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1.
J Evol Biol ; 36(8): 1166-1184, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-37394735

RESUMO

Hybridization following secondary contact of genetically divergent populations can influence the range expansion of invasive species, though specific outcomes depend on the environmental dependence of hybrid fitness. Here, using two genetically and ecologically divergent threespine stickleback lineages that differ in their history of freshwater colonization, we estimate fitness variation of parental lineages and hybrids in semi-natural freshwater ponds with contrasting histories of nutrient loading. In our experiment, we found that fish from the older freshwater lineage (Lake Geneva) and hybrids outperformed fish from the younger freshwater lineage (Lake Constance) in terms of both growth and survival, regardless of the environmental context of our ponds. Across all ponds, hybrids exhibited the highest survival. Although wild-caught adult populations differed in their functional and defence morphology, it is unclear which of these traits underlie the fitness differences observed among juveniles in our experiment. Overall, our work suggests that when hybrid fitness is insensitive to environmental conditions, as observed here, introgression may promote population expansion into unoccupied habitats and accelerate invasion success.


Assuntos
Smegmamorpha , Lagoas , Animais , Ecossistema , Masculino , Feminino
2.
Microb Ecol ; 85(4): 1578-1589, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-35486140

RESUMO

Host genotype may shape host-associated bacterial communities (commonly referred to as microbiomes). We sought to determine (a) whether bacterial communities vary among host genotypes in the water flea Daphnia galeata and (b) if this difference is driven by the genetic distance between host genotypes, by using D. galeata genotypes hatched from sediments of different time periods. We used 16S amplicon sequencing to profile the gut and body bacterial communities of eight D. galeata genotypes hatched from resting eggs; these were isolated from two distinct sediment layers (dating to 1989 and 2009) of a single sediment core of the lake Greifensee, and maintained in a common garden in laboratory cultures for 5 years. In general, bacterial community composition varied in both the Daphnia guts and bodies; but not between genotypes from different sediment layers. Specifically, genetic distances between host genotypes did not correlate with beta diversity of bacterial communities in Daphnia guts and bodies. Our results indicate that Daphnia bacterial community structure is to some extent determined by a host genetic component, but that genetic distances between hosts do not correlate with diverging bacterial communities.


Assuntos
Bactérias , Daphnia , Animais , Daphnia/genética , Daphnia/microbiologia , Bactérias/genética , Genótipo , Lagos
3.
Mol Phylogenet Evol ; 151: 106891, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32562822

RESUMO

Caullerya mesnili is a common and virulent parasite of the water flea, Daphnia. It was classified within the Haplosporidia (Rhizaria) for over a century. However, a recent molecular phylogeny based on the 18S rRNA gene suggested it belonged to the Ichthyosporea, a class of protists closely related to animals within the Opisthokonta clade. The exact phylogenetic position of C. mesnili remained uncertain because it appeared in the 18S rRNA tree with a very long branch and separated from all other taxa, suggesting that its position could be artifactual. A better understanding of its phylogenetic position has been constrained by a lack of molecular markers and the difficulty of obtaining a suitable quantity and quality of DNA from in vitro cultures, as this intracellular parasite cannot be cultured without its host. We isolated and collected spores of C. mesnili and sequenced genomic libraries. Phylogenetic analyses of a newly generated multi-protein data set (22 proteins, 4998 amino acids) and of sequences from the 18S rRNA gene both placed C. mesnili within the Ichthyophonida sub-clade of Ichthyosporea, as sister-taxon to Abeoforma whisleri and Pirum gemmata. Our study highlights the utility of metagenomic approaches for obtaining genomic information from intracellular parasites and for more accurate phylogenetic placement in evolutionary studies.


