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Earthworms and Nematodes: The Ecological and Functional Interactions

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Chapter 3
Earthworms and Nematodes: The Ecological and
Functional Interactions
Jair Alves Dionísio, Wilian Carlo Demetrio and
Arlei Maceda
Additional information is available at the end of the chapter
http://dx.doi.org/10.5772/intechopen.74211
Abstract
Soil invertebrate organisms are responsible for several biochemical processes indispens-
able for the correct functioning of ecosystems. Because of the high diversity of animals that
occurs in the soil environment, some invertebrates such as earthworms and nematodes are
highly important in trophic chains, with high number of species and the effect that they
exert on both natural and agricultural systems. However, although numerous studies
have evaluated the implications of these organisms in soil processes and their conse-
quences on crop productivity, the interaction between earthworms and nematodes has
received little attention in recent years. This chapter reviews studies focusing on the
elucidation of the interaction between earthworms and nematodes in diverse situations
in which they occur, for example, the vermicompost process and the native and agricul-
tural systems. Several studies have shown that the direct and/or indirect action of earth-
worms can highly modify nematode populations. In addition, in the presence of
earthworms, the damage caused by phytonematodes can be reduced in some crops.
Keywords: biological control, plant growth, vermicomposting, plant parasitic nematode,
soil food web
1. Introduction
The first studies on earthworms were initiated by Darwin, with the classic The Formation of
Vegetable Mold through the Action of Worms, with observations on their Habits[1]. Since
then, thousands of studies related to the biology and ecology of earthworms have been
performed worldwide. However, even in ancient Rome, these invertebrates had already
© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.
attracted the attention of Aristotle, who described them as the intestines of the earthin
340BC [2].
At present, the importance of earthworms for the functioning of natural and agricultural ecosys-
tems is recognized [36]. These organisms can influence the growth of plants via several mech-
anisms, which were described by Edwards [2] and Scheu [7], such as increasing soil organic
matter mineralization; modifications of soil porosity and aggregation that change the availability
of water and oxygen to plants; production of plant growth regulators via the stimulation of
microbial activity; pest and parasite control; and stimulation of symbiotic microorganisms.
However, the benefits mediated by these organisms in the soils led to erroneous interpretations,
mainly because of their high diversity; there are about 3500 earthworm species described world-
wide, with potential of more than 7000 species [810]. In addition, also it is high the diversity of
earthworms occurring in an area with natural vegetation or agricultural system. This has already
been noted by Steffen et al. [11], who identified about 56 earthworm species in natural and agricul-
tural ecosystems, of which 26 were native and 30 exotic, belonging to six families. In addition, the
greatest diversity of these species was related to the type of ecosystem evaluated: their richness is
greater in areas of forest fragments and native fields. Brown et al. [12] evaluated earthworm
populations in different land use systems and observed high earthworm abundance in conservation
systems with values ranging from 116 to 179 ind. m
2
in no-tillage and minimum tillage, respec-
tively. The authors suggested that the greater presence of these organisms can be attributed to the
lack of soil management in no-tillage, promoting the accumulation of organic material on the soil
surface, and small mechanical movement, benefiting the community of these organisms. In addi-
tion to the effect of management on earthworm populations, Tanck et al. [13] found seasonality
effects in the communities of Amynthas spp. (exotic earthworm) under no-tillage and native forests,
with densities of about 170 and 93 ind m
2
and biomass of 50 and 65 g m
2
,respectively.
The remarkable diversity of earthworm species can be divided into three distinct ecological
categories: epigeic, anecic, and endogeic [14]. Epigeic earthworms comprise animals living on
the soil surface, by using the litter and organic horizons as habitat, feeding on organic materials at
the beginning of the decomposition process, and incapable of digging galleries in the soil;they are
normally used in vermicompost processes. Conversely, endogeic species live in greater depths of
soil; are geophageous, taking from the soil the food necessary for their survival; and include most
of the earthworms described. The anecic earthworms are organisms that live in the soil-surface
interface and are considered the most active of the three categories mentioned above [15].
These ecological categories are based on the environments in which earthworms live, ingesting
and transporting organic and mineral particles at different distances horizontally and verti-
cally in the soil profile [1618]. Because of their size and dietary habits, earthworms also
unintentionally ingest a large diversity of organisms, ranging from microorganisms such as
bacteria and fungi to small animals such as nematodes [15, 19, 20].
Nematodes are highly representative invertebrates in soils, with densities ranging from 106 to
10
7
m
2
and biomass of up to 100 kg ha
1
[21]. Like earthworms, these organisms also present
remarkable ecological diversity, with free-living speciesbacteriophages, plant-parasitic,
mycophages, omnivores, and predatorsresponsible for the regulation of several trophic
chains in the soil, and parasitic nematodes of plants or animals [22]. Population densities of
Earthworms - The Ecological Engineers of Soil18
these animals are of the order of 10
6
m
2
and can consume up to 800 kg ha
1
of bacteria [23].
However, plant-parasitic nematodes, a group with high agricultural interest, and bacterio-
phages, nematodes that feed on both pathogenic and saprophytic bacteria and other beneficial
species, are the most representative groups in soils [24].
