Description of Aporcella daklakensis sp. n. (Nematoda: Dorylaimida: Aporcelaimidae), associated with coffee plantations in Central Highland of Vietnam.

A new species of the genus Aporcella, collected in replanted coffee orchards in Central Highland of Vietnam, is described and illustrated. Aporcella daklakensis sp. n. is characterized by its 1.63-1.98 mm long body, lip region offset by weak constriction and 14-15 µm broad, odontostyle 13-15 µm long or equal to lip region diameter, neck 400-565 µm long, pharyngeal expansion 205-335 µm long and occupying 51-60% of the total neck length, female genital system diovarian with very poorly developed genital tract and transverse vulva (V = 53-59), tail conical with rounded terminus (31-39 µm, c = 43-57, c' = 1.0-1.4), visibly subdigitate and bearing cuticular irregularities at its ventral side, and male absent. The new species is compared with its closest Aporcella representatives.

Description of Crassolabium unicum sp. n. (Nematoda: Dorylaimida: Qudsianematidae) from Vietnam.

Crassolabium unicum sp. n., collected from a natural habitat in Vietnam, is described and illustrated. The new species is characterized by its 0.770.94 mm long body, three-layered cuticle, lip region offset by depression and 1213.5 µm broad, odontostyle 13.515 µm long with wide aperture occupying 3646% of its length, neck 235260 µm long, pharyngeal expansion 117131 µm long or occupying 4752% of total neck length, anterior part of intestine presenting very distinct folds, female genital system didelphic-amphidelphic, uterus simple and 2843 µm or 0.70.9 body diameters, vulva transverse (V = 4552), prerectum bearing a blind postrectal sac, caudal region short and rounded (2125 µm, c = 4561, c' = 0.60.8) with two (dorsal and ventral) lacunae between outer and intermediate cuticle layers, and male unknown. It is compared with the similar representatives of the genus.

Morphological and molecular characterization of Epidorylaimus procerus sp. n. (Dorylaimida: Qudsianematidae) from Vietnam.

Epidorylaimus procerus sp. n., collected from a natural habitat in Vietnam, is described and illustrated. It is distinguishable by its 2.16 to 2.46-mm-long body, lip region offset by depression and 15 to 17-µm broad, odontostyle 32 to 35-µm long, neck 415 to 461-µm long, pharyngeal expansion occupying 47 to 52% of the total neck length, uterus 76 to 130-µm long or 1.0 to 1.5-body diameters, vulva transverse (V = 40-43), caudal region conical elongate (157-186 µm, c =12.1-14.4, c' = 4.4-5.5) with blister-like bodies, and hyaline portion occupying one-fourth its length, and males absent. Molecular analysis shows a close relationship of the new species and E. lugdunensis, supporting monophyly of the genus Epidorylaimus.

Description of Geocenamus vietnamensis sp. n. (Nematoda: Merliniidae) from Vietnam.

A new species of the genus Geocenamus was isolated from soil and root samples from the rhizosphere of Casuarina equisetifolia (Casuarinaceae) in Quang Nam province, Vietnam. This species is characterized by a round-to-hexagonal labial disc, the presence of a labial region, which is continuous or slightly offset from the body with six sectors, lateral sectors of first labial annulus being smaller than the submedian sectors, the presence of six to seven labial annules; the absence of deirids; stylet length 24 to 28 µâ€Šm long, body length 776 to 979 µâ€Šm long; lateral field with six to eight lateral lines, without areolation at mid-body and with areolation in outer bands at the tail region and a pointed tail terminus. Geocenamus vietnamensis n. sp. most closely resembles G. boghiae in having a non-sclerotized head framework and lacking a bursa in the males. It can be clearly distinguished from all other species of the genus Geocenamus by these characteristics. The combination of morphology, morphometric features, and phylogenetic trees, based on D2-D3 of 28S and ITS rDNA sequences, showed that this new species can be clearly separated from all other sequenced species. This record is the first for Geocenamus in Vietnam.A new species of the genus Geocenamus was isolated from soil and root samples from the rhizosphere of Casuarina equisetifolia (Casuarinaceae) in Quang Nam province, Vietnam. This species is characterized by a round-to-hexagonal labial disc, the presence of a labial region, which is continuous or slightly offset from the body with six sectors, lateral sectors of first labial annulus being smaller than the submedian sectors, the presence of six to seven labial annules; the absence of deirids; stylet length 24 to 28 µâ€Šm long, body length 776 to 979 µâ€Šm long; lateral field with six to eight lateral lines, without areolation at mid-body and with areolation in outer bands at the tail region and a pointed tail terminus. Geocenamus vietnamensis n. sp. most closely resembles G. boghiae in having a non-sclerotized head framework and lacking a bursa in the males. It can be clearly distinguished from all other species of the genus Geocenamus by these characteristics. The combination of morphology, morphometric features, and phylogenetic trees, based on D2­D3 of 28S and ITS rDNA sequences, showed that this new species can be clearly separated from all other sequenced species. This record is the first for Geocenamus in Vietnam.

