73 research outputs found
Orders out of chaos â molecular phylogenetics reveals the complexity of shark and stingray tapeworm relationships
Novel molecular data are presented to resolve the long-standing issue of the non-monophyly of the elasmobranch-hosted tapeworm order Tetraphyllidea relative to the other acetabulate eucestode orders. Bayesian Inference analyses of various combinations of full ssrDNA, and full or partial lsrDNA (D1-D3), sequence data, which included 134 species representing 97 genera across the 15 eucestode orders, were conducted. New ssrDNA data were generated for 82 species, partial lsrDNA data for 53 species, and full lsrDNA data for 29 species. The monophyly of each of the elasmobranch-hosted orders Cathetocephalidea, Litobothriidea, Lecanicephalidea, and Rhinebothriidea was confirmed, as was the non-monophyly of the Tetraphyllidea. Two relatively stable groups of tetraphyllidean taxa emerged and are hereby designated as new orders. The Onchoproteocephalidea n. ord. is established to recognize the integrated nature of one undescribed and ten described genera of hook-bearing tetraphyllideans, previously of the family Onchobothriidae, with the members of the order Proteocephalidea. The Phyllobothriidea n. ord. is established for a subset of 12 non-hooked genera characterized by scoleces bearing four bothridia each with an anterior accessory sucker; most parasitise sharks and have been assigned to the Phyllobothriidae at one time or another. Tentative ordinal placements are suggested for 8 additional genera; placements for the remaining tetraphyllidean genera have not yet emerged. We propose these 17 genera remain in the âTetraphyllideaâ. Among these, particularly labile across analyses were Anthobothrium, Megalonchos, Carpobothrium, Calliobothrium, and Caulobothrium. The unique association of Chimaerocestus with holocephalans, rather than with elasmobranchs, appears to represent a host-switching event. Both of the non-elasmobranch hosted clades of acetabulate cestodes (i.e., Proteocephalidea and Cyclophyllidea and their kin) appear to have had their origins with elasmobranch cestodes. Across analyses, the sister group to the clade of âterrestrialâ cestode orders was found to be an elasmobranch-hosted genus; as was the sister to the freshwater fish and tetrapod-hosted Proteocephalidea. Whilst further data are required to resolve outstanding nomenclatural and phylogenetic issues, the present analyses contribute significantly to an understanding of the evolutionary radiation of the entire Cestoda. Clearly, elasmobranch tapeworms comprise the backbone of cestode phylogeny
The phylogenetic position of Acoela as revealed by the complete mitochondrial genome of Symsagittifera roscoffensis
<p>Abstract</p> <p>Background</p> <p>Acoels are simply organized unsegmented worms, lacking hindgut and anus. Several publications over recent years challenge the long-held view that acoels are early offshoots of the flatworms. Instead a basal position as sister group to all other bilaterian animals was suggested, mainly based on molecular evidence. This led to the view that features of acoels might reflect those of the last common ancestor of Bilateria, and resulted in several evo-devo studies trying to interpret bilaterian evolution using acoels as a proxy model for the "Urbilateria".</p> <p>Results</p> <p>We describe the first complete mitochondrial genome sequence of a member of the Acoela, <it>Symsagittifera roscoffensis</it>. Gene content and circular organization of the mitochondrial genome does not significantly differ from other bilaterian animals. However, gene order shows no similarity to any other mitochondrial genome within the Metazoa. Phylogenetic analyses of concatenated alignments of amino acid sequences from protein coding genes support a position of Acoela and Nemertodermatida as the sister group to all other Bilateria. Our data provided no support for a sister group relationship between Xenoturbellida and Acoela or Acoelomorpha. The phylogenetic position of <it>Xenoturbella bocki </it>as sister group to or part of the deuterostomes was also unstable.</p> <p>Conclusions</p> <p>Our phylogenetic analysis supports the view that acoels and nemertodermatids are the earliest divergent extant lineage of Bilateria. As such they remain a valid source for seeking primitive characters present in the last common ancestor of Bilateria. Gene order of mitochondrial genomes seems to be very variable among Acoela and Nemertodermatida and the groundplan for the metazoan mitochondrial genome remains elusive. More data are needed to interpret mitochondrial genome evolution at the base of Bilateria.</p
Using 454 technology for long-PCR based sequencing of the complete mitochondrial genome from single Haemonchus contortus (Nematoda)
