Two atypical new species of the genus Sectonema Thorne, 1930 (Nematoda, Dorylaimida, Aporcelaimidae) from Vietnam

  • Thi Anh Duong Nguyen Department of Terrestrial Ecology, Zoological Institute, University of Cologne, Zülpicher Straße 47b, 50674 Cologne; Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam; and Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Campus ‘Las Lagunillas’ s/n, Edificio B3, 23071 Jaén, Spain
  • Joaquín Abolafia Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Campus ‘Las Lagunillas’ s/n, Edificio B3, 23071 Jaén
  • Michael Bonkowski Department of Terrestrial Ecology, Zoological Institute, University of Cologne, Zülpicher Straße 47b, 50674 Cologne
  • Reyes Peña-Santiago Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Campus ‘Las Lagunillas’ s/n, Edificio B3, 23071 Jaén
  • Sergio Álvarez-Ortega Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Campus ‘Las Lagunillas’ s/n, Edificio B3, 23071 Jaén
Keywords: D2–D3 expansion segments of LSU ribosomal DNA, morphology, morphometrics, taxonomy, SEM

Abstract

Two new species of the genus Sectonema from natural habitats of northern Vietnam are studied. This paper includes their descriptions, measurements, line illustrations, and light microscope (LM) and scanning electron microscope (SEM) pictures. Sectonema tropicum sp. nov. is characterized by a 2.56–3.24 mm long body, 19–21 μm broad lip region, odontostyle 20–21 μm long at its ventral side, 730–834 μm long neck, pharyngeal expansion occupying 52–59% of total neck length, uterus a simple tube-like structure 150–242 μm long or 1.2–2.5 times the body diameter, pars refringens vaginae present, V = 48–52, short (31–40 μm, c = 70–91, c’ = 0.5–0.6) and rounded tail, 91–97 μm long spicules, and only one weakly developed ventromedian supplement. Sectonema vietnamense sp. nov. is characterized by its slender (a = 33–49) and 2.71–4.25 mm long body, 14–16 μm broad lip region, odontostyle 8–9 μm long at its ventral side, 716–918 μm long neck, pharyngeal expansion occupying 63–67% of total neck length, uterus simple and 209–242 μm long or 2.5–2.9 times the corresponding body diameter, pars refringens vaginae absent, V = 54, short (34–39 μm, c = 70–115, c’ = 0.6–0.8) and rounded tail, 59–75 μm long spicules, and three or four irregularly spaced ventromedian supplements bearing hiatus. Both species are also characterized by their nearly continuous lip region, an atypical feature in this genus. Molecular analysis of S. tropicum sp. nov. confirms that Sectonema is a natural (monophyletic) taxon, very close to Metaporcelaimus.

References

Abolafia J. & Peña-Santiago R. 2005. Nematodes of the order Rhabditida from Andalucía Oriental: Pseudacrobeles elongatus (de Man, 1880) comb. n. Nematology 7 (6): 917–926. http://dx.doi.org/10.1163/156854105776186415

Álvarez-Ortega S., Nguyen T.A.D., Abolafia J., Vu T.T.T. & Peña-Santiago R. 2015. Three new species of the genus Aporcelaimoides Heyns, 1965 from Vietnam (Nematoda, Dorylaimida, Aporcelaimidae), and an updated taxonomy of the genus. ZooKeys 516: 1–26. http://dx.doi.org/10.3897/zookeys.516.10087

Álvarez-Ortega S. & Peña-Santiago R. 2013. Taxonomy of the genus Aporcelaimellus Heyns, 1965 (Nematoda, Dorylaimida, Aporcelaimidae). Zootaxa 3669: 243–260. http://dx.doi.org/10.11646/zootaxa.3669.3.3

Álvarez-Ortega S., Subbotin S.A. & Peña-Santiago R. 2013a. Morphological and molecular characterization of Californian species of the genus Metaporcelaimus Lordello, 1965 (Dorylaimida, Aporcelaimidae), with a new concept of the genus. Nematology 15 (3): 251–278. http://dx.doi.org/10.1163/15685411-00002674

Álvarez-Ortega S., Subbotin S.A. & Peña-Santiago R. 2013b. Morphological and molecular characterization of Californian species of the genus Aporcelaimellus Heyns, 1965 (Dorylaimida: Aporcelaimidae). Nematology 15 (4): 431–439. http://dx.doi.org/10.1163/15685411-00002691

Baermann G. 1917. Eine einfache Methode zur Auffindung von Ankylostomum (Nematoden) Larven in Erdproben. Geneeskunding Tijdschrift voor Nederlandsch-Indië 57: 131–137.