Two new species of the genus Metaxonchium Coomans Nair, 1975 (Nematoda, Dorylaimida, Belondiridae) from Vietnam.

Two new species of the genus Metaxonchium are described from natural habitats of Vietnam. Metaxonchium bonkowskii sp. n. is characterized by its 1.69-2.23 mm long body, lip region offset by weak constriction and 9.5-10.5 µm broad, odontostyle 11-13 µm long, neck 673-868 µm long with the pharyngeal expansion occupying 66-77% of its length, anterior genital branch reduced to a uterine sac 75-135 µm long or 4-7% of body length, posterior uterus tetrapartite and including a Z-like differentiation, V = 51-55, and female tail short and rounded (37-51 µm, c = 66-97, c' = 0.5-0.7). Metaxonchium silvaticum sp. n is characterized by its 1.28-1.43 mm long body, lip region offset by weak depression and 7.0 µm broad, odontostyle 8-9 µm long, neck 502-630 µm long with the pharyngeal expansion occupying 65-76% of its length, anterior genital branch reduced to a uterine sac 65-80 µm long or 4-6% of body length, posterior uterus tripartite, non-echinophor, V = 52-57, tail short and rounded (18-23 µm, c = 56-74, c' = 0.6-0.8) with abundant blister-like or saccate bodies, spicules 41 µm long, and seven spaced ventromedian supplements.

Morphological and Molecular Characteristics of Pratylenchus haiduongensis sp. n., a New Species of Root-Lesion Nematodes Associated with Carrot in Vietnam.

Pratylenchus haiduongensis sp. n. is described as associated with carrot (Daucus carota subsp. sativus (Hoffm.) Schübl. & G. Martens) in Hai Duong Province, Vietnam. P. haiduongensis sp. n. is characterized by the lip region with three annuli and slightly separated from the body. Stylet knobs are rounded (never indented anteriorly). The lateral field includes four incisures, bearing areolation at the pharynx region and tail region and occasionally appears in the vulval region. Sometimes the appearances of oblique broken striaes divide the lateral field into five or six incisures. The ovary is distinct with one row of oocytes. Spermatheca is oval in shape with round central cavity, without sperm or reduced in some specimens. The postvuval uterine sac is long surpassing the vulva body diameter by 2 to 2.5 times (PUS = 31 to 65 µm). High vulva position with V = 66 to 75%. The tail shape can be subhemispherical with a smooth, slightly indented, broadly smooth, or cleft terminus observed in some specimens. The matrix code of P. haiduongensis sp. n. is: A2, B1, C4, D(1,3), E1, F(5,6), G(1,2), H(1,4); I(1,2,3,4), J1, K(1,2) according to Castillo and Vovlas (2007). The LSU-D2D3 segment and the ITS-rDNA region of this species were amplified and sequenced. The morphological characters and molecular phylogenetic analyses confirmed that this is a new species of the genus Pratylenchus in Vietnam.

Re-description of Cephalobus topali Andrássy, 1970 (Rhabditida, Cephalobidae) from Vietnam, and transfer to Acrobeloides (Cobb, 1924) Thorne, 1937.

