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Guiglielmoni N, Villegas LI, Kirangwa J, Schiffer PH. Revisiting genomes of non-model species with long reads yields new insights into their biology and evolution. Front Genet 2024; 15:1308527. [PMID: 38384712 PMCID: PMC10879605 DOI: 10.3389/fgene.2024.1308527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 01/04/2024] [Indexed: 02/23/2024] Open
Abstract
High-quality genomes obtained using long-read data allow not only for a better understanding of heterozygosity levels, repeat content, and more accurate gene annotation and prediction when compared to those obtained with short-read technologies, but also allow to understand haplotype divergence. Advances in long-read sequencing technologies in the last years have made it possible to produce such high-quality assemblies for non-model organisms. This allows us to revisit genomes, which have been problematic to scaffold to chromosome-scale with previous generations of data and assembly software. Nematoda, one of the most diverse and speciose animal phyla within metazoans, remains poorly studied, and many previously assembled genomes are fragmented. Using long reads obtained with Nanopore R10.4.1 and PacBio HiFi, we generated highly contiguous assemblies of a diploid nematode of the Mermithidae family, for which no closely related genomes are available to date, as well as a collapsed assembly and a phased assembly for a triploid nematode from the Panagrolaimidae family. Both genomes had been analysed before, but the fragmented assemblies had scaffold sizes comparable to the length of long reads prior to assembly. Our new assemblies illustrate how long-read technologies allow for a much better representation of species genomes. We are now able to conduct more accurate downstream assays based on more complete gene and transposable element predictions.
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2
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Rödelsperger C. Comparative Genomics of Sex, Chromosomes, and Sex Chromosomes in Caenorhabditis elegans and Other Nematodes. Methods Mol Biol 2024; 2802:455-472. [PMID: 38819568 DOI: 10.1007/978-1-0716-3838-5_15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2024]
Abstract
The nematode phylum has evolved a remarkable diversity of reproductive modes, including the repeated emergence of asexuality and hermaphroditism across divergent clades. The species-richness and small genome size of nematodes make them ideal systems for investigating the genome-wide causes and consequences of such major transitions. The availability of functional annotations for most Caenorhabditis elegans genes further allows the linking of patterns of gene content evolution with biological processes. Such gene-centric studies were recently complemented by investigations of chromosome evolution that made use of the first chromosome-scale genome assemblies outside the Caenorhabditis genus. This review highlights recent comparative genomic studies of reproductive mode evolution addressing the hybrid origin of asexuality and the parallel gene loss following the emergence of hermaphroditism. It further summarizes ongoing efforts to characterize ancient linkage blocks called Nigon elements, which form central units of chromosome evolution. Fusions between Nigon elements have been demonstrated to impact recombination and speciation. Finally, multiple recent fusions between autosomal and the sex-linked Nigon element reveal insights into the dynamic evolution of sex chromosomes across various timescales.
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Affiliation(s)
- Christian Rödelsperger
- Department for Integrative Evolutionary Biology, Max Planck Institute for Biology, Tübingen, Germany.
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3
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Shatilovich A, Gade VR, Pippel M, Hoffmeyer TT, Tchesunov AV, Stevens L, Winkler S, Hughes GM, Traikov S, Hiller M, Rivkina E, Schiffer PH, Myers EW, Kurzchalia TV. A novel nematode species from the Siberian permafrost shares adaptive mechanisms for cryptobiotic survival with C. elegans dauer larva. PLoS Genet 2023; 19:e1010798. [PMID: 37498820 PMCID: PMC10374039 DOI: 10.1371/journal.pgen.1010798] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 05/24/2023] [Indexed: 07/29/2023] Open
Abstract
Some organisms in nature have developed the ability to enter a state of suspended metabolism called cryptobiosis when environmental conditions are unfavorable. This state-transition requires execution of a combination of genetic and biochemical pathways that enable the organism to survive for prolonged periods. Recently, nematode individuals have been reanimated from Siberian permafrost after remaining in cryptobiosis. Preliminary analysis indicates that these nematodes belong to the genera Panagrolaimus and Plectus. Here, we present precise radiocarbon dating indicating that the Panagrolaimus individuals have remained in cryptobiosis since the late Pleistocene (~46,000 years). Phylogenetic inference based on our genome assembly and a detailed morphological analysis demonstrate that they belong to an undescribed species, which we named Panagrolaimus kolymaensis. Comparative genome analysis revealed that the molecular toolkit for cryptobiosis in P. kolymaensis and in C. elegans is partly orthologous. We show that biochemical mechanisms employed by these two species to survive desiccation and freezing under laboratory conditions are similar. Our experimental evidence also reveals that C. elegans dauer larvae can remain viable for longer periods in suspended animation than previously reported. Altogether, our findings demonstrate that nematodes evolved mechanisms potentially allowing them to suspend life over geological time scales.
