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Comparison of centrifugal and other methods for standardization of extraction of nematodes from soil
Annals of Applied Biology
Abstract
The extraction of many genera of nematodes from four different soil types by sedimentation, mobility, sieving and centrifuging was compared. All methods were found to extract similar numbers of nematodes. Centrifuging was the most versatile technique and the best for clay soils. Baerman sieving was generally poor and particularly so for sands and for the genus Tylen-chorhynchus. Rotylenchus was the only genus of those identified that was extracted equally well by all techniques. Centrifugal extraction was selected as the routine method for surveys as it was effective on all soil types, was less likely to be subject to variation and, although poor for Longidorus, extracted a wider spectrum of nematodes.
... Except for the effect of soil inhibitors on real-time PCR assay, another possible explanation for overestimation could be the crude process of nematode extraction or sampling errors from nematode suspensions for microscopic nematode counting. There are several methods used for vermiform nematodes extraction from soil samples, such as Baermann funnel extraction, Whitehead & Hemming tray extraction and sugar centrifugal flotation (Harrison & Green, 1976). Compared with the funnel and tray methods that usually need days to extract nematodes from a sample, the sieving and sucrosecentrifugation method could extract nematodes from a soil sample in an hour and was selected as the routine method for nematode assay with the advantages of effectiveness, less variation and a wider spectrum of nematode extraction (Harrison & Green, 1976). ...
... There are several methods used for vermiform nematodes extraction from soil samples, such as Baermann funnel extraction, Whitehead & Hemming tray extraction and sugar centrifugal flotation (Harrison & Green, 1976). Compared with the funnel and tray methods that usually need days to extract nematodes from a sample, the sieving and sucrosecentrifugation method could extract nematodes from a soil sample in an hour and was selected as the routine method for nematode assay with the advantages of effectiveness, less variation and a wider spectrum of nematode extraction (Harrison & Green, 1976). Subsequently, it was found that the centrifugation method had a better recovery of Trichodorids (Decraemer et al., 1979). ...
The ectoparasitic stubby root nematode, Paratrichodorus allius, transmits tobacco rattle virus, which causes corky ringspot disease resulting in significant economic losses in the potato industry. A diagnostic method for direct quantification of P. Allius from soil DNA using TaqMan probe and SYBR Green real-time PCR assays was developed to assist the potato industry in management of this important vector. Specificity of primers/probe designed from the internal transcribed spacer of ribosomal DNA of P. Allius was demonstrated by in silico analysis and experimental PCR tests with no cross reactions using non-target nematode species and nematode communities. The SYBR Green method was more sensitive than the TaqMan probe method during detection using serial diluted DNA templates. Standard curves were generated from serial dilutions of DNA extracted from autoclaved soil with artificially inoculated P. Allius individuals and were validated by high correlations between the numbers of target nematodes quantified by the assays and added to the soil. Moreover, the numbers of P. Allius determined by the real-time PCR assays and estimated by the microscopic method in 17 field soil samples presented positive correlation relationships (R² = 0.80 and 0.86). Although the quantification using TaqMan probe overestimated the target nematodes compared to using SYBR Green in eight out of ten field soil samples, results of the two methods correlated well (R² = 0.92). This is the first report of P. Allius quantification from soil DNA extracts using real-time PCR, providing a rapid and sensitive diagnostic method obviating time-consuming manual nematode extraction from soil and microscopic identification and quantification. © 2017
... Nematodes were extracted using the centrifugation method 82 and then fixed with TAF (triethanolamine, formaldehyde) or 4% formaldehyde solution heated at 65°C. The centrifugal method has been widely reported as the most versatile technique showing extraction efficiency for larger numbers of nematodes, especially of the less mobile forms (please see referenced studies [83][84][85] ). Temporary mass-slides were prepared from each sample and used for examination. ...