Recently, specimens of Cephalobus topali, collected from an agricultural area from northern Vietnam, are described, including SEM study. They are characterized by their its 306-347 µm long body in females, lateral field with two alae or 3-4 longitudinal incisures, lip region with three pairs of asymmetrical conoid lips, three low and rounded labial probolae separate from the corresponding pair of lips by an incisure, U-shaped primary axils without guard processes, V-shaped secondary axils without guard processes, pharyngeal corpus slightly fusiform and 2.6-3.1 times the isthmus length, spermatheca and postvulval sac poorly developed, female tail conoid (18-24 µm, c = 12.7-17.0, c' = 1.8-2.7) with rounded terminus ending in an acute or wart-shaped mucro, phasmid at 29-34% of tail length, and male unknown. SEM pictures reveal that lip region pattern significantly differs from that found in members of Cephalobus and fits that observed in Acrobeloides, so that the species is transferred to this genus. Cephalobus quadrilineatus is provisionally maintained as different from C. topali.

Two new species of the genus Aporcelinus Andrássy, 2009 (Nematoda, Dorylaimida, Aporcelaimidae) from Vietnam.

Two new species of Aporcelinus from Vietnamese natural habitats are studied, described and illustrated, including line drawings and light microscope (LM) pictures. Aporcelinus paramamillatus sp. n. is characterized by its 1.71-2.14 mm long body, lip region 21-22 µm broad, odontostyle 22-24 µm long at its ventral side, neck 451-503 µm long, uterus tripartite and 71-94 µm long, V = 53-54, tail conical with finely rounded tip, ending in a short peg-like terminus, occasionally slightly re-curved dorsad (24-34 µm, c = 50-77, c' = 0.6-0.9) and unknown male. Aporcelinus paraseychellensis sp. n. is distinguished by its 1.20-1.46 mm long body, lip region 16-18 µm broad, odontostyle 20 µm long at its ventral side, neck 354-368 µm long, uterus tripartite and 176-241 µm long, V = 52-54, tail conical with acute tip and hardly re-curved dorsad, spicules 62 µm long, and 12 regularly spaced ventromedian supplements lacking hiatus.

Three new species of the genus Aporcelaimoides Heyns, 1965 from Vietnam (Nematoda, Dorylaimida, Aporcelaimidae), with an updated taxonomy of the genus.

Three new species of Aporcelaimoides from natural habitats in Vietnam are studied, described and illustrated, including line drawings, LM and/or SEM pictures. Aporcelaimoidesbrevistylum sp. n. is characterized by its body 1.95-2.90 mm long, lip region offset by deep constriction and 17-18 µm broad, ventral side of mural odontostyle 11-14 µm long with aperture occupying 62-71% of its length, neck 663-767 µm long, pharyngeal expansion occupying 58-66% of total neck length, uterus a simple tube 85-182 µm long, pars refringens vaginae absent, V = 55-63, tail short and rounded (34-46 µm, c = 49-76, c' = 0.6-0.8), spicules 67-86 µm long, and one ventromedian supplement out the range of spicules. Aporcelaimoidesminor sp. n. is distinguished in having body 2.09-2.61 mm long, lip region offset by deep constriction and 19-20 µm broad, mural odontostyle 14-16 µm long at its ventral side with aperture occupying 73-84% of its length, neck 579-649 µm long, pharyngeal expansion occupying 57-66% of total neck length, uterus a simple tube 44-69 µm long, pars refringens vaginae well developed, V = 48-56, female tail very short, rounded conoid or truncate (14-26 µm, c = 90-146, c' = 0.3-0.6), and male unknown. Aporcelaimoidessilvaticum sp. n. is characterized by its body 2.09-2.60 mm long, lip region offset by depression and 17-18 µm broad, mural odontostyle 11-12 µm long at its ventral side with aperture occupying 60-66% of its length, neck 597-720 µm long, pharyngeal expansion occupying 58-64% of total neck length, uterus a simple tube 128-243 µm long, pars refringens vaginae well developed, V = 58-60, tail short and rounded (27-37 µm, c = 67-94, c' = 0.6-0.7), spicules 64-75 µm long, and two or three widely spaced ventromedian supplements bearing hiatus. The genus Aporcelaimoides is restored, its diagnosis emended, and three species of Sectonema, namely Sectonemaamazonicum, Sectonemahaguei and Sectonemamoderatum, transferred to it. An updated list of its species, a key to their identification and a tabular compendium with the most important morphometric features are also presented.