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Affiliation(s)
- Anastasia Shatilovich
- Institute of Physicochemical and Biological Problems in Soil Science RAS, Pushchino, Russia
- Zoological Institute RAS, St. Petersburg, Russia
| | - Vamshidhar R. Gade
- Max Planck Institute for Molecular Cell Biology and Genetics, Dresden, Germany
- Institute of Biochemistry, ETH Zürich, Zürich, Switzerland
| | | | | | - Alexei V. Tchesunov
- Department of Invertebrate Zoology, Lomonosov Moscow State University, Moscow, Russia
| | - Lewis Stevens
- Tree of Life, Wellcome Sanger Institute, Cambridge, United Kingdom
| | - Sylke Winkler
- Max Planck Institute for Molecular Cell Biology and Genetics, Dresden, Germany
- DRESDEN concept Genome Center, Dresden, Germany
| | - Graham M. Hughes
- School of Biology and Environmental Science, University College Dublin, Belfield, Dublin, Ireland
| | - Sofia Traikov
- Max Planck Institute for Molecular Cell Biology and Genetics, Dresden, Germany
| | - Michael Hiller
- Center for Systems Biology, Dresden, Germany
- LOEWE Centre for Translational Biodiversity Genomics, Senckenberg Society for Nature Research & Goethe University, Frankfurt am Main, Germany
| | - Elizaveta Rivkina
- Institute of Physicochemical and Biological Problems in Soil Science RAS, Pushchino, Russia
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4
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Xu LY, Wu WT, Bi N, Yan ZJ, Yang F, Yang WJ, Yang JS. A cytological revisit on parthenogenetic Artemia and the deficiency of a meiosis-specific recombinase DMC1 in the possible transition from bisexuality to parthenogenesis. Chromosoma 2023:10.1007/s00412-023-00790-x. [PMID: 36939898 DOI: 10.1007/s00412-023-00790-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Revised: 02/20/2023] [Accepted: 02/27/2023] [Indexed: 03/21/2023]
Abstract
Although parthenogenesis is widespread in nature and known to have close relationships with bisexuality, the transitional mechanism is poorly understood. Artemia is an ideal model to address this issue because bisexuality and "contagious" obligate parthenogenesis independently exist in its congeneric members. In the present study, we first performed chromosome spreading and immunofluorescence to compare meiotic processes of Artemia adopting two distinct reproductive ways. The results showed that, unlike conventional meiosis in bisexual Artemia, meiosis II in parthenogenic Artemia is entirely absent and anaphase I is followed by a single mitosis-like equational division. Interspecific comparative transcriptomics showed that two central molecules in homologous recombination (HR), Dmc1 and Rad51, exhibited significantly higher expression in bisexual versus parthenogenetic Artemia. qRT-PCR indicated that the expression of both genes peaked at the early oogenesis and gradually decreased afterward. Knocking-down by RNAi of Dmc1 in unfertilized females of bisexual Artemia resulted in a severe deficiency of homologous chromosome pairing and produced univalents at the middle oogenesis stage, which was similar to that of parthenogenic Artemia, while in contrast, silencing Rad51 led to no significant chromosome morphological change. Our results indicated that Dmc1 is vital for HR in bisexual Artemia, and the deficiency of Dmc1 may be correlated with or even possibly one of core factors in the transition from bisexuality to parthenogenesis.
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Affiliation(s)
- Lian-Ying Xu
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Wen-Tao Wu
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Ning Bi
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Zhi-Jun Yan
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Fan Yang
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Wei-Jun Yang
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Jin-Shu Yang
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China.
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5
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Bezerra-Santos MA, Mendoza-Roldan JA, DiGeronimo PM, Ward E, Noden B, De Luca F, Fanelli E, Valenzano D, Lia RP, Otranto D. Into the large ears: otitis externa associated with nematodes, mites, and bacteria in Asian elephants (Elephas maximus). Parasit Vectors 2023; 16:87. [PMID: 36879281 PMCID: PMC9987081 DOI: 10.1186/s13071-023-05708-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 02/17/2023] [Indexed: 03/08/2023] Open
Abstract
BACKGROUND The Asian elephant (Elephas maximus), which is an endangered species, harbors several parasites. Among the ectoparasites that it harbors, ear mites of the genus Loxanoetus have the potential to cause external otitis, an inflammation that may also be associated with the presence of other microorganisms. We assessed the relationships between ear mites, nematodes, yeast, bacterial rods, and cocci sampled from the ears of captive Asian elephants in Thailand. In addition, we discuss the possibility that dust-bathing behavior may be triggered by ear mite infestation, and that this in turn may lead to contamination of the ears with soil microorganisms. METHODS Legally owned captive Asian elephants (n = 64) were sampled. Ear swabs were individually collected from both ears and microscopically examined for the presence of mites, nematodes, yeast, bacterial rods, cocci, and host cells. Mites and nematodes were identified to species level using morphological and molecular methods. RESULTS Loxanoetus lenae mites were present in 43.8% (n = 28/64) of the animals (19 animals with mites in one ear and nine animals with mites in both ears). Nematodes of the genus Panagrolaimus were detected in 23.4% (n = 15/64) of the animals (10 with nematodes in one ear and five with nematodes in both ears). In adult elephants (Fisher's exact test, P = 0.0278) and female elephants (Fisher's exact test, P = 0.0107), the presence of nematodes in both ears was significantly associated with the presence of mites. In addition, higher categorical burdens of nematodes were also significantly associated with the presence of mites (Fisher's exact test, P = 0.0234) and epithelial cells (Fisher's exact test, P = 0.0108), and marginally significantly associated with bacterial cocci (Fisher's exact test, P = 0.0499). CONCLUSIONS The presence of L. lenae mites in the ear canals of the Asian elephants was significantly associated with the occurrence of other microorganisms, such as soil nematodes, bacteria and yeasts. The presence of mites in their ears may increase the dust-bathing behavior of elephants which, if confirmed, represents a further paradigmatic example of a parasitic infestation affecting animal behavior.
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Affiliation(s)
| | | | | | - Erica Ward
- Wildlife and Animal Welfare Institute, Wrentham, MA, USA
| | - Bruce Noden
- Department of Entomology and Plant Pathology, Oklahoma State University, Oklahoma, USA
| | - Francesca De Luca
- Institute for the Sustainable Protection of Plants, National Research Council, Bari, Italy
| | - Elena Fanelli
- Institute for the Sustainable Protection of Plants, National Research Council, Bari, Italy
| | - Domenico Valenzano
- Department of Soil, Plant and Food Sciences, University of Bari, Bari, Italy
| | - Riccardo Paolo Lia
- Department of Veterinary Medicine, University of Bari, Valenzano, Bari, Italy
| | - Domenico Otranto
- Department of Veterinary Medicine, University of Bari, Valenzano, Bari, Italy. .,Department of Pathobiology, Faculty of Veterinary Science, Bu-Ali Sina University, Hamedan, Iran.
