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Volume 7, Part 2 (1999)


Kiontke, K.

The Rhabditis (Rhabditella) octopleura species complex and descriptions of three new species

Summary:
Rhabditis (Rhabditella) arizonae sp. n. from compost, R. (R.) cacti sp. n. from rotting saguaro cactus tissue, and R. (R.) typhae sp. n. from insect tunnels in Typha latifolia are described. Crossmating experiments revealed that the three species are prezygotically isolated from each other. They form, together with R. octopleura and R. leptura, a complex of species which are ecologically separated but morphologically similar. An identification key for Rhabditella species and a diagnostic table for the species from the "R. octopleura" complex are presented. Rhabdibicauda jagdishi is synonymized with R. axei, and the synonymization of R. leptura with R. octopleura is rescinded. Within the species of the subgenus Rhabditella the shape and size of the stoma is variable. Notes on stoma dimorphism are presented. The systematic position of Rhabditella as the sister group of Rhabditis (Cephaloboides) + Rhabditis (Diploscapteroides) is confirmed.

Key words: dimorphism, identification key, Rhabditis, Rhabditella, saguaro cactus, SEM, sibling species, synonymization, Typha.

 


Yeow, H.-W., Finney-Crawley, J.R., Lawlor, J. and King, I.W.

Free-living nematode assemblages downstream from a pulp and paper mill in Humber Arm, Newfoundland

Summary:
The composition of benthic nematode populations was studied at two depths at each of three sites 0.8, 2.0 and 4.0 km downstream from a pulp and paper mill situated at the head of the Humber Arm, Corner Brook. Nematodes from 29 genera were identified. Extremely high relative abundance of Monhystera was observed at both depths at the site (DeGrouchy Point) closest to the mill. At the other two locations (Church Cove and Birchy Point), population compositions were found to differ both between each location and between depths. Population diversity, evenness and richness values decreased with increasing proximity to the mill. The Maturity Indices at Church Cove and Birchy Point were similar, and both were higher than those at DeGrouchy Point. Indications were that moderate amounts of purely organic detritus associated with sewage outfall had a somewhat positive impact on the population measures such as diversity and richness, while the opposite was true for the mill effluent which contained chemical pollutants in addition to organic waste.

Key words: pulp and paper mill, effluent, sewage, depth, population diversity, evenness, richness, Maturity Index.


Voronov, D.A.

The embryonic development of Pontonema vulgare (Enoplida: Oncholaimidae) with a discussion of nematode phylogeny

Summary:
The cell lineage in embryonic development of the marine nematode Pontonema vulgare (Enoplida, Oncholaimidae) was studied using cell labelling by fluorescent dye. After labelling at the two-cell stage, the border between labelled and unlabelled cells is different in different Lima bean and comma stage embryos crossing them in left-right, anterior-posterior, or intermediate direction. Therefore, in contrast to the majority of nematodes, P. vulgare has a variable type of development. However, as in other nematodes all the endoderm is derived from a single blastomere of the eight-cell stage, and the gastrulation process in P. vulgare is comparable to that in other nematodes. In general, the development of P. vulgare is similar to that in the previously studied Enoplus brevis (Enoplida, Enoplidae). Using the type of development, all nematodes can be placed in one of three major groups: 1, with variable cleavage (order Enoplida); 2, with invariant cleavage and anterior localization of endoderm material at the two-cell stage (remaining Enoplea); 3, with invariant cleavage and posterior localization of endoderm material at the two-cell stage (Chromadorea and Secernentea). This classification is independently supported by molecular phylogeny studies and by several anatomical characters.

Key  words: nematode, embrionic development, cell lineage, cleavage, gastrulation, phylogeny.


Gagarin, V.G.

Peritobrilus vipriensis sp. n. (Enoplida: Tobrilidae) and Allodorylaimus rarus sp. n. (Dorylaimida: Qudsianematidae) from Northern Siberia

Summary:
Peritobrilus vipriensis sp. n. and Allodorylaimus rarus sp. n. are described from fresh-water bodies of the Lena estuary from the Laptev Sea. Peritobrilus vipriensis sp. n. is similar to P. heptapapillatus and P. peregrinator, but differed from the first species by having a different stoma construction, shorter tail, and longer spicules, and from the second species by having shorter cephalic setae, a longer tail, fewer supplementary organs and longer spicules. Allodorylaimus rarus sp. n. resembles A. bokori from which it differs by having a shorter spear and longer spicules.

