Specimens examined (n=4): Four females in good condition (Figs 1, 2).

Measurements: See Table 2.

Female: Slender nematodes of medium size. Habitus very weakly curved ventrad upon fixation. Body cylindrical, tapering towards both ends, but more so towards the anterior one. Cuticle bearing fine transverse striations, about 2.0 µm thick at neck region, 2.0 µm at mid-body, and 8–10 µm at tail. Lateral chords 7–8 µm wide or occupying one-fifth of mid-body diameter. Lip region cap-like, offset from adjacent body by a constriction, twice as wide as high and less than one-fifth (16–18%) of body diameter at neck base; lips separate, their inner portion forming liplets; papillae low, hardly protruding. Amphid fovea cup-shaped, its opening at level of the cephalic constriction and occupying 6 µm or ca three-fourths of lip region diameter. Odontostyle fusiform, as long as lip region diameter, with aperture occupying one-third of its total length. Guiding ring simple but distinct, located at 9 µm or 1.1 times the lip region diameter from the anterior end. Odontophore simple, rod-like. Pharynxbipartite, consisting of a slender muscular anterior section, which bears a minute (but perceptible) mucro at its beginning (observed in the four specimens examined); a deep constriction separating both sections; basal expansion nearly cylindrical, occupying 63–71% of total neck length and surrounded by a distinct spiral muscular sheath. Cardia conoid to cylindroid. Genital system mono-opisthodelphic, with the anterior branch reduced to an uterine sac ca twice the body diameter long whereas the posterior one is well developed: reflexed ovary does not reach the oviduct-uterus junction, oocytes first in two rows and then apparently in a single row; oviduct joining the ovary sub-terminally and consisting of a slender portion with prismatic cells and a moderately developed pars dilatata with distinct lumen; conspicuous sphincter between oviduct and uterus; uterus long, tripartite, consisting of a proximal wider region, narrower and longer intermediate section and a nearly sphaerical distal part; vagina 20–23 µm long, extending inwards ca one-half of body diameter, with pars proximalis surrounded by a very perceptible sphincter, pars refringens totally absent and pars distalis well developed; vulva a transverse slit. Prerectum long, 4.7–5.2 anal body widths long. Rectum shorter, 0.8–0.9 times anal body width. Tail short and rounded.

Male: Not found.

Axonchium thoubalicum Dhanachand and Jairajpuri 1981 was collected in Cuc Phuong National Park, in soil around roots of Parashorea chinensis in karst forest.

This species is known to occur onlyin India, from where it was originally described on the basis of three females and one male, and later reported by Gambhir and Dhanachand (1990), who provided measurements of two females and two males. The Vietnamese material herein examined perfectly fits the general morphology of the type material (females) (unfortunately, male was not collected in Vietnam), especially concerning the genital system. Moreover, the morphometrics of the two Indian populations and the Vietnamese one largely overlap in spite of the few number of available specimens in the three cases. The ranges of several ratios and measurements, however, are significantly widened, for instance c = 50–70 vs 53–55 in type material, V = 47–57 vs 52–54, etc. Thus, no reasonable uncertainty persists on the identity of this material.

This is the first record of this genus and this species in Vietnam, which might display a Oriental biogeographical range.

Specimens examined (n=4): One female and three males in good condition (Fig. 3).

Mesurements: See Table 2.

Adult: Slender to very slender nematodes of small size. Habitus upon fixation nearly straight in female and slightly curved ventrad in males, especially in posterior body region. Body cylindrical, tapering towards both ends, but more so towards the anterior extremity. Cuticle thin, bearing fine transverse striations throughout the body. Lateral chords 4 µm wide, occupying ca one-fifth (20%) of mid-body diameter. Lip region continuous, tapering, somewhat truncate, 1.7 times as wide as high and ca one-fourth (25%) of body diameter at neck base; labial framework weakly sclerotized; lips amalgamated, with low papillae. Amphid fovea difficult to observe in the specimens examined. Odontostyle very short and narrow, but having perceptible lumen and aperture. Guiding ring simple. Pharynx consisting of a slender and weakly muscular anterior region which enlarges rather abruptly, pharyngeal expansion nearly cylindrical, occupying about one-half of total neck length and surrounded by a weak but well distinguishable spiral muscular sheath. Cardia rounded conoid, enveloped by the intestinal wall.

Female: Genital system mono-opisthodelphic. Anterior branch rudimentary, reduced to a uterine sac up to 1.5 times the corresponding body diameter long. Posterior branch well developed, but the detailed composition of its tract indistinguishable in the only one specimen examined. Tail rounded, slightly clavate, with the outer cuticle layer visibly thickened and showing radial striation.

Male: Genital system diorchic, with opposite testes. In addition to the ad-cloacal pair, situated at 5 µm from cloacal aperture, there are two ventromedian supplements, the posteriormost of which is located out of the range of the spicules, at 45 µm from the ad-cloacal pair. Spicules dorylaimoid, slightly curved ventral, 6.3 times as long as wide and 1.2 times as long as anal body diameter. Lateral guiding pieces difficult to observe. Tail short and rounded, visibly concaveventrally, the outer cuticle layer less expanded than in the female. Caudal pores, if present, obscure.

