbalance accounts for tree shape convergence of large trees. SIGNIFICANCE There is no evidence for any universal scaling in the tree of life. Instead, there is a need for improved methods of tree analysis that can be used to discriminate the noise due to outgroups from the phylogenetic signal within the taxon of interest, and to evaluate realistic models of evolution, correcting the retrospective perspective and explicitly recognizing extinction as a driving force. Artifacts are pervasive, and can only be overcome through understanding the structure and biological meaning of phylogenetic trees. Catalan Abstract in Translation S1.
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Affiliation(s)
- Cristian R Altaba
- Laboratory of Human Systematics, University of the Balearic Islands, Balearic Islands, Spain.
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Mateos E, Giribet G. Exploring the molecular diversity of terrestrial nemerteans (Hoplonemertea, Monostilifera, Acteonemertidae) in a continental landmass. ZOOL SCR 2008. [DOI: 10.1111/j.1463-6409.2008.00324.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
The advent of numerical methods for analysing phylogenetic relationships, along with the study of morphology and molecular data, has driven our understanding of animal relationships for the past three decades. Within the protostome branch of the animal tree of life, these data have sufficed to establish its two main side branches, the moulting Ecdysozoa and the non-moulting Lophotrochozoa. In this review, I explore our current knowledge of protostome relationships and discuss progress and future perspectives and strategies to increase resolution within the main lophotrochozoan clades. Novel approaches to coding morphological characters are needed by scoring real observations on species selected as terminals. Still, methodological issues, for example, how to deal with inapplicable characters or the coding of absences, may require novel algorithmic developments. Taxon sampling is another key issue, as phyla should include enough species so as to represent their span of anatomical disparity. On the molecular side, phylogenomics is playing an increasingly important role in elucidating animal relationships, but genomic sampling is still fairly limited within the lophotrochozoan protostomes, for which only three phyla are represented in currently available phylogenies. Future work should therefore concentrate on generating novel morphological observations and on producing genomic data for the lophotrochozoan side of the animal tree of life.
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Affiliation(s)
- Gonzalo Giribet
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
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Mini-Hemoglobins from Nemertean Worms. Methods Enzymol 2008. [DOI: 10.1016/s0076-6879(08)36028-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Abstract
We estimated the phylogenetic position of the pseudosegmented ribbon worm Annulonemertes minusculus to test proposed evolutionary hypotheses to explain these body constrictions. The analysis is based on 18S rDNA sequences and shows that the species belongs to an apomorphic clade of hoplonemertean species. The segmentation has no phylogenetic bearing as previously discussed, but is a derived character probably coupled to the species' interstitial habitat.
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Affiliation(s)
- Per Sundberg
- Department of Zoology, Göteborg University, PO Box 463, 405 30 Göteborg, Sweden.
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Turbeville JM. Ultrastructure of the pseudocnidae of the palaeonemerteansCephalothrixcf.rufifronsandCarinomella lacteaand an assessment of their phylogenetic utility. J NAT HIST 2006. [DOI: 10.1080/00222930600834006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Strand M, Hjelmgren A, Sundberg P. GenusBaseodiscus(Nemertea: Heteronemertea): Molecular identification of a new species in a phylogenetic context. J NAT HIST 2005. [DOI: 10.1080/00222930500370952] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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STRAND MALIN, SUNDBERG PER. Delimiting species in the hoplonemertean genus Tetrastemma (phylum Nemertea): morphology is not concordant with phylogeny as evidenced from mtDNA sequences. Biol J Linn Soc Lond 2005. [DOI: 10.1111/j.1095-8312.2005.00535.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Strand M, Sundberg P. Genus Tetrastemma Ehrenberg, 1831 (Phylum Nemertea)--a natural group? Phylogenetic relationships inferred from partial 18S rRNA sequences. Mol Phylogenet Evol 2005; 37:144-52. [PMID: 16182152 DOI: 10.1016/j.ympev.2005.02.006] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2004] [Revised: 01/25/2005] [Accepted: 02/07/2005] [Indexed: 11/30/2022]
Abstract
We investigated the monophyletic status of the hoplonemertean taxon Tetrastemma by reconstructing the phylogeny for 22 specimens assigned to this genus, together with another 25 specimens from closely related hoplonemertean genera. The phylogeny was based on partial 18S rRNA sequences using Bayesian and maximum likelihood analyses. The included Tetrastemma-species formed a well-supported clade, although the within-taxon relationships were unsettled. We conclude that the name Tetrastemma refers to a monophyletic taxon, but that it cannot be defined by morphological synapomorphies, and our results do not imply that all the over 100 species assigned to this genus belong to it. The results furthermore indicate that the genera Amphiporus and Emplectonema are non-monophyletic.