Considering the small size of free-living and plant-parasitic nematodes, they are inevitably
ingested by other organisms, mainly by earthworms [25]. Several studies have attempted to
elucidate the interactions between these groups of invertebrates; however, because of the
remarkable ecological variability already mentioned, the results have not been consistent, and
these interactions have not been clearly defined [2628]. Thus, little is known about the effects
of earthworms on microbial diversity and soil microfauna [29].
In this context, a series of studies were performed in order to elucidate the interactions
between earthworms and nematodes, as well as the implications of these interactions with
other soil organisms and plants in natural and agricultural systems. A simplified version of
these interactions is shown in Figure 1.
Figure 1. Interactions between earthworms and nematodes in the soils.
Earthworms and Nematodes: The Ecological and Functional Interactions
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19
2. Effects of earthworms on nematode communities
The effects of earthworms on nematode communities (free living or phytonematodes) can be
analyzed under four different situations. First, the effects of earthworms on the populations of
nematodes during the vermicomposting process of unstabilized organic residues; second, the
effects of the products generated by the action of earthworms (vermicompost) or the
byproducts (vermicompost tea) as controlling agents of phytonematodes; third, when soil
interaction only occurs between worms and nematodes; and fourth, when the interaction of
earthworms and phytonematodes occurs in the presence of plants, the latter being more
complex, with greater variability of results and thus greater difficulty of interpretation.
2.1. Earthworms and nematodes in vermicomposting process
Because of the high diversity of organisms involved and the ecological complexity of soils, the
interactions between earthworms and nematodes have been completely dependent on the
particularities of the surveys conducted. Domínguez et al. [28] evaluated the effects of Eisenia
fetida (earthworms worldwide used in vermicomposting) on the population of free-living
nematodes (bacteriophages and fungivorous) in cattle manure and sewage sludge. In both
substrates, bacteriophage nematode populations were reduced during the evaluated period in
the presence of earthworms. However, assessment of the fluctuations in nematode populations
revealed that fungivorous communities were more affected by the presence of oligochaetes
(Figure 2). The fungi represent one of the main food sources for earthworms, which might
Figure 2. Fungivore nematode abundance (mean SE) in the presence and absence of the earthworm Eisenia andrei
during vermicomposting of cow manure. The figure includes the results of repeated-measures ANOVA for the presence
of earthworms (Source: Redrawn from [28]).
Earthworms - The Ecological Engineers of Soil20
explain the greater effect of vermicomposts on fungivorous populations than on bacteriophage
populations. Conversely, earthworms can also facilitate the dispersion of these microorgan-
isms by the excretion of their spores in the coprolites [30]. However, the dispersion of
nematophagous fungi by earthworms might also be responsible for the reduction of the
nematode populations in the substrates evaluated [31]. Monroy et al. [32] also observed a
reduction of bacteriophage populations by the activity of several earthworm species. Kokhia
et al. [33] showed that the changes in nematode communities by earthworms did not occur
only at the population level, but rather led to the restructuring of all biodiversity when these
invertebrates were present.
The effect of earthworms on nematode populations can be attributed to the direct ingestion
and digestion, or reduction by indirect effects [34]. The indirect effect is attributed to the
reduction of fungal populations by integrating the diet of the earthworms, thereby reducing
communities of fungivorous nematodes [30].
2.1.1. Vermicomposting and byproducts in the control of nematodes
Although the action of vermicompost earthworms shows the reduction of populations of free-
living nematodes, the application of vermicompost in soils has shown to have adverse effects.
Arancon et al. [35] observed a reduction of the communities of plant-parasitic nematodes after
the application of vermicompost from different plant materials. However, considering the
effect similar to the use of organic compounds in this experiment, the addition of organic
materials to the soil was assumed to increase the availability of food for fungivorous and
bacteriophage nematodes, increasing the competition between them with other groups.
Gabour et al. [36] also observed this effect of vermicompost application on the populations of
the plant-parasitic nematode Rotylenchulus reniformis.
In addition to vermicompost, recent studies have shown that the application of vermicompost
tea has the potential to control plant parasitic nematodes. In this sense, Edwards et al. [37]
observed a significant suppression in the number of galls caused by Meloidogyne hapla in
tomato crop when the plants were subjected to aerated vermicompost tea (Figure 3).
Mechanisms of nematode control by vermicompost tea are still poorly understood. The effects
of this substance are likely caused by the death of nematodes by the release of toxic substances
such as hydrogen sulfate, ammonia, and nitrite produced during vermicomposting process
[38]; promotion of the growth of nematode predatory fungi that attack their cysts [39]; favor-
ing of rhizobacteria that produce toxic enzymes and toxins [40]; or indirectly by favoring
populations of microorganisms, bacteria, and fungi, which serve as food for predatory or
omnivorous nematodes, or arthropods such as mites, which are selectively opposed to para-
sitic nematodes of the plant [41].
