Impacts of permethrin contamination on nematode density and diversity: A microcosm study on benthic meiofauna from a Mediterranean coastal lagoon

Biologia ◽  
2012 ◽  
Vol 67 (2) ◽  
Author(s):  
Amel Soltani ◽  
Hela Louati ◽  
Amel Hanachi ◽  
Fida Ben Salem ◽  
Naceur Essid ◽  
...  
Keyword(s):  
Multivariate Analyses ◽  
Species Abundance ◽  
Nematode Species ◽  
Nematode Density ◽  
Resistant Species ◽  
Microcosm Study ◽  
Nematode Abundance ◽  
Specific Tolerance ◽  
Different Levels ◽  
Mediterranean Coastal Lagoon

AbstractA microcosm experiment was used to examine the response of nematode in terms of density and diversity at different levels of permethrin contamination. The sediments were contaminated with three permethrin concentrations [P1: low (5 mg kg−1), P2: medium (25 mg kg−1) and P3: high (250 mg kg−1)] and the effects were evaluated after 30 days. The results from univariate and multivariate analyses showed significant differences between nematode assemblages from uncontaminated control and those from permethrin treatments. All univariate indices changed significantly at all the levels of permethrin contamination. In fact, the total nematode abundance (I), Shannon-Weaner index (H′), species richness (d), evenness (J′) and number of species (S) decreased significantly in all the contaminated microcosms. In addition, the results from multivariate analyses of the species abundance data demonstrated that permethrin affects the responses of nematode species. These significant modifications in nematode community structures with response to permethrin contamination were the consequences of a different specific tolerance to this pesticide. Thus, Araeolaimus bioculatus, Calomicrolaimus honestus, Oncholaimus campylocercoides and Theristus pertenuis characterized by increased abundances in all treated replicates, appeared to be “permethrin-resistant” species. Daptonema trabeculosum was eliminated in all the doses tested and seemed to be a very sensitive species to permethrin contamination.

A microcosm experiment on the effects of permethrin on a free-living nematode assemblage

Nematology ◽  
2011 ◽  
Vol 13 (8) ◽  
pp. 901-909 ◽  
Author(s):  
Badreddine Sellami ◽  
Fehmi Boufahja ◽  
Hamouda Beyrem ◽  
Patricia Aïssa ◽  
Mohamed Dellali ◽  
...  
Keyword(s):  
Low Dose ◽  
Multivariate Analyses ◽  
Nematode Species ◽  
Microcosm Experiment ◽  
Free Living ◽  
Resistant Species ◽  
Free Living Nematode ◽  
Abundance And Diversity ◽  
Contamination Levels ◽  
The Impact

AbstractMicrocosms were used to assess the impact of permethrin on the abundance and diversity of free-living marine nematodes. The nematodes were exposed to three permethrin concentrations (50, 100 and 150 μg l–1), and the effects were examined after 25 days. The abundances of nematodes at all permethrin concentrations significantly exceeded those in the controls. Multivariate analyses demonstrated that responses of nematode species to permethrin treatments were varied: Pselionema sp., Prochromadorella neapolitana and Spirinia gerlachi were eliminated at the low dose and seemed to be species intolerant to permethrin; Trichotheristus mirabilis and Xyala striata, which increased with increasing contamination levels, seemed to be 'opportunistic' and/or 'resistant' species. Results showed significant differences between univariate measures of diversity of control nematodes and those from permethrin- contaminated microcosms, where all decreased significantly with increasing abundance of the most tolerant species to permethrin. The use of microcosms has allowed the effects of permethrin on nematodes to be assessed individually, which is not possible in the field.

scholarly journals Employee Satisfaction in Labor-Owned and Managed Workplaces: Helping Climate and Participation Spillover to Non-Owners