Belondira murtazai Siddiqi 1968 was collected in Cuc Phuong National Park, in soil around roots of Parashorea chinensis in karst forest.

Above description fits very well the original one of this species by Siddiqi (1968) and the revised one by Ferris et al. (1983), the latter based on the study of type material. A few minor differences, however, may be noted in the morphometrics of Indian and Vietnamese populations, but their ranges widely overlap, for instance slightly smaller general size (L = 0.77–0.94 vs 0.85–1.06 mm in type material as described by Siddiqi) and somewhat longer odontostyle (3–5 vs 3–4 µm). A major tentative difference between both populations is the length of the prevulval uterine sac (up to 1.5 vs 2.3–3.0 times the body diameter); nevertheless, the morphometrics given by Siddiqi certainly covers only a few out of the 12 female paratypes as Ferris et al., who examined two female paratypes loaned by Siddiqi, stated (p. 26) that the “anterior uterine branch is 1.7–2.0 body widths long”, and their Fig. 11E shows that this structure is hardly more than 1.5 times the body diameter. Ferris et al. (op. cit.) regarded Belondira rafiqi Suryawanshi, 1972, also recorded in India, as a junior synonym of Belondira murtazai, a decision that seems to be well supported and is herein followed.

This is the first record of this genus and this species in Vietnam, which might display a Oriental biogeographical range.

Specimens examined (n=21): Twenty females and one male in good condition (Figs 4, 5).

Mesurements: See Table 2.

Adult: Very slender nematodes of medium size. Habitus slightly curved ventrad after fixation. Body cylindrical, gradually tapering towards both extremities, but more so towards the posterior end. Cuticle thin, with fine transverse striations. Lateral chords 9–12 µm wide, occupying ca one-third of mid-body diameter. Lip region continuous, somewhat truncate, 1.7–2.0 times as wide as high and ca one-fifth (20%) of body diameter at neck base; labial framework well developed, having distinct labial and post-labial sclerotizations; lips amalgamated, with low papillae. Amphid fovea cup-shaped. Cheilostom a truncate cone, lacking any differentiation. Odontostyle rather strong, 1.2–1.4 times the lip region width long, with distinct lumen and aperture, which occupies ca one-fourth of its length. Guiding ring simple, located at 7 µm or one lip region diameter from the anterior end. Odontophore rod-like, 1.3 times the odontostyle length. Pharynx consisting of a slender part that enlarges gradually, and the basal expansion nearly cylindrical, occupying 50–56% of total neck length and surrounded by a distinct spiral muscular sheath. Cardia rounded conoid, as long as wide.

Female: Genital system mono-opisthodelphic. Anterior branch nearly lacking or reduced to a very short, vestigial sac. Posterior branch well developed: ovary 72–90 µm long, reaching and occasionally surpassing the oviduct-uterus junction, with oocytes first in several rows and then apparently in one row; oviduct joining the ovary subterminally and consisting of a slender portion with prismatic cells and moderately developed pars dilatata with distinct lumen; a marked sphincter separates oviduct and uterus; uterus 60–70 µm long or 2.0–2.5 times the corresponding body diameter. Vagina 13–16 µm long or extending inwards ca one-half of body diameter: pars proximalis as long as wide, with somewhat sigmoid walls and enveloped by weak circular musculature; pars refringens lacking; pars distalis well developed. Vulva a pre-equatorial, transverse slit. Prerectum 6.3–6.5 anal body widths long. Rectum as long as one anal body width. Tail elongate, made of two sections of about equal length: the anterior onewider, and tapering gradually the posterior narrower and cylindrical, visibly clavate at the end; hyaline portion one-third to two-fifths of tail length.

Male: Genital system diorchic, with opposite testes. In addition to the ad-cloacal pair, situated at 9 µm from the cloacal aperture, one ventromedian supplement within the range of spicules, located at 15 µm from ad-cloacal pair. Spicules dorylaimoid, slightly curved ventrad and relatively slender, 7 times as long as wide and 2 times as long as anal body diameter. Lateral guiding pieces not well seen. Tail elongate, made of two sections of about equal length:anterior one wider and tapering gradually at both sides, posterior narrower and cylindrical, visibly clavate at the end; hyaline portion one-third to two-fifths of tail length.

Oxybelondira paraperplexa was collected in Cuc Phuong National Park and Huu Lien Nature Reserve in North Vietnam, and Phong Nha – Ke Bang National Park in central Vietnam, collected in soil samples from karst forests.

This is the first record of Oxybelondira paraperplexa after its original description from Manipur, India by Ahmad and Jairajpuri (1979), the the male is described for the first time. The Vietnamese females are identical to the type material, but new morphological data are herein provided and the ranges of the morphometrics appreciably widened.