2.2. Earthworms and nematodes in the soils
Poinar [42] reviewed several works and published a list regarding the natural relationships
between oligochaetes and nematodes, with more than 150 nematode citations, also containing
a brief summary of the groups of nematodes, mainly endoparasite species, found in
Earthworms and Nematodes: The Ecological and Functional Interactions
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21
earthworms. However, it does not present information on these endoparasites in presence of
some tropical earthworm species such as Pontoscolex corethrurus and Amynthas spp. (especially
A. gracilis and A. corticis), which are frequently used in studies evaluating the interaction
between these organisms [26, 4346].
The effects of geophageous earthworms on soil nematodes also differ across studies, and this
variability occurs among studies that use the same worm species, which is probably related to
the high diversity of these organisms, especially nematodes found in situ. Dash et al. [34]
observed reductions of nematode populations in the soil in the presence of Lampito mauritii,an
effect that occurred without the distinction of groups; however, plant-parasitic species were less
affected, likely because of the low palatability of this group, which is lower than that of the free
life forms. Senapati [47] also evaluated the effect of L. mauritii on nematode communities, but the
results showed an increase in bacteriophage populations and a decrease in plant-parasitic
populations, whereas Tao et al. [48] evaluated effects in the presence of Metaphire guillelmi in field
experiments and revealed reduction of all groups of nematodes to the depth of 20 cm.
Studies by Boyer et al. [43] on P. corethrurus, an exotic earthworm distributed globally in
tropical regions, in the laboratory by using sterilized soil showed that this species had the
potential to reduce phytonematodes. They suggested that some compounds such as proteo-
lytic enzymes released into the digestive system of earthworms seem to have an antagonistic
effect on these invertebrates (Figure 4).
Further, Villenave et al. [46] evaluated the interaction between nematodes and P. corethrurus
and found an increase in the population of soil nematodes, mainly of the plant-parasitic
Figure 3. Mean numbers of Meloidogyne hapla galls (mean SE) on tomato roots infested with the nematodes and treated
with soil drenches of vermicompost tea. Columns with different letters are significantly different (p< 0.05). All plants were
grown in MM 360 and received all needed nutrients (Source: Redrawn from [37]).
Earthworms - The Ecological Engineers of Soil22
species, in a field experiment. Although these studies differed in the methodological approach,
and a greater number of interactions might occur in experiments in which the substrate is not
sterilized, a key factor to be observed is the earthworm density that was used in each experi-
ment. Boyer et al. [43] used a small amount of soil (200 g) and a large number of earthworms,
which would represent around 2000 m
2
individuals (up to 20 cm deep). However, in the
experiment by Villenave et al. [46], the densities were approximately 122 earthworms m
2
.
However, the disagreement in the results of the studies mentioned above was not necessarily
an effect of the methodology used, since another factor to be considered in these interactions
is the time of coexistence between worms and nematodes, which was 35 and 150 days for
[43, 46], respectively. Experiments with Lumbricus rubellus [27] showed a reduction of the
general density of soil nematodes; however, this effect occurred in a pronounced way in the
first 60 days, with a reduction of bacteriophages and increase in plant-parasitic species after
this period. The interaction between earthworms and nematodes, in addition to being depen-
dent on all the variables already discussed, is also influenced by the presence of plants. Yeates
[49] studied the interaction of these three components and observed the same results as those
of Ilieva-Makulec and Makulec [27]. According to Yeates [49], the positive effect of earthworms
on root development also increases the rhizospheric area, which is a highly complex zone in
which frequent release of cells, mucilages, exudates, and lysates that contain amino acids,
enzymes, proteins, sugars, carbohydrate complexes, alcohols, vitamins, and hormones [50],
thereby increasing the food for microorganisms and thus for nematodes (Figure 5). Räty and
Huhta [51] showed that some abiotic conditions such as soil pH also modify the behavior of
earthworms and nematodes in the soil.
Figure 4. Living and dead J2 larvae and total eggs per polystyrene (PS) transparent tube obtained 5 weeks after exposure
of J2 Heterodera sacchari to the Pontoscolex corethrurus gut contents, the P. corethrurus gut alone, aqueous soil extracts
(Andisol), or phosphate buffer. (Source: Redrawn from [43]).
Earthworms and Nematodes: The Ecological and Functional Interactions
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23
The effect of earthworms on the environment are not only restricted to the changes that occur
in the soil ingested by these animals. Tiunov et al. [52] evaluated the populations of nematodes
on the walls of the galleries of L. terrestris and found communities of bacteriophage nematodes
associated with this environment. Thus, like coprolites, the walls of earthworm galleries are
rich in nitrogen compounds that promote the development of microorganisms in these sites,
which might also favor the development of nematodes.
In addition to all the results cited above, earthworms can also act as a transport vehicle for
these small invertebrates. Shapiro et al. [53] reported the ability of L. terrestris and A. trapezoides
to disperse within the soil Steinernema carpocapsae, the parasitic nematode of over 250 species of
insects.
2.3. Interaction between earthworms and nematodes and their effects on plants
Few studies have investigated the effects of earthworm and nematode interactions on plant
growth [26, 44, 45, 54].
