Occurrence of nematodes, tardigrades and rotifers on ice-free areas in East Antarctica

Nematodes, rotifers and tardigrades were collected on three nunataks (mountain peaks penetrating the ice sheet) in Vestfjella, on six nunataks in Heimefrontfjella and on the Schirmacher Oasis in East Antarctica in the austral summers of 1996/97 and 2001/02. Most samples were taken on the nunatak Basen in Vestfjella where the Swedish station Wasa is located. The microfauna was patchily distributed and the highest densities of animals were found on sites with visible vegetation of mosses, lichens or algae. Thirty-four taxa of nematodes and tardigrades were found. Only seven of these occurred regularly in apparently actively reproducing populations. Other occasional records of nematodes had very few specimens. The highest number of species was found on the nunatak Basen. Rotifers, found in 66% of the samples, were the most frequent animal group. Nematodes occurred in 37% of the samples and tardigrades in 42%. The most frequent nematodes were Plectus and Panagrolaimus, occurring in 26% and 5% of the samples, respectively. Macrobiotus, Hebesuncus and Acutuncus were the most frequent and abundant tardigrades. The pattern of animal distribution can be related to both habitat characteristics and to the geographic position of the nunatak. The communities are little organised and the distribution of the fauna has similarities with an early phase of colonisation.     

Improved quantification of active soil microfauna by a "counting crew"

 Recently, a comparative study revealed that the predominately used most probable number (MPN) method yields seriously biased estimates for active soil ciliates (Protozoa). The direct counting method, in contrast, gave reliable and reproducible data with a high level of discrimination between the invstigated sites between the investigated sites. However, this method requires that fresh soil samples are used, limiting its versatility. In order to overcome this problem a team ("counting crew") of 13 people was trained to carry out direct counts of soil microfauna simultaneously. The densities of active ciliates, rotifers, nematodes and tardigrades in the litter layer of a spruce stand were assessed by the direct counting technique. It could be shown that there was no significant influence of individual crew members on ciliate, rotifer or nematode numbers. The ciliate abundance did not vary significantly in the bulk sample with time of day. A significant increase in active ciliates was observed when counts took longer than 90 min. Comparing our results to literature data obtained by diverse extraction methods revealed that the direct counting method is very efficient for microscopic soil metazoa as well. If a counting crew is available, more precise and realistic data on active soil microfauna can be obtained. Received: 19 December 1997     

Effects of mineral and organic fertilizers on the microfauna in a high-altitude reafforestation trial

Summary Protozoa (testate amoebae, ciliates), small metazoa (rotifers, nematodes), and soil enzymes (catalase, cellulase) were investigated in a reafforested fertilized site at the alpine timberline. Side-dressings of mineral and organic fertilizers were applied alone (90 g NPK; 90, 180, 300, and 450 g dried bacterial biomass per spruce seedling) and in combination with magnesite (90 g NPK+300 g Mg; 90, 180, and 300 g bacterial biomass + 300 g Mg each; 30 g dried fungal biomass + 270 g Mg). One-third of each quantity was applied in 1986, and two-thirds in 1988. None of the treatments caused a significant decrease in the biological parameters investigated in comparison with untreated controls. The soil life was more or less stimulated depending on the amount of organic material contained in the fertilizers and the quantity; 180–270 g organic material per seedling proved to be the most effective. Dried bacterial biomass increased the pH by about 0.5 units, catalase activity by about 70%, and the number of ciliates and nematodes by 150–400%. The ciliate biomass and the number of ciliate species were likewise increased. The organomineral fertilizers increased pH by up to two units and also stimulated the soil life, but where the organic content was less than 180 g per seedling, efficiency decreased markedly. The least biological activity was observed in the control soil and in soil fertilized with NPK. Testaceans, rotifers, and cellulolytic activities were only slightly (insignificantly) affected by the treatments. A pooled evaluation of the data (organic versus organomineral versus mineral treatments) and community analyses showed that the organic fertilizer caused a more pronounced increase in the soil life and greater changes in community structure than the mineral combinations. Two years after application of the fertilizers, the differences between the treatments and the unfertilized controls had diminished.     