There is a significant lack of research on how climate change influences long-term temporal trends in the biodiversity of soil organisms. Nematodes may be specifically adequate to test soil biodiversity changes, because they account for ~80% of all Metazoans and play key roles in the functioning of terrestrial ecosystems. Here, we report on the first synthesis study focused on temporal trends of nematode fauna over a period of 14 years (1986–1999) across the Carpathian Ecoregion. We provide new evidence that wetter conditions associated to global change contributes to driving nematode diversity at genus/family level. We observed opposite trends in soil nematode alpha diversity (increase) and beta diversity (decrease) consistent across ecosystem types and soil horizons, providing strong evidence for the influence of climate change on soil biodiversity at large spatial scales. An increase in the community functional uniformity along with a decline in beta diversity indicated more homogenous soil conditions over time. The Soil Stability Index (metric devised to assess soil homeostasis based on the functional composition of nematode communities) increased over time, indicating a decline of soil disturbances and more complex soil food webs. Our results highlight the importance of nematodes as powerful indicators of soil biodiversity trends affected by multiple facets of environmental change in long-term soil monitoring.
... Any DNA extraction protocol must address extraction efficiency and soil-based PCR-inhibitors binding to template DNA which can vary among soil types (Peham et al., 2017). When nematodes are recovered from soil before DNA extraction, elutriation techniques can be categorized into three groups: i) densitybased; ii) size-based; and iii) mobility-based methods ( Fig. 2) (Harrison and Green, 1976;Schouten and Arp, 1991;Viaene et al., 2021). Mobility-based methods such as the Baermann funnel method and its adaptations (the Whitehead tray (Whitehead and Hemming, 1965) and Oostenbrink elutriator (Oostenbrink, 1954)), were the most commonly used approaches in the surveyed publications (50%), followed by density protocols (centrifugal flotation, automated zonal centrifugation) (27%) ( Table S1). ...
... Nematodes were extracted from 100 cm 3 of soil using centrifugation and sugar-floatation techniques (Harrison and Green, 1976). Nematodes were also extracted from four 3.8-cm-diam. ...
Habteweld, A., M. L. Mendes, R. N. Inserra, and W. T. Crow. 2021. Phylogenetic relationships of Belonolaimus longicaudatus populations associated with turfgrasses in the southeastern USA. Nematropica 51:41-55. The D2-D3 and ITS regions of rDNA from 31 populations of Belonolaimus longicaudatus associated with turfgrasses in different locations of southeastern USA were sequenced and subjected to phylogenetic analysis. The result showed that there were variations in DNA sequences among populations and morphology and morphometric characters as well. The phylogenetic analysis using D2-D3 LSU and ITS1-5.8S-ITS2 rDNA sequences grouped the south Florida populations together with 91 and 81% support, separated from a subclade containing other B. longicaudatus populations from other localities. The south Florida populations as a group tended to have smaller mean stylet knob width and stylet/tail length and shorter mean lip, stylet, and esophagus lengths. Principal components analysis of seven selected morphometric characters also showed correlations among populations related to the subclade to which they belong. Overall, results suggest that the populations from turfgrasses in south Florida fit morphologically with the paratypes of B. longicaudatus described by Rau (1958) from central Florida, which had a stylet and tail length ratio value ≤ 1. Conversely, the populations from other localities grouping in a different subclade in the phylogenetic tree had the highest range of stylet and tail length values >1. Although parasitism to turfgrasses by the B. longicaudatus populations grouping in the two different subclades results in serious damage, more studies are needed to define many biological, ecological and genetic aspects of these populations from turfgrasses. RESUMEN Habteweld, A., M. L. Mendes, R. N. Inserra, y W. T. Crow. 2021. Relaciones filogenéticas de algunas poblaciones de Belonolaimus longicaudatus asociadas a césped en el Sureste de los Estados Unidos. Nematropica 51:41-55. Las regiones D2-D3 e ITS de ADNr de 31 poblaciones de B. longicaudatus asociadas a césped en 42 NEMATROPICA, Vol. 51, No. 2, 2021 diferentes localidades del Sureste de los Estados Unidos fueron secuenciadas y utilizadas en un análisis filogenético. El resulto mostró variaciones en las secuencias de ADN entre poblaciones, así como en los caracteres morfológicos y morfométricos. El análisis filogenético basado en secuencias de ADNr de D2-D3 LSU y ITS1-5.8S-ITS2 agrupó las poblaciones del Sur de Florida, con un soporte de 91 y 81%, separado de un subclado formado por otras poblaciones de B. longicaudatus de otras localidades. Las poblaciones del Sur de la Florida como grupo tendieron a poseer una menor media en el ancho de los nódulos del estilete y estilete/cola; menor media en labio, estilete y longitud del esófago. Un análisis de componentes principales de siete caracteres morfométricos seleccionados también mostró correlaciones entre poblaciones relacionadas al subclado que pertenecen. Los resultados generales sugieren que las poblaciones de césped en el Sur de Florida se ajustan morfológicamente a los paratipos de B. longicaudatus descritos por Rau (1958) del Centro de Florida, el cual posee un radio St/T con valor ≤ 1. Al contrario, las poblaciones de otras localidades agrupadas en diferente subclado en el árbol filogenético posee el rango más alto de valores St/T >1. Aunque el parasitismo del césped por poblaciones de B. longicaudatus que se agrupan en dos subclados diferentes da como resultado un daño grave, se necesitan más estudios para definir muchos aspectos biológicos, ecológicos y genéticos de estas poblaciones en césped. Palabras clave: Belonolaimus longicaudatus, D2-D3, ITS, filogenética, Sur de Florida, nematodo del aguijón, césped
... The extraction efficiency from soil, therefore, is a critical step in establishing disease pressures presented by nematodes or the conditions of soil health. To achieve high nematode extraction efficiency, various methods and modifications have been developed over time (Oostenbrink, 1954;Seinhorst, 1956;Harrison & Green, 1976;Viaene et al., 2021) with variations being introduced locally, depending on the availability or access to certain materials. ...