Dionísio et al. [26] evaluated the effect of the inoculation of earthworms P. corethrurus and
Amynthas spp. in tomato plants infested with the plant-parasitic species Meloidogyne paranaensis
in a greenhouse. Six adult worms of Amynthas spp. or P. corethrurus, isolated or in the same
proportion (3, 3), were inoculated in pots containing soil sterilized in a steam oven. After 1
week, tomato seedlings (Rutgerscultivar) were transplanted into the pots, and 5 mL of a
suspension of M. paranaensis containing 5000 eggs and/or juveniles was inoculated per pot. The
authors observed a reduction in the number of galls plant per plant after 65 days in the
treatments in which the earthworms were inoculated, with reduction varying from 39.2 to
55.2% for Amynthas spp. and P. corethrurus, respectively (Figure 6). Nonetheless, the combina-
tion of the two species resulted in the reduction of 50.0% incidence of galls.
The authors indicated that the action of the earthworms occurred probably after the inocula-
tion of the nematodes, because tomato is highly susceptible to attack by nematodes, especially
Figure 5. Effects of earthworms on the growth of bean roots (Source: Authors).
Earthworms - The Ecological Engineers of Soil24
at the seedling stage [55]. Thus, two explanations were presented. First, the earthworms
Amynthas spp. and P. corethrurus are epigeic and endogeic, respectively, and ingested a greater
(P. corethrurus) or smaller (Amynthas spp.) soil quantity. Further, they might also have ingested
eggs/juveniles of M. paranaensis, which might have been destroyed or inactivated in the pas-
sage through the digestive system, thereby reducing the possibility of gall formation in plants.
Second, the eggshell of M. paranaensis might have been destroyed by the enzymes in the
digestive tract of earthworms, mainly chitinase [30], releasing the larvae inside. Thus, the
released larvae remained in the infested state in the tissues, coelom, and hemocele without
essential development and, normally, without growth, what is called as paratenosis [56].
Therefore, future experiments are needed to perform parasitological tests of the earthworm
tissues to better interpret the results.
Contrary results are cited by Lafont et al. [44] evaluating the effects of P. corethrurus and
Radopholus similis (cave nematodes) on banana plants (Musa acuminata, subgroup Cavendish,
Grande-Naine). The study was conducted in a greenhouse by using pots containing soil,
which was previously frozen (20C) for 2 days to eliminate the native microfauna. The total
biomass of inoculated P. corethrurus was 5.0 (g pot
1
); 4 weeks later, the plants were inoculated
with a R. similis suspension containing 450 eggs. The results showed the absence of the control
of nematodes in the soil; however, the plants developed better in the presence of earthworms
(Figure 7) and also showed a reduction in the severity of necrosis in the root system. Similar
Figure 6. Galls per tomato plant (Solanum lycopersicum Rutger) inoculated with earthworms (Amynthas spp. and
P. corethrurus) and plant parasite nematodes. Letters indicate statistical differences (p< 0.05) by Tukeys test (Modified
from [26]).
Earthworms and Nematodes: The Ecological and Functional Interactions
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25
results have also been reported by Loranger-Merciris [45] by using P. corethrurus in banana
plants infected with R. similis,Helicotylenchus multicinctus, and Pratylenchus coffeae.
The reduction of nematode damage in plants in the presence of earthworms was also observed
by Demetrio et al. [54], who evaluated the potential of the earthworm Amynthas spp. in
reducing the infection of Meloidogyne javanica (worldwide parasite of tomato crop) as well as
the effects of the inoculation of these organisms on some soil biological attributes. Under
similar conditions as those used in [26], different densities of Amynthas spp. were inoculated
(0, 2, 4, 6, and 8 animals per pot) in the presence of tomato plants, which received a suspension
containing 3000 eggs and/or juveniles of M. javanica. At the end of the experiment, the increase
in carbon content of the microbial biomass and positive correlation of this attribute with the
dry mass of the plants was verified. The results of this experiment showed that the earthworms
were not able to reduce the infection of the plant-parasitic species in the tomato roots; how-
ever, in the presence of these invertebrates, the damage caused was reduced. Further, a
positive correlation was noted between the number of inoculated earthworms and the dry
mass of tomato (Figure 8a).
The better development of plants even with the formation of galls in the presence of earth-
worms can be attributed to several factors: physical changes of the soil by the action of these
invertebrates, since galleries formed are normally used by plants as a preferred route for root
growth, in addition to facilitate the infiltration of water and oxygen throughout the soil profile
[57]. Second, chemical changes, which might increase the availability of P and N mainly,
because of the acceleration of nutrient cycling, as well as the continuous deposition of NH
4+
Figure 7. Shoot dry and root fresh biomass of banana plants under different treatments at the end of the experiment:
N- E- Absence of fauna; N- E+ P. corethrurus earthworms alone; N+ E- R. similis nematodes alone; N+ E+ earthworms plus
nematodes. Bars indicate standard errors, n = 12. For each treatment, the means with the same letter are not significantly
different based on Bonferroni test at p< 0.05 (Source: Adapted from [44]).
