Species Composition Of Nematodes Research Articles

Changes in soil nematode communities under the impact of fertilizers

Changes taking place in the communities of soil nematodes of an artificially sown meadow under the impact of annually applied mineral fertilizers have been studied in a field experiment for nine years. It is shown that changes in the species composition, trophic structure, and numbers of nematodes from different genera depend on the fertilizer applied and on the competitiveness of the plant species grown. The spectra of nematode genera sensitive to the complete mineral fertilizer (NPK) and to the particular nutrients have been identified with the use of a number of parameters, including the maturity index of nematode communities, the biotope preferences of the particular nematode genera, and the general pattern of nematode habitats. The results obtained in this study can be used to assess the effect of mineral fertilizers on the soil fauna and to suggest optimum application rates of mineral fertilizers ensuring the sustainable development of meadow herbs. The use of the data on the trophic structure of nematode communities for predicting the ways of organic matter decomposition in the soil is discussed.

Species composition and distribution of free-living marine nematodes in Vostok Bay, Sea of Japan

The qualitative and quantitative composition of free-living marine nematodes have been studied in Vostok Bay (Peter the Great Bay, Sea of Japan). It is found that the population density of nematodes in the bottom sediments of Vostok Bay shows an uneven distribution. The mean population density equaled 56800 ± 23400 specimens/m2. A correlation has been revealed between the population density of nematodes and the substrate type. Altogether, 85 species of nematodes have been found; they were dominated by Sabatieria palmaris, Rhabdodemania orientalis, Araeolaimus parvibulbosus, Oncholaimium paraolium, Doryolaimopsis peculiaris, and Metachromadora itoi. Six taxocenoses of nematodes were distinguished, taking into account the species dominating in the population density and using cluster analysis of the obtained data. The dominating trophic assemblage of nematodes was “scrapers.” In general, the species composition of nematodes in Vostok Bay is characterized by the relatively great similarity with that in other areas of Peter the Great Bay (Sea of Japan).

Composition and distribution of meiobenthos in amursky bay (peter the great bay, the east sea)

Qualitative and quantitative composition of meiobenthos was studied in Amursky Bay (Peter the Great Bay, the East Sea). Ten taxonomic groups were found, where nematodes were dominant. Density of meiobenthos in ground sediments of the Bay were not uniform, and the average density was measured at 126.4±62.3 ind. m-2. 56 species of nematodes were detected, and dominant species wereSabatieria palmaris, Paracanthonchus macrodon, Sphaerolaimus limosus, S. gracilis andOncholaimium ramosum. Five taxocenes of nematodes were allocated based on the results of cluster analysis and species domination according to density. Low diversity in species composition of nematodes was noted in the northwestern part of the Bay, which is a zone of desalination, and in the eastern part, which is exposed to household drains.

Species composition and seasonal variation of marine nematodes on Futian mudflat in Shenzhen estuary

Species composition and seasonal variation of marine nematodes on Futian mudflat in Shenzhen estuary

Effects of microbivore species composition and basal resource enrichment on trophic-level biomasses in an experimental microbial-based soil food web.

