Mononchidae Chitwood, 1937

Gusakov, Vladimir A. & Gagarin, Vladimir G., 2017, An annotated checklist of the main representatives of meiobenthos from inland water bodies of Central and Southern Vietnam. I. Roundworms (Nematoda), Zootaxa 4300 (1), pp. 1-43 : 28-29

Family Mononchidae Chitwood, 1937

85. * Cobbonchus Andrássy, 1958 sp.— {71} (0, 0, 0, 9; 1)

Population structure and abundance. Three juvenile specimens and one female (more than 1 x10 3 /m2).

Ecology and distribution. Representatives of this genus occur both in water and terrestrial habitats ( Zullini & Peneva 2006; Andrássy 2009b). Not previously recorded in Vietnam.

Remarks. In terms of size and general body shape, the single female from Vietnam resembles the widespread amphibiont species C. palustris (Cobb, 1917) Andrássy, 1958 ( Zullini & Peneva 2006; Ahmad & Jairajpuri 2010) but differs in some morphometric parameters. It deviates to a greater extent from other species of Cobbonchus .

86. Mononchus aquaticus Coetzee, 1968 — {3, 16, 28, 29, 32} (5, 11, 8, 0; 7)

Population structure and abundance. Very numerous at site 3—about 100 juvenile individuals, 127 females and 9 gravid females (86 x10 3 /m2). In the other two quantitative samples—1 to 7 juvenile specimens and females (up to 3 x10 3 /m2) and in qualitative samples 28 and 29—1–13 females.

Ecology and distribution. Hydrobiont. Aquatic biotopes are the main habitats but was registered in wet soil as well. One of the most widespread species of the genus. Was found on the territories of many countries in Europe, Asia (including Vietnam), Africa, in some countries of North, Central and South America, in Caribbean basin ( Saint Lucia), on the islands of Mauritius and Sakhalin ( Zullini & Peneva 2006; Nguyen 2007; Andrássy 2009b; Ahmad & Jairajpuri 2010).

87. Mononchus truncatus Bastian, 1865 — {63–66, 69, 70} (0, 0, 0, 55; 8)

Population structure and abundance. 1 to 3 juvenile individuals and females (including gravid) at each site (up to 1 x10 3 /m2).

Ecology and distribution. Likely an amphibiont. Prefers water bodies but occurs more often than the previously described species in semi-aquatic biotopes and wet soil. Cosmopolitan. Recorded many times in Vietnam ( Zullini & Peneva 2006; Nguyen 2007; Andrássy 2009b).

88. Mononchus Bastian, 1865 sp.— {57} (0, 0, 8, 0; 1)

Population structure and abundance. One juvenile of an unidentified species.