... Soil samples were collected from Beef Farm Prairie, Osceola County in Florida, with latitude 28.087400 and longitude 80.897847, and submitted to the NAL for nematode diagnosis in December 2015. Nematodes were extracted from 100 cm 3 of soil using centrifugation and sugar floatation techniques (Harrison and Green, 1976). ...
Hirschmanniella dicksoni n. sp. isolated from the rhizosphere soil of limpograss is described and illustrated based on morphology and molecular characters. The new species is characterized by its body length, 1,582 to 1,929 µm, hemispherical lip region with 6 to 7 an-nules, stylet length 19 to 21 µm, irregularly areolated lateral fields, oval spermatheca filled with rounded sperm, intestine not overlapping the rectum, and tail length 103 to 149 µm, usually with ventral projection with subterminal notch. Males are similar to the females except for their shorter body length and presence of secondary sexual characteristics , with spicules length 19 to 30 µm. The new species is closely related with H. mucronata, H. belli, and H. oryzae. Compared with these three species, the new species has a relatively longer tail and a terminus shape tail with a ventral projection with a subterminal notch. Other morphological and morphometric characteristics that separate these species are as follows: lip region, number of lip annuli, and spicules length. Molecular sequence analysis using the D2-D3 expansion segments of 28S and the ITS rRNA sequences showed that the new species is genetically distinct. D2-D3 sequence of H. dicksoni n. sp. showed 99 and 95% sequence homology with an undescribed species of Hirschmanniella isolated from the Colorado River in Yuma, Arizona, and H. oryzae, respectively. ITS sequence of the new species also showed 88% sequence homology with H. oryzae. The phylogenetic analysis of D2-D3 and ITS region grouped H. dicksoni n. sp., as sister species, with H. oryzae.
... Baermann incubation was clearly superior for some genus while centrifugation was the better method for others ( Table 2). Present data and results from previous work [14,2] confirm the advantage of centrifugation over Baermann incubation in the recovery of sluggish plant-parasitic. ...
Three experiments were conducted to find out the feeding type and age structure of nematodes in different soil habitats; to know the efficiency of different extraction techniques of nematodes and to observe the hatching behavior of Meloidogyne juvenile in a Baermann device. Bacterivore, Omnivore, Predator, Fungivore and Plant Parasitic nematodes were recorded in the soil of flower, vegetable, moss, grass, and corn and compost habitats. Bacterivore was the highest feeder (67.5%) in the soil habitats. In comparison of nematode extraction methods, Seinhorst method extracted more cysts (188), but less juvenile (34) and eggs (18) from cysts than stirring (145, 87 and 50, respectively) while AZC was found superior (936) over Cobb method (204) in extracting nematodes. The AZC method also extracted huge juvenile number from roots which was higher than Baermann funnel method. In Baermann funnel, juvenile hatched more in favorable condition than unfavorable condition which led to an increasing and decreasing pattern of hatching.