Coomans A. & Loof P.A.A. 1986. Observations on the glands of the male reproductive system in dorylaims and its phylogenetic importance. Revue de Nématologie 9 (3): 261–265.

Flegg J.J.M. 1967. Extraction of Xiphinema and Longidorus species from soil by a modification of Cobb’s decanting and sieving technique. Annals of Applied Biology 60 (3): 429–437. http://dx.doi.org/10.1111/j.1744-7348.1967.tb04497.x

Holterman M., Rybarczyk K., van den Elsen S., van Megen H., Mooyman P., Peña-Santiago R., Bongers T., Bakker J. & Helder J. 2008. A ribosomal DNA-based framework for the detection and quantification of stress-sensitive nematode families in terrestrial habitats. Molecular Ecology Resources 8 (1): 23–34. http://dx.doi.org/10.1111/j.1471-8286.2007.01963.x

Huelsenbeck J.P. & Ronquist F. 2001. MRBAYES: Bayesian inference of phylogenetic trees. Bioinformatics 17 (8): 754–755. http://dx.doi.org/10.1093/bioinformatics/17.8.754

Loof P.A.A. & Coomans A. 1970. On the development and location of the oesophageal gland nuclei in the Dorylaimina. Proceedings of the IXth International Nematology Symposium (Warsaw, Poland, 1967): 79–161.

Nicholas K.B., Nicholas Jr H.B. & Deerfield II D.W. 1997. GeneDoc: analysis and visualization of genetic variation. EMBnet News 4: 1–14.

Nylander J.A.A. 2002. MrModeltest v1.0b. Department of Systematic Zoology, Uppsala University.

Peña-Santiago R., Abolafia J. & Álvarez-Ortega S. 2014. New proposal for a detailed description of the dorylaim spicule (Nematoda: Dorylaimida). Nematology 16 (9): 1091–1095. http://dx.doi.org/10.1163/15685411-00002834

Peña-Santiago R. & Álvarez-Ortega S. 2014a. Studies on the genus Sectonema Thorne, 1930 (Dorylaimida: Aporcelaimidae). Re-description of S. ventrale, the type species of the genus. Nematology 16 (9): 1097–1104. http://dx.doi.org/10.1163/15685411-00002837

Peña-Santiago R. & Álvarez-Ortega S. 2014b. Re-description of three species of the genus Sectonema Thorne, 1930 (Nematoda: Dorylaimida: Aporcelaimidae) originally studied by E. Altherr. Zootaxa 3881: 63–74. http://dx.doi.org/10.11646/zootaxa.3881.1.5

Ronquist F. & Huelsenbeck J. 2003. MrBayes 3: Bayesian phylogenetic inference under mixed models. Bioinformatics 19 (12): 1572–1574. http://dx.doi.org/10.1093/bioinformatics/btg180

Siddiqi M.R. 1964. Studies on Discolaimus spp. (Nematoda: Dorylaimidae) from India. Zeitschrift für Zoologische Systematik und Evolutionsforschung 2: 174–184. http://dx.doi.org/10.1111/j.1439-0469.1964.tb00720.x

Subbotin S.A., Sturhan D., Chizhov V.N., Vovlas N. & Baldwin J.G. 2006. Phylogenetic analysis of Tylenchida Thorne, 1949 as inferred from D2 and D3 expansion fragments of the 28S rRNA gene sequences. Nematology 8 (3): 455–474. http://dx.doi.org/10.1163/156854106778493420

Swofford D.L. 2003. PAUP*: phylogenetic analysis using parsimony (*and other methods). Version 4.0b 10. Sunderland, MA, USA, Sinauer Associates.

Tamura K., Stecher G., Peterson D., Filipski A. & Kumar S. 2013. MEGA6: Molecular Evolutionary Genetics Analysis version 6.0. Molecular Biology and Evolution 30: 2725–2729. http://dx.doi.org/10.1093/molbev/mst197

Thompson J.D., Gibson T.J., Plewniak F., Jeanmougin F. & Higgins D.G. 1997. The ClustalX windows interface: flexible strategies for multiple sequence alignment aided by quality analysis tools. Nucleic Acids Research 25 (24): 4876–4882. http://dx.doi.org/10.1093/nar/25.24.4876

Published
2016-01-15
How to Cite
Nguyen, T. A. D., Abolafia, J., Bonkowski, M., Peña-Santiago, R., & Álvarez-Ortega, S. (2016). Two atypical new species of the genus Sectonema Thorne, 1930 (Nematoda, Dorylaimida, Aporcelaimidae) from Vietnam. European Journal of Taxonomy, (171). https://doi.org/10.5852/ejt.2016.171