• Editorial
• V.N. Chizhov and N.N. Zakharenkova. Occurrence in Russia of Wachekitylenchus bovieni (Wachek, 1955) Slobodianiuc, 1986 (Tylenchida: Parasitylenchidae) a parasite of beetles belonging to the genus Bembidion (Carabidae), 3-6.
• A.V.Tchesunov and S.E. Spiridonov. Nematimermis enoplivora gen. n., sp. n. (Nematoda: Mermithoidea) from marine free-living nematodes Enoplus spp., 7-16.
• S.A. Subbotin. Evolution of modified food cells induced by sedentary nematodes in plant roots, 17-26.
• S.K. Khurramov and S.A. Subbotin. Xiphinema species from the Surchandarja region of Uzbekistan, 27-30.
• S.E. Spiridonov. Nematodes of the family Ungellidae Chitwood, 1950 from Laotian earthworms, 31-40.
• V.V. Kulikov. New species of the marine free-living nematodes of the genus Rhips Cobb, 1920 (Chromadorida: Chromadoridae) from the Kuril Islands waters, 41-45.
• O.I. Smolanko and O.I. Belogurov. Apodontium bellum sp.n. and Aequalodontium gemellum gen.n, sp.n. (Nematoda: Axonolaimidae) with remarks on Apodontium morphology, 47-54.
• R. Neilson, B. Boag and C.A. Hackett. Observations on the use of Taylor's power law to describe the horizontal spatial distribution of marine nematodes in an intertidal estuarine environment, 55-64.
• J.M. Halbrendt. Virus-vector Longidoridae and their associated viruses in the Americas, 65-68.
• Book Reviews, 69-71.

Chizhov, V.N. and Zakharenkova, N.N.

Occurrence in Russia of Wachekitylenchus bovieni (Wachek, 1955) Slobodianiuc, 1986 (Tylenchida: Parasitylenchidae) - a parasite of beetles belonging to the genus Bembidion (Carabidae)

Summary:
Additional information about the morphology, biology and distribution of Wachekitylenchus bovieni (Wachek, 1955) Slobodianiuc, 1986 is given. Also a degenerated male formed inside a parthenogenetic female is described.

Tchesunov, A.V. and Spiridonov, S.E.

Nematimermis enoplivora gen.n.,sp.n.(Nematoda: Mermithoidea) from marine free-living nematodes Enoplus spp.

Summary:
Nematimermis enoplivora gen.n., sp.n. is described from the pseudocoel of marine free-living nematodes Enoplus spp. Infestation of the littoral and sublittoral nematodes E. brevis and E. communis respectively from Kandalalsha Bay of the White Sea by juveniles and mature females was observed during the summer seasons of 1986-1988. Four large and two smaller stichocytes were present near the oesophageal tube of parasitic juveniles. N. enoplivora gen. n., sp. n. grows to maturity inside the host, and almost all inner tissues are strongly degenerated in females filled with juvenile-bearing eggs. N. enoplivora gen. n., sp. n. is probably an aberrant marine form of the family Tetradonematidae.

Key words: mermithids, tetradonematids, Nentatimermis gen. n., marine host.
 

Subbotin, S.A.

Evolution of modified food cells induced by sedentary nematodes in plant roots

Summary:
The development of modified food cells induced by sedentary nematodes in plant roots are discussed as an example of host-parasite coevolution. The main principles of this evolutionary process are reviewed. Analysis of structures of the modified cells suggests that evolution of these cells is connected with increases of cellular functional activity. Intensification of modified cell function is achieved through multiplication of cell protoplast, proliferation and polymerization of organelles and intensification of contact between cell wall and protoplasm. Increase of functional activity matches the evolution of modified cell development, from nonhypertrophic nurse cells and single giant cell to syncytia and more specialized coenocytes. Increased internal organisation of the modified cells is generally coincident with the level of evolutionary advancement of the nematode. The hypothesis of different levels of evolutionary development of modified cells can be used to help determine systematic and phylogenetic relationships between nematodes.

Key words: host-parasite coevolution, plant reaction, sedentary nematodes, modified food cell.

Khurramov, S.K. and Subbotin, S.A.

Xiphinema species from the Surchandarja region of Uzbekistan

Summary:
A preliminary survey of Xiphinema species was carried out in the Surchandarja region of Uzbel:istan. Three species of Xiphinema: X. brevicolle, X. index and X. pachtaicum were found in the rhizosphere of subtropical wood cultures. The latter two species were widespread in the region. Morphological characteristics, morphometrics and the distribution of the species are presented.

Key words: Xiphinema spp., distribution, morphometrics, Uzbekistan.

Spiridonov, S.E.

