Methods for cleaning turbid nematode suspensions collected from different land-use types and soil types

Highlights

• Soil nematode samples can be quite turbid, which are not satisfactory for microscopy.

• Three methods were designed for cleaning turbid nematode suspensions.

• Nematode abundance did not significantly differ among control and the three methods.

• Repeated centrifugation had slightly higher recovery rate of nematodes than the other methods.

Abstract

Soil nematodes are useful ecological indicators and can be extracted from soil by a variety of techniques. Because the extracted nematode samples (suspensions) can be quite turbid (i.e., they contain soil particles and organic particles in addition to nematodes), quantitative and taxonomic analyses of the nematodes by microscopy can be difficult. In this study, the following three methods for cleaning turbid suspensions obtained from Baermann funnels were assessed: repeated centrifugation at 692.5´g for 1 min, repeated settling at low-temperature (4°C) for 24 h, and a combination of low-temperature settling and centrifugation. Nematodes were extracted with Baermann funnels from soil samples collected from four land-use types (since land-use type can affect the turbidity of nematode suspensions), and the resulting suspensions were cleaned by the three methods before nematode abundance was assessed. As a control, samples (i.e., suspensions) were simply diluted with water, and nematodes were counted in the entire volume. The results showed that, within each land-use type, nematode abundance did not significantly differ between the control and the three cleaning methods. Averaged across all land-use types, however, the nematode recovery rate was slightly higher with repeated centrifugation than with the other two cleaning methods. Therefore, the proposed methods are sound for cleaning turbid nematode suspensions, and repeated centrifugation is the most efficient method.

Graphical abstract

Keywords

Soil nematodes / Purification method / Centrifugation / Low-temperature settlement / Luvisols / Acrisols

References

[1] Abebe, E., Andrássy, I., Traunspurger, W., 2006. Freshwater nematodes: ecology and taxonomy. CABI.

[2] Aira, M., Domínguez, J., 2020. Soil under dead or live organic matter systems: Effect of European shag (Phalacrocorax aristotelis L.) nesting on soil nematodes and nutrient mineralization. Soil Ecology Letters 2, 40–46

[3] Barker, K., Carter, C., Sasser, J., 1985. An advanced treatise on Meloidogyne. Volume II: Methodology. United States Agency for International Development, Raleigh, vi+ 223 pp. pp.

[4] Bongers, T., Ferris, H., 1999. Nematode community structure as a bioindicator in environmental monitoring. Trends in Ecology & Evolution 14, 224–228

[5] Chen, X., Xue, W., Xue, J., Griffiths, B.S., Liu, M., 2020. Contribution of bacterivorous nematodes to soil resistance and resilience under copper or heat stress. Soil Ecology Letters 2, 220–229

[6] Coleman, D., Wall, D., 2015. Soil Fauna: Occurrence, Biodiversity, and Roles in Ecosystem Function, In: Paul, E. (Ed.), Soil Microbiology, Ecology and Biochemistry. Academic, Boston, pp. 111–149.

[7] Coleman, D.C., Blair, J.M., Elliott, E.T., Wall, D.H., 1999. Soil Invertebrates. In: Robertson, G.P., Coleman, D.C., Bledsoe, C.S., Sollins, P. (Eds.), Standard Soil Methods for Long-term Ecological Research. Oxford University Press, New York, pp. 349–377.

[8] Coleman, D.C., Crossley, D.A. Jr, 1996. Fundamentals of soil ecology. Academic Press, London, xii+ 205 pp. pp.

[9] FAO, 2006. World reference base for soil resources 2006. World Soil Resources Reports No. 103. FAO, Rome.

[10] Ferris, H., Tuomisto, H., 2015. Unearthing the role of biological diversity in soil health. Soil Biology & Biochemistry 85, 101–109

[11] Freckman, D., Baldwin, J., 1990. Nematoda, In: Dindal, D.L. (Ed.), Soil Biology Guide. Wiley, New York, pp. 155–200.

[12] Geisen, S., Snoek, L.B., ten Hooven, F.C., Duyts, H., Kostenko, O., Bloem, J., Martens, H., Quist, C.W., Helder, J.A., der Putten, W.H., 2018. Integrating quantitative morphological and qualitative molecular methods to analyse soil nematode community responses to plant range expansion. Methods in Ecology and Evolution 9, 1366–1378

[13] Huang, F., Wei, H., Cao, J., 2018. Response characteristics of soil microbes on maize straw amendment-A typical comparison between subtropical limestone soil and red soil. Journal of Southern Agriculture, 49.

[14] Li, J., Peng, P., Zhao, J., 2020. Assessment of soil nematode diversity based on different taxonomic levels and functional groups. Soil Ecology Letters 2, 33–39

[15] Neher, D.A., 2001. Role of nematodes in soil health and their use as indicators. Journal of Nematology 33, 161–168.

[16] Neher, D.A., Darby, B.J., 2009. General community indices that can be used for analysis of nematode assemblages, In: Wilson, M.J., Kakouli-Duarte, T. (Eds.), Nematodes as Environmental Indicators. CABI, Wallingford, pp. 107–123.

[17] Sarathchandra, S.U., Ghani, A., Yeates, G.W., Burch, G., Cox, N.R., 2001. Effect of nitrogen and phosphate fertilisers on microbial and nematode diversity in pasture soils. Soil Biology & Biochemistry 33, 953–964

[18] Seinhorst, J.W., 1962. Modifications of the clutriation method for extracting nematodes from soil. Nematologica 8, 117–128

[19] Wright, C.J., Coleman, D.C., 2000. Cross-site comparison of soil microbial biomass, soil nutrient status, and nematode trophic groups. Pedobiologia 44, 2–23

[20] Xiao, M., Chen, X., Li, Y., He, X., Shen, Y., Su, Y., 2014. Carbon release from brown limestone and red soils in response to addition of Fe(OH)₃ and CaCO₃. Chinese Journal of Ecology 33, 2936–2942 (in Chinese with English abstract).

[21] Zhang, X., Liang, W., Qi, L., 2013. Forest Soil Nematodes in Changbai Mountain-Morphology and Distribution. China Agricultural Press, Beijing.

[22] Zhang, X., Wu, X., Zhang, S., Xing, Y., Liang, W., 2019. Organic amendment effects on nematode distribution within aggregate fractions in agricultural soils. Soil Ecology Letters 1, 147–156

[23] Zhao, J., Wan, S., Li, Z., Shao, Y., Xu, G., Liu, Z., Zhou, L., Fu, S., 2012. Dicranopteris-dominated understory as major driver of intensive forest ecosystem in humid subtropical and tropical region. Soil Biology & Biochemistry 49, 78–87

[24] Zhao, J., Xun, R., He, X., Zhang, W., Fu, W., Wang, K., 2015. Size spectra of soil nematode assemblages under different land use types. Soil Biology & Biochemistry 85, 130–136

Acknowledgments

This study was supported by the Natural Science Fund of China (41877055); Natural Science Foundation for Distinguished Young Scholars of Hunan Province given to Jie Zhao; the Guangxi Natural Science Foundation Program (2018GXNSFAA281008); the Foundation for Young Scholars in Western China of CAS given to Jie Zhao (A class); and the program of the Youth Innovation Promotion Association of Chinese Academy of Sciences (Y201969). The authors have no conflict of interest.

Electronic supplementary material

Supplementary material is available in the online version of this article at https://doi.org/10.1007/s42832-021-0115-1 and is accessible for authorized users.

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