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Volume 10, Part 1 (2002)

Farias, P.R.S, Barbosa, J.C. Vieira, S.R., Sánchez-Vila, X. and Ferraz, L.C.C.B.

Geostatistical analysis of the spatial distribution of Rotylenchulus reniformis on cotton cultivated under crop rotation

The spatial distribution of Rotylenchulus reniformis on cotton cultivated in crop rotation with sorghum-peanut-velvetbean was studied using geostatistics. The experimental field, which had been continuously cropped with cotton during 20 years, comprised two 32 x 48 m-grids, each divided in sixty-four 4 x 6m sampling plots. For all crops, 300 cm3 of soil samples were taken at the center of each plot at crop germination (Pi) and again at harvest (Pf), from which the numbers of nematodes were determined. The results revealedthat the spatial distribution of R. reniformis was highly aggregated and with the aid of the geostatistical techniques the nematode intensities were mapped and the risk areas accurately identified. Consequently, geostatistics is here considered a useful tool for planning nematode control strategies, particularly in Precision Agriculture.

Key words: cotton, crop rotation, geostatistics, Rotylenchulus reniformis, spatial distribution.

Fürst von Lieven, A.

Functional morphology, origin and phylogenetic implications of the feeding mechanism of Tylopharynx foetida (Nematoda: Diplogastrina)

The buccal cavity of Tylopharynx foetida was examined using Nomarski optics. Video sequences of feeding worms were analysed to understand the function of stomatal structures. Comparison of mouthpart morphology and function throughout the Diplogastrina shows that the stomatal structures in Tylopharynx do not differ qualitatively from those of Mononchoides or Neodiplogaster. This study shows that Tylopharynx feeds on fungal hyphae by ripping apart the cell wall with stegostomatal teeth. The teeth are pushed out of the buccal cavity by elongation of the pharynx during each pumping cycle. This observation provides evidence for the theoretical model for pharynx function in Ascaris developed by Bennet-Clark (1976). The homologization of structures in Tylopharynx and other Diplogastrina provided a basis to reconstruct the transformations that led to the peculiarities in stoma morphology of Tylopharynx, such as subdorsal knobs and longitudinal protractor muscles.

Key words: Bennet-Clark model, buccal cavity, dung nematodes, protractor muscles.

Giannakou, I.O, Gowen, S.R. and Davies, K.G.

Aspects on the attachment of Pasteuria penetrans on root-knot nematodes

Variability in spore attachment of the bacterial parasite Pasteuria penetrans to second stage juveniles of Meloidogyne javanica and M. incognita populations originating from different locations were recorded. Culture of an isolate of Pasteuria penetrans on a Meloidogyne population did not reveal a high compatibility with the nematode population in subsequent attachment tests. However, culture of Pasteuria on a mixed Meloidogyne javanica / M. incognita population resulted in high attachment ability on both species. Serological studies revealed differences between sub-populations of Pasteuria that were created by passaging the same Pasteuria isolate with different Meloidogyne species.

Key words:  M. incognita, monoclonal antibodies, biological control, spore adhesion.

Wouts, W.M. and Sturhan, D.

The Ogma septemlineata sp. n. (Nematoda: Criconematidae) from Germany

Ogma septemlineata sp. n. is described from specimens collected from a spruce forest and river bank vegetation in southern Germany. The species is characterised by seven rows of long cuticular scales, two subventral rows, two sublateral rows on either side of the body, and one dorsal row. The dorsal row posteriorly abruptly terminates near the level of the vulva. The scales are apically divided into two or three, rarely four, appendages, except on the anteriormost body annules where they generally remain undivided. Scales of similar shape are present in O. murrayi Southern, 1914 and O. fagini Escuer & Bello, 1996, species with at least eight rows of scales that are not all divided at the tip. Ogma septemlineata sp. n. further differs from O. murrayi in the lack of a fringe of spines on the lip annules, the presence of a collar, a longer stylet (99-103 vs 78-93 µm), lower number of body annules (R = 52-55 vs 62-75), position of the excretory pore near the level of the stylet base (Rex = 15-17 vs 20-26), and a blunt tail terminus (sharp in O. murrayi). 

Key words: Criconematidae, description, new species, spruce forest.

Tchesunov, A.V and Sturhan, D.

Redescription of Dintheria tenuissima de Man, 1921 (Nematoda: Bastianidae)

Dintheria tenuissima, originally described from a single male in the Netherlands and reported also from Siberia, was found at two sites in western and northern Germany. Based on several males, females and juveniles a redescription of the species is given. Some newly revealed morphological details, such as dorsally coiled amphids, antidromously reflexed ovaries and the presence of two circles of six and four cephalic setae confirm the position of Dintheria within the family Bastianidae. Dintheria differs from Bastiania, the only other genus of Bastianidae, mainly by absence of copulative setae and larger wart-shaped supplementary organs in the males and subcylindrical tail curved ventrad, with blunt terminus without a mucro. An emended diagnosis of the genus is given.

Key words: Bastianidae, diagnosis, Dintheria tenuissima, Germany, redescription, soil nematodes, taxonomy.

Yushin, V.V., Coomans, A., Borgonie, G. and Malakhov, V.V.

Ultrastructural study of the tadpole stage of the primitive marine nematode Enoplus demani (Enoplia: Enoplida)

The ultrastructure of the tadpole (1˝ fold) embryo of the free-living marine nematode Enoplus demani was studied. The cells of the tadpole embryo show no distinct cyto-differentiation. Cytoplasm contains mitochondria and is filled with yolk granules and lipid droplets; nuclei contain clumps of condensed chromatin. The cells at the different stages of the mitotic cycle occur frequently in all the primordial embryonic layers. The centrosomes of the mitotic spindles include centrioles. The cells of the epidermis and the intestine form distinct layers of polarized cells underlain by basal lamina and connected at the apical ends by adherent junctions. The apical membranes of epidermal cells are slightly undulated, occasional cisternae of RER and Golgi bodies occur in the apical cytoplasm. The epidermis of the head-end forms many small funnel-shaped invaginations, interpreted here as the result of morphogenetic cell movement associated with cephalic sensilla formation. There is no distinct lumen in the tadpole intestine, rare microvilli occur squeezed between the apical membranes of intestinal cells. Presumptive muscle cells have no myofilaments, but mitochondria are abundant at the future basal (contractile) part of the cells. The pair of primordial germ cells (PGC) are positioned in the blastocoel latero-ventrally to the mid-part of the intestine. These cells are about twice the diameter of other cells of the embryo. The cytoplasm of PGC does not differ from the cytoplasm of somatic cells of the embryo, and specific P-granules are absent. Data on cell structure of E. demani tadpole embryo are compared with data on cell differentiation in Caenorhabditis elegans.

Key words: Caenorhabditis elegans, centriole, development, Enoplus demani, germ cells, nematodes, P-granules, ultrastructure.