Earthworms - The Ecological Engineers of Soil26
by earthworms, both by the production of casts and organo-mineral excrements. These pro-
cesses could stimulate communities of nitrifying bacteria and growth-regulating-hormone
producers, as well as the deposition of mucus-rich nitrogen compounds on the walls of the
galleries [7, 47, 48].
The physico-chemical variations promoted by the earthworms alter the biological component
of the soil, thereby mainly stimulating the microorganisms (Figure 8b) that can be reflected in
the colonization of the roots by arbuscular mycorrhizal fungi [58]. This contributes to the
greater absorption of nutrients, mainly phosphorus; the development of plant growth-
promoting rhizobacteria [59] such as Pseudomonas spp. fluorescents [60], which produce
siderophores, that is, increase the availability of Fe
2+
to plants; or to the production of antibi-
otics that inhibit the effects caused by clinical and subclinical pathogens [61]. These physico-
chemical and biological factors can favor the development of plants and compensate for the
damage caused by plant-parasitic species in the roots.
The results of these studies showed that earthworms have a remarkable potential to be used as
an alternative in the biological control of plant-parasitic species in several crops; however,
further studies are needed to elucidate the mechanisms involved in this process as well as to
reveal the interactions with other plants.
3. Final considerations
The complete understanding of the effects of earthworms on nematode communities requires
further studies. Considering the studies performed in controlled systems, earthworms seem
capable of altering the communities of these invertebrates; however, the effects of other factors
such as non-sterilization of the soil and addition of vegetal components could change the
number of interactions that exist in this environment, often leading to the generation of
Figure 8. Effects of the levels of earthworms (Amynthas spp.) and nematodes (Meloidogyne javanica) in (a) dry mass of
tomato plants; (b) soil microbial biomass (Source: Modified from [54]). *,** significance at p < 0.05 and p < 0.01, respec-
tively.
Earthworms and Nematodes: The Ecological and Functional Interactions
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27
contradictory results. The lack of adequate and standardized methodologies for determining
the interaction between these organisms and the different habits of life of the nematodes and
earthworm species are factors that contribute to the differences found among studies. Never-
theless, this ecological complexity is a part of the soil; therefore, it should be considered in
future studies.
Because of the potential to reduce the damage caused by plant-parasitic species, studies with
different ecological categories of earthworms need to be performed to understand the interac-
tions occurring in different species and the use of these invertebrates as a tool in the biological
control of plant-parasitic nematodes.
Author details
Jair Alves Dionísio
1
*, Wilian Carlo Demetrio
1
and Arlei Maceda
2
*Address all correspondence to: jair@ufpr.br
1 Federal University of Paraná, Curitiba, Brazil
2 Agricultural Defense Agency of Paraná, Curitiba, Brazil
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Earthworms - The Ecological Engineers of Soil32
... Earthworms ingest large quantities of soil and consequently also ingest nematodes that are then digested by the proteolytic enzymes in earthworms' gut, serving as amino acid source (Pokarzhewskii et al. 1997;Edwards 2004;Monroy et al. 2008). Nematode predation by earthworms can therefore result in strong decrease from 30 to 70% of nematode abundance (Dash et al. 1980;Yeates 1981;Hyvönen et al. 1994;Räty and Huhta 2003;Dionísio et al. 2018). However, the transformation of litter in casts and the redistribution of organic matter in the soil profile by earthworms promotes bacterial over fungal communities and may result in more abundant nematodes communities, notably bacterivore nematodes (Roessner 1986;Senapati 1992;Winding et al. 1997;Ilieva-Makulec and Makulec 2007). ...
... In our case, Aporrectodea icterica may have play a particular role in soil bioturbation as this particular species produced more numerous and longer burrows resulting in higher bioturbation than the other two species Aporrectodea caliginosa and Allolobophora chlorotica (Capowiez et al. 2015). This intense burrowing activity may lead to higher passive nematode ingestion by earthworm with strong consequences for soil micro food web (Dash et al. 1980;Monroy et al. 2008;Dionísio et al. 2018). On the opposite, anecic earthworms create fewer, vertical and (semi)permanent burrows (Capowiez et al. 2015), which leaves larger volume of soil undisturbed, and allow nematodes to establish themselves at vicinity of the burrow walls (Tiunov et al. 2001;Savin et al. 2004;Andriuzzi et al. 2016). ...
... La modification des communautés microbiennes par l'activité de la macrofaune est également susceptible d'influencer les communautés de nématodes par effet bottom-up. De plus, les nématodes sont des organismes aquatiques qui vivent et se déplacent dans l'eau interstitielle du sol et ils sont donc sensibles aux modifications des flux d'eau induites par les ingénieurs du sol tels que les vers de terre(Dionísio et al. 2018). Les interactions entre microfaune et macrofaune son toutefois très peu étudiées, notamment l'effet des macroarthropodes saprophages(Bastow 2011). ...