... In August 2014, heavily galled tomato roots and soil samples from a commercial vegetable field in Naples, FL were submitted to the UF/IFAS, Nematode Assay Laboratory (Gainesville, FL) for diagnosis and species identification. Second-stage juveniles (J2) were extracted from the soil samples using the sugar-floatation method (Harrison and Green 1976) and used for further molecular characterization. Ten singleegg masses (SEM) were extracted from the infected roots and propagated on tomato (Solanum lycopersicum L. 'Rutgers') grown in autoclaved sand in the greenhouse at 28°C. ...
Meloidogyne haplanaria is a species originally found infesting peanut in Texas and, more recently, in Arkansas. In this study, we confirmed the presence of M. haplanaria in Florida based on morphological and molecular characterization. This species was identified from a sample submitted for diagnosis collected from Mi-resistant tomato rootstock grown in Naples, FL. The major diagnostic criteria to distinguish M. haplanaria from other closely related root-knot nematode (RKN) species are based onmorphological differences and host range tests, which are time consuming and labor intensive and require living or well-preserved specimens. In our study, we provide an easy diagnostic strategy to distinguish M. haplanaria from other RKN species based on amplification of two mitochondrial DNA regions. These regions span the intergenic spacer and part of the adjacent large subunit ribosomal RNA gene (lrDNA) and sequence polymorphisms in lrDNA revealed by the restriction pattern following digestion with the restriction enzymes HinfI and MnlI. A unique haplotype pattern, which has not been observed in any of the RKN species described thus far, was observed in M. haplanaria. The outcome of molecular analysis of M. haplanaria aligned with morphological measurement and characteristics as well as perineal pattern originally described for M. haplanaria.
... Owing to exchanges between subsoil and aerial parts of ecosystems and the possible high proportion of production which occurs below ground, herbage production is a crude measure of pasture production (Cooper 1975). Comparative studies of nematode extraction have indicated that recoveries are influenced by the technique used, and soil type, as well as showing bias with regard to nematode genera (in so far as taxonomic position affects morphology and activity) (Whitehead & Hemming 1965;Harrison & GreenDownloaded by[In biological studies biomass is generally more important than numerical abundance. However, owing to the great changes in individual biomass of nematodes from the first stage to adulthood (e.g., 16 times in Pungentus -Yeates 1973a)(Yeates 1979a) and the changing age composition of each population (Yeates 1972Yeates , 1973b), no single biomass value can be meaningfully assigned to a species. ...
Mean totals for nematode populations found in 12 samples of 0–10 cm soil from grazed pastures, taken monthly, are 1 500 000 per m for Rotoiti loamy sand, 1 030 000 per mfor Kokotau silt loam, 4 750 000 per m for Kaitoke silt loam, 960 000 per m for Judgeford silt loam, and 790 000 per m for Pomare silt loam. These totals are positively correlated with annual herbage production at the sites. Population levels of the 40 taxa distinguished (most of them genera) were poorly correlated with seasonal variation in the environmental factors measured; the factors operating are unknown because of inadequate knowledge of nematode biology. Genera contributing at least 4% to total numbers at two or more sites are Cephalenchus, Helicotylenchus, Pratylenchus, Paratylenchus, Cephalobus, Heterocephalobus, Anaplectus, Chronogaster, Pungentus, and Aporcelaimus. Mean and maximum population levels are given for each genus and site; this information is useful in estimating any damage these nematodes may cause and in determining their role in cycling nutrients in the soil.
... Extraction efficacy of the modified Baermann's Funnel method: Baermann's Funnel method has been widely used for its low set up input and it's convenience of operation. A critical analysis of different extraction methods was made and concluded that the Baerman method was the most efficient and that there was no significant difference between the number of nematodes extracted by the sedimentation and sieving techniques (Harrison and Green, 1976). Thus, the extraction efficacy of this method was tested in this study. ...
For quarantine sampling, it is of fundamental importance to determine the probability of finding an infestation when a specified number of units are inspected. In general, current sampling procedures assume 100% probability (perfect) of detecting a pest if it is present within a unit. Ideally, a nematode extraction method should remove all stages of all species with 100% efficiency regardless of season, temperature, or other environmental conditions; in practice however, no method approaches these criteria. In this study we determined the probability of detecting nematode infestations for quarantine sampling with imperfect extraction efficacy. Also, the required sample and the risk involved in detecting nematode infestations with imperfect extraction efficacy are presented. Moreover, we developed a computer program to calculate confidence levels for different scenarios with varying proportions of infestation and efficacy of detection. In addition, a case study, presenting the extraction efficacy of the modified Baermann's Funnel method on Aphelenchoides besseyi, is used to exemplify the use of our program to calculate the probability of detecting nematode infestations in quarantine sampling with imperfect extraction efficacy. The result has important implications for quarantine programs and highlights the need for a very large number of samples if perfect extraction efficacy is not achieved in such programs. We believe that the results of the study will be useful for the determination of realistic goals in the implementation of quarantine sampling.