Key words: freshwater bodies, free-living nematodes, Peritobrilus vipriensis sp. n., Allodorylaimus rarus sp. n., Siberia.

Ferris, V.R., Subbotin, S.A. Ireholm, A., Spiegel, Y., Faghihi, J. and Ferris, J.M.

Ribosomal DNA sequence analysis of Heterodera filipjevi and H. latipons isolates from Russia and comparisons with other nematode isolates

Summary:
Ribosomal DNA (ITS rDNA) sequence data for two geographically separated isolates of Heterodera filipjevi from Russia were identical, and were 99.7% similar to rDNA sequence from Swedish East and West Gotland strains of H. avenae. These data are consistent with the view that the 'Gotland strain' of H. avenae and H. filipjevi are conspecific. The ITS rDNA sequence from an isolate of H. latipons from the Rostov region of Russia was 98.1% similar to the ITS rDNA sequence of an isolate from Gilat, Israel, the type locality of H. latipons, which suggests the possibility that the two morphologically similar, but geographically separated, isolates might be sibling species.

Key words: Heterodera avenae, H. filipjevi, H. latipons, ribosomal DNA, rDNA sequence, phylogenetic analysis, Russia, Israel, Sweden.

 

Zheng, L.J.and Brown, D.J.F.

Xiphinema insigne Loos, 1949 and X. hunaniense Wang & Wu, 1992 from Hangzhou, China, and synonymization of X. savaryi Lamberti, Troccoli & Agostinelli, 1997 with X. insigne, and X. siamense Lamberti, Troccoli & Agostinelli,1997 with X. radicicola Goodey, 1936 (Nematoda: Longidoridae)

Summary:
Descriptions and illustrations are given for five populations of X. insigne from five different hosts and for a population of X. hunaniense from Camellia japonica, each occurring in the Hangzhou region, China. Both species have four juvenile development stages (JDS) and morphometrics of the second, third and fourth JDS are presented. The study, which includes a morphological comparison of several long-tailed Xiphinema species, confirms a proposal to reject the synonymization of X. hunaniense with X. radicicola. Also, that X. savaryi be considered a junior synonym of X. insigne and that X. siamense be considered a junior synonym of X. radiciciola.

Key words: junior synonyms, morphology, taxonomy, valid species. 

 

Elbadri, G.A.A., Geraert, E. and Moens, M.

Morphological differences among Radopholus similis (Cobb, 1893) Thorne, 1949 populations

Summary:
Descriptions and illustrations are given for five populations of X. insigne from five different hosts and for a population of X. hunaniense from Camellia japonica, each occurring in the Hangzhou region, China. Both species have four juvenile development stages (JDS) and morphometrics of the second, third and fourth JDS are presented. The study, which includes a morphological comparison of several long-tailed Xiphinema species, confirms a proposal to reject the synonymization of X. hunaniense with X. radicicola. Also, that X. savaryi be considered a junior synonym of X. insigne and that X. siamense be considered a junior synonym of X. radiciciola.

Key words: banana, black pepper, morphology, morphometrics, ornamentals, Radopholus similis, SEM, taxonomy. 

 

Grammatikaki, G., Vovlas, N. Kaltsikes, P.J. and Sonnino, A.

Response of potato gametoclones to infection of four root-knot nematode (Meloidogyne) species

Summary:
Forty-six potato gametoclones were obtained from three anther donor genotypes (H2258, AH 78/8015.37a and F115). The response of the anther - derived clones to infection of four root-knot nematode species (Meloidogyne incognita, M. javanica, M. arenaria and M. hapla) was evaluated in a glasshouse experiment. Nematode reproduction rates on different gametoclones was estimated by evaluating egg-masses and galling index for each nematode species. In resistant gametoclones, examined microscopically 21 and 60 days after inoculation, infection sites were absent, or when present exhibited necrotic tissues and giant cells, but were undersised resulting in suppression of nematode development. In the roots of susceptible gametoclones, the nematode completed its development and the egg-laying females fed on well developed giant cells that had with numerous hypertrophied nuclei and granulated cytoplasm. Thirteen anther- derived lines (28%) were resistant to at least one species of root-knot nematode. The resistance to root-knot nematodes was retained through the anther culture process, even when the ploidy level was reduced, indicating that the resistance mechanism is not influenced by the number of alleles involved. Variation for resistance among the gametoclones may be explained by the induction of de novo variability during the regeneration process.

Key  words: Solanum tuberosum, anther culture, breeding, gametoclonal variation, resistance.