Vladimir G. Gagarin

Four new species of free-living marine nematodes of the family Comesomatidae (Nematoda: Araeolaimida) from coast of Vietnam.

Specimens of four new nematode species of the family Comesomatidae were isolated from the sediments of littoral zone of South China Sea at the coast of Vietnam and described and illustrated. Sabatieria curvispiculata sp. n. is characterized by the long and slender tail, short cephalic setae and strongly curved spicules in males. Setosabatiera orientalis sp. n. is close to S. australis Riera, Nunez, Brito, 2006, but differs from it in the comparatively shorter and more slender tail, small-er number of amphidial fovea turns, greater number of precloacal supplements in males and shape and structure of spic-ules. Dorylaimopsis intermedia sp. n. is morphologically closest to D. mediterranea Grimaldi-de Zio, 1968 and D. magellanense Chen, Vincx, 1968, but differs from both species in the longer outer labial setae and absence of precloacal supplements in males. D. brevispiculata sp. n. is similar to D. turneri Zhang, 1992 and D. coomansi Muthumbi, Soetaert, Vincx, 1977, but differs from both species in the shape of outer labial sensillae and absence of precloacal supplements in males. A pictorial key for determination of valid species in the genus Setosabatieria Rouville, 1903 is given.

Free-living nematodes of the Tra Ly River in the Red River mouth, Vietnam

In samples of the Tra Ly River in the Red River mouth (Northern Vietnam), 46 species of free-living nematodes have been found, five of which are new to science. The species dominant in abundance were Ptycholaimellus adocius Dashchenko et Belogurov, 1984; Dichrocuadora affinis Gagarin et Nguyen Vu Thanh, 2011; and Tripyloides minor sp.n. The species composition of nematodes is listed and the new species Tripyloides minor sp. n. is described and illustrated. The nematode described and illustrated by Riemann (1970) from watercourses of Colombia as Tripyloides amazonicus (Gerlach, 1957) is recognized as a valid species (Tripyloides riemanni nom.n).

Two new species of free-living nematodes (Nematoda and Chromadorea) from mangrove thicket in Vietnam

Illustrated descriptions of two new species of free-living nematodes found in the dense mangrove thicket in river estuaries of Vietnam are given. Metachromadora (Metachromadoroides) orientalis sp. n. is morphologically similar to M. (M.) zaixsi Pastor de Ward, 2004, but it has longer and thicker tail, a more anterior position of the vulva, a different shape of amphidial foveae, a larger pharyngeal basal bulb, and longer spicules, and males have differently armed tails. Morphologically, Terschellingia lutosa sp. n. is closer to T. elegans Gagarin, Nguyen Vu Thanh, 2003 and T. supplementata Tchesunov, 1978 and differs from both of them by a less slender tail, a wider body at the area of head setae, and longer spicules. An identification key to the valid species of the genus Metachromadora (Metachromadoroides) is given.

Three new species of nematodes (Nematoda: Enoplida) from coastal waters of Vietnam

Three new species of free-living nematodes of the order Enoplida from coastal shallow waters of northern Vietnam are described and illustrated. Paramesacanthion vietnamicum sp. n. is morphologically close to P. oxycephalum (Ditlevsen, 1926), P. truncum Vitiello, 1971, and P. hirsutum Warwick, 1970; however, it differs in lacking subcephalic setae and in having articulate cephalic setae in the males. Viscosia pygmaea sp. n. is morphologically similar to V. parva Kreis, 1929 but differs in having a shorter body and a shorter and thicker tail in the females. V. pygmaea is distinguished from V. megalaima (Ditlevsen, 1928) by its shorter body, longer cephalic setae, more slender tail, and the position of the vulva. Viscosia longicaudatoides sp. n. can be distinguished from V. parva and V. timmi Gagarin, Nguyen Vu Thanh, 2007 by its thinner body, longer and more slender tail, and shorter and narrower stoma. In contrast to V. timmi, it has short spicules and lacks vesicle-like cells between the gut and the longitudinal chords.

