An annotated checklist of the main representatives of meiobenthos from inland water bodies of Central and Southern Vietnam. I. Roundworms (Nematoda) Author Gusakov, Vladimir A. Author Gagarin, Vladimir G. text Zootaxa 2017 4300 1 1 43 journal article 32584 10.11646/zootaxa.4300.1.1 7eb2410e-8578-432a-88f8-bc129d0a5b08 1175-5326 837117 5FA0C659-9C52-4ABB-9CB6-1FB5CDDDF9F8 Family Aphanolaimidae Chitwood, 1936 114. Aphanolaiminae Chitwood, 1936 gen. sp.— {54} (0, 4, 0, 0; 1 ) Population structure and abundance. Single juvenile individual. 115. Paraphanolaimus asiaticus Gagarin, Nguyen & Nguyen, 2003 — {41} (0, 4, 0, 0; 1 ) Population structure and abundance. Single male. Ecology and distribution. Likely an amphibiont. Prefers aquatic biotopes but may be found in wet soil along brooks and ditches. First found in two water bodies of northern Vietnam ; later collected in many other provinces of the country. Not yet reported outside Vietnam (Gagarin et al. 2003; Nguyen 2007 ; Gagarin & Nguyen 2008b ). 116. Paraphanolaimus Micoletzky, 1922 spp.— {29, 40, 68} (0, 7, 0, 9; 4 ) Population structure and abundance. In qualitative sample 29—two juvenile specimens and five gravid females containing juveniles, at the other sites—single juvenile individuals. Ecology and distribution. Species of the genus Paraphanolaimus occur both in bottom sediments of water bodies and in wet soil ( Andrássy 2005 ; Holovachov & De Ley 2006b ). Remarks. No other representatives of this genus have been reported from Vietnam except for P. asiaticus described above. In terms of general size and body proportions, length of head setae and some other features, the females found in sample 29 are close P. asiaticus . All females contained eggs with well-developed juveniles, but have a straight vagina. Females of P. asiaticus are also ovoviviparous, but their vagina is distinctly curved anteriad (Gagarin et al. 2003). Two other species with these specific features (ovoviviparity and vagina directed anteriorly) are known in the genus: P. behningi Micoletzky, 1923 and P. embryonophorus (Alekseev & Naumova, 1977) Andrássy, 1981 . However, there is no described species in which the presence of juveniles in intrauterine eggs combined with a straight vagina occur, as seen in our specimens from Vietnam . All other species with straight vagina are oviparous ( Holovachov & Sturhan 2003 ; Holovachov & De Ley 2006b ). Thus, the specific identity of our specimens remains unresolved. Perhaps these species belong to an unknown representative of the genus, the description of which is postponed owing to strong body deformation of the available specimens (although not affecting vagina shape), until new material is obtained.