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6
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Rinkevich B, Ballarin L, Martinez P, Somorjai I, Ben-Hamo O, Borisenko I, Berezikov E, Ereskovsky A, Gazave E, Khnykin D, Manni L, Petukhova O, Rosner A, Röttinger E, Spagnuolo A, Sugni M, Tiozzo S, Hobmayer B. A pan-metazoan concept for adult stem cells: the wobbling Penrose landscape. Biol Rev Camb Philos Soc 2021; 97:299-325. [PMID: 34617397 PMCID: PMC9292022 DOI: 10.1111/brv.12801] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Revised: 09/20/2021] [Accepted: 09/22/2021] [Indexed: 12/17/2022]
Abstract
Adult stem cells (ASCs) in vertebrates and model invertebrates (e.g. Drosophila melanogaster) are typically long‐lived, lineage‐restricted, clonogenic and quiescent cells with somatic descendants and tissue/organ‐restricted activities. Such ASCs are mostly rare, morphologically undifferentiated, and undergo asymmetric cell division. Characterized by ‘stemness’ gene expression, they can regulate tissue/organ homeostasis, repair and regeneration. By contrast, analysis of other animal phyla shows that ASCs emerge at different life stages, present both differentiated and undifferentiated phenotypes, and may possess amoeboid movement. Usually pluri/totipotent, they may express germ‐cell markers, but often lack germ‐line sequestering, and typically do not reside in discrete niches. ASCs may constitute up to 40% of animal cells, and participate in a range of biological phenomena, from whole‐body regeneration, dormancy, and agametic asexual reproduction, to indeterminate growth. They are considered legitimate units of selection. Conceptualizing this divergence, we present an alternative stemness metaphor to the Waddington landscape: the ‘wobbling Penrose’ landscape. Here, totipotent ASCs adopt ascending/descending courses of an ‘Escherian stairwell’, in a lifelong totipotency pathway. ASCs may also travel along lower stemness echelons to reach fully differentiated states. However, from any starting state, cells can change their stemness status, underscoring their dynamic cellular potencies. Thus, vertebrate ASCs may reflect just one metazoan ASC archetype.
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Affiliation(s)
- Baruch Rinkevich
- Israel Oceanographic & Limnological Research, National Institute of Oceanography, POB 9753, Tel Shikmona, Haifa, 3109701, Israel
| | - Loriano Ballarin
- Department of Biology, University of Padova, Via Ugo Bassi 58/B, Padova, 35121, Italy
| | - Pedro Martinez
- Departament de Genètica, Microbiologia i Estadística, Universitat de Barcelona, Av. Diagonal 643, Barcelona, 08028, Spain.,Institut Català de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys 23, Barcelona, 08010, Spain
| | - Ildiko Somorjai
- School of Biology, University of St Andrews, St Andrews, Fife, KY16 9ST, Scotland, UK
| | - Oshrat Ben-Hamo
- Israel Oceanographic & Limnological Research, National Institute of Oceanography, POB 9753, Tel Shikmona, Haifa, 3109701, Israel
| | - Ilya Borisenko
- Department of Embryology, Faculty of Biology, Saint-Petersburg State University, University Embankment, 7/9, Saint-Petersburg, 199034, Russia
| | - Eugene Berezikov
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Antonius Deusinglaan 1, Groningen, 9713 AV, The Netherlands
| | - Alexander Ereskovsky
- Department of Embryology, Faculty of Biology, Saint-Petersburg State University, University Embankment, 7/9, Saint-Petersburg, 199034, Russia.,Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale (IMBE), Aix Marseille University, CNRS, IRD, Avignon University, Jardin du Pharo, 58 Boulevard Charles Livon, Marseille, 13007, France.,Koltzov Institute of Developmental Biology of Russian Academy of Sciences, Ulitsa Vavilova, 26, Moscow, 119334, Russia
| | - Eve Gazave
- Université de Paris, CNRS, Institut Jacques Monod, Paris, F-75006, France
| | - Denis Khnykin
- Department of Pathology, Oslo University Hospital, Bygg 19, Gaustad Sykehus, Sognsvannsveien 21, Oslo, 0188, Norway
| | - Lucia Manni
- Department of Biology, University of Padova, Via Ugo Bassi 58/B, Padova, 35121, Italy
| | - Olga Petukhova
- Collection of Vertebrate Cell Cultures, Institute of Cytology, Russian Academy of Sciences, Tikhoretsky Ave. 4, St. Petersburg, 194064, Russia
| | - Amalia Rosner
- Israel Oceanographic & Limnological Research, National Institute of Oceanography, POB 9753, Tel Shikmona, Haifa, 3109701, Israel
| | - Eric Röttinger
- Université Côte d'Azur, CNRS, INSERM, Institute for Research on Cancer and Aging, Nice (IRCAN), Nice, 06107, France.,Université Côte d'Azur, Federative Research Institute - Marine Resources (IFR MARRES), 28 Avenue de Valrose, Nice, 06103, France
| | - Antonietta Spagnuolo
- Department of Biology and Evolution of Marine Organisms, Stazione Zoologica Anton Dohrn, Villa Comunale, Naples, 80121, Italy
| | - Michela Sugni
- Department of Environmental Science and Policy (ESP), Università degli Studi di Milano, Via Celoria 26, Milan, 20133, Italy
| | - Stefano Tiozzo
- Sorbonne Université, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), 06234 Villefranche-sur-Mer, Villefranche sur Mer, Cedex, France
| | - Bert Hobmayer
- Institute of Zoology and Center for Molecular Biosciences, University of Innsbruck, Technikerstr, Innsbruck, 256020, Austria
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7
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Van Goor J, Shakes DC, Haag ES. Fisher vs. the Worms: Extraordinary Sex Ratios in Nematodes and the Mechanisms that Produce Them. Cells 2021; 10:1793. [PMID: 34359962 PMCID: PMC8303164 DOI: 10.3390/cells10071793] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 07/08/2021] [Accepted: 07/13/2021] [Indexed: 01/20/2023] Open
Abstract
Parker, Baker, and Smith provided the first robust theory explaining why anisogamy evolves in parallel in multicellular organisms. Anisogamy sets the stage for the emergence of separate sexes, and for another phenomenon with which Parker is associated: sperm competition. In outcrossing taxa with separate sexes, Fisher proposed that the sex ratio will tend towards unity in large, randomly mating populations due to a fitness advantage that accrues in individuals of the rarer sex. This creates a vast excess of sperm over that required to fertilize all available eggs, and intense competition as a result. However, small, inbred populations can experience selection for skewed sex ratios. This is widely appreciated in haplodiploid organisms, in which females can control the sex ratio behaviorally. In this review, we discuss recent research in nematodes that has characterized the mechanisms underlying highly skewed sex ratios in fully diploid systems. These include self-fertile hermaphroditism and the adaptive elimination of sperm competition factors, facultative parthenogenesis, non-Mendelian meiotic oddities involving the sex chromosomes, and environmental sex determination. By connecting sex ratio evolution and sperm biology in surprising ways, these phenomena link two "seminal" contributions of G. A. Parker.