Two species of Dorylaimids (Nematoda) from waterbodies of Vietnam

The new species Crocodorylaimus minor sp. n. is described, and Aporcella maitai (Yeates, 1967) comb. n. is redescribed. C. minor sp. n. resembles C. dadayi (Thorne et Schwanger, 1936), but differs from it in a shorter body, shorter odontostyle, absence of vulvar papillae, slenderer tail in females, and shorter spicules. Aporcelaimellus maitai Yeates, 1967 is transfered to the genus Aporcella Andrássy, 2002, taking the name Aporcella maitai (Yeates, 1967) comb. n. Aporcelaimellus heynsi Baqri et Jairajpuri, 1968 and Aporcelaimellusglandus Botha et Heyns 1991 are synonymized under Aporcella maitai (Yeates, 1967) comb. n. Identification keys to the valid species of the genera Crocodorylaimus and Aporcella are provided.

A new genus and two new species of marine free-living nematodes from the coastal waters of Southern Vietnam

A new genus and two new species of free-living marine nematodes from sediments in the coastal zone of the South China Sea (Vietnam) are described. Cyartonemoides gen. n. morphologically resembles Cyartonema Cobb, 1920, but differs from it in having a well-developed cephalic capsule. Cyartonemoides foetidus gen. n., sp. n. is the type and the only species of the genus. Campylaimus abnormis sp. n. differs from all species of the genus Campylaimus Cobb, 1920 by the shape of the amphidial fovea and shorter lateral fields.

Two New Nematode Species (Nematoda) from the Mangroves of the Yen River Delta, Vietnam

An illustrated description of two free-living nematode species, Belbolla gracilis sp. n. and Pseudolella mangrovi sp. n., which were discovered in the sediments of the mangroves in the Yen River Estuary in Vietnam, is provided. Beldolla gracilis sp. n. is similar to B. heptabulba Timm, 1961 and B. warwick Huang, Zhang, 2005 in its oesophagus morphology but it differs from these species in its longer and more slender tail, longer stoma, and longer spicules. Pseudolella mangrovi sp. n. is similar to P. capera Tchesunov, 1978 and P. parva Gagarin, Nguyen Vu Thanh, 2006 in the morphology and the shape of the amphidal fovea, but it is characterized by a shorter body and longer spicules.

Two new nematode species of the genus Daptonema Cobb, 1920 (Nematoda, Xyalidae) from mangrove forest estuary of the Red River (Vietnam)

Illustrated discriptions are given of two new marine free-living nematode species of the genus Daptonema Cobb, 1920, D. paraoxyuroides sp. n. and D. balatum sp. n., found in the estuary of the Red River in North Vietnam. D. paraoxyuroides sp. n. resembles D. oxyuroides, but differs from it in its shorter and thicker body, less slender tail, shorter cephalic setae, and shorter spicules. D. balatum sp. n. differs from all known valid species of the genus Daptonema by the special structure of the copulative apparatus of males.

Two new species of Theristus Bastian, 1865 (Nematoda: Xyalidae) from the interstitial zone of Lake Baikal, Siberia, Russia

Theristus tsalolikhini sp. n. and T. psammophilus sp. n. from the interstitial zone of Lake Baikal, Russia, are described from numerous females and males. Theristus tsalolikhini sp. n. is similar to T. ruffoi, but differs from it by the presence of elongate spermatheca, narrower labial region, shorter outer labial setae, larger amphidial fovea, more anterior position of amphidial fovea and shorter spicules and gubernaculum. Theristus psammophilus sp. n. is similar to T. athesinus, but differs from it by the presence of an elongate spermatheca, shorter outer labial setae, more anterior position of the amphidial fovea and longer spicules and gubernaculum. A pictorial key is provided for males of freshwater and groundwater species of Theristus.

A review of the genus Arctidorylaimus Mulvey & Anderson, 1979 (Nematoda: Dorylaimida) with descriptions of Arctidorylaimus gigas sp. n. and A. kurenkovi sp. n. from Russia

Arctidorylaimus gigas sp. n. and Arctidorylaimus kurenkovi sp. n. from the Kuriljskoe Lake (Kamchatka Peninsula, Russia) are described from numerous mature females and males. The diagnosis of the genus Arctidorylaimus Mulvey & Anderson, 1979 is emended. The species Arctidorylaimus fluviatilis (Altherr, 1958) comb. n. is transferred from the genus Labronema. A key is given to the species of the genus Arctidorylaimus.