Assuntos
Daphnia/parasitologia , Mesomycetozoea/classificação , Mesomycetozoea/genética , Fases de Leitura Aberta/genética , Parasitos/classificação , Parasitos/genética , Filogenia , Animais , Sequência de Bases , Evolução Biológica , Funções Verossimilhança , RNA Ribossômico 18S/genética
4.
Proc Biol Sci ; 286(1913): 20191857, 2019 10 23.
Artigo em Inglês | MEDLINE | ID: mdl-31615363

RESUMO

A major challenge in ecology is to understand determinants of ecosystem functioning and stability in the face of disturbance. Some important species can strongly shape community structure and ecosystem functioning, but their impacts and interactions on ecosystem-level responses to disturbance are less well known. Shallow ponds provide a model system in which to study the effects of such species because some taxa mitigate transitions between alternative ecosystem states caused by eutrophication. We performed pond experiments to test how two foundation species (a macrophyte and a mussel) affected the biomass of planktonic primary producers and its stability in response to nutrient additions. Individually, each species reduced phytoplankton biomass and tended to increase rates of recovery from disturbance, but together the species reversed these effects, particularly with larger nutrient additions. This reversal was mediated by high cyanobacterial dominance of the community and a resulting loss of trait evenness. Effects of the foundation species on primary producer biomass were associated with effects on other ecosystem properties, including turbidity and dissolved oxygen. Our work highlights the important role of foundation species and their interactive effects in determining responses of ecosystem functioning to disturbance.


Assuntos
Ecossistema , Animais , Biomassa , Cianobactérias , Eutrofização , Fitoplâncton , Lagoas
5.
BMC Genomics ; 19(1): 932, 2018 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-30547741

RESUMO

BACKGROUND: Regulatory circuits of infection in the emerging experimental model system, water flea Daphnia and their microparasites, remain largely unknown. Here we provide the first molecular insights into the response of Daphnia galeata to its highly virulent and common parasite Caullerya mesnili, an ichthyosporean that infects the gut epithelium. We generated a transcriptomic dataset using RNAseq from parasite-exposed (vs. control) Daphnia, at two time points (4 and 48 h) after parasite exposure. RESULTS: We found a down-regulation of metabolism and immunity-related genes, at 48 h (but not 4 h) after parasite exposure. These genes are involved in lipid metabolism and fatty acid biosynthesis, as well as microbe recognition (e.g. c-type lectins) and pathogen attack (e.g. gut chitin). CONCLUSIONS: General metabolic suppression implies host energy shift from reproduction to survival, which is in agreement with the known drastic reduction in Daphnia fecundity after Caullerya infection. The down-regulation of gut chitin indicates a possible interaction between the peritrophic matrix and the evading host immune system. Our study provides the first description of host transcriptional responses in this very promising host-parasite experimental system.


Assuntos
Daphnia/genética , Sistema Imunitário/metabolismo , Intestinos/parasitologia , Metabolismo dos Lipídeos/genética , Mesomycetozoea/fisiologia , Animais , Daphnia/metabolismo , Regulação para Baixo , Ácido Graxo Sintases/genética , Interações Hospedeiro-Parasita , Sistema Imunitário/parasitologia , RNA/química , RNA/isolamento & purificação , RNA/metabolismo , Análise de Sequência de RNA , Transcriptoma
6.
Appl Environ Microbiol ; 82(21): 6472-6482, 2016 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-27565621