<p>Abstract</p> <p>Background</p> <p>Mitochondrial (mt) genomes represent a rich source of molecular markers for a range of applications, including population genetics, systematics, epidemiology and ecology. In the present study, we used 454 technology (or the GS20, massively parallel picolitre reactor platform) to determine the complete mt genome of <it>Haemonchus contortus </it>(Nematoda: Trichostrongylidae), a parasite of substantial agricultural, veterinary and economic significance. We validate this approach by comparison with mt sequences from publicly available expressed sequence tag (EST) and genomic survey sequence (GSS) data sets.</p> <p>Results</p> <p>The complete mt genome of <it>Haemonchus contortus </it>was sequenced directly from long-PCR amplified template utilizing genomic DNA (~20â40 ng) from a single adult male using 454 technology. A single contig was assembled and compared against mt sequences mined from publicly available EST (NemBLAST) and GSS datasets. The comparison demonstrated that the 454 technology platform is reliable for the sequencing of AT-rich mt genomes from nematodes. The mt genome sequenced for <it>Haemonchus contortus </it>was 14,055 bp in length and was highly AT-rich (78.1%). In accordance with other chromadorean nematodes studied to date, the mt genome of <it>H. contortus </it>contained 36 genes (12 protein coding, 22 tRNAs, <it>rrnL </it>and <it>rrnS</it>) and was similar in structure, size and gene arrangement to those characterized previously for members of the Strongylida.</p> <p>Conclusion</p> <p>The present study demonstrates the utility of 454 technology for the rapid determination of mt genome sequences from tiny amounts of DNA and reveals a wealth of mt genomic data in current databases available for mining. This approach provides a novel platform for high-throughput sequencing of mt genomes from nematodes and other organisms.</p
The mitochondrial genomes of Ancylostoma caninum and Bunostomum phlebotomum â two hookworms of animal health and zoonotic importance
<p>Abstract</p> <p>Background</p> <p>Hookworms are blood-feeding nematodes that parasitize the small intestines of many mammals, including humans and cattle. These nematodes are of major socioeconomic importance and cause disease, mainly as a consequence of anaemia (particularly in children or young animals), resulting in impaired development and sometimes deaths. Studying genetic variability within and among hookworm populations is central to addressing epidemiological and ecological questions, thus assisting in the control of hookworm disease. Mitochondrial (mt) genes are known to provide useful population markers for hookworms, but mt genome sequence data are scant.</p> <p>Results</p> <p>The present study characterizes the complete mt genomes of two species of hookworm, <it>Ancylostoma caninum </it>(from dogs) and <it>Bunostomum phlebotomum </it>(from cattle), each sequenced (by 454 technology or primer-walking), following long-PCR amplification from genomic DNA (~20â40 ng) isolated from individual adult worms. These mt genomes were 13717 bp and 13790 bp in size, respectively, and each contained 12 protein coding, 22 transfer RNA and 2 ribosomal RNA genes, typical for other secernentean nematodes. In addition, phylogenetic analysis (by Bayesian inference and maximum likelihood) of concatenated mt protein sequence data sets for 12 nematodes (including <it>Ancylostoma caninum </it>and <it>Bunostomum phlebotomum</it>), representing the Ascaridida, Spirurida and Strongylida, was conducted. The analysis yielded maximum statistical support for the formation of monophyletic clades for each recognized nematode order assessed, except for the Rhabditida.</p> <p>Conclusion</p> <p>The mt genomes characterized herein represent a rich source of population genetic markers for epidemiological and ecological studies. The strong statistical support for the construction of phylogenetic clades and consistency between the two different tree-building methods employed indicate the value of using whole mt genome data sets for systematic studies of nematodes. The grouping of the Spirurida and Ascaridida to the exclusion of the Strongylida was not supported in the present analysis, a finding which conflicts with the current evolutionary hypothesis for the Nematoda based on nuclear ribosomal gene data.</p
Renal trematode infection due to Paratanaisia bragai in zoo housed Columbiformes and a Red Bird-of-Paradise (Paradisaea rubra)
Trematode infections affect a diverse range of avian species and the organs that are parasitised are also very varied. The family Eucotylidae contains seven genera of renal flukes that parasitise various birds. In birds, mild to severe lesions have been reported for species of the genus Paratanaisia, which was originally described from columbiform and galliform specimens collected in South America and has been identified in a number of wild avian species. This paper investigates eight cases of renal trematode infection at Chester Zoo in the UK due to Paratanaisia bragai in five previously unreported species: red bird-of-paradise, Socorro dove, Mindanao bleeding heart dove, laughing dove and emerald dove. Pathological changes, which varied between species, are discussed. A known intermediate snail host Allopeas clavulinum was present in the enclosures but there was no direct evidence of trematode infection. The size of the snails, possible low prevalence and the difficulty of visualising sporocysts contributed to this. Thus the development and application of further molecular diagnostic markers that can be applied to snail tissues is warranted. Parasite identification was confirmed utilizing DNA amplification from formalin-fixed paraffin-embedded tissues using PCR and trematode specific primers. Sequencing full ssrDNA and D1-D3 lsrDNA confirmed the identity in all cases as P. bragai. However, the short 310Â bp fragment used provides insufficient variation or sequence length for wider application. The epidemiology, pathology and consequences for the management of these endangered species are discussed. Preliminary work on developing an effective ante mortem diagnostic PCR test kit is also highlighted