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Affiliation(s)
- Justin Van Goor
- Department of Biology, University of Maryland, College Park, MD 20742, USA;
| | - Diane C. Shakes
- Department of Biology, William and Mary, Williamsburg, VA 23187, USA;
| | - Eric S. Haag
- Department of Biology, University of Maryland, College Park, MD 20742, USA;
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8
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Howe DK, Ha AD, Colton A, De Ley IT, Rae RG, Ross J, Wilson M, Nermut J, Zhao Z, Mc Donnell RJ, Denver DR. Phylogenetic evidence for the invasion of a commercialized European Phasmarhabditis hermaphrodita lineage into North America and New Zealand. PLoS One 2020; 15:e0237249. [PMID: 32804938 PMCID: PMC7430733 DOI: 10.1371/journal.pone.0237249] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Accepted: 07/22/2020] [Indexed: 11/24/2022] Open
Abstract
Biological control (biocontrol) as a component of pest management strategies reduces reliance on synthetic chemicals, and seemingly offers a natural approach that minimizes environmental impact. However, introducing a new organism to new environments as a classical biocontrol agent can have broad and unanticipated biodiversity effects and conservation consequences. Nematodes are currently used in a variety of commercial biocontrol applications, including the use of Phasmarhabditis hermaphrodita as an agent targeting pest slug and snail species. This species was originally discovered in Germany, and is generally thought to have European origins. P. hermaphrodita is sold under the trade name Nemaslug®, and is available only in European markets. However, this nematode species was discovered in New Zealand and the western United States, though its specific origins remained unclear. In this study, we analyzed 45 nematode strains representing eight different Phasmarhabditis species, collected from nine countries around the world. A segment of nematode mitochondrial DNA (mtDNA) was sequenced and subjected to phylogenetic analyses. Our mtDNA phylogenies were overall consistent with previous analyses based on nuclear ribosomal RNA (rRNA) loci. The recently discovered P. hermaphrodita strains in New Zealand and the United States had mtDNA haplotypes nearly identical to that of Nemaslug®, and these were placed together in an intraspecific monophyletic clade with high support in maximum likelihood and Bayesian analyses. We also examined bacteria that co-cultured with the nematode strains isolated in Oregon, USA, by analyzing 16S rRNA sequences. Eight different bacterial genera were found to associate with these nematodes, though Moraxella osloensis, the bacteria species used in the Nemaslug® formulation, was not detected. This study provided evidence that nematodes deriving from the Nemaslug® biocontrol product have invaded countries where its use is prohibited by regulatory agencies and not commercially available.