Thesis
Les communautés du sol sont extrêmement diverses et comprendre leur distribution et leur structure est un défi scientifique car elles sont influencées par de nombreux facteurs abiotiques et biotiques. Etudier les organismes du sol est cependant primordial car ils interviennent dans de nombreux processus du sol, tels que la décomposition des matières organiques et le recyclage des éléments nutritifs. Il est maintenant établi que les macroinvertébrés du sol sont à la fois influencés par leur environnement et peuvent également l'affecter par leurs activités d'alimentation et de déplacement. Cependant, nos connaissances des processus fins impliqués dans la structuration de leurs communautés et dans la façon dont ils influencent le fonctionnement du sol restent souvent limitées. Pour combler ces lacunes, ma thèse de doctorat se concentre dans un premier temps sur les facteurs abiotiques et biotiques qui façonnent les communautés de macroinvertébrés des sols forestiers tempérés, avant d'étudier leur rôle dans la décomposition de la litière et la manière dont ils influencent les autres organismes du sol dans le contexte des changements climatiques.Le premier volet de la thèse (chapitres 1 et 2) est une approche in situ, où les communautés de macrofaune ont été étudiées dans des forêts de composition et de diversité spécifique en arbres variables le long d’un gradient latitudinal européen (incluant des sites en Italie, Roumanie, Pologne et Finlande). Le premier chapitre étudie l'importance relative de la diversité des arbres, de leur type fonctionnel et de l’environnement physique dans la structuration des assemblages de macrofaune prédatrice et sapro-géophage. Dans un second chapitre, je me suis plus particulièrement intéressé aux communautés de coléoptères carabiques en appliquant une approche basée sur les traits fonctionnels à l’aide de mesure individuelles et de données tirées de la littérature. L’objectif étant de décrire comment l’environnement forestier et les ressources alimentaires influencent la structure fonctionnelle des communautés de ces insectes prédateurs.Le deuxième volet de la thèse développe des approches expérimentales et se concentre sur l’importance fonctionnelle de la macrofaune sapro-géophage, et notamment les interactions qu’elle entretient avec les plantes d’une part (chapitre 3) et d’autres organismes du sol tels que les nématodes d’autre part (chapitre 4). Les préférences alimentaires de six espèces de macro-arthropodes sapro-géophages communément rencontrées dans les forêts européennes sont décrites dans un premier temps et discutées au regard des caractéristiques physiques, chimiques, et morphologiques des litières. Les conséquences de ces préférences alimentaires sur les propriétés des boulettes fécales produites par ces invertébrés d’une part, et leurs implications pour la décomposition des litières d’autre part sont discutées. Enfin, dans une expérience contrôlée en mésocosme, nous avons étudié la réaction des communautés de nématodes à une sécheresse simulée et la manière dont la diversité fonctionnelle de la macrofaune saprophage peut limiter les effets délétères de la sécheresse.L'importance de la biodiversité du sol, à différents niveaux trophiques et dans ses dimensions taxonomiques et fonctionnelles, est discutée du point de vue du fonctionnement du sol et des écosystèmes forestiers tempérés. Les résultats sont ensuite discutés afin d’identifier des pratiques de gestion sylvicoles permettant de préserver la biodiversité des sols et les fonctions qu’elle assure à l’échelle de l’écosystème, en dépit des changements globaux.
... The management of fungal foliar diseases of wheat (leaf rust) still relies on planting resistant cultivars and intensive use of synthetic fungicides that constantly raise environmental and health concerns (Figueroa et al. 2018). There are conflicting reports over the use of fungicides where in most cases, the environmental damage caused due to unbalanced application outweighed its yield benefits (Dionísio et al. 2018;Sassenrath et al. 2019). Integration of eco-friendly measures that promotes the use of soil fauna and gradual replacement of synthetic fungicides with increasing reliance on biocontrol methods such as soil worm and their extracts would enhance sustainable food production (Bach et al. 2020). ...
... Soil worms are among the most investigated soil fauna, because of their indisputable importance in the function of soil ecosystem (Dionísio et al. 2018). Activities of worms vary with different biotic and abiotic components of the soil, possesses and suppressive properties against phytopathogenic diseases (Pritchard 2011). ...
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Leaf rust caused by Puccinia triticina is an important disease of wheat worldwide. Different experiments were conducted to determine efficacy of redworm and its extracts against leaf rust on wheat seedlings. The first experiment involved the use of vermicast and artificial soil as planting substrates, and living worms were introduced into soil for four months. This significantly influenced leaf rust severity, with the lowest severity recorded among inoculated plants grown in vermicast (12% severity), followed by soil pulverised with 30 worms (30%) and 20 worms (40%), while control had the highest rust severity (>70%). Second experiment watered the inoculated seedlings with the extracts (vermicast and vermiwash) which resulted into significant lower leaf rust severity of 35% and 53%, respectively while untreated plants had >85% disease severity. Vermicast, which had the highest leaf rust suppression, was further tested, whereby it reduced leaf rust infection up to 30% with increase in seedling shoot and root growth of 21% and 17%, respectively. Redworm enhances resistance to leaf rust infection on inoculated plant via increase in growth that suppresses rust development.