Previous theoretical and empirical evidence suggests that species composition within trophic levels may profoundly affect the response of trophic-level biomasses to enhanced basal resources. To test whether species composition of microbivorous nematodes has such an effect in microbial-based soil food webs, I created three microcosm food webs, consisting of bacteria, fungi, bacterial-feeding nematodes (Acrobeloides tricornus, Caenorhabditis elegans), fungal-feeding nematodes (Aphelenchus avenae, Aphelenchoides sp.) and a predatory nematode (Prionchulus punctatus). The food webs differed in species composition at the second trophic level: food web A included A. tricornus and Aph. avenae, food web B included C. elegans and Aphelenchoides sp., and food web AB included all four species. I increased basal resources by adding glucose to half of the replicates of each food web, and sampled microcosms destructively four times during a 22-week experiment to estimate the biomass of organisms at each trophic level. Microbivore species composition significantly affected bacterivore and fungivore biomass but not bacterial, fungal or predator biomass. Greatest bacterivore and fungivore biomass was found in food web A, intermediate biomass in food web AB, and smallest biomass in food web B. Basal resource addition increased the biomass of microbes and microbivores but did not affect predator biomass. Importantly, microbivore species composition did not significantly modify the effect of additional resources on trophic-level biomasses. The presence of a competitor reduced the biomass of A. tricornus and Aph. avenae, in that the biomass of these species was less in food web AB than in food web A, whereas the biomass of C. elegans and Aphelenchoides sp. was not affected by their potential competitors. The biomass of Aph. avenae increased with additional resources in the absence of the competitor only, while the biomass of A. tricornus and Aphelenchoides sp. increased also in the presence of their competitors. The results imply that microbivore species composition may determine the second-level biomass in simple microbe-nematode food webs, but may not significantly affect biomass at other levels or modify the response of trophic-level biomasses to enhanced basal resources. The study also shows that even if the role of predation in a food web is diminished, the positive response of organisms to increased resource availability may still be hindered by competition.

Effects of secondary treated sewage effluent application on the populations of microfauna in a hardwood plantation soil: Bolivar HIAT trial

In this study we measured the effects of using of secondary treated sewage effluent for irrigation (3.5 y) of a hardwood plantation ( Eucalyptus or Casuarina) on the abundance and species composition of protozoa and nematodes in soil. Measurable populations of protozoa and free-living nematodes were observed in all treatments. Application of secondary treated sewage effluent had a stimulatory effect on the abundance of total and active protozoa and altered the species composition of all groups of protozoa and nematodes. In general populations were higher in soils under dripper lines than between dripper lines. Populations of protozoa were highest under Eucalyptus receiving sewage effluent and the difference between `under dripper line' and `between dripper line' was maximum in Casuarina plantation. A number of protozoan species belonging to genera Acanthamoeba (group 3 species such as A. castellanii) and Naegleria (i.e. potentially pathogenic protozoa) were observed in plots irrigated with secondary treated sewage effluent. Large (>50 μm) amoebae and ciliate species were mainly observed in soils receiving sewage effluent. Bacterial feeding nematodes were the dominant group of free-living nematodes in all soils, and effluent irrigation increased their percentage especially in soil under dripper lines. Overall results in this study suggest that where heavy metal contamination is minimal, irrigation with secondary treated sewage effluent does not have significant negative effects on the abundance of protozoa and nematodes. Significant increases in the abundance of active protozoa and changes in species composition of protozoa and nematodes suggest an increased microbial turnover in effluent treated soils.

Ecology of free-living nematodes from the continental shelf of the central great barrier reef province

Nematode assemblages from five sites on the continental shelf of the central Great Barrier Reef (GBR) along a transect ranging from inshore muddy quartz to offshore carbonate sands were examined in austral spring (October 1987) and summer (January 1988). Assemblages at all sites were characterized by very even distributions (low dominance) of families, genera and species. Average per cent abundances of the dominant family (Chromadoridae), genus ( Theristus) and species ( Spilophorella paradoxa), respectively, were 16, 10 and 8% of the total number of specimens identified. The diversity of species ( H′ = 3·35–4·08) from the GBR was higher than that normally calculated for shelf nematode assemblages; species richness (SR = 10·64–16·67) and evenness (J′ = 0·82–0·91) values approximate those characteristic of deep-sea nematode assemblages, suggesting equitable exploitation of the interstitial environment on the GBR shelf by many species. This was also indicated by a nodal analysis of the 22 dominant species, which exhibited no strong preference for any particular sediment or site. Non-selective deposit and epistrate feeders were the most abundant trophic types among the nematodes. The abundance of non-selective deposit feeders was significantly greater in the summer than spring assemblages, accompanying differences also observed in the per cent composition of several species. Shortterm fluctuations in species composition and high species diversity of nematodes on the central Great Barrier Reef shelf may be the result of high sediment heterogeneity (caused by cyclones and frequent prawn trawling), a rich bacterial flora, continuous warm temperatures and low macroinfaunal abundance.