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Affiliation(s)
- Dana K. Howe
- Department of Integrative Biology, Oregon State University, Corvallis, Oregon, United States of America
- * E-mail:
| | - Anh D. Ha
- Department of Integrative Biology, Oregon State University, Corvallis, Oregon, United States of America
| | - Andrew Colton
- Department of Crop and Soil Science, Oregon State University, Corvallis, Oregon, United States of America
| | - Irma Tandingan De Ley
- Department of Nematology, University of California-Riverside, Riverside, California, United States of America
| | - Robbie G. Rae
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, United Kingdom
| | - Jenna Ross
- Department of Conservation Ecology and Entomology, Faculty of AgriSciences, Stellenbosch University, Matieland, South Africa
- Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, United Kingdom
- Crop Health and Protection (CHAP), National Agri-Food Innovation Campus, Sand Hutton, York, United Kingdom
| | - Michael Wilson
- Independent Researcher/Consultant, Hamilton, New Zealand
| | - Jiří Nermut
- Biology Centre CAS, Institute of Entomology, Branišovská, České Budějovice, Czech Republic
| | - Zhongying Zhao
- Department of Biology, Hong Kong Baptist University, Hong Kong SAR, China
| | - Rory J. Mc Donnell
- Department of Crop and Soil Science, Oregon State University, Corvallis, Oregon, United States of America
| | - Dee R. Denver
- Department of Integrative Biology, Oregon State University, Corvallis, Oregon, United States of America
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9
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Schiffer PH, Danchin EGJ, Burnell AM, Creevey CJ, Wong S, Dix I, O'Mahony G, Culleton BA, Rancurel C, Stier G, Martínez-Salazar EA, Marconi A, Trivedi U, Kroiher M, Thorne MAS, Schierenberg E, Wiehe T, Blaxter M. Signatures of the Evolution of Parthenogenesis and Cryptobiosis in the Genomes of Panagrolaimid Nematodes. iScience 2019; 21:587-602. [PMID: 31759330 PMCID: PMC6889759 DOI: 10.1016/j.isci.2019.10.039] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 07/17/2019] [Accepted: 10/21/2019] [Indexed: 12/12/2022] Open
Abstract
Most animal species reproduce sexually and fully parthenogenetic lineages are usually short lived in evolution. Still, parthenogenesis may be advantageous as it avoids the cost of sex and permits colonization by single individuals. Panagrolaimid nematodes have colonized environments ranging from arid deserts to Arctic and Antarctic biomes. Many are obligatory meiotic parthenogens, and most have cryptobiotic abilities, being able to survive repeated cycles of complete desiccation and freezing. To identify systems that may contribute to these striking abilities, we sequenced and compared the genomes and transcriptomes of parthenogenetic and outcrossing panagrolaimid species, including cryptobionts and non-cryptobionts. The parthenogens are triploids, most likely originating through hybridization. Adaptation to cryptobiosis shaped the genomes of panagrolaimid nematodes and is associated with the expansion of gene families and signatures of selection on genes involved in cryptobiosis. All panagrolaimids have acquired genes through horizontal gene transfer, some of which are likely to contribute to cryptobiosis.
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Affiliation(s)
- Philipp H Schiffer
- CLOE, Department for Biosciences, University College London, London, UK; Zoologisches Institut, Universität zu Köln, 50674 Köln, Germany; Institut für Genetik, Universität zu Köln, 50674 Köln, Germany.
| | | | - Ann M Burnell
- Maynooth University Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | | | - Simon Wong
- Irish Centre for High-End Computing, Tower Building, Trinity Technology & Enterprise Campus, Grand Canal Quay, Dublin D02 HP83, Ireland
| | - Ilona Dix
- Maynooth University Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - Georgina O'Mahony
- Maynooth University Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - Bridget A Culleton
- Maynooth University Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland; Megazyme, Bray Business Park, Bray, Co. Wicklow A98 YV29, Ireland
| | | | - Gary Stier
- Zoologisches Institut, Universität zu Köln, 50674 Köln, Germany
| | - Elizabeth A Martínez-Salazar
- Unidad Académica de Ciencias Biológicas, Laboratorio de Colecciones Biológicas y Sistemática Molecular, Universidad Autónoma de Zacatecas, Zacatecas, México
| | - Aleksandra Marconi
- Institute of Evolutionary Biology, The University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Urmi Trivedi
- Edinburgh Genomics, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Michael Kroiher
- Zoologisches Institut, Universität zu Köln, 50674 Köln, Germany
| | - Michael A S Thorne
- British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK
| | | | - Thomas Wiehe
- Institut für Genetik, Universität zu Köln, 50674 Köln, Germany
| | - Mark Blaxter
- Institute of Evolutionary Biology, The University of Edinburgh, Edinburgh EH9 3FL, UK; Edinburgh Genomics, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
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10
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Ragsdale EJ, Koutsovoulos G, Biddle JF. A draft genome for a species of Halicephalobus (Panagrolaimidae). J Nematol 2019; 51:1-4. [PMID: 31814372 PMCID: PMC6909384 DOI: 10.21307/jofnem-2019-068] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Indexed: 12/19/2022] Open
Abstract
Halicephalobus is a clade of small, exclusively parthenogenic nematodes that have sometimes colonized remarkable habitats. Given their phylogenetic closeness to other parthenogenic panagrolaimid species with which they likely share a sexually reproducing ancestor, Halicephalobus species provide a point of comparison for parallelisms in the evolution of asexuality. Here, we present a draft genome of a putatively new species of Halicephalobus isolated from termites in Japan.
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Affiliation(s)
- Erik J Ragsdale
- Department of Biology, Indiana University , 915 E. 3rd St. , Bloomington , IN , 47405
| | | | - Joseph F Biddle
- Department of Biology, Indiana University , 915 E. 3rd St. , Bloomington , IN , 47405
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Morphological and molecular characterization of Tarantobelus arachnicida gen. n., sp. n. (Nematoda, Rhabditida, Brevibuccidae), a parasitic nematode of tarantulas. J Helminthol 2017; 92:491-503. [PMID: 28693649 DOI: 10.1017/s0022149x17000566] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A new genus and new species, Tarantobelus arachnicida, was found in the oral opening of tarantula spiders bred in captivity in Poland. The new species is characterized by having a small body (0.77-0.95 mm long in females and 0.66-0.84 mm in males), cuticle poorly annulated by transverse incisures, lateral field inconspicuous, lips separated with small cuticular flaps topping each lip, stoma panagrolaimoid with gymnostom well developed with robust and refringent rhabdia, pharynx panagrolaimoid with isthmus slightly longer than the basal bulb, intestine with cardiac (anterior) and rectal (posterior) areas with narrower walls. Mature females with intestinal cells including needle crystal packs, excretory pore at isthmus level, female reproductive system panagrolaimoid with post-vulval sac 0.4-0.8 times the length of the corresponding body diameter and having very thick walls, vulva very prominent, female rectum 0.8-1.3 times the length of the anal body diameter, female tail conical with acute tip with phasmids at 58-62% of its length. Male tail conical with long and thin mucro, spicules ventrad bent having rounded manubrium and thick gubernaculum. Description, measurements and illustrations of the new species are provided. Molecular analyses show its relationship with Brevibucca and Cuticonema. On the other hand, Medibulla and its corresponding subfamily Medibullinae, previously in Osstellidae, are transferred to Panagrolaimidae, being Shahnematinae, the junior synonym of Medibullinae. Indocephalobus, recently proposed and located in the family Panagrolaimidae, is considered a junior synonym of Diplogastrellus (Diplogasteromorpha), and its only species, I. zebrae, is considered a junior synonym of D. gracilis. In addition, a key to identification of panagrolaimoid genera is included.