... Nematodes are found in all soil types thanks to their great morphological and functional adaptability. These features, combined with their abundance, found to be 3.2 million/m 2 (Van Den Hoogen, 2019), omnipresence in all the types of ecosystems (Dionísio et al., 2018) and the introduction of ecological and functional indices (Bongers, 1990;Ferris et al., 2001;Ferris & Bongers, 2009) have led to the intensive use of nematodes as bioindicators of quality and health of soil over the last 30 years (Du Preez et al., 2022). Bioindicators are organisms or communities of organisms that can be used or observed to evaluate an environmental condition or provide information about an ecosystem. ...
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A general limitation of ecological investigations based on nematodes is related to the difficult and time-consuming taxonomic identification of species. Therefore, nematologists are investing many efforts to develop alternative approaches as proxies applicable in biomonitoring assessment. Recently, an alternative method that combines morpho-functional traits was proposed for detecting assemblage changes of marine nematodes. In view of the promising results, it was tested the same approach to document taxonomic structure changes of soil free-living and plant parasitic nematodes. Specifically, this attempt was carried out using three data sets that include studies from various European regions and different types of ecosystems: forests, grasslands and maize crops. Multivariate statistical analysis revealed that the simple combination of the four traits (i.e., buccal cavity cuticularization occurrence, amphideal fovea size and shape, morphology of the cuticle and pharynx) in a single code number perfectly mirrors the taxonomic structure trends of the nematode assemblage at genus level. Therefore, we predict that similar results can be also obtained by directly encoding nematode specimens with the selected traits and we point to new important advances if this procedure can be coupled with advanced machine learning.
... De manière générale, les vers de terre se nourrissent principalement de matière organique à la surface et dans le sol mais peuvent également consommer des micro-organismes comme des nématodes. (Dionísio et al. 2018 A un temps d'exposition de 24 heures, des modifications sur l'activité enzymatique, de la bioaccumulation de NPs dans l'organisme ainsi qu'une augmentation de l'apoptose 7 ont été détectées dès 10 mg/L. De plus, une baisse de la phagocytose 8 dès 0,1 mg/L a également été relevée . ...
Thesis
L’impact des NPs TiO2 manufacturées a été évalué par la méthodologie de l’analyse du cycle de vie à une échelle de site spécifique. Une première approche a été menée dans le but de les détecter dans l’environnement. Les données expérimentales collectées sur le terrain ont permis de caractériser ces nanoparticules pour l’écotoxicité terrestre à une échelle locale. Les NPs TiO2 ont été détectées dans l’eau et les sédiments de la rivière de la Thur ainsi que dans les sols de la zone d’étude jusqu’à 2,5 km d’un site de production. Le temps de résidence (facteur de devenir) des NPs TiO2 dans les sols de la région de Thann est d’environ 8500 ans. Un facteur d’effet spécifique (12,46 PAF.m3.kg-1) a également été élaboré à l’aide de données provenant d’une synthèse bibliographique sur la toxicité des NPs TiO2 pour les organismes de l’écosystème terrestre. La détermination de ces deux paramètres a permis de calculer le premier facteur de caractérisation des NPs TiO2 pour l’écotoxicité terrestre de la région de Thann (1,06.105 PAF.m3.an.kg-1).
... However, the reported results have been extremely variable with positive, negative and neutral responses of soil nematode populations (especially density of these organisms) to presence of earthworms in the environment. The high variability in the observed results was related to several experimental conditions, such as ecological group of earthworms, feeding habit of soil nematodes (e.g., freeliving and plant parasitic species), earthworm densities (which is related to their burrowing activity) and differences associated with the greenhouse and field conditions of the experiments (Dionísio et al., 2018). Therefore, the effects of earthworms on soil nematode communities are not clear. ...
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Earthworms are ecosystem engineers and are able to induce considerable changes in soil. These modifications go beyond physical and chemical aspects, as earthworms also act as regulators of communities of microorganisms and invertebrates. Although several studies have sought to clarify the effects of earthworms on soil nematode communities, the observed effects are highly variable, and there is no consensus on these interactions. In this work, fifteen studies representing 187 observations evaluating the impact of earthworms on soil nematode communities were synthesized in a meta-analysis. Our results showed that earthworms reduced soil nematode abundance by 27%. Nevertheless, this effect depends on the ecological category of earthworm and their densities, as well as experimental conditions. Anecic earthworms exhibited a greater capacity for modifying soil nematode communities than other ecological categories of earthworms. High earthworm densities also had stronger effects on soil nematodes than lower densities (< 100 ind. m−2). However, we found that the presence of plants in experiments cancels out the negative effects of earthworms on soil nematodes, suggesting that earthworms did not affect nematode densities in these environments.
Chapter
This chapter presents various types of plant nematode biopesticides and their valuable products. In this chapter, classification and analysis of different types of plant nematode biopesticides are presented, whose details are given in the following chapters. Predaceous nematodes, predaceous and parasitic fungi, predaceous and parasitic protozoan, biochemical plant nematode pesticides, viruses, rickettsia, bacteria, tardigrades, earthworms, collembolans, enchytraeids, turbellarians, mites, antagonistic plants and plant products, microbial decomposition products, nanobiopesticides, plant and animal exudates, semiochemicals, pheromones, RNA interference, etc., are described as various types of plant nematode biopesticides. Their beneficial biological control traits which include renewability, biodegradability, long-term effectivity, low-dose effectiveness, decomposability, cost effectiveness, targeted and broad actions, etc., are also discussed.