RESUMO

We reconstructed cyanobacterial community structure and phylogeny using DNA that was isolated from layers of stratified sediments spanning 200 years of lake history in the perialpine lakes Greifensee and Lake Zurich (Switzerland). Community analysis based on amplification and sequencing of a 400-nucleotide (nt)-long 16S rRNA fragment specific to Cyanobacteria revealed operational taxonomic units (OTUs) capturing the whole phylum, including representatives of a newly characterized clade termed Melainabacteria, which shares common ancestry with Cyanobacteria and has not been previously described in lakes. The reconstruction of cyanobacterial richness and phylogenetic structure was validated using a data set consisting of 40 years of pelagic microscopic counts from each lake. We identified the OTUs assigned to common taxa known to be present in Greifensee and Lake Zurich and found a strong and significant relationship (adjusted R2 = 0.89; P < 0.001) between pelagic species richness in water and OTU richness in the sediments. The water-sediment richness relationship varied between cyanobacterial orders, indicating that the richness of Chroococcales and Synechococcales may be underestimated by microscopy. PCR detection of the microcystin synthetase gene mcyA confirmed the presence of potentially toxic cyanobacterial taxa over recent years in Greifensee and throughout the last century in Lake Zurich. The approach presented in this study demonstrates that it is possible to reconstruct past pelagic cyanobacterial communities in lakes where the integrity of the sedimentary archive is well preserved and to explore changes in phylogenetic and functional diversity over decade-to-century timescales. IMPORTANCE: Cyanobacterial blooms can produce toxins that affect water quality, especially under eutrophic conditions, which are a consequence of human-induced climate warming and increased nutrient availability. Lakes worldwide have suffered from regular cyanobacterial blooms over the last century. The lack of long-term data limits our understanding of how these blooms form. We successfully reconstructed the past diversity of whole cyanobacterial communities over two hundred years by sequencing genes preserved in the sediments of two perialpine lakes in Switzerland. We identified changes in diversity over time and validated our results using existing data collected in the same two lakes over the past 40 years. This work shows the potential of our approach for addressing important ecological questions about the effects of a changing environment on lake ecology.


Assuntos
Cianobactérias/genética , DNA Bacteriano/genética , Sedimentos Geológicos/microbiologia , Lagos/microbiologia , Consórcios Microbianos , Cianobactérias/classificação , Cianobactérias/fisiologia , Consórcios Microbianos/genética , Consórcios Microbianos/fisiologia , Filogenia , RNA Ribossômico 16S/genética , Suíça , Qualidade da Água
7.
Environ Sci Technol ; 50(7): 3416-24, 2016 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-26943751

RESUMO

Zooplankton communities can be strongly affected by cyanobacterial blooms, especially species of genus Daphnia, which are key-species in lake ecosystems. Here, we explored the effect of microcystin/nonmicrocystin (MC/non-MC) producing cyanobacteria in the diet of experimental Daphnia galeata populations composed of eight genotypes. We used D. galeata clones hatched from ephippia 10 to 60 years old, which were first tested in monocultures, and then exposed for 10 weeks as mixed populations to three food treatments consisting of green algae combined with cyanobacteria able/unable of producing MC. We measured the expression of nine genes potentially involved in Daphnia acclimation to cyanobacteria: six protease genes, one ubiquitin-conjugating enzyme gene, and two rRNA genes, and then we tracked the dynamics of the genotypes in mixed populations. The expression pattern of one protease and the ubiquitin-conjugating enzyme genes was positively correlated with the increased fitness of competing clones in the presence of cyanobacteria, suggesting physiological plasticity. The genotype dynamics in mixed populations was only partially related to the growth rates of clones in monocultures and varied strongly with the food. Our results revealed strong intraspecific differences in the tolerance of D. galeata clones to MC/non-MC-producing cyanobacteria in their diet, suggesting microevolutionary effects.


Assuntos
Cianobactérias/metabolismo , Daphnia/genética , Aptidão Genética , Genética Populacional , Aclimatação , Animais , Clorófitas , Daphnia/fisiologia , Ecossistema , Cadeia Alimentar , Perfilação da Expressão Gênica , Genótipo , Humanos , Lagos , Microcistinas/metabolismo , Repetições de Microssatélites , Grupos Populacionais , Suíça , Zooplâncton
8.
Ecol Lett ; 18(7): 597-611, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-25960188