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Wharton DA, Marshall CJ, Egeter B. Comparisons between two Antarctic nematodes: cultured Panagrolaimus sp. DAW1 and field-sourced Panagrolaimus davidi. NEMATOLOGY 2017. [DOI: 10.1163/15685411-00003066] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The Antarctic nematodePanagrolaimus davidican survive intracellular freezing. Genetic studies indicate the culture strain (now designated asPanagrolaimussp. DAW1) is a different species to theP. davidiof field origin. This paper reports further attempts both to isolate DAW1 from Antarctic soils and to cultureP. davidiitself. Sequencing of the 18S rRNA gene of 151 individuals indicates that DAW1 is rare in the field, but characterising two new isolates shows that, nevertheless, it is present.Panagrolaimus davidiis common in the field, but cannot be cultured using the media tested here. These two species are difficult to distinguish morphologically, apart from the absence of males in DAW1 and its longer recurved tail. Whilst it is possible that DAW1 is an introduced species, the sites at Shackleton’s hut at Cape Royds are dominated byP. davidi, which is clearly an endemic species.
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Affiliation(s)
- David A. Wharton
- Department of Zoology, Otago, University of Otago, P.O. Box 56, Dunedin, New Zealand
| | - Craig J. Marshall
- Department of Biochemistry/Genetics, Otago, University of Otago, P.O. Box 56, Dunedin, New Zealand
| | - Bastian Egeter
- Department of Zoology, Otago, University of Otago, P.O. Box 56, Dunedin, New Zealand
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McGill LM, Fitzpatrick DA, Pisani D, Burnell AM. Estimation of phylogenetic divergence times in Panagrolaimidae and other nematodes using relaxed molecular clocks calibrated with insect and crustacean fossils. NEMATOLOGY 2017. [DOI: 10.1163/15685411-00003096] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
This study presents the use of relaxed molecular clock methods to infer the dates of divergence between Panagrolaimus species. Autocorrelated relaxed tree methods, combined with well characterised fossil calibration dates, yield estimates of nematode divergence dates in accordance with the palaeontological age of fossil ascarid eggs and with the previously estimated date of 18 Ma (range 11.6 to 29.9 Ma) for the divergence of the Caenorhabditis lineage. Our data indicate that Panagrolaimus davidi from Antarctica separated ca 21.98 Ma from its currently known, most closely related strain. Thus, P. davidi may have existed in Antarctica prior to the Last Glacial Maximum, although this seems unlikely as it shares physiological and life history traits with closely related nematodes from temperate climates. These traits may have facilitated colonisation of Antarctica by P. davidi after the quaternary glaciation, analogous to the colonisation of Surtsey Island, Iceland, by P. superbus after its volcanic formation. This study demonstrates that autocorrelated relaxed tree methods combined with well characterised fossil calibration dates may be used as a method to estimate the divergence dates within nematodes in order to gain insight into their evolutionary history.
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Affiliation(s)
- Lorraine M. McGill
- Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - David A. Fitzpatrick
- Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
| | - Davide Pisani
- Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
- School of Biological Sciences and School of Earth Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK
| | - Ann M. Burnell
- Department of Biology, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland
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Seybold AC, Wharton DA, Thorne MAS, Marshall CJ. Establishing RNAi in a Non-Model Organism: The Antarctic Nematode Panagrolaimus sp. DAW1. PLoS One 2016; 11:e0166228. [PMID: 27832164 PMCID: PMC5104476 DOI: 10.1371/journal.pone.0166228] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 10/03/2016] [Indexed: 12/02/2022] Open
Abstract
The Antarctic nematode Panagrolaimus sp. DAW1 is one of the only organisms known to survive extensive intracellular freezing throughout its tissues. Although the physiological mechanisms of this extreme adaptation are partly understood, the molecular mechanisms remain largely unknown. RNAi is a method that allows the examination of gene function in a direct, targeted manner, by knocking out specific mRNAs and revealing the effects on the phenotype. In this study we have explored the viability of RNAi in Panagrolaimus sp. DAW1. In the first trial, nematodes were fed E. coli expressing Panagrolaimus sp. DAW1 dsRNA of the embryonic lethal genes rps-2 and dhc, and the blister gene duox. Pd-rps-2(RNAi)-treated nematodes showed a significant decrease in larval hatching. However, qPCR showed no significant decrease in the amount of rps-2 mRNA in Pd-rps-2(RNAi)-treated animals. Several soaking protocols for dsRNA uptake were investigated using the fluorescent dye FITC. Desiccation-enhanced soaking showed the strongest uptake of FITC and resulted in a significant and consistent decrease of mRNA levels of two of the four tested genes (rps-2 and tps-2a), suggesting effective uptake of dsRNA-containing solution by the nematode. These findings suggest that RNAi by desiccation-enhanced soaking is viable in Panagrolaimus sp. DAW1 and provide the first functional genomic approach to investigate freezing tolerance in this non-model organism. RNAi, in conjunction with qPCR, can be used to screen for candidate genes involved in intracellular freezing tolerance in Panagrolaimus sp. DAW1.
