Optimizing for taxonomic coverage: a comparison of methods to recover mesofauna from soil

Abstract

Manipulating soil properties to modify the dynamics between nematodes and their natural enemies has been proposed to conserve services such as the biological control of insect pests by entomopathogenic nematodes. Many soil microarthropods including acari mites and collembola are natural enemies of nematodes; however, little is known about the naturally occurring assemblages of these two soil dwelling groups and how they might be influenced by soil conditions. A method to efficiently recover both nematodes and microarthropods from environmental samples would be helpful to characterize communities of these two groups in different habitats. Because samples of nematodes extracted from soil by sucrose centrifugation (SC) also contain soil mites, collembola, protozoans, and fungal and bacterial propagules, the efficiency of SC to recover microarthropods was compared to more conventional methods of microarthropod recovery such as heptane flotation (HF), Berlese funnels (BF), and a modified flotation Berlese method (FBF). Microarthropods were identified using an inverted microscope to class in one experiment and to order in a second. Significantly more microarthropods of all taxa were recovered by SC than with either Berlese method (BF or FBF). In total, 40% more microarthropods comprising seven orders were recovered by HF compared to SC, but the difference was not significant. Ecological indices (diversity, richness, and evenness) derived from HF and SC were congruent and significantly higher than those derived from BF. Excessive organic matter in the HF extractions, compared to those of SC, BF, and FBF, made mite detection and identification difficult and time consuming. Moreover, unlike SC, neither HF nor any Berlese method recovered nematodes. Accordingly, we found SC to be the most efficient method for microarthropod extraction, making it an ideal method for studies of communities of nematodes and many of their natural enemies in the soil.

Sustainable green tea production through agroecological management and land conversion practices for restoring soil health, crop productivity and economic efficiency: Evidence from Northern Vietnam

“…Active methods such as the Baermann funnel and passive approaches such as filtering and flotation‐centrifugation are among the most recognized practices for sampling and extracting soil fauna, which are based on different physicochemical principles of soil fauna (Domingo‐Quero & Alonso‐Zarazaga, 2010). Dritsoulas and Duncan (2020) indicated that passive extraction methods consistently recovered significantly more soil microarthropods compared with the active techniques. This is in accordance with our findings since the ecological indices (abundance, richness and Shannon index) derived from the centrifugation method were constantly greater than the figures for the funnel techniques, though the differences were not always significant (Figure 3).…”

“…Soil mesofauna was extracted using two protocols: the heated funnel as described by Edwards (1991) and the modified centrifugal method (Dritsoulas & Duncan, 2020). For the funnel method, a thin layer of fine fresh soil (50 g per sample) was spread on a fine sieve or a small plastic basket and applied heat on top for 72 h. Under the effect of heat, soil mesofauna moved downward and was collected in the plastic tubes, which were tightly connected to funnels and filled with 70% alcohol.…”

Upgrading Strategies for Managing Nematode Pests on Profitable Crops

“…Sampling reliability/precision levels may be boosted and tailored with the current progress and advancements in processing PPN sampling rate [ 10 ] as well as PPN counting [ 12 ] to a several folds increase. Likewise, the extraction method chosen should provide the most authentic and relevant soil fauna/flora data [ 11 , 13 ]. Abd-Elgawad [ 11 ] presented tables to demonstrate considerably different funds needed to sample two nematode taxa with low and high action thresholds, root-knot nematodes (RKNs) on berseem clover and citrus nematodes on citrus trees, respectively, at various accuracy and precision levels.…”

Optimizing Sampling and Extraction Methods for Plant-Parasitic and Entomopathogenic Nematodes

“…Baermann funnel method and its modifications can extract only live nematodes. Selecting a method may sometimes require further tests to find the most efficient extraction method of the existing fauna and flora related to IPM [ 15 ].…”

“…Sucrose centrifugation is the most efficient method for microarthropod extraction. It is) used [ 15 ] as a model to study nematodes and their natural enemies such as collembolan and acari mites. Such techniques as species-specific primers and probes in quantitative polymerase chain reaction (qPCR) assessment, colony culture to count colony forming units per unit of root weight, sucrose centrifugation, Baermann funnel, sieving, or baiting with EPN-susceptible host may vary in the extraction efficiency [ 6 , 14 , 16 ].…”