RESUMO

Forecasts of ecological dynamics in changing environments are increasingly important, and are available for a plethora of variables, such as species abundance and distribution, community structure and ecosystem processes. There is, however, a general absence of knowledge about how far into the future, or other dimensions (space, temperature, phylogenetic distance), useful ecological forecasts can be made, and about how features of ecological systems relate to these distances. The ecological forecast horizon is the dimensional distance for which useful forecasts can be made. Five case studies illustrate the influence of various sources of uncertainty (e.g. parameter uncertainty, environmental variation, demographic stochasticity and evolution), level of ecological organisation (e.g. population or community), and organismal properties (e.g. body size or number of trophic links) on temporal, spatial and phylogenetic forecast horizons. Insights from these case studies demonstrate that the ecological forecast horizon is a flexible and powerful tool for researching and communicating ecological predictability. It also has potential for motivating and guiding agenda setting for ecological forecasting research and development.


Assuntos
Ecologia/métodos , Previsões , Evolução Biológica , Ecossistema , Modelos Estatísticos , Filogenia
9.
Mol Ecol ; 24(16): 4074-93, 2015 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-26122166

RESUMO

Biological invasions are a global issue with far-reaching consequences for single species, communities and whole ecosystems. Our understanding of modes and mechanisms of biological invasions requires knowledge of the genetic processes associated with successful invasions. In many instances, this information is particularly difficult to obtain as the initial phases of the invasion process often pass unnoticed and we rely on inferences from contemporary population genetic data. Here, we combined historic information with the genetic analysis of resting eggs to reconstruct the invasion of Daphnia pulicaria into Lower Lake Constance (LLC) in the 1970s from the resting egg bank in the sediments. We identified the invader as 'European D. pulicaria' originating from meso- and eutrophic lowland lakes and ponds in Central Europe. The founding population was characterized by extremely low genetic variation in the resting egg bank that increased considerably over time. Furthermore, strong evidence for selfing and/or biparental inbreeding was found during the initial phase of the invasion, followed by a drop of selfing rate to low levels in subsequent decades. Moreover, the increase in genetic variation was most pronounced during early stages of the invasion, suggesting additional introductions during this period. Our study highlights that genetic data covering the entire invasion process from its beginning can be crucial to accurately reconstruct the invasion history of a species. We show that propagule banks can preserve such information enabling the study of population genetic dynamics and sources of genetic variation in successful invasive populations.


Assuntos
Daphnia/genética , Genética Populacional , Óvulo , Animais , Núcleo Celular/genética , DNA Mitocondrial/genética , Frequência do Gene , Marcadores Genéticos , Variação Genética , Genótipo , Sedimentos Geológicos , Alemanha , Endogamia , Espécies Introduzidas , Lagos , Repetições de Microssatélites , Modelos Genéticos , Dados de Sequência Molecular , Filogenia , Dinâmica Populacional , Análise de Sequência de DNA , Suíça
10.
Microb Ecol ; 68(3): 645-56, 2014 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24863129

RESUMO

Parasite environments are heterogeneous at different levels. The first level of variability is the host itself. The second level represents the external environment for the hosts, to which parasites may be exposed during part of their life cycle. Both levels are expected to affect parasite fitness traits. We disentangle the main and interaction effects of variation in the immediate host environment, here the diatom Asterionella formosa (variables host cell volume and host condition through herbicide pre-exposure) and variation in the external environment (variables host density and acute herbicide exposure) on three fitness traits (infection success, development time and reproductive output) of a chytrid parasite. Herbicide exposure only decreased infection success in a low host density environment. This result reinforces the hypothesis that chytrid zoospores use photosynthesis-dependent chemical cues to locate its host. At high host densities, chemotaxis becomes less relevant due to increasing chance contact rates between host and parasite, thereby following the mass-action principle in epidemiology. Theoretical support for this finding is provided by an agent-based simulation model. The immediate host environment (cell volume) substantially affected parasite reproductive output and also interacted with the external herbicide exposed environment. On the contrary, changes in the immediate host environment through herbicide pre-exposure did not increase infection success, though it had subtle effects on zoospore development time and reproductive output. This study shows that both immediate host and external environment as well as their interaction have significant effects on parasite fitness. Disentangling these effects improves our understanding of the processes underlying parasite spread and disease dynamics.