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Affiliation(s)
- Anna C. Seybold
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - David A. Wharton
- Department of Zoology, University of Otago, Dunedin, New Zealand
| | - Michael A. S. Thorne
- British Antarctic Survey, Natural Environment Research Council, Cambridge, United Kingdom
| | - Craig J. Marshall
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
- Genetics Otago, University of Otago, Dunedin, New Zealand
- * E-mail:
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Seddiqi E, Shokoohi E, Divsalar N, Abolafia J. Descriptions of four known species of the families Panagrolaimidae and Alloionematidae (Nematoda: Rhabditida) from Iran. TROPICAL ZOOLOGY 2016. [DOI: 10.1080/03946975.2016.1177384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Cold tolerance of the Antarctic nematodes Plectus murrayi and Scottnema lindsayae. J Comp Physiol B 2015; 185:281-9. [PMID: 25576363 DOI: 10.1007/s00360-014-0884-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 12/16/2014] [Accepted: 12/25/2014] [Indexed: 10/24/2022]
Abstract
The cold tolerance of the Antarctic nematodes Scottnema lindsayae and Plectus murrayi was determined using material freshly isolated from the field. Both species could survive low temperatures but the survival of S. lindsayae was greater than that of P. murrayi. Field soil temperatures in late spring-early summer indicated a minimum temperature of -19.5 °C and a maximum cooling rate of 0.71 °C min(-1). In P. murrayi grown in culture, there was no significant effect of acclimation, nor of the two culture media used, on survival after freezing but survival was greater if freezing was seeded at -1 °C than at lower temperatures. The freezing survival ability of P. murrayi is much less than that of Panagrolaimus davidi CB1, another Antarctic nematode. Cryomicroscopy indicates that P. murrayi can survive low temperatures by either cryoprotective dehydration or freezing tolerance, but that freezing tolerance is the dominant strategy. Measurable thermal hysteresis was detected only in highly concentrated extracts of the nematodes, indicating the presence of an antifreeze protein, but at the concentrations likely to be found in vivo, the major function of the ice active protein involved is probably recrystallization inhibition.
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Thorne MAS, Kagoshima H, Clark MS, Marshall CJ, Wharton DA. Molecular analysis of the cold tolerant Antarctic nematode, Panagrolaimus davidi. PLoS One 2014; 9:e104526. [PMID: 25098249 PMCID: PMC4123951 DOI: 10.1371/journal.pone.0104526] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 07/11/2014] [Indexed: 01/25/2023] Open
Abstract
Isolated and established in culture from the Antarctic in 1988, the nematode Panagrolaimus davidi has proven to be an ideal model for the study of adaptation to the cold. Not only is it the best-documented example of an organism surviving intracellular freezing but it is also able to undergo cryoprotective dehydration. As part of an ongoing effort to develop a molecular understanding of this remarkable organism, we have assembled both a transcriptome and a set of genomic scaffolds. We provide an overview of the transcriptome and a survey of genes involved in temperature stress. We also explore, in silico, the possibility that P. davidi will be susceptible to an environmental RNAi response, important for further functional studies.
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Affiliation(s)
- Michael A. S. Thorne
- British Antarctic Survey, Natural Environment Research Council, Cambridge, United Kingdom
- * E-mail:
| | - Hiroshi Kagoshima
- Transdisciplinary Research Integration Center, Research Organization of Information and Systems, Tokyo, Japan
- National Institute of Genetics, Mishima, Japan
| | - Melody S. Clark
- British Antarctic Survey, Natural Environment Research Council, Cambridge, United Kingdom
| | - Craig J. Marshall
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - David A. Wharton
- Department of Zoology, University of Otago, Dunedin, New Zealand
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Schiffer PH, Nsah NA, Grotehusmann H, Kroiher M, Loer C, Schierenberg E. Developmental variations among Panagrolaimid nematodes indicate developmental system drift within a small taxonomic unit. Dev Genes Evol 2014; 224:183-8. [PMID: 24849338 DOI: 10.1007/s00427-014-0471-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 04/29/2014] [Indexed: 01/26/2023]
Abstract
Comparative studies of nematode embryogenesis among different clades revealed considerable variations. However, to what extent developmental differences exist between closely related species has mostly remained nebulous. Here, we explore the correlation between phylogenetic neighborhood and developmental variation in a restricted and morphologically particularly uniform taxonomic group (Panagrolaimidae) to determine to what extent (1) morphological and developmental characters go along with molecular data and thus can serve as diagnostic tools for the definition of kinship and (2) developmental system drift (DSD; modifications of developmental patterns without corresponding morphological changes) can be found within a small taxonomic unit. Our molecular approaches firmly support subdivision of Panagrolaimid nematodes into two monophyletic groups. These can be discriminated by distinct peculiarities in early embryonic cell lineages and a mirror-image expression pattern of the gene skn-1. This suggests major changes in the logic of cell specification and the action of DSD in the studied representatives of the two neighboring nematode taxa.
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Affiliation(s)
- Philipp H Schiffer
- Zoological Institute, Cologne Biocenter, University of Cologne, Cologne, Germany,
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Ionic regulation in the Antarctic nematode Panagrolaimus davidi, measured using electron probe X-ray microanalysis. J Comp Physiol B 2014; 184:415-23. [PMID: 24604292 DOI: 10.1007/s00360-014-0818-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 01/30/2014] [Accepted: 02/12/2014] [Indexed: 10/25/2022]
Abstract
The element composition of the pseudocoelomic fluid of the Antarctic nematode Panagrolaimus davidi was analysed by electron probe X-ray microanalysis after absorbing the fluid into Sephadex G-25 beads, and after producing calibration curves by analysing various concentrations of elements of interest absorbed into beads. The nematodes maintain higher concentrations of sodium and potassium in their pseudocoelomic fluid than in the external medium but lower concentrations of magnesium and calcium. When external concentrations of specific ions were elevated there was evidence for the regulation of internal concentrations of sodium, potassium, magnesium and chlorine. The time course of changes in response to exposure to elevated levels of KCl shows an increase in internal concentrations of potassium and chlorine up to 2 h after exposure, followed by a decline. This is consistent with a model of ionic regulation proposed for Caenorhabditis elegans which suggests that high concentrations of ionic osmolytes are replaced by compatible organic osmolytes.