Seasonal species composition, density and role of nematodes in activated-sludge effluent treatment works

The species composition, seasonal distribution and role of the nematode communities in two oxidation ditch activated-sludge effluent treatment works in Cumbria, U.K. were investigated for a 12 month period (1982/83). The Diplogasteridae, and Diplogasteritus nudicapitatus in particular, dominated the nematode community in the mixed liquor, with lesser numbers of the family Rhabditidae. No correlation was apparent between seasonal patterns of nematode species composition and densities and COD, ammonia, nitrate, nitrite, chloride or inorganic phosphate in the sewage; there was a correlation with BOD 5. Maximum numbers occurred at suboptimal temperatures indicating that temperature is overriden by a combination of other factors related to sewage quality and loading. Total daily energy contributions by the nematodes indicate that their role in bacterial grazing and decomposition processes in activated sludge is negligible. This is attributable to the unstable nature of the mechanical environment and an unfavourable relationship between nematode doubling time and sewage retention times.

Population structure and species composition of the free-living nematodes inhabiting sands of the New York Bight Apex

The free-living nematodes inhabiting silty and medium to coarse sands at nine stations in the New York Bight Apex were studied from August 1973 to September 1974. Average population densities (no. 10 cm−2) ranged from 221 to 1381; no significant differences in density associated with sediment type, organic carbon or heavy metal concentrations were observed. In medium sands with low organic carbon and low heavy metal concentrations the nematode fauna was characterized by: (1) dominance by members of the families Chromadoridae and Desmodoridae; (2), low relative abundance of the family Comesomatidae; and (3), high species diversity. In silty sands, and also in medium sands with high organic carbon and/or high heavy metal concentrations, the fauna was marked by: (1) low relative abundances of the Chromadoridae and Desmodoridae; (2), high dominance of the Comesomatidae; and (3), low species diversity. In medium sands species diversity was significantly inversely correlated with increased concentrations of Cr, Cu, Pb and Zn. However, no such relationship existed in silty sands. Contaminated medium sands were also marked by high relative abundances of the comesomatid Sabatieria pulchra, which may be able to tolerate stressed sands much better than the normal inhabitants of such sediments; species belonging to the families Chromadoridae and Desmodoridae.

Population distribution and structure of the free-living nematodes of Long Island Sound

The distribution and structure of nematode populations in 4 sedimentary environments (muds, muddy sands, fine sands and medium-coarse sands) in Long Island Sound were studied. Mean population densities were highest in muds and muddy sands. Cluster analysis suggested the presence of two basic faunistic units; a mud unit characterized by high species dominance, low species diversity and low species endemism, and a sand unit characterized by low species dominance, high species diversity and high species endemism. Species diversity in all habitats was a direct function of both species richness and equitability. Limited niche separation among deposit feeders, usually the dominant nematode trophic type in muddy sediments, is proposed as the cause for the high species dominance so often characteristic of shallow marine muds. The study afforded the opportunity to examine the quantitative and qualitative aspects of population structure in relation to environmental impact (as indicated by large differences in the heavy metal and organic carbon concentrations within each of the 4 sedimentary regimes). Within each sediment type no differences in population densities, species composition or species diversity of nematodes existed between heavily impacted and apparently non-impacted sediments, or between Long Island Sound and similar coastal regions. These findings cast doubt on (1) the use of heavy metal and organic carbon concentrations as indicators of environmental stress for marine nematodes; (2) the use of diversity indices alone as indicators of environmental deterioration; and (3) the usefulness of field monitoring studies alone for the assessment of pollution impact on marine nematodes.

The Vertical Distribution of Ciliophora and Nematoda in the Sediments of Loch Leven, Kinross

SynopsisThe species composition of ciliates and nematodes in the mud of Loch Leven was investigated: 59 species of Ciliophora and 14 species of Nematoda were recorded. The ciliate species composition varied widely throughout the 11-month sampling period, whereas that of the nematodes was more constant.The vertical distribution of ciliates and nematodes at four sites is described and related to the findings of other workers. Two distinct patterns of vertical distribution occurred, one typical of ciliates, the other of nematodes.