Assuntos
Quitridiomicetos/fisiologia , Diatomáceas/parasitologia , Meio Ambiente , Interações Hospedeiro-Parasita , Quitridiomicetos/genética , Aptidão Genética , Herbicidas
11.
Evol Appl ; 17(1): e13620, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-38283608

RESUMO

Human activities have facilitated the invasion of freshwater ecosystems by various organisms. Especially, invasive bivalves such as the quagga mussels, Dreissena bugensis, have the potential to alter ecosystem function as they heavily affect the food web. Quagga mussels occur in high abundance, have a high filtration rate, quickly spread within and between waterbodies via pelagic larvae, and colonize various substrates. They have invaded various waterbodies across the Northern Hemisphere. In Central Europe, they have invaded multiple large and deep perialpine lakes with first recordings in Lake Geneva in 2015 and 2016 in Lake Constance. In the deep perialpine lakes, quagga mussels quickly colonized the littoral zone but are also abundant deeper (>80 m), where they are often thinner and brighter shelled. We analysed 675 quagga mussels using ddRAD sequencing to gain in-depth insights into the genetic population structure of quagga mussels across Central European lakes and across various sites and depth habitats in Lake Constance. We revealed substantial genetic differentiation amongst quagga mussel populations from three unconnected lakes, and all populations showed high genetic diversity and effective population size. In Lake Constance, we detected no genetic differentiation amongst quagga mussels sampled across different sites and depth habitats. We also did not identify any convincing candidate loci evidential for adaptation along a depth gradient and a transplant experiment showed no indications of local adaptation to living in the deep based on investigating growth and survival. Hence, the shallow-water and the deep-water morphotypes seem to be a result of phenotypic plasticity rather than local adaptation to depth. In conclusion, our ddRAD approach revealed insight into the establishment of genetically distinct quagga mussel populations in three perialpine lakes and suggests that phenotypic plasticity and life history traits (broadcast spawner with high fecundity and dispersing pelagic larvae) facilitate the fast spread and colonization of various depth habitats by the quagga mussel.

12.
Front Microbiol ; 15: 1310374, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38628870

RESUMO

Eutrophication due to nutrient addition can result in major alterations in aquatic ecosystem productivity. Foundation species, individually and interactively, whether present as invasive species or as instruments of ecosystem management and restoration, can have unwanted effects like stabilizing turbid eutrophic states. In this study, we used whole-pond experimental manipulations to investigate the impacts of disturbance by nutrient additions in the presence and absence of two foundation species: Dreissena polymorpha (a freshwater mussel) and Myriophyllum spicatum (a macrophyte). We tracked how nutrient additions to ponds changed the prokaryotic and eukaryotic communities, using 16S, 18S, and COI amplicon sequencing. The nutrient disturbance and foundation species imposed strong selection on the prokaryotic communities, but not on the microbial eukaryotic communities. The prokaryotic communities changed increasingly over time as the nutrient disturbance intensified. Post-disturbance, the foundation species stabilized the prokaryotic communities as observed by the reduced rate of change in community composition. Our analysis suggests that prokaryotic community change contributed both directly and indirectly to major changes in ecosystem properties, including pH and dissolved oxygen. Our work shows that nutrient disturbance and foundation species strongly affect the prokaryotic community composition and stability, and that the presence of foundation species can, in some cases, promote the emergence and persistence of a turbid eutrophic ecosystem state.

