| 1. |
- Appeltans, W., et al.
(författare)
-
The Magnitude of Global Marine Species Diversity
- 2012
-
Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 22:23, s. 2189-2202
-
Tidskriftsartikel (refereegranskat)abstract
- Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results: There are similar to 226,000 eukaryotic marine species described. More species were described in the past decade (similar to 20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are similar to 170,000 synonyms, that 58,000-72,000 species are collected but not yet described, and that 482,000-741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7-1.0 million marine species. Past rates of description of new species indicate there may be 0.5 +/- 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions: Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century.
|
|
| 2. |
- Andrade, S. C. S., et al.
(författare)
-
Disentangling ribbon worm relationships: multi-locus analysis supports traditional classification of the phylum Nemertea
- 2012
-
Ingår i: Cladistics. - : Wiley. - 0748-3007. ; 28:2, s. 141-159
-
Tidskriftsartikel (refereegranskat)abstract
- The phylogenetic relationships of selected members of the phylum Nemertea are explored by means of six markers amplified from the genomic DNA of freshly collected specimens (the nuclear 18S rRNA and 28S rRNA genes, histones H3 and H4, and the mitochondrial genes 16S rRNA and cytochrome c oxidase subunit I). These include all previous markers and regions used in earlier phylogenetic analyses of nemerteans, therefore acting as a scaffold to which one could pinpoint any previously published study. Our results, based on analyses of static and dynamic homology concepts under probabilistic and parsimony frameworks, agree in the non-monophyly of Palaeonemertea and in the monophyly of Heteronemerta and Hoplonemertea. The position of Hubrechtella and the Pilidiophora hypothesis are, however, sensitive to analytical method, as is the monophyly of the non-hubrechtiid palaeonemerteans. Our results are, however, consistent with the main division of Hoplonemertea into Polystilifera and Monostilifera, the last named being divided into Cratenemertea and Distromatonemertea, as well as into the main division of Heteronemertea into Baseodiscus and the remaining species. The study also continues to highlight the deficient taxonomy at the family and generic level within Nemertea and sheds light on the areas of the tree that require further refinement.
|
|
| 3. |
- Ament-Velasquez, Sandra Lorena, et al.
(författare)
-
Population genomics of sexual and asexual lineages in fissiparous ribbon worms (Lineus, Nemertea) : hybridization, polyploidy and the Meselson effect
- 2016
-
Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 25:14, s. 3356-3369
-
Tidskriftsartikel (refereegranskat)abstract
- Comparative population genetics in asexual vs. sexual species offers the opportunity to investigate the impact of asexuality on genome evolution. Here, we analyse coding sequence polymorphism and divergence patterns in the fascinating Lineus ribbon worms, a group of marine, carnivorous nemerteans with unusual regeneration abilities, and in which asexual reproduction by fissiparity is documented. The population genomics of the fissiparous L. pseudolacteus is characterized by an extremely high level of heterozygosity and unexpectedly elevated pi(N)/pi(S) ratio, in apparent agreement with theoretical expectations under clonal evolution. Analysis of among-species allele sharing and read-count distribution, however, reveals that L. pseudolacteus is a triploid hybrid between Atlantic populations of L. sanguineus and L. lacteus. We model and quantify the relative impact of hybridity, polyploidy and asexuality on molecular variation patterns in L. pseudolacteus and conclude that (i) the peculiarities of L. pseudolacteus population genomics result in the first place from hybridization and (ii) the accumulation of new mutations through the Meselson effect is more than compensated by processes of heterozygosity erosion, such as gene conversion or gene copy loss. This study illustrates the complexity of the evolutionary processes associated with asexuality and identifies L. pseudolacteus as a promising model to study the first steps of polyploid genome evolution in an asexual context.
|
|
| 4. |
- ANDRADE, S.C.S, et al.
(författare)
-
A transcriptomic approach to ribbon worm systematics (Nemertea): resolving the Pilidiophora problem.