... The Baermann and centrifugation steps did not interfere with each other in the sequential extraction process and they extracted different taxa or body size of nematodes in a complementary manner. Furthermore, it was reported that soaking soil in water before centrifugal extraction improved the recovery of nematodes (Harrison and Green, 1976). Although the Baermann method is popularly used by soil ecologists (Fu et al., 2000; Coyne et al., 2001; Liang et al., 2002; Forge et al., 2003; Há ně l, 2004; Viketoft et al., 2005; Adl et al., 2006; Keith et al., 2006; Christensen et al., 2007; Pavao-Zuckerman and Coleman, 2007), we found this method could be insufficient to distinguish between the nematode communities in the presence and absence of rice straw mulching in a paddy field. ...
The effects of management in maintaining high rice yield with less water have received increasing attention in sub-tropical regions where seasonal drought is very severe. To test whether water management affects soil ecological process we compared the soil nematode communities in paddy field soils following water management treatments imposed during late rice cropping. The treatments were continuously flooded rice cultivation (CF), non-continuously flooded rice cultivations without (ZM) and with (M) rice straw mulching. A sequential extraction procedure involving Baermann extraction (Baermann) followed by centrifugal sugar flotation (centrifugation) was used to extract the whole nematode community. Based on the analysis of nematode abundance, genera composition, trophic groups and other ecological indices (Margalef richness index, Shannon index, maturity index, enrichment index and structure index), water management significantly affected the nematode community, with the non-continuously flooded condition, in particular combination with rice straw mulching (M), stimulating nematode development. There was a high abundance, richness, and structure in the nematode community in mulched treatments, indicating improved biodiversity and biological interactions. We hypothesize that soil microclimate and available food resources are affected by water management and directly or indirectly influence the establishment of different nematode communities. We suggested that studies aiming to test natural or anthropogenic influences on nematodes might be distorted by sole use of the Baermann method. Although the Baermann step in a sequential extraction procedure gave valuable information on nematode responses to soil treatments, it was not sufficient to detect effects on the whole nematode community. Our results demonstrate that the sequential extraction procedure is an effective tool to obtain comprehensive information on the whole nematode community, with both steps providing complementary ecologically relevant information, on how the soil ecosystem is affected by human management.
... For several extraction methods, such as the centrifuge otation technique (Harrison & Green, 1976), Baermann wet funnel method (Sohlenius, 1980; McSorley & Frederick, 1991) and the blender-cottonwool method (Schouten & Arp, 1991), it was demonstrated that increasing the sample size reduces the extraction eff ciency. In these methods, nematodes are easily lost in the amount of debris on the lters, sieves, or in the supernatant of the centrifuge tube. ...
The Oostenbrink elutriator-cottonwool filter method is widely used to extract nematodes from soil or litter samples. Nevertheless, its extraction efficiency with respect to nematode body dimensions and life strategy has hardly been investigated. In this study, losses in the elutriator, through the sieves and on the cottonwool filter were estimated by adding known numbers of nematodes to sterile soil samples or to clean water. No significant losses were observed in the elutriator, but through the sieves losses of 20-35% were measured, a strong relationship (y = 1 - 2.0998e(-0.0075L)) was found between extraction efficiency of the sieves and nematode body length. Through the filter losses of 32-50% were measured, but due to mortality or inactivation of nematodes in the inoculum these losses were possibly overestimated. Soil did not significantly affect the extraction efficiency of the sieves and filter, but nematodes were more efficiently extracted from small (50 g) than from large samples (250 g). The recovery of nematodes from fresh soil samples after an extraction time of 1, 2 and 3 days through the cottonwool filter was 59, 73 and 82% compared to the total after 7 days of extraction. Nematode body width, the presence of tail glands, c-ratio and life strategy (cp-group) all seem to affect the extraction rate through the filter. The recovery was related to nematode body length and extraction time by the equation y = exp(-L * exp(-0.63737 * T - 5.82756)). The estimated total extraction efficiency of the Oostenbrink elutriator-cottonwool filter method after 1 day of extraction appeared to be 49% for 330 mum long nematodes and was lower for all other sizes.
