title: Sectonema caobangense sp. n. from Vietnam (Nematoda, Dorylaimida, Aporcelaimidae).
abstract: Sectonema caobangense sp. n. from evergreen forest soil in Vietnam is described, including scanning electron micrograph (SEM) observations and D2-D3 LSU rDNA analysis. The new species is characterized by its 3.12 to 5.80 mm long body, lip region offset by deep constriction and 21 to 23 μm broad, mural tooth 13 to 14 μm long at its ventral side, 940 to 1,112 μm long neck, pharyngeal expansion occupying 61% to 69% of total neck length, uterus a long simple tube-like structure 292 to 363 μm long or 2.7 to 2.9 times the corresponding body diameter, pars refringens vaginae well developed, V = 48 to 56, short (36-51 μm, c = 77-132, c' = 0.5-0.8) and rounded tail, 87 to 99 μm long spicules, and four or five irregularly spaced ventromedian supplements bearing hiatus. Sectonema caobangense sp. n. differs from the typical pattern of Sectonema in the nature of the stomatal protrusible structure, bearing a mural tooth attached to the ventral side of the stoma. Molecular data obtained and the derived evolutionary trees support a close phylogenetic relationship with other Sectonema species.
authors.affiliation: Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Campus 'Las Lagunillas' s/n, Edificio B3, 23071- Jaén, Spain.
authors.forename: Sergio
authors.initials: S
authors.lastname: Álvarez-Ortega
authors.affiliation: Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Campus 'Las Lagunillas' s/n, Edificio B3, 23071- Jaén, Spain.; Department of Terrestrial Ecology, Zoological Institute, University of Cologne, Zülpicher Straße 47b, D-50674 Cologne, Germany.; Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Vietnam.
authors.forename: Thi Anh
authors.initials: TA
authors.lastname: Duong Nguyen
authors.affiliation: Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Campus 'Las Lagunillas' s/n, Edificio B3, 23071- Jaén, Spain.
authors.forename: Joaquín
authors.initials: J
authors.lastname: Abolafia
authors.affiliation: Department of Terrestrial Ecology, Zoological Institute, University of Cologne, Zülpicher Straße 47b, D-50674 Cologne, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Bonkowski
authors.affiliation: Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Campus 'Las Lagunillas' s/n, Edificio B3, 23071- Jaén, Spain.
authors.forename: Reyes
authors.initials: R
authors.lastname: Peña-Santiago
keywords: Bayesian inference; LSU ribosomal DNA; SEM; description; maximum likelihood; morphology; morphometrics; taxonomy