- 2014
-
Ingår i: Molecular biology and evolution. - : Oxford University Press (OUP). - 0737-4038 .- 1537-1719. ; 31:12, s. 3206-3215
-
Tidskriftsartikel (refereegranskat)abstract
- Resolving the deep relationships of ancient animal lineages has proven difficult using standard Sanger-sequencing approaches with a handful of markers. We thus reassess the relatively well-studied phylogeny of the phylum Nemertea (ribbon worms)—for which the targeted gene approaches had resolved many clades but had left key phylogenetic gaps—by using a phylogenomic approach using Illumina-based de novo assembled transcriptomes and automatic orthology prediction methods. The analysis of a concatenated data set of 2,779 genes (411,138 amino acids) with about 78% gene occupancy and a reduced version with 95% gene occupancy, under evolutionary models accounting or not for site-specific amino acid replacement patterns results in a well-supported phylogeny that recovers all major accepted nemertean clades with the monophyly of Heteronemertea, Hoplonemertea, Monostilifera, being well supported. Significantly, all the ambiguous patterns inferred from Sanger-based approaches were resolved, namely the monophyly of Palaeonemertea and Pilidiophora. By testing for possible conflict in the analyzed supermatrix, we observed that concatenation was the best solution, and the results of the analyses should settle prior debates on nemertean phylogeny. The study highlights the importance, feasibility, and completeness of Illumina-based phylogenomic data matrices.
|
|
| 5. |
- Chen, Hai-Xia, et al.
(författare)
-
Mutation and selection cause codon usage and bias in mitochondrial genomes of ribbon worms (Nemertea)
- 2014
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:1
-
Tidskriftsartikel (refereegranskat)abstract
- The phenomenon of codon usage bias is known to exist in many genomes and it is mainly determined by mutation and selection. To understand the patterns of codon usage in nemertean mitochondrial genomes, we use bioinformatic approaches to analyze the protein-coding sequences of eight nemertean species. Neutrality analysis did not find a significant correlation between GC12 and GC3. ENc-plot showed a few genes on or close to the expected curve, but the majority of points with low-ENc values are below it. ENc-plot suggested that mutational bias plays a major role in shaping codon usage. The Parity Rule 2 plot (PR2) analysis showed that GC and AT were not used proportionally and we propose that codons containing A or U at third position are used preferentially in nemertean species, regardless of whether corresponding tRNAs are encoded in the mitochondrial DNA. Context-dependent analysis indicated that the nucleotide at the second codon position slightly affects synonymous codon choices. These results suggested that mutational and selection forces are probably acting to codon usage bias in nemertean mitochondrial genomes. 7copy; 2014 Chen et al.
|
|
| 6. |
- Kajihara, H., et al.
(författare)
-
Taxonomic Identity of a Tetrodotoxin-Accumulating Ribbon-worm Cephalothrix simula (Nemertea: Palaeonemertea): A Species Artificially Introduced from the Pacific to Europe
- 2013
-
Ingår i: Zoological Science. - : Zoological Society of Japan. - 0289-0003. ; 30:11, s. 985-997
-
Tidskriftsartikel (refereegranskat)abstract
- We compared the anatomy of the holotype of the palaeonemertean Cephalothrix simula (Iwata, 1952) with that of the holotypes of Cephalothrix hongkongiensis Sundberg, Gibson and Olsson, 2003 and Cephalothrix fasciculus (Iwata, 1952), as well as additional specimens from Fukue (type locality of C. simula) and Hiroshima, Japan. While there was no major morphological discordance between these specimens, we found discrepancies between the actual morphology and some statements in the original description of C. simula with respect to supposedly species-specific characters. Our observation indicates that these three species cannot be discriminated by the anatomical characters so far used to distinguish congeners. For objectivity of scientific names, topogenetypes of the mitochondrial cytochrome c oxidase subunit I (COI) sequences are designated for C. simula, C. hongkongiensis, and C. fasciculus. Analysis of COI sequence showed that the Hiroshima population can be identified as C. simula, which has been found in previous studies from Trieste, Italy, and also from both the Mediterranean and Atlantic coasts of the Iberian Peninsula, indicating an artificial introduction via (1) ballast water, (2) ship-fouling communities, or (3) the commercially cultured oyster Crassostrea gigas (Thunberg, 1793) brought from Japan to France in 1970s. Cephalothrix simula is known to be toxic, as it contains large amounts of tetrodotoxin (TTX). We report here that the grass puffer Takifugu niphobles (Jordan and Snyder, 1901)-also known to contain TTX-consumes C. simula. We suggest that the puffer may be able to accumulate TTX by eating C. simula.
|
|
| 7. |
|
|