Changes in soil nematode populations indicate an annual life cycle at Cape Hallett, Antarctica

Soil biological studies have suggested that generations of terrestrial nematodes in continental Antarctica may take many years. We sampled soil nematodes at three sites in the Adélie penguin colony at Cape Hallett on four dates in a two month sampling period (16 November 2002–18 January 2003). The size class distribution of over 3500 nematodes, and the occurrence of adults, indicate an annual life cycle of the bacterial-feeding Panagrolaimus davidi and Plectus murrayi, at each site. Nematode abundance ranged from 2 to 1375/g dry soil. Moderate temperatures and the regular presence of free water underlie this biological activity and related contribution to soil processes.     

Evidence for multiple anthelmintic resistance in sheep and goats reared under the same management in coastal Kenya

Four experiments, two with sheep and two with goats, were carried out to determine the efficacy of ivermectin, fenbendazole, levamisole, closantel and some of their combinations by faecal egg count reduction tests. In the first experiment, injectable ivermectin, oral ivermectin, fenbendazole and levamisole were tested in 6-month-old lambs, and their reduction percentages were 77%, 13%, 42% and 92%, respectively. In the second experiment, with yearling sheep, the reduction percentages were 35% for injectable ivermectin, 32% for fenbendazole, 99% for levamisole, 48% for closantel, 92% for injectable ivermectin combined with fenbendazole, 99% for injectable ivermectin combined with levamisole, and 100% for fenbendazole combined with levamisole. In the study with 18-month-old goats given the same dose rates as those recommended for sheep, the reduction percentages were 73% for injectable ivermectin, 25% for fenbendazole, and 78% for levamisole. Another group of 14-month-old goats was treated with dose rates 1.5 times those recommended for sheep and the reduction percentages were 93% for levamisole, 92% for injectable ivermectin, and 97% for a combination of levamisole and ivermectin. In all experiments with sheep and goats the gastrointestinal nematode parasites identified by larval cultures were Haemonchus contortus, Trichostrongylus spp. and Oesophagostomum spp. The gastrointestinal nematodes of both sheep and goats on this farm are resistant to ivermectin and fenbendazole, whereas levamisole is still effective in sheep, but not in goats. The results are discussed in relation to the farm as a source of breeding stock to smallholder farmers and its potential to spread anthelmintic resistance.     

伞滑刃线虫属分种检索

依据2004年以前发表的所有伞滑刃属新种原始报道的资料,分析了伞滑刃属73个相关种的所有形态学分类特征,编制了64个伞滑刃属有效种的分类检索表.     

Morphological and molecular diversity at a regional scale: A step closer to understanding Antarctic nematode biogeography

Antarctica is one of the harshest environments on earth and yet life has managed to persist on the continent for millions of years. While most of the continent is covered by snow and ice, in some coastal and mountain regions that do not have permanent cover terrestrial invertebrate fauna dominate. Nematodes are one of the most common taxa present in these environments, but despite their abundance very little work on diversity and distribution has been performed for the Phylum across the Antarctic continent. We examined nematodes from 123 limno-terrestrial samples from the vicinity of the Australian Antarctic Stations (62.8°E–110.5°E) using the mitochondrial cytochrome c oxidase subunit I (COI) gene, and morphological analyses. We identified the nematodes Plectus murrayi, Pl.cf. frigophilus, Scottnema cf. lindsayae, Halomonhystera cf. halophila, H. cf. continentalis and Eudorylaimus spp. The distribution of these species appears to be determined by habitat type and salinity. We also made comparisons using the COI gene with nematodes from localised sampling from Dronning Maud Land, Francis Island (Antarctic Peninsula), and Tierra del Fuego (TF), and also with COI sequences from other worldwide locations. Contrasting levels of COI sequence divergence were identified among genera and species, ranging from low levels for Pl. murrayi (≤0.5%), medium levels for S. cf. lindsayae (≤2.1%) and Halomonhystera (≤4.3%), and high within Pl.cf. frigophilus (≤8.4%). Distribution ranges varied according to the species, with widespread ranges within Antarctica for Pl. murrayi and Scottnema cf. lindsayae (a range of over 2000 km); and distribution beyond Antarctica to TF for Pl.cf. frigophilus. Our results reveal the presence of cryptic species even when conservative approaches are applied in species delimitation.     