Stem and bulb nematodes (Ditylenchus dipsaci) are plant parasites that can cause severe damage to garlic crops in Ontario, Canada, and other garlic growing regions. Accurate soil sampling is important to determine the risk of nematode damage before planting garlic in a field. However, it is not clear where the nematode is most concentrated in the soil profile or how the nematode is best extracted. A field survey and laboratory experiments were conducted in the fall of 2015 and 2018 to determine the distribution of stem and bulb nematode in the soil profile and to determine the most effective extraction method. The soil in 20 garlic fields throughout southern Ontario was sampled and the top 5 cm and the bottom 5-20 cm of soil were collected in a single core and then separated. Nematodes were extracted from all soil samples using both the Baermann pan and sugar centrifugal flotation methods. Significantly more stem and bulb nematodes were extracted from the top 5 cm of soil and using the sugar centrifugal flotation method. An additional extraction efficacy experiment was conducted using a known quantity of stem and bulb nematodes in soil to compare various extraction methods, and the sugar centrifugal flotation method continued to be the more effective method. These results demonstrate that only the top 5 cm of soil should be collected and assessed for populations of stem and bulb nematode in fields intended for garlic production, and the sugar centrifugal flotation method should be the extraction method of choice.
In 1977 and 1978 the effect of nematodes and oxamyl treatment on the growth of a pea crop was examined at a site known to be ‘pea sick’ in an area of heavy clay loam soil in Worcestershire, In 1977, Heterodera goettingiana lieb., Helicotylenchus vulgaris Yuen and Pratylenchus thornei Sher & Allen were associated with decreased pea plant growth. The losses caused by each were additive but complicated by an inverse relationship between numbers of Het. goettingiana and Hel. vulgaris. Crop losses and the benefits of nematicide application could be predicted by using multiple regiession coefficients to account for the effects of all species. In 1978, when numbers of Het. goettingiana were great, crop loss in nematicide-treated plots was correlated with numbers of the nematode.
Thin, poor quality crowns were correlated with small populations of Pratylenchus penetrans (Cobb) Chitwood & Oteifa in the roots of celery plants grown in a field in Cheshire, England, in 1975. P. penetrans invaded the petioles and reproduced there but caused no obvious damage. The presence of waterlogged, translucent petioles in some plants was not related to the concentration of P. penetrans in the soil, roots or petioles.
Oxamyl treatment at drilling greatly increased the growth of the plants, the yield and quality of the peas harvested, in soil infested by small or large numbers of Heterodera goettingiana. Treated plants were continuing to set pods when non-treated plants were senescing. Rhizobium nodulation, sap nitrate and tissue nitrogen content were increased in treated plants. Oxamyl applied to growing plants reduced later nematode invasion and enabled root nodulation to proceed with an increase in tissue nitrogen but no increase in yield. Oxamyl applied at drilling in April was inactive against invasion by H. goettingiana in June, which enabled the nematode to multiply equally in treated and non-treated plots. The most economic treatments were at the smallest rates, giving the greatest increase in yield/kg of oxamyl applied.
Methods for extraction of nematodes from soil vary in their efficiency and therefore may affect perception of nematode community structure. An active extraction method (Baermann incubation) was compared with a passive method (centrifugation) for all taxa of the nematode communities in sandy soils in five experiments. Baermann incubation recovered only 30% of the numbers of herbivores recovered by centrifugation, and was particularly inefficient for recovery of Acrobeles, Alaimus, Hemicriconemoides, Hoplolaimus, and Mesocriconema. In contrast, centrifugation recovered only 22% of the number of omnivores and 12% of predators that were extracted by Baermann incubation, and was inferior in recovery of Aphelenchoides, Eudorylaimus, Nygolaimus, Tylencholaimellus, Tylencholaimus, and Xiphinema. Percent composition of the nematode community was consistently affected by extraction method, with a higher percentage of omnivores and predators recovered by Baermann and a higher percentage of herbivores recovered by centrifugation. A combination of extraction methods is proposed to optimize recovery efficiency for every taxon in the community. Baermann incubation for 96 h, rather than 48 h, increased the detection of uncommon taxa in samples.