13.
Environ Microbiol ; 15(3): 837-47, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23046213

RESUMO

Parasites play an important role in the regulation of host population growth. How these ubiquitous stressors interact with anthropogenic stressors is less often studied. In a full factorial experiment we explored the independent and combined effects of the widely used herbicide diuron and a chytrid parasite on the fitness of genetically different monoclonal diatom populations. Furthermore, we evaluated how herbicide exposure influenced infection dynamics, parasite fitness and the impact of infectious disease on host populations. We found no evidence of host genetic variation for diuron sensitivity and parasite resistance. Instead, host population phenotype was a decisive factor in controlling parasite growth. Although herbicide exposure initially posed a constraint on disease transmission, it enhanced the spread of disease over time. Consequently, the nature of the parasite-toxicant stressor interaction shifted from antagonistic (on exponential host growth) towards additive (on final uninfected host density). We conclude that herbicide exposure can modify infection dynamics and impact of disease on host populations through the complex interplay between host and parasite growth dynamics and host population phenotype.


Assuntos
Quitridiomicetos/efeitos dos fármacos , Quitridiomicetos/fisiologia , Diatomáceas/efeitos dos fármacos , Diatomáceas/parasitologia , Diurona/toxicidade , Herbicidas/toxicidade , Interações Hospedeiro-Parasita/efeitos dos fármacos
14.
Environ Sci Technol ; 47(18): 10667-75, 2013 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-23919732

RESUMO

Organic contaminants detected in sediments from Lake Greifensee and other compounds falling in the log Dow range from 1 to 7 were selected to study the bioconcentration of organic contaminants in sediments in Daphnia resting eggs (ephippia). Our results show that octocrylene, tonalide, triclocarban, and other personal care products, along with pesticides and biocides can accumulate in ephippia with log BCF values up to 3. Data on the uptake and depuration kinetics show a better fit toward a two compartment organism model over a single compartment model due to the differences in ephippial egg content in the environment. The obtained BCFs correlate with hydrophobicity for neutral compounds. Independence between BCF and hydrophobicity was observed for partially ionized compounds with log Dow values around 1. Internal concentrations in ephippia in the environment were predicted based on sediment concentrations using the equilibrium partitioning model and calculated BCFs. Estimated internal concentration values ranged between 1 and 68,000 µg/kglip with triclocarban having the highest internal concentrations followed by tonalide and triclosan. The outcomes indicate that contaminants can be taken up by ephippia from the water column or the pore water in the sediment and might influence fitness and sexual reproduction in the aquatic key species of the genus Daphnia.


Assuntos
Daphnia , Compostos Orgânicos/metabolismo , Poluentes Químicos da Água/metabolismo , Zigoto/metabolismo , Animais , Cosméticos/análise , Cosméticos/metabolismo , Sedimentos Geológicos/análise , Modelos Biológicos , Compostos Orgânicos/análise , Praguicidas/análise , Praguicidas/metabolismo , Preparações Farmacêuticas/análise , Preparações Farmacêuticas/metabolismo , Poluentes Químicos da Água/análise
15.
Proc Biol Sci ; 279(1740): 2936-44, 2012 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-22513861

RESUMO

Whether exotic species invade new habitats successfully depends on (i) a change in the invaded habitat that makes it suitable for the invader and (ii) a genetic change in the invading taxon that enhances its fitness in the new habitat, or both. We dissect the causes of invasions of Swiss lakes, north of the Alps, by Daphnia galeata (a zooplankter typical of eutrophic lakes, e.g. those south of the Alps, which are also warmer) by comparing the fitness performance of eight geographically distributed clones that were fed algal-food typical of oligotrophic versus eutrophic conditions at two temperatures. Daphnia longispina, native to oligotrophic Swiss lakes, served as a reference. Daphnia galeata requires eutrophic food to persist, whereas D. longispina survives and grows on oligotrophic food but does even better on eutrophic food. Invasion by D. galeata is further explained because invading clones from the north perform better on eutrophic food and at cooler temperatures than native clones from the south, suggesting a local response to countergradient selection. Our data support the hypothesis that populations of the invader in northern lakes are dominated by well-adapted genotypes. Our results illustrate how environmental change (i.e. eutrophication) and local adaptation can act together to drive a successful invasion.