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Earthworms are a representative soil invertebrate, and their living habits are known to influence a large diversity of organisms. The objective of this study was to evaluate the ability of Amynthas spp. to change the biological attributes of soil, and its potential to reduce infection by root-knot nematodes on tomato crop. The study was conducted in the greenhouse of the Diagnostic Center Marcos Enrietti, Federal University of Paraná, Brazil. The treatments earthworms at the following densities: control (absence of earthworms), two, four, six, and eight, which were inoculated into different pots, with five replicates per group. In each pot, a single tomato plant (Solanum lycopersicum) was used, and a suspension of Meloidogyne javanica containing 3000 eggs and/or juveniles was added 14 days after seeding. During the experiment, edaphic respiration was evaluated at 96-h intervals. After 91 days, soil microbial biomass carbon (MBC), microbial soil respiration (MSR), the metabolic quotient (qCO2), dry mass of roots (DMR), dry mass of plants (DMP), and the number of root galls were determined per plant. We observed that inoculation with higher earthworm densities increased the MBC. Furthermore, the lowest earthworm density (two animals) resulted in a MBC that was 75% higher than that of the control treatment (earthworms absent). There was a positive correlation between MBC and DMP, and a negative correlation between MBC and qCO2. The DMR was not influenced by inoculation with earthworms. A linear increase in DMP was observed with earthworms; however, gall formations on the tomato root were not suppressed.
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Full-text available
Earthworms are a representative soil invertebrate, and their living habits are known to influence a large diversity of organisms. The objective of this study was to evaluate the ability of Amynthas spp. to change the biological attributes of soil, and its potential to reduce infection by root-knot nematodes on tomato crop. The study was conducted in the greenhouse of the Diagnostic Center Marcos Enrietti, Federal University of Paraná, Brazil. The treatments earthworms at the following densities: control (absence of earthworms), two, four, six, and eight, which were inoculated into different pots, with five replicates per group. In each pot, a single tomato plant (Solanum lycopersicum) was used, and a suspension of Meloidogyne javanica containing 3000 eggs and/or juveniles was added 14 days after seeding. During the experiment, edaphic respiration was evaluated at 96-h intervals. After 91 days, soil microbial biomass carbon (MBC), microbial soil respiration (MSR), the metabolic quotient (qCO2), dry mass of roots (DMR), dry mass of plants (DMP), and the number of root galls were determined per plant. We observed that inoculation with higher earthworm densities increased the MBC. Furthermore, the lowest earthworm density (two animals) resulted in a MBC that was 75% higher than that of the control treatment (earthworms absent). There was a positive correlation between MBC and DMP, and a negative correlation between MBC and qCO2. The DMR was not influenced by inoculation with earthworms. A linear increase in DMP was observed with earthworms; however, gall formations on the tomato root were not suppressed.
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Greenhouse trials show that solid vermicomposts can suppress plant parasitic nematodes in the field. In the demonstration, tomato plants were intentionally infested with Meloidogyne hapla and treated with vermicompost or thermophilic compost teas. Vermicompost teas can suppress spider mite, mealy bug and aphid populations in the field. Water control, aerated thermophilic compost tea were applied to the plants which in turn was assessed for damages. It was showed that the suppression of aphids is particularly important since they are key vectors in the transmission of plant viruses. It was also shown that the sooner a tea is used after it is brewed, the more effective it is in influencing plant growth and suppressing diseases.
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Two laboratory experiments were conducted to determine the most effective method of using vermicompost for reniform nematode (Rotylenchulus reniformis) management in Hawaiian soils. The trials were conducted in January 2014 and June 2014 using 1-mon-old and 6-mon-old vermicompost. The vermicomposts were incorporated into reniform nematode-infested soil at 0%, 0.5%, 1.0%, and 2.0% (w/w) in 10-cm-d plastic pots. After 3 wk, nematodes were extracted using the Baermann funnel technique, and reniform nematodes were counted under an inverted microscope. Soil incorporation of 1-mon-old vermicompost at 1.0% resulted in the greatest reduction in reniform nematode numbers, but when the study was repeated with 6-mon-old vermicompost, a 1% vermicompost amendment did not decrease reniform nematode numbers. It appears that incorporation of 1-mon-old vermicompost at 1% to field soils will lower existing reniform nematode population density.
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Chapter
The great importance of the soil biota in soil pedogenesis and in the maintenance of structure and fertility is not always fully appreciated by physical and chemical soil scientists. Earthworms are arguably the most important components of the soil biota in terms of soil formation and maintenance of soil structure and fertility. Although not numerically dominant, their large size makes them one of the major contributors to invertebrate biomass in soils. Their activities are important for maintaining soil fertility in a variety of ways in forests, grasslands, and agroecosystems.
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