Active extraction techniques, dependent on the behavior of soil animals, and passive techniques, dependent on specific gravity or sedimentation rate, are widely used in the extraction of both nematodes and microarthropods. No method is completely suitable for extraction of both nematodes and microarthropods. Since no extraction method is 100% efficient, the estimation of extraction efficiency can provide a basis for evaluating extraction performance and comparing results of different methods.
Six species of Paratylenchus Micoletzky, 1922, two of them new, are reported from the Amazon Basin of Brazil. P. colbrani is reported for the first time in Brazil. Extended ranges, along with additional measurements and descriptions, are given for P. leptus, P. salubris, and P. perlatus. P. mimulus Raski, 1975 is synonymized with P. salubris Raski, 1975. P. flectospiculus n. sp. is distinguished by four lines in the lateral field, short stylet (21-24 mum), and spicules with distinct distal bend ventrad. P. rostrocaudatus n. sp. is distinguished by three lines in the lateral field, short stylet (15-16 mum), and beaked tail terminus.
When 200 ml. dispersed soil is sedimented from an obliquely rising water current in a simple compartmented tank about three-quarters of the nematodes are extracted. About 95% of the nematodes in the concentrated suspension can be separated finally from mineral and heavy organic particles by centrifugal notation. When mobile nematodes were finally separated from soil particles by paper tissue, this sedimentation method extracted as many nematodes from sand and loam as Seinhorst's two-flask and elutriation methods, but in one test extracted fewer Tylenchorhynchus from clay and in another fewer Paratylenchus from clay than the elutriation method. The method is quicker (4 or 6 instead of 30–45 min.) and easier.
Mobile nematodes can be extracted from 300 ml. soil spread out on paper tissue in 23. 33 cm. trays of 8 mesh/cm. phosphor-bronze gauze, just resting on shallow water. The suspension obtained after 24 hr. at 16–18°C. was concentrated to 10–15 ml. without loss by sedimentation in two tapered cylinders, one of 8 cm. bore, the other of 2.6 cm. bore. This method usually extracted significantly more nematodes than the sedimentation, two-flask and elutriation methods.
For separating eelworms from soil a sample of 500 g is weighted out and stirred with about 700 cm3 of water in a beaker.
The suspension is then sieved through a 2 mm domestic sieve and transferred to an erlenmeyer flask of 21. The flask is filled
with water, a funnel is mounted on it as shown in fig. 1 and the flask is inverted and placed with the outlet of the funnel
in a 11 erlenmeyer flask, filled with water (Fig. 2 I). In fig. 2 the subsequent positions of the erlenmeyers and beakers
used are shown. The erlenmeyers are shaken when shifted from one position to the next. Twenty minutes after the beginning
of the separation process erlenmeyer A contains no particles larger than 50 µ but some 50% of the smaller nematodes in the
sample. Another 25% are found in erlenmeyer B and beaker C at the end of the separation process. Some 75% of the larger nematodes
are found in beaker C. The contents of A and B are sieved through 50 µ sieves; the contents of C through 100 µ sieves. Soils
with a low content of organic particles with diameters between 50 µ and 100 µ may be treated after phase I and III (Fig. 2)
only. The contents of both erlenmeyers can then be sieved through 50 µ sieves.
Methodes d'esthtion des populations de nematodes SEINHORST
- Judith M Harrison
- C D Green
- A Kermarrec
- J B Berge
JUDITH M. HARRISON AND C. D. GREEN KERMARREc, A. & BERGE, J. B. (1972). Methodes d'esthtion des populations de nematodes SEINHORST, J. W. (1955). Een eenvoudige methode voor het afscheiden van aaltjesuit grond.
A comparison of some quantitative methods of des sols et des racines Tijdrchrzft over plantmziekten 61,188-190. extracting small venniform nematodes from soil
- A G Whitehead
- J R Hemming
WHITEHEAD, A. G. & HEMMING, J. R. (1965). A comparison of some quantitative methods of des sols et des racines. Bulletin de Icr S o d 1 2 d'Ecohgie 3, 151-169. Tijdrchrzft over plantmziekten 61,188-190. extracting small venniform nematodes from soil. Annals of Applied Biology 55, 25-38.
Comparison of two centrifugal flotation techniques with Seinhorst's elutriation for efficiency of nematode extraction from soil
- Dunn R. A.
Methodes d'estimation des populations de nematodes des sols et des racines
- Kermarrec A.