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Affiliation(s)
- Malin Strand
- Göteborg University, Department of Zoology, Gothenborg, Sweden
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Nielsen C. Trochophora larvae: cell-lineages, ciliary bands and body regions. 2. Other groups and general discussion. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2005; 304:401-47. [PMID: 15915468 DOI: 10.1002/jez.b.21050] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The embryology of sipunculans, entoprocts, nemertines, platyhelminths (excluding acoelomorphs), rotifers, ectoprocts, phoronids, brachiopods, echinoderms and enteropneusts is reviewed with special emphasis on cell-lineage and differentiation of ectodermal structures. A group Spiralia comprising the four first-mentioned phyla plus annelids and molluscs seems well defined through the presence of spiral cleavage with early blastomere specification, prototroch with characteristic cell-lineage, cerebral ganglia developing from cells of the first micromere quartet (i.e., the episphere) and a ventral nervous system developing from the hyposphere. The planktotrophic trochophore was probably the larval type of the ancestor of this group. Another group comprising phoronids, brachiopods, echinoderms and enteropneusts appears equally well delimited. It is characterized by radial cleavage with late blastomere specification, possibly by the presence of a neotroch consisting of monociliate cells, by the absence of cerebral ganglia and of a well-defined brain and paired longitudinal nerve cords developing in connection with the blastopore, and by coelomic organization. Its ancestral larval type was probably a dipleurula. Several characters link rotifers with the spiralians, although they do not show the spiral pattern in the cleavage. Ectoprocts are still a problematic group, but some characters indicate spiralian affinities.
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Affiliation(s)
- Claus Nielsen
- Zoological Museum (University of Copenhagen), Universitetsparken 15, DK-2100 Copenhagen, Denmark.
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Sundberg P, Gibson R, Olsson U. Phylogenetic analysis of a group of palaeonemerteans (Nemertea) including two new species from Queensland and the Great Barrier Reef, Australia. ZOOL SCR 2003. [DOI: 10.1046/j.1463-6409.2002.00032.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Abstract
We present the most extensive phylogenetic analysis to date, to our knowledge, of higher-level nemertean relationships, based on sequence data from four different genes (the nuclear genes for nuclear large subunit rRNA (28S rRNA) and histone H3 (H3), and the mitochondrial genes for mitochondrial large subunit rRNA (16S rRNA) and cytochrome c oxidase subunit I (COI)). Well-supported clades are, in general, compatible with earlier, more limited, analyses, and current classification is largely in agreement with our results, although there are some notable exceptions. Bdellonemertea (represented by Malacobdella) is found to be a part of Monostilifera, and Polystilifera is the monophyletic sister group to Monostilifera. Cratenemertidae is the sister group to the remaining monostiliferans (including Malacobdella), a group to which we apply the new name Distromatonemertea. Heteronemertea is monophyletic and forms a clade with Hubrechtella; for this clade we introduce the name Pilidiophora. Finally, Pilidiophora and Hoplonemertea (with Malacobdella) form a monophyletic group, and we introduce the name Neonemertea to refer to this group. Palaeonemertea is found to be non-monophyletic and basal among nemerteans.
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Affiliation(s)
- Mikael Thollesson
- Systematic Biology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560-0163, USA.
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