Assuntos
Adaptação Fisiológica/fisiologia , Migração Animal , Daphnia/fisiologia , Lagos , Adaptação Fisiológica/genética , Animais , Temperatura Baixa , Daphnia/classificação , Daphnia/genética , Ecossistema , Eutrofização , Variação Genética , Suíça
16.
Proc Natl Acad Sci U S A ; 106(12): 4758-63, 2009 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-19273852

RESUMO

The overenrichment (eutrophication) of aquatic ecosystems with nutrients leading to algal blooms and anoxic conditions has been a persistent and widespread environmental problem. Although there are many studies on the ecological impact of elevated phosphorus (P) levels (e.g., decrease in biodiversity and water quality), little is known about the evolutionary consequences for animal species. We reconstructed the genetic architecture of a Daphnia species complex in 2 European lakes using diapausing eggs that were isolated from sediment layers covering the past 100 years. Changes in total P were clearly associated with a shift in species composition and the population structure of evolutionary lineages. Although environmental conditions were largely re-established after peak eutrophication during the 1970s and 1980s, original species composition and the genetic architecture of species were not restored but evolved along new evolutionary trajectories. Our data demonstrate that anthropogenically induced temporal alterations of habitats are associated with long-lasting changes in communities and species via interspecific hybridization and introgression.


Assuntos
Daphnia/genética , Fenômenos Ecológicos e Ambientais , Eutrofização , Animais , DNA Mitocondrial/genética , Europa (Continente) , Água Doce , Genótipo , Humanos , Fatores de Tempo
17.
FEMS Microbiol Ecol ; 98(10)2022 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-36026529

RESUMO

Host-associated bacterial communities play an important role in host fitness and resistance to diseases. Yet, few studies have investigated tripartite interaction between a host, parasite and host-associated bacterial communities in natural settings. Here, we use 16S rRNA gene amplicon sequencing to compare gut- and body- bacterial communities of wild water fleas belonging to the Daphnia longispina complex, between uninfected hosts and those infected with the common and virulent eukaryotic gut parasite Caullerya mesnili (Family: Ichthyosporea). We report community-level changes in host-associated bacteria with the presence of the parasite infection; namely decreased alpha diversity and increased beta diversity at the site of infection, i.e. host gut (but not host body). We also report decreased abundance of bacterial taxa proposed elsewhere to be beneficial for the host, and an appearance of taxa specifically associated with infected hosts. Our study highlights the host-microbiota-infection link in a natural system and raises questions about the role of host-associated microbiota in natural disease epidemics as well as the functional roles of bacteria specifically associated with infected hosts.


Assuntos
Mesomycetozoea , Parasitos , Animais , Bactérias/genética , Daphnia/genética , Daphnia/microbiologia , Daphnia/parasitologia , Eucariotos/genética , Interações Hospedeiro-Parasita , Mesomycetozoea/genética , Parasitos/genética , RNA Ribossômico 16S/genética
18.
Biol Lett ; 7(1): 108-11, 2011 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-20702454

RESUMO

Both host susceptibility and parasite infectivity commonly have a genetic basis, and can therefore be shaped by coevolution. However, these traits are often sensitive to environmental variation, resulting in genotype-by-environment interactions. We tested the influence of temperature on host-parasite genetic specificity in the Daphnia longispina hybrid complex, exposed to the protozoan parasite Caullerya mesnili. Infection rates were higher at low temperature. Furthermore, significant differences between host clones, but not between host taxa, and a host genotype-by-temperature interaction were observed.