2021 ◽  
Vol 13 (6) ◽  
pp. 3278
Author(s):  
Renée De Reuver ◽  
Brigitte Kroon ◽  
Damian Madinabeitia Olabarria ◽  
Unai Elorza Iñurritegui
Keyword(s):  
Survey Data ◽  
Corporate Responsibility ◽  
Employee Satisfaction ◽  
Multivariate Analyses ◽  
Archival Data ◽  
Temporary Employees ◽  
Employment Contracts ◽  
Employee Wellbeing ◽  
Worker Cooperatives ◽  
Different Levels

In contrast to shareholder-owned organizations, worker-owned cooperative organizations foster employee wellbeing such as employee satisfaction as an important outcome by itself. Due to expansions and economic fluctuations, larger worker-owned cooperations nowadays use mixtures of employment contracts resulting in varying shares of co-owners, contracted and temporary employees in workplaces. In the current paper, we research if this situation challenges the moral commitment of worker cooperatives to their employees, which derive from the cooperative philosophy on corporate responsibility. Where previous research contrasted employee wellbeing in worker cooperatives with share- holder owner organizations, this paper describes how various shares of co-owners in workplaces change mediating processes of helping climate and workplace participation and ultimately result in different levels of employee satisfaction. Archival data combined with survey data of 5907 employees in 99 hypermarkets were tested with multivariate analyses, and indicated that the helping climate and workplace participation positively mediated the association between the share of co-owners in hypermarkets and employee satisfaction. The findings imply that traditional worker-owned cooperatives, where a majority of all workers are owners, had more success in fostering cooperative values as a strategic outcome.

Seasonal distribution of abundance, biomass and secondary production of free-living nematodes and their community composition in different stream micro-habitats

Nematology ◽  
2020 ◽  
Vol 22 (4) ◽  
pp. 401-422 ◽  
Author(s):  
Henrike Brüchner-Hüttemann ◽  
Walter Traunspurger
Keyword(s):  
Species Composition ◽  
Leaf Litter ◽  
Secondary Production ◽  
Dead Wood ◽  
Nematode Species ◽  
Species Number ◽  
Order Stream ◽  
Nematode Communities ◽  
Feeding Types ◽  
Nematode Abundance

Summary The nematode communities of four different micro-habitats in an unpolluted first-order stream were investigated over a 13-month period in a study of the sediment and the biofilms on dead wood, macrophytes and leaf litter. Nematode abundances, biomass and secondary production were analysed, together with the species composition, proportion of feeding types and diversity of the nematode communities of the micro-habitats. Differences between the investigated micro-habitats in terms of seasonal variations, species composition, proportion of feeding types and diversity were expected. The annual mean values of nematode abundance, biomass and secondary production differed significantly between the micro-habitats. Abundances were highest on dead wood, whereas biomass and secondary production were highest in sediment. In the sediment and on leaf litter, nematode abundance and biomass showed pronounced seasonal patterns. The largest contribution to the total secondary production of the stream was from sediment nematodes. In total, 108 nematode species were detected in the micro-habitats during the 13-month study. Comparisons between them revealed differences in nematode species composition. The annual mean species number was significantly higher in sediment and on leaf litter than on dead wood and macrophytes, whereas the annual mean Shannon-Wiener index was significantly higher in sediment than at all other micro-habitats. All micro-habitats in the studied stream, as well as the stream as a whole, were dominated by nematode species belonging to the deposit feeders. Our study clearly showed that the composition of nematode communities from different micro-habitats within a single stream reach can differ markedly.

scholarly journals Simulating the Effectiveness of Improvement Cuts and Commercial Thinning to Enhance Fire Resistance in West Coast Dry Mixed Conifer Forests

2019 ◽  
Vol 66 (2) ◽  
pp. 157-177
Author(s):  
Theresa B Jain ◽  
Jeremy S Fried ◽  
Sara M Loreno
Keyword(s):  
Fire Resistance ◽  
Species Abundance ◽  
Post Treatment ◽  
Conifer Forests ◽  
Mixed Conifer ◽  
Short Term ◽  
Resistant Species ◽  
Commercial Thinning ◽  
Mixed Conifer Forests ◽  
Tree Survival