Nematodes of the family Ungellidae Chitwood, 1950 from Laotian earthworms.

Summary:
Four new species of Sicotiema Timm, 1966 and Synoecizema Iaotense sp. n. are described from laotian earthworms. Siconema inaeqwcrazsum sp. n. is distinguished by the thin cephalic hooks, circular suckers in both sexes and mammilate ornamentation on the egg surface. S. aequicrassum sp. n. is similar to S. itiueqwcrassum sp. n., but differs in egg-shell, oesophagus and hook measurements. Siconema Iaotense sp. n. is characterized by very large cephalic hooks. Siconema aculeatum sp. n. has very characteristic rod-like appendages on the egg surface. A unique feature of Synoectema Iaotense sp. n. is the presence of a singular cephalic hook.

Key words: Drilonematoidea, Siconema, Synoecnema, new species, earthworm hosts.

Kulikov, V.V.

New species of the marine free-living nematodes of the genus Rhips Cobb, 1920 (Chromadorida: Chromadoridae) from the Kuril Islands waters.

Summary:
Rhips orientalis sp. n. was found in the sandy sediments at a depth of 33 m, close to Shumshu Island (Northern Kuril). It is distinguished from the five known species of the genus by the larger size of its body, oesophagus and spicula measurements, structure of the anterior end cuticle and the values of the De Man indices 'b' and 'c'. A key for the identification of Rhips species is given.

Key words: new species, key, Rhips spp, marine nematodes, Chromadoridae, Kuril Islands.

Smolanko, O.I. and Belogurov, O.I.

Apodontium bellum sp.n. and Aequalodontium gemellum gen.n, sp.n. (Nematoda: Axonolaimidae) with remarks on Apodontium morphology

Summary:
Apodontiurn bellum sp. n. and Aequalodontium gemellum gen. n., sp. n. are described from coarse-sand bottom samples collected close to the East coast of Iturup Island (Kuril Archipelago). The original description of Apodontium pacificum Cobb, 1920 is discussed. Some structures mentioned by Cobb for A. pacificum are reconsidered. A new genus Aequalodontium, proposed for A. gemellum sp. n., resembles Margonema, Apodontium and Parascolaimus but differs from Margonema and Apodontium in having telamon, by the shape of the amphidial pouch and the spicula capitulum. Aequalodontium can be distinguished from Parascolaimus only by the presence of the anterior male gonad.

Key words: Apodontium bellum sp. n., Aequalodontium gemellum gen. n., sp. n., marine nematodes, Axonolaimidae, morphology.

Neilson, R., Boag, B. and Hackett, C.A.

Observations on the use of Taylor's power law to describe the horizontal spatial distribution of marine nematodes in an intertidal estuarine environment

Summary:
The horizontal spatial distribution of marine nematodes at species, genera and family level in an intertidal estuarine environment have been investigated using Taylor's power law index of aggregation B. Different transfomations were investigated for their ability to normalise the distributions. Nine of the 15 nematode species; six of the eight genera and five of the six families investigated had B values not significantly different from 2.0. For these a logarithmic transformation would stabilise the variance of the distributions prior to further statistical analysis. The remaining species, genera and families had b values which were significantly less than 2.0. For these a variance-stabilising transformation is given by z=x1-B/2. Some of the detailed information yielded at species and genera level was lost after re-analysing the data at family level.

Key words: aggregation, estuarine, marine nematodes, patchiness, spatial distribution, Taylor's power law.

Halbrendt, J.M.

Virus-vector Longidoridae and their associated viruses in the Americas

Summary:
Five Xiphinema and one Longidorus species have been identified as natural vectors of nepoviruses in the Americas. Xiphinema index is the vector of grapevine fanleaf virus (GFLV) and was the first virus vector to be identified. Evidence suggests that the X. index - GFLV association probably evolved elsewhere and was imported to the Americas with grapevines. All native Xiphinema vectors belong to the Xiphinema americanum-group of nematodes and transmit tomato ringspot, tobacco ringspot,cherry rasp leaf, or peach rosette mosaic nepoviruses. Longidorus diadecturus is also a vector of peach rosette mosaic nepovirus. The ability of X. index and L. diadecturus to transmit associated nepoviruses is clear but controversy surrounds the X. americanum-group vectors and their associated nepoviruses. The controversy stems from the reappraisal of the group in 1979 which casts doubt on the identity of some vectors. The X. americanum-group vectors are unusual in that they have only three juvenile stages and apparently lack the high degree of specificity reported for other nematode-virus associations. Several unnatural virus-vector associations have also been reported.

Key words: nematode-virus association, Xiphinema, Longidorus, America.