Assuntos
Daphnia/genética , Daphnia/parasitologia , Hibridização Genética , Mesomycetozoea/fisiologia , Temperatura , Animais , Ecossistema , Genótipo , Interações Hospedeiro-Parasita
19.
Environ Sci Technol ; 45(11): 4980-7, 2011 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-21539304

RESUMO

The organothiophosphate diazinon inhibits the target site acetylcholinesterase only after activation to its metabolite diazoxon. Commonly, the toxicity of xenobiotics toward aquatic organisms is expressed as a function of the external concentration and the resulting effect on the individual level after fixed exposure times. This approach does not account for the time dependency of internal processes such as uptake, metabolism, and interaction of the toxicant with the target site. Here, we develop a mechanistic toxicodynamic model for Daphnia magna and diazoxon, which accounts for the inhibition of the internal target site acetylcholinesterase and its link to the observable effect, immobilization, and mortality. The model was parametrized by experiments performed in vitro with the active metabolite diazoxon on enzyme extracts and in vivo with the parent compound diazinon. The mechanism of acetylcholinesterase inhibition was shown to occur irreversibly in two steps via formation of a reversible enzyme-inhibitor complex. The corresponding kinetic parameters revealed a very high sensitivity of acetylcholinesterase from D. magna toward diazoxon, which corresponds well with the high toxicity of diazinon toward this species. Recovery of enzyme activity but no recovery from immobilization was observed after in vivo exposure to diazinon. The toxicodynamic model combining all in vitro and in vivo parameters was successfully applied to describe the time course of immobilization in dependence of acetylcholinesterase activity during exposure to diazinon. The threshold value for enzyme activity below which immobilization set in amounted to 40% of the control activity. Furthermore, the model enabled the prediction of the time-dependent diazoxon concentration directly present at the target site.


Assuntos
Inibidores da Colinesterase/toxicidade , Daphnia/efeitos dos fármacos , Modelos Biológicos , Compostos Organofosforados/toxicidade , Animais , Daphnia/enzimologia , Diazinon/metabolismo , Diazinon/toxicidade , Cinética
20.
Environ Sci Technol ; 45(11): 4995-5002, 2011 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-21561125

RESUMO

A toxicokinetic model for Daphnia magna , which simulates the internal concentration of the insecticide diazinon, its detoxification product 2-isopropyl-6-methyl-4-pyrimidinol, and its active metabolite diazoxon, is presented. During in vivo exposure to diazinon with and without inhibition of cytochrome P450 by piperonyl butoxide, the parent compound as well as its metabolites were quantified with high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) in extracts of D. magna . Rate constants of all relevant toxicokinetic steps were obtained by modeling the time course of the internal concentrations with a multicomponent first-order kinetics model. When cytochrome P450 was inhibited, the kinetic bioconcentration factor (BCF) of diazinon increased from 17.8 to 51.0 mL·g(ww)(-1). This clearly indicates that diazinon is biotransformed to a high degree by cytochrome P450 in D. magna . The dominant elimination step of diazinon was shown to be its oxidative dearylation to pyrimidinol (62% of total elimination) with a corresponding rate constant of 0.16 h(-1). In contrast, oxidative activation to diazoxon with a rate constant of 0.02 h(-1) amounted to only 8% of the total elimination. During exposure to diazinon, the active metabolite diazoxon could be detected only in very low concentrations (approximately 0.5% of the parent compound), presumably due to a very fast reaction with the target site acetylcholinesterase. During the exposure experiments (no feeding of daphnids), an exponential decline of the lipid content in D. magna with a first-order rate constant of 0.013 h(-1) was observed. For short exposure times (≤ 24 h), this had only a minor influence on the determined TK parameters. Such a TK model containing detailed biotransformation processes is an important tool for estimation of the toxic potential of chemicals, particularly, when active metabolites are formed inside an organism.


Assuntos
Daphnia/metabolismo , Diazinon/farmacocinética , Inseticidas/farmacocinética , Modelos Biológicos , Animais , Biotransformação , Sistema Enzimático do Citocromo P-450/metabolismo , Diazinon/metabolismo , Diazinon/toxicidade , Inseticidas/metabolismo , Inseticidas/toxicidade , Metabolismo dos Lipídeos , Compostos Organofosforados/análise , Pirimidinas/análise , Medição de Risco
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