Pooling as a Strategy for the Timely Diagnosis of Soil-Transmitted Helminths in Stool: Value and Reproducibility
Background: The strategy of pooling stool specimens has been extensively used in the field of parasitology in order to facilitate the screening of large numbers of samples whilst minimizing the prohibitive cost of single sample analysis. The aim of this study was to develop a standardized reproducible pooling protocol for stool samples, validated between two different laboratories, without jeopardizing the sensitivity of the quantitative polymerase chain reaction (qPCR) assays employed for the detection of soil-transmitted helminths (STHs). Two distinct experimental phases were recruited. First, the sensitivity and specificity of the established protocol was assessed by real-time PCR for each one of the STHs. Secondly, agreement and reproducibility of the protocol between the two different laboratories were tested. The need for multiple stool sampling to avoid false negative results was also assessed. Finally, a cost exercise was conducted which included labour cost in low- and high-wage settings, consumable cost, prevalence of a single STH species, and a simple distribution pattern of the positive samples in pools to estimate time and money savings suggested by the strategy. Results: The sensitivity of the pooling method was variable among the STH species but consistent between the two laboratories. Estimates of specificity indicate a \u27pooling approach\u27 can yield a low frequency of \u27missed\u27 infections. There were no significant differences regarding the execution of the protocol and the subsequent STH detection between the two laboratories, which suggests in most cases the protocol is reproducible by adequately trained staff. Finally, given the high degree of agreement, there appears to be little or no need for multiple sampling of either individuals or pools. Conclusions: Our results suggest that the pooling protocol developed herein is a robust and efficient strategy for the detection of STHs in \u27pools-of-five\u27. There is notable complexity of the pool preparation to ensure even distribution of helminth DNA throughout. Therefore, at a given setting, cost of labour among other logistical and epidemiological factors, is the more concerning and determining factor when choosing pooling strategies, rather than losing sensitivity and/or specificity of the molecular assay or the method
Complete mitochondrial genomes and nuclear ribosomal RNA operons of two species of Diplostomum (Platyhelminthes: Trematoda): a molecular resource for taxonomy and molecular epidemiology of important fish pathogens
© 2015 Brabec et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License
(http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium,
provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://
creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. The attached file is the published version of the article
Australian spiny mountain crayfish and their temnocephalan ectosymbionts: an ancient association on the edge of coextinction?
Australian spiny mountain crayfish (Euastacus, Parastacidae) and their ecotosymbiotic temnocephalan flatworms (Temnocephalida, Platyhelminthes) may have co-occurred and interacted through deep time, during a period of major environmental change. Therefore, reconstructing the history of their association is of evolutionary, ecological, and conservation significance. Here, time-calibrated Bayesian phylogenies of Euastacus species and their temnocephalans (Temnohaswellia and Temnosewellia) indicate near-synchronous diversifications from the Cretaceous. Statistically significant cophylogeny correlations between associated clades suggest linked evolutionary histories. However, there is a stronger signal of codivergence and greater host specificity in Temnosewellia, which co-occurs with Euastacus across its range. Phylogeography and analyses of evolutionary distinctiveness (ED) suggest that regional differences in the impact of climate warming and drying had major effects both on crayfish and associated temnocephalans. In particular, Euastacus and Temnosewellia show strong latitudinal gradients in ED and, conversely, in geographical range size, with the most distinctive, northern lineages facing the greatest risk of extinction. Therefore, environmental change has, in some cases, strengthened ecological and evolutionary associations, leaving host-specific temnocephalans vulnerable to coextinction with endangered hosts. Consequently, the extinction of all Euastacus species currently endangered (75%) predicts coextinction of approximately 60% of the studied temnocephalans, with greatest loss of the most evolutionarily distinctive lineages
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