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. © The Willi Hennig Society 2011.

BackgroundIt has been suggested that statistical parsimony network analysis could be used to get an indication of species represented in a set of nucleotide data, and the approach has been used to discuss species boundaries in some taxa.Methodology/Principal FindingsBased on 635 base pairs of the mitochondrial protein-coding gene cytochrome c oxidase I (COI), we analyzed 152 nemertean specimens using statistical parsimony network analysis with the connection probability set to 95%. The analysis revealed 15 distinct networks together with seven singletons. Statistical parsimony yielded three networks supporting the species status of Cephalothrix rufifrons, C. major and C. spiralis as they currently have been delineated by morphological characters and geographical location. Many other networks contained haplotypes from nearby geographical locations. Cladistic structure by maximum likelihood analysis overall supported the network analysis, but indicated a false positive result where subnetworks should have been connected into one network/species. This probably is caused by undersampling of the intraspecific haplotype diversity.Conclusions/SignificanceStatistical parsimony network analysis provides a rapid and useful tool for detecting possible undescribed/cryptic species among cephalotrichid nemerteans based on COI gene. It should be combined with phylogenetic analysis to get indications of false positive results, i.e., subnetworks that would have been connected with more extensive haplotype sampling.

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and evolutionary origins of parthenogenetic Artemia (Crustacea: Anostraca) with different ploidies. -Zoologica Scripta, 45, 421-436. Using two nuclear (ITS1 and Na + /K + ATPase) and three mitochondrial (COI, 16S and 12S) markers, we determined the genetic variation and evolutionary relationship of parthenogenetic and bisexual Artemia. Our analyses revealed that mitochondrial genes had higher genetic variation than nuclear genes and that the 16S showed more variety than the other mitochondrial genes in parthenogenetic populations. Triploid parthenogens showed lower genetic variation than diploid ones, whereas the tetra-and pentaploids had greater genetic distance than diploid parthenogens. No shared haplotype was found between individuals of parthenogenetic populations and Asian bisexual species with the exception of Na + /K + ATPase (Artemia tibetiana). Only mitochondrial markers can demonstrate phylogenetic relationships, and showed that the parthenogenetic Artemia is a polyphyletic group in which the diploid lineages share a common ancestor with Artemia urmiana while tetraploids are closely related to Artemia sinica. The triploid and pentaploid linages are likely to be directly derived from diploid and tetraploid parthenogens, respectively. Subsequently, west Asia is origin for di-/ triploids, and tetra-/pentaploids rose from East Asia.

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.

The quiescent Artemia cysts of seven geographical origins in China were examined with scanning and transmission electron microscopes. SEM observations on cysts of these Artemia strains showed that the surface topography of cyst shells could be categorized into 6 types: complete smooth surface; smooth surface with sparsely distributed glabrate humps; surface with densely arranged wart-like humps that are composed of packed minute tubercles; rugged surface, with densely arranged tubercles not piling up to form larger humps; shallow-pocked surface; and surface with numerous and densely spaced pore-like fossulae. Some of the patterns were strain specific [e.g., cysts from Ga Hai (GH) are characterized by having a surface with wart-like ornaments that are composed of packed minute tubercles, rugged surface is only found in Chengkou (CK) cysts], and apparent intrastrain variation of cyst surface topography was found in Xizang (XZ), Jingyu Hu, and Xie Chi (SIN) strains. TEM studies on the ultrastructure of cyst shells revealed an apparent divergence in the structure of outer cuticular membrane (OCM) among Artemia strains. In CK, Aqqikkol Hu (AQK), SIN, and GH strains, it is a normal, asymmetrical, and multi-layered structure similar to those described in previous works. In XZ, JYH, and Lagkor Co (LGC) strains, however, the OCM is not obviously multi-layered and the borderlines between OCM and adjacent layers seem indistinct. The present results suggest that the diversity of the surface topography of Artemia cysts may be an available tool for identifying certain Artemia strains as well as for tracking the origins of some Artemia cysts, and the hypoplastic OCM may be a characteristic of the species A. tibetiana.

The bipyridyl herbicide, diquat, is a potent prooxidant that generates superoxide anions through redox cycling in vivo. Exposure to elevated levels of this compound causes acute hepatic and renal toxicity as well as death in rodents. In the present study, we investigated whether melatonin, a free radical scavenger and antioxidant, could protect against diquat-induced hepatic and renal damage and whether the indole would improve survival of Kunming mice given a lethal dose of diquat. When mice were intraperitoneally (i.p.) given a single dose of diquat (50 mg/kg body weight), liver and kidney injuries were observed at 6 hr as indicated by elevated serum levels of both alanine aminotransferase (ALT) activity and blood urea nitrogen (BUN). In addition, lipid peroxidation levels in both liver and kidney showed significant increases as shown by elevated concentrations of F(2)-isoprostanes. The administration of melatonin (20 mg/kg) 30 min before the diquat injection resulted in a significant reduction in serum levels of ALT and BUN as well as hepatic and renal F(2)-isoprostanes levels. For the survival study, 75 mg/kg diquat was administered i.p. into mice to induce acute death. Without melatonin treatment, 10 of 23 (43.5%) mice died within 24 hr after diquat injection. Pretreatment with melatonin (20 mg/kg) 30 min prior to the injection of diquat and thereafter at 4-hr intervals until the end of the observation period (24 hr), reduced the death rate to two of 22 (9.1%) mice. Chi-squared test revealed a significant difference with P< or = 0.05. In conclusion, melatonin, a broad spectrum antioxidant, reduces hepatic and renal damage and lowers the death rate in diquat-treated mice.

Turbeville, J.M. , Strand, M. (2016). The future of nemertean taxonomy (phylum Nemertea)a proposal. -Zoologica Scripta, 45: 579-582.