• S.E. Spiridonov. Four new species and new subspecies of the genus Homungella Timm, 1966 (Rhabditida: Drilonematoidea) from Laos and Vietnam, 1-13.
• D.J. Hunt. A synopsis of the Hethidae (Nematoda: Rhigonematida) with descriptions of five new species of Heth Cobb, 1898 from diplopods from Papua New Guinea, 15-31.
• D.A. Voronov and L.P. Nezlin. Neurons containing catecholamine in juveniles of eight species of free-living marine nematodes, 33-40.
• M.B. Popova, G.L. Zelenskii and S.A. Subbotin. An assessment of resistance in cultivars of Oryza sativa L. to Aphlenchoides besseyi Christie, 1942, 41-44.
• G.W. Yeates, B. Boag and R.W. Small. Species diversity and biogeography of Mononchoidea (Nematoda), 45-54.
• S.E. Spiridonov and P. van Luc. Cephalobium montanum sp.n. (Rhabditida: Cephalobiidae) from the hind gut of the cricket Teleogryllus derelictus, Gorochov collected in Vietnam, 55-59.
• S.A. Subbotin, D. Sturhan and A.Y. Ryss. Occurrence of nematode-parasitic bacteria of the genus Pasteuria in the former USSR, 61-64.
• E.S. Ivanova. Parasitic nematodes of earthworms: II. Two new species of Dicelis Dujardin, 1845 from Siberia and a key to the species of the genus, 65-74.
• In Memoriam, 75-76.
• Book Reviews, 77-78.

Spiridonov, S.E.

Four new species and new subspecies of the genus Homungella Timm, 1966 (Rhabditida: Drilonematoidea) from Laos and Vietnam

Summary:
Four new Homungella species are described from the coelomic cavity of Indochina earthworms of the genus Pheretima. Homungella kishonense sp. n. is characterized by a thin-walled hook, amphidial opening connected to head armature and smooth egg-shell; H. laotense sp. n. is distinguished by a slight development of the head armature, which does not engulf the amphidial opening, and slightly mammillated egg-shells; H. mekongianum sp. n. has a large cephalic hook, strongly armoured head end and the egg-shell is densely covered with rod-like projections; H. seponense sp. n. is characterised by the amphidial opening incorporated in the thick cuticular belt of head armature, curved thick-walled hook and rod-like projections on the egg-shell. Specimens of H. ornithorhynchum Ivanova & Spiridonov, 1987 (nom. emend.), previously described from Vietnam were found in Laos. These are described as representatives of a new subspecies for this species. A dichotomous key for identification of Homungella is presented.

Key words: new species, Homungella, Homungellidae, Drilonematoidea, earthworm hosts, South-East Asia, identification key, sub-species.

Hunt, D.J.

A synopsis of the Hethidae (Nematoda: Rhigonematida) with descriptions of five new species of Heth Cobb, 1898 from diplopods from Papua New Guinea

Summary:
Five new species of the genus Heth Cobb, 1898: H. costata sp. n., H. ortonwilliamsi sp. n., H. xaniophora sp. n., H. sutherlandi sp. n. and H. zeuglocantha sp. n. are described from two species of diplopod from Papua New Guinea. The new species can be distinguished mainly on the basis of their cuticular ornamentation and disposition of lateral spines of the female cervical region and presence or absence of cuticular somatic ridges or lateral alae. Scanning electron micrographs of the cephalic and cervical regions of three of the species are presented. A synopsis of the family Hethidae is provided together with a list of species and a diagnosis of the genus Heth. Also, a bibliography is appended.

Key words: Rhigonematida, Hethidae, Heth, generic diagnosis, new species, diplopod hosts, scanning electron microscopy, Papua New Guinea.

Voronov, D.A. and Nezlin, L.P.

Neurons containing catecholamine in juveniles of eight species of free-living marine nematodes

Summary:
The occurrence, number and distribution of neurons containing catecholamine (CC) was determined using histofluorescent techniques with first stage juveniles of eight species belonging to the subclass Adenophorea. This feature was demonstrated to be species-specific. In all species, two pairs of cephalic CC neurons innervating four cephalic sensillae were observed. The number and localization of the remaining CC neurons (somatic neurons) vary between different species and correspond to the somatic sensillae. The pattern of CC neurons in the juveniles of marine Adenophorea is similar to that in juveniles and adults of Secernentea but not to that of adult Adenophorea.

Key words: catecholamines, neurons, first stage juveniles, Enoplus brevis, Enoplus communis, Pontonema vulgare, Odoncholaimus lepidus, Chromodoropsis vivipara, Paracanthonhus macrodon, Theristus setosus, Sphaerolaimus balticus.