Soil faunal communities from mofette fields: Effects of high geogenic carbon dioxide concentration

Mofette fields, i.e. geogenic, cold CO₂-exhaling gas vents occurring naturally in regions of tectonic or volcanic disturbances provide an excellent opportunity to investigate long-term responses of the soil biota to increased CO₂ concentrations. The upper centimeters of mofette soils present a small-scale mosaic of different CO₂ and O₂ concentrations: From up to 100% CO₂ and 0% O₂ around local degassing vents to ambient soil atmosphere (<2% CO₂). The present field study investigated the influence of CO₂ on the community structure of Collembola as representatives of the air-filled fraction of the pore system and of Nematoda as inhabitants of soil water films.Canonical correspondence analyses revealed strong correlations between soil faunal communities and environmental measures, above all CO₂ concentration, organic matter content and plant coverage. An increase in CO₂ concentration was followed by a steady decline in collembolan and nematode species richness and collembolan densities, but below a threshold of 62% CO₂ had no significant effect on overall nematode densities. Collembolans developed viable populations at up to 20% CO₂, where some mofettophilous species had their highest densities and frequencies, but other more general species also occurred (66% of overall collembolan densities). Nematodes, on the other hand, maintained individual-rich populations at up to 62% CO₂, but above 20% CO₂ nematode communities consisted almost entirely (97.6%) of three mofettophilous species: one feeding on bacteria, one on fungi and one on plant roots. Likely a combination of active and passive life phases together with temporal and micro-scale changes in environmental conditions allows survival of few mofettophilous species under CO₂ conditions too extreme for most other species. The finding that mofettophilous species maintained denser populations in high CO₂ patches, with species optima between 3% and 40% CO₂, indicates that they even profit from CO₂ degassing, presumably via changes in food supply or due to the lack of competitors.     

Risk assessment of the cultivation of a stacked Bt-maize variety (MON89034 × MON88017) for nematode communities

Genetically modified Bt-maize MON89034 × MON88017 contains three different genes derived from Bacillus thuringiensis (Bt) which enable protection against insect pests, due to expression of three different insecticidal crystal proteins (Cry proteins), i.e., Cry1A.105 and Cry2Ab2 against the European corn borer and Cry3Bb1 against the Western corn root worm. Nematodes are important organisms in agricultural soil ecosystems, and on fields with Bt-maize cultivation they will be exposed to Cry proteins released into the soil from roots or plant residues. The objective of this study was to analyze in a field experiment the effect of Bt-maize MON89034 × MON88017 on nematodes as non-target organisms. Nematode communities from soil planted with the Bt-maize were compared to those from soil planted with the near-isogenic cultivar (with and without chemical insecticide treatment) and two conventional maize cultivars. The experimental field consisted of 40 plots in a completely randomized block design (eight plots for each treatment), which were monitored over two growing seasons (2008 and 2009) at six sampling dates for nematode diversity at the genus level in the rhizosphere soil. Physicochemical soil properties and Cry protein concentrations were also analyzed. Nematodes showed very high abundances, as well as a high diversity of taxa and functional guilds, indicating the relevance of maize fields as their habitat. Neither Bt-maize cultivation, nor insecticide treatment adversely affected abundance or community structure of nematode assemblages in field plots compared to several non-Bt cultivars including a near-isogenic cultivar. This confirmed the risk estimations based on the analyzed soil concentrations of extractable Cry protein, not exceeding 4.8 ng g⁻¹ soil dry weight and thus revealing a safe toxicity-exposure ratio of >20.     

卢斯垫刃线虫新种和广东垫刃线虫新种描述（线虫门：垫刃科）

卢斯垫刃线虫新种 (Tylenchuslucin .sp .)和广东垫刃线虫新种 (Tylenchusguangdongensisn .sp .)分别采集于广东省深圳光明农场的玉米 (Zeamays)和宝安马田菜场的葱 (Alliumfistulosum)根际土壤。前者以角质层无明显环纹、有明显的后阴子宫囊等特征明显区别于相似种小垫刃线虫 (TylenchusminorXie&Feng ,1997)和拟小垫刃线虫 (TylenchusparaminorXie&Feng ,1997) ;以口针长 8.3～ 10 .4μm、后阴子宫囊明显和尾短于或等于肛阴距等特征明显区别于相似种微针垫刃线虫 (TylenchusstylolusXie&Feng ,1995 )。后者以头部环纹明显、后阴子宫囊显著等特征区别于相似种小垫刃线虫 (T .minor)和拟小垫刃线虫 (T .paraminor) ;以尾长于肛阴距 ,交合刺较长等特征区别于相似种卢斯垫刃线虫新种 (T .lucin .sp .)和亚戴维恩垫刃线虫 (T .subdavaineiMukhina,1981)。