Abstract Nine multipurpose silvicultural treatments, formulated as a synthesis of recently implemented prescriptions offered by forest managers, were simulated to evaluate their effectiveness at enhancing fire resistance. The Forest Vegetation Simulator was applied, within the BioSum Framework, on over 3,000 Forest Inventory and Analysis plots representing 5 million hectares of dry mixed conifer forests in eastern Washington and Oregon and California’s Sierra Nevada Mountains. We developed a composite fire-resistance score based on four fuel modification principals and metrics: fuel strata gap, canopy bulk density, proportion of basal area in resistant species, and predicted tree survival. The trajectories of stands with and without treatment were compared to evaluate effectiveness immediately post-treatment, and over the three decades that followed. Seventy percent of these forests could be effectively treated in the short term by at least one prescription. Pretreatment forest condition, particularly fire-resistant species abundance, strongly influenced short-term treatment success, and the post-treatment stand dynamics that limit treatment longevity. Treatment effectiveness endured only 10 or 20 years, depending on fire-resistant species abundance, owing to growing space for crown expansion generated by treatment plus regeneration and release and growth of understory tree strata.

Gastric Nematode Communities in Lizards From the Great Victoria Desert, and an Hypothesis for Their Evolution

1995 ◽  
Vol 43 (2) ◽  
pp. 141 ◽  
Author(s):  
HI Jones
Keyword(s):  
Host Species ◽  
Species Abundance ◽  
Nematode Species ◽  
Geographical Range ◽  
Infection Prevalence ◽  
Intermediate Hosts ◽  
Epidemiological Evidence ◽  
Lizard Species ◽  
Evolutionary Phase ◽  
Paratenic Hosts

This study examines the biology of gastric nematodes in two communities of lizards from the Great Victoria Desert, and develops an hypothesis for their evolution. Abbreviata antarctica A. hastaspicula, A, levicauda, A. tumidocapitis, Skrjabinoptera goldmanae, Kreisiella chrysocampa, Physalopteroides filicauda, Wanaristrongylus ctenoti and W. papangawurpae were recovered from 3023 lizards of 45 species from two different habitats. Genera in the Physalopterinae (Abbreviata, Skrjabinoptera and Kreisiella) exhibited narrow host specificities, Abbreviara and Skrjabinoptera occurring as adults only in larger host species (Varanus gouldii, V. tristis and Pogona minor). P. filicauda and encysted larvae of Physalopterinae occurred widely in the smaller lizard species in all five families represented. Eight of the nine nematode species were recovered from both lizard populations, and differences in prevalence and number of host species infected are discussed in terms of core hosts providing an infective pool. Associations were derived between parameters of infection (prevalence, intensity and abundance) and host size across and within species; abundance of nematodes in Ctenotus skinks correlated with host geographical range. Epidemiological evidence is presented that suggests that termites are intermediate hosts to species of Physalopterinae, and that Orthoptera may be intermediate hosts to P.filicauda. It is suggested that species in the Physalopterinae arose in smaller lizards (where they are now represented by the morphologically primitive Kreisiella), and that they were acquired by large predatory species by host capture, and in which they are now speciating. The small lizards now act as paratenic hosts to their larvae, and the niches left vacant have been occupied by P. filicauda. It is concluded that P.filicauda is at an early non-interactive phase and that Abbreviata and Skrjabinoptera are at an evolutionary phase, and are evolving along with their hosts. Thus, the two principal nematode groups arose at different times in response to the radiation and ecology of their hosts, and are at different stages in their own evolution.

scholarly journals Linking signal detection theory and encoding models to reveal independent neural representations from neuroimaging data

2018 ◽  
Author(s):  
Fabian A. Soto ◽  
Lauren E. Vucovich ◽  
F. G. Ashby
Keyword(s):  
Signal Detection Theory ◽  
Multivariate Analyses ◽  
Research Approach ◽  
Face Identity ◽  
Integrative Research ◽  
Neural Representations ◽  
Neuroimaging Data ◽  
Psychophysical Studies ◽  
First Time ◽  
Different Levels