Popova, M.B., Zelenskii, G.L. and Subbotin, S.A.

An assessment of resistance in cultivars of Oryza sativa L. to Aphelenchoides besseyi Christie, 1942

Summary:
The rice leaf nematode Aphelenchoides besseyi is widely distributed and causes substantial reductions in crop yields in the rice-growing regions of Russia. Methods for controlling this nematode include the use of resistant cultivars. An assessment of 1003 rice cultivars from different ecologo-geographic origin for their resistance to A. besseyi was made in the glasshouse. Three cultivars were immune, 10 highly resistant, 164 moderately resistant and 826 susceptible and highly susceptible to A. besseyi. High and moderately resistant cultivars reduced nematode population levels but some development was observed with nematodes remaining at the end of vegetative period. The potential for using tolerant cultivars to control A. besseyi is discussed.

Key words: Aphelenchoides besseyi, resistance, rice, Oryza sativa, cultivars, nematodes.

Yeates, G.W. , Boag, B. and Small, R.W.

Species diversity and biogeography of Mononchoidea (Nematoda)

Summary:
The mononchid faunae of 12 distinct geographical areas were compiled from the literature and species distribution analysed with regard to diversity, extent of area and distance from the equator. Results suggest while some species have a cosmopolitan distribution the majority are restricted to one area. At the generic level 11 out of 28 were recorded from only one area. A study of patterns of geographical distribution indicated that Anatonchinae were more prevalent in the Northern Hemisphere, Cobbonchus in the Southern Hemisphere aud Mononchinae did not occur in either New Caledonia or New Zealand. No association was found between number of species and the size of the area. It is suggested that the diversity of species probably reflects habitat diversity. A trend for an increased diversity towards the equator was found.

Key words: biogeography, distribution, diversity, latitudinal gradients, Mononchoidea, nematodes.

Spiridonov, S.E. and Van Luc, P.

Cephalobium montanum sp. n (Rhabditida: Cephalobiidae) from the hind gut of the cricket Teleogryllus derellctus Gorochov collected in Vietnam

Summary:
Cephalobium montanum sp. n. is described from the hind gut of the large tropical cricket Teleogryllus derelictus Gorochov collected in Quang Tri province of Vietnam. This new species resembles the type species C. microbivorum in the size of egg-shells, but differs in the shape and size of spicules and gubernaculum. The shape of spicules in C. montanum sp. n. and C. microvatum Rao & Rao, 1965 are similar but these are longer in the former species. Also, the structure of the stoma and oesophagus are very similar in these species but the egg-shells are much smaller in the latter.

Key words: Cephalobium montanum sp. n., Rhabditida, intestinal habitat, cricket host.

Subbotin, S.A., Sturhan, D. and Ryss, A. Yu.

Occurrence of nematode-parasitic bacteria of the genus Pasteuria in the former USSR

Summary:
Examination of nematodes mounted on microscope slides and additional specimens collected from several countries of the former USSR revealed the presence of nematode-parasitic bacteria of the genus Pasteuria. The bacteria were associated with soil and aquatic nematodes originating from many different biotopes. Pasteuria spores were found attached to the cuticle and/or internally in a total of 31 nematode species (24 identified species) belonging 22 genera, 14 families and 6 orders.

Key words: nematodes, parasites, bacteria, Pasteuria, hosts, distribution, USSR.

Ivanova, E.S.

Parasitic nematodes of earthworms: II. Two new species of Dicelis Dujardin, 1845 from Siberia and a key to the species of the genus.

Summary:
Two new species of Dicelis are described from earthworms collected in Western and North-Eastern Siberia. D. sibirica sp. n. is similar to D. nira, but can be distinguished by the shape of the spicular apparatus, egg shell ornamentation and morphometric differences. D. rubidi sp. n. is similar to D. nira and D. sibirica sp. n. in the shape of the male tail and to D. rossica and D. hyrcanus in the shape of the female tail. D. rubidi sp. n. differs from D. nira by having more numerous genital papillae; from D. sibirica sp. n. by the shape of the amphids and different structure of the egg shell; from D. rossica by egg shell ornamentation and smaller suckers and amphids and from D. hyrcanus by the different position and size of suckers and more numerous genital papillae. The composition of the genus Dicelis is reviewed and only 11 species are considered valid. A dichotomous key for the identification of
Dicelis species is provided.

Key words: Drilonematidae, morphology, Dicelis, D. sibirica sp. n., D. rubidi sp. n., earthworm host, identification key, taxonomic revision, species list.