Genetic differentiation in pesticide resistance between urban and rural populations of a nontarget freshwater keystone interactor, Daphnia magna

Multigenerational and transgenerational effects of azoxystrobin on Folsomia candida

Soil organisms are exposed to various pollutants during several generations. However standard toxicity tests are often based on exposure in only one generation. Research of multigenerational (MG) and transgenerational (TG) effects are still quite scarce, however evidence accumulates that effects observed in one generation can be significantly different in some of the following generations, with different effects observed. Some studies suggest adaptation to pollutants, while others report severe effects in following generations. Azoxystrobin is commonly used in the prevention and treatment of fungal diseases in a wide range of economically important crops. The main aim of this study was to assess the toxic effects of azoxystrobin (AZO) on F. candida over 3 generations through the application of biochemical and population level biomarkers. Results of reproduction tests showed a significant decrease in estimated EC50 values, with EC50 for F0 being estimated at 104.44 mga.i./kgD.W.soil and only 15.4 mga.i./kgD.W.soil for F1. In F1 a significant reduction in the number of juveniles was observed, and at AZO concentration of 50 mga.i./kgD.W and higher, F1 did not reproduce. Significant oxidative stress was observed in all generations, with increased SOD and lipid damage that slowly decreased in subsequent generations. Transgenerational effects were also observed, with a significantly reduced number of juveniles in F1 and significant oxidative stress and lipid damage in all generations. IBRv2 showed that F1 was most affected, followed by F0, and least affected was F3. When considering the whole body energy budget, F1 to F3 had significantly higher WBEB compared to F0, and a shift in proportion of energy reserves occurred in F1, where the proportion of lipids increased while protein decreased. Results of this research show that considering standard toxicity tests, risks for populations of soil organisms are possibly severely underestimated. Therefore, standard toxicity guidelines should be supplemented by multigenerational tests, when possible.

Variation of Tolerance to Isothiazolinones Among Daphnia pulex Clones

Isothiazolinones are a family of broad-spectrum biocides widely used in industry and consumer products. Chloro- and methyl-isothiazolinones (CMIT and MIT) are documented as strong irritants, yet they are still used in a wide variety of applications, including cosmetics, cleansers, hygienic products, and various industrial applications. The subsequent substantial release of these molecules from urban sources into freshwater environments, and their potential impacts on aquatic species, have nevertheless received little attention so far, with few studies reporting on the toxicity of either CMIT or MIT to nontarget organisms. The present study addresses this current knowledge gap by evaluating the acute toxicity to Daphnia pulex (Cladocera) of CMIT/MIT (3:1) and MIT, the two formulations most commonly used by manufacturers. In addition, genetic diversity is known to be