AbstractMany research questions in visual perception involve determining whether stimulus properties are represented and processed independently. In visual neuroscience, there is great interest in determining whether important object dimensions are represented independently in the brain. For example, theories of face recognition have proposed either completely or partially independent processing of identity and emotional expression. Unfortunately, most previous research has only vaguely defined what is meant by “independence,” which hinders its precise quantification and testing. This article develops a new quantitative framework that links signal detection theory from psychophysics and encoding models from computational neuroscience, focusing on a special form of independence defined in the psychophysics literature: perceptual separability. The new theory allowed us, for the first time, to precisely define separability of neural representations and to theoretically link behavioral and brain measures of separability. The framework formally specifies the relation between these different levels of perceptual and brain representation, providing the tools for a truly integrative research approach. In particular, the theory identifies exactly what valid inferences can be made about independent encoding of stimulus dimensions from the results of multivariate analyses of neuroimaging data and psychophysical studies. In addition, commonly used operational tests of independence are re-interpreted within this new theoretical framework, providing insights on their correct use and interpretation. Finally, we apply this new framework to the study of separability of brain representations of face identity and emotional expression (neutral/sad) in a human fMRI study with male and female participants.Author SummaryA common question in vision research is whether certain stimulus properties, like face identity and expression, are represented and processed independently. We develop a theoretical framework that allowed us, for the first time, to link behavioral and brain measures of independence. Unlike previous approaches, our framework formally specifies the relation between these different levels of perceptual and brain representation, providing the tools for a truly integrative research approach in the study of independence. This allows to identify what kind of inferences can be made about brain representations from multivariate analyses of neuroimaging data or psychophysical studies. We apply this framework to the study of independent processing of face identity and expression.

Interactions among bacterial-feeding nematode species at different levels of food availability

2009 ◽  
Vol 156 (4) ◽  
pp. 629-640 ◽  
Author(s):  
Giovanni A. P. dos Santos ◽  
Sofie Derycke ◽  
Verônica G. F. Genevois ◽  
Luana C. B. B. Coelho ◽  
Maria T. S. Correia ◽  
...  
Keyword(s):  
Food Availability ◽  
Nematode Species ◽  
Different Levels

The relationship between nematode infections and ontogeny and diet of the lizard Tropidurus torquatus (Wied, 1820) (Squamata: Tropiduridae) from the Atlantic Rainforest in south-eastern Brazil

2012 ◽  
Vol 87 (3) ◽  
pp. 364-370 ◽  
Author(s):  
F.B. Pereira ◽  
S.C. Gomides ◽  
B.M. Sousa ◽  
S. de Souza Lima ◽  
J.L. Luque
Keyword(s):  
Diet Composition ◽  
Nematode Species ◽  
Intermediate Hosts ◽  
South Eastern ◽  
Eastern Brazil ◽  
Negative Effect ◽  
Rocky Outcrop ◽  
Nematode Abundance ◽  
The Relationship ◽  
Host Body Size

AbstractThe aim of the present study was to investigate the relationship between nematode infection and the ontogeny and diet of the lizard Tropidurus torquatus from a rocky outcrop in the state of Minas Gerais, south-eastern Brazil. Eighty-nine of 110 lizards examined (81.9%) harboured nematodes. Two nematode species were identified, namely, Physaloptera lutzi in the stomach and Parapharyngodon bainae in the intestine, with prevalence values of 67.3 and 60.0%, respectively. The lizard diet was composed mainly of ants, other hymenopterans, beetles and flowers of the species Centrosema coriaceum (Fabaceae). Host body size was positively correlated with nematode abundance, with adults more heavily parasitized than juveniles. The consumption of C. coriaceum had a negative effect on the abundance of both nematode species, suggesting that this plant may possess anthelmintic properties. The probability of a higher worm burden in adult hosts is likely linked with a longer exposure time to infective stages. Beetles, ants and hymenopterans appear to be the main intermediate hosts for P. lutzi. In general, ontogeny and diet composition determine the structure of the helminth community in this species of lizard.

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