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Kanzaki N, Ragsdale EJ, Herrmann M, Susoy V, Sommer RJ. Two androdioecious and one dioecious new species of pristionchus (nematoda: diplogastridae): new reference points for the evolution of reproductive mode. J Nematol 2013; 45:172-194. [PMID: 24115783 PMCID: PMC3792836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Indexed: 06/02/2023] Open
Abstract
Rhabditid nematodes are one of a few animal taxa in which androdioecious reproduction, involving hermaphrodites and males, is found. In the genus Pristionchus, several cases of androdioecy are known, including the model species P. pacificus. A comprehensive understanding of the evolution of reproductive mode depends on dense taxon sampling and careful morphological and phylogenetic reconstruction. In this article, two new androdioecious species, P. boliviae n. sp. and P. mayeri n. sp., and one gonochoristic outgroup, P. atlanticus n. sp., are described on morphological, molecular, and biological evidence. Their phylogenetic relationships are inferred from 26 ribosomal protein genes and a partial SSU rRNA gene. Based on current representation, the new androdioecious species are sister taxa, indicating either speciation from an androdioecious ancestor or rapid convergent evolution in closely related species. Male sexual characters distinguish the new species, and new characters for six closely related Pristionchus species are presented. Male papillae are unusually variable in P. boliviae n. sp. and P. mayeri n. sp., consistent with the predictions of "selfing syndrome." Description and phylogeny of new androdioecious species, supported by fuller outgroup representation, establish new reference points for mechanistic studies in the Pristionchus system by expanding its comparative context.
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Affiliation(s)
- Natsumi Kanzaki
- Forest Pathology Laboratory, Forestry and Forest Products Research Institute, 1 Matsunosato, Tsukuba, Ibaraki 305-8687 Japan
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The ability of the Antarctic nematode Panagrolaimus davidi to survive intracellular freezing is dependent upon nutritional status. J Comp Physiol B 2012; 183:181-8. [DOI: 10.1007/s00360-012-0697-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 06/25/2012] [Accepted: 07/11/2012] [Indexed: 10/28/2022]
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Reproductive mode evolution in nematodes: insights from molecular phylogenies and recently discovered species. Mol Phylogenet Evol 2011; 61:584-92. [PMID: 21787872 DOI: 10.1016/j.ympev.2011.07.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Revised: 07/06/2011] [Accepted: 07/08/2011] [Indexed: 11/21/2022]
Abstract
The Phylum Nematoda has long been known to contain a great diversity of species that vary in reproductive mode, though our understanding of the evolutionary origins, causes and consequences of nematode reproductive mode change have only recently started to mature. Here we bring together and analyze recent progress on reproductive mode evolution throughout the phylum, resulting from the application of molecular phylogenetic approaches and newly discovered nematode species. Reproductive mode variation is reviewed in multiple free-living, animal-parasitic and plant-parasitic nematode groups. Discussion ranges from the model nematode Caenorhabditis elegans and its close relatives, to the plant-parasitic nematodes of the Meloidogyne genus where there is extreme variation in reproductive mode between and even within species, to the vertebrate-parasitic genus Strongyloides and related genera where reproductive mode varies across generations (heterogony). Multiple evolutionary transitions from dioecous (obligately outcrossing) to hermaphroditism and parthenogenesis in the phylum are discussed, along with one case of an evolutionary transition from hermaphroditism to doioecy in the Oscheius genus. We consider the roles of underlying genetic mechanisms in promoting reproductive plasticity in this phylum, as well as the potential evolutionary forces promoting transitions in reproductive mode.
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Hermosilla C, Coumbe KM, Habershon-Butcher J, Schöniger S. Fatal equine meningoencephalitis in the United Kingdom caused by the panagrolaimid nematode Halicephalobus gingivalis: case report and review of the literature. Equine Vet J 2011; 43:759-63. [PMID: 21496093 DOI: 10.1111/j.2042-3306.2010.00332.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A fatal case of eosinophilic and granulomatous meningoencephalitis caused by the free-living panagrolaimid nematode Halicephalobus gingivalis is reported in a 10-year-old Welsh gelding in the United Kingdom. Clinical examination first revealed behavioural abnormalities which rapidly progressed to severe ataxia, reduced mentation status and cranial nerve signs. Despite symptomatic treatment no amelioration of neurological signs was achieved and the horse was subjected to euthanasia. A complete post mortem examination revealed eosinophilic and granulomatous meningoencephalitis mainly affecting the cerebellum and brain stem with intralesional adult nematodes, larvae and eggs. There was also eosinophilic meningitis of the cervical spinal cord. The intralesional nematodes were morphologically consistent with the panagrolaimid nematode H. gingivalis. Although infection by this facultative neurotropic parasite is extremely rare, it needs to be considered in the differential diagnosis of central nervous signs in horses and, in particular, other equine helminthic infection of the central nervous system. This fatal case is unusual since lesions were locally very extensive and the nematodes did not colonise haematogenously to other organs as seen often in equine halicephalobosis. As the taxonomy of H. gingivalis has changed and some recent reports in the literature still refer to this species as Micronema deletrix or Halicephalobus deletrix, we here provide a short update of the species and some insights on the order Tylenchida, which contains free-living nematodes with parasitic tendencies.
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Affiliation(s)
- C Hermosilla
- Department of Pathology and Infectious Diseases, Royal Veterinary College, Hatfield, Hertfordshire, UK.
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