1,721,036 research outputs found
Morphological differences between free-living soil and freshwater nematodes in relation to their environments
No full textThere is no single feature to distinguish free-living soil nematodes from freshwater nematodes, also because all free-living
nematodes are essentially aquatic. This notwithstanding, by examining the frequencies of some characters of 1141 European species,
differences of qualitative/quantitative characters between soil and freshwater nematodes were found. In particular, aquatic and semiaquatic
species are, on average, longer and slimmer than soil species, have a longer tail, greater body weight, smooth cuticle and larger
amphids. A new body parameter, length of the pharynx in relation to the length of the whole digestive tract (e), was also taken into
consideration
Editorial for Special Issue “Meiofauna Biodiversity and Ecology”
Full text linkMeiofauna are a component of aquatic environments from polar to tropical regions.
They may colonize all types of habitats and include very enigmatic and exclusive taxa. The biodiversity
of this component in marine ecosystems is far from being accurately estimated, but this would be
a new challenge given the importance that meiofaunal components may play in marine ecosystem
functioning and processes. This Special Issue collects many interesting topics in research on meiofauna
contributing to plugging a gap on several key issues in their biodiversity, distribution, and ecology,
from numerous regions that include the USA, Brazil, French Guiana, Costa Rica, Mexico, Cuba, Italy,
Kuwait, Vietnam, Madagascar, the Maldives, and South Korea
Taxonomic and functional biodiversity variations of free living nematodes across an extreme environmental gradient: a study case in a Blue Hole cave
No full textSimple Is the Best: An Alternative Method for the Analysis of Free-Living Nematode Assemblage Structure
Full text linkAn alternative approach to notice changes of the nematode community structure was
evaluated in five study cases in the Mediterranean Sea. In detail, we suggested a combination of
morpho-functional traits (i.e., amphid, cuticle, buccal cavity, and tail shape) as an alternative to the
taxonomic identification of nematodes. The results clearly demonstrated that the matrixes made
using the trait code numbers perfectly mirror the changes of the nematode community structure
at the genus level. The combination of the morpho-functional traits more frequently observed in
areas under human pressure were ascribable to genera belonging to Xyalidae, Linhomoeidae and
Chromadoridae families. This approach might greatly speed the analyses of nematode fauna in
biomonitoring programs and might also be adopted for other meiobenthic organisms that may be
categorized in functional groups opening new perspectives in the ecological assessment of meiofauna
Joint analysis of macrofaunal and meiofaunal assemblages improves the assessment of lagoonal environmental heterogeneity
No full textMatching datasets of macrofaunal and meiofaunal assemblages were jointly analyzed for the first time in a
coastal lagoon (Cabras Lagoon, Sardinia) in relation to the lagoonal environmental heterogeneity. Within the
common faunal list, indicator species/taxa for different environmental conditions were found evenly for both
assemblages, with the two faunal components responding distinctly to the putative environmental gradients
according to their autecology. The relationship between the number of individuals and species/taxa richness of
both assemblages showed an exponential increase at increasing salinity and DO concentrations in water as expected
basing on the confinement theory. Along the trophic gradient, the two metrics of both macrofaunal and
meiofaunal assemblages showed a similar belt-shaped curve in agreement with theoretical predictions and
quantitative field studies, with a peak at intermediate OM values followed by a sharp decrease at OM above 12%
at the most confined site. While not a causality measure, our results indicate that these simple benthic-OM relationships
applied to both faunal components represent a valuable screening-level indicator for evaluating the
likelihood of reduced sediment quality and associated bioeffects in eutrophic lagoons. The present study demonstrates
that macrofaunal and meiofaunal assemblages in coastal lagoons, as commonly shown in marine waters,
are coherent and distinct entities and that their joint use represents a more comprehensive and robust tool to
assess the environmental heterogeneity and quality of these highly variable systems
Meiofaunal Dynamics and Heterogeneity along Salinity and Trophic Gradients in a Mediterranean Transitional System
No full textThe spatiotemporal variation in meiofaunal assemblages were investigated for the first
time in the Cabras Lagoon, the largest transitional system in the Sardinian Island (W-Mediterranean
Sea). Two main environmental (salinity and trophic) gradients highlighted a significant separation
of the three study sites across the lagoon, which were consistent through time. The environmental
variability and habitat heterogeneity of the Cabras Lagoon influenced the meiofauna. In particular,
salinity and dissolved oxygen, primarily, shaped the meiofaunal assemblage structure at the seaward
site which was significantly dierent from both the riverine and the organically enriched sites. On the
other hand, the trophic components (e.g., organic matter, Chlorophyll-a, and phaeopigments) and the
dierent degrees of confinement and saprobity among sites were the secondary factors contributing
mostly to the separation between the latter two sites. The lack of significant dierences in the
temporal comparison of the meiofaunal assemblage structure along with the very low contribution
of temperature to the meiofaunal ordination indicated that this assemblage was more aected by
spatial rather than by temporal variation. This pattern was also supported by significant dierences
between the three sites in several univariate measures, including total number of individuals,
number of taxa, Pielou’s evenness, and the ratio between nematodes and copepods. Thus, the present
study corroborates the hypothesis that meiofaunal organisms are good indicators of the spatial
heterogeneity in transitional waters (TWs) and could have a greater species richness than that
expected. Indeed, the Cabras Lagoon overall showed one of the highest meiofaunal richness values
found from both Mediterranean and European TWs
Joint analysis of macrofaunal and meiofaunal assemblages improves the assessment of lagoonal environmental heterogeneity
No full textMatching datasets of macrofaunal and meiofaunal assemblages were jointly analyzed for the first time in a
coastal lagoon (Cabras Lagoon, Sardinia) in relation to the lagoonal environmental heterogeneity. Within the
common faunal list, indicator species/taxa for different environmental conditions were found evenly for both
assemblages, with the two faunal components responding distinctly to the putative environmental gradients
according to their autecology. The relationship between the number of individuals and species/taxa richness of
both assemblages showed an exponential increase at increasing salinity and DO concentrations in water as expected
basing on the confinement theory. Along the trophic gradient, the two metrics of both macrofaunal and
meiofaunal assemblages showed a similar belt-shaped curve in agreement with theoretical predictions and
quantitative field studies, with a peak at intermediate OM values followed by a sharp decrease at OM above 12%
at the most confined site. While not a causality measure, our results indicate that these simple benthic-OM relationships
applied to both faunal components represent a valuable screening-level indicator for evaluating the
likelihood of reduced sediment quality and associated bioeffects in eutrophic lagoons. The present study demonstrates
that macrofaunal and meiofaunal assemblages in coastal lagoons, as commonly shown in marine waters,
are coherent and distinct entities and that their joint use represents a more comprehensive and robust tool to
assess the environmental heterogeneity and quality of these highly variable systems
Simple, inexpensive, and rapid approach to detect changes in the structure of soil free-living nematodes.
No full textA general limitation of ecological investigations based on nematodes is related to the diffi cult and
time-consuming taxonomic identifi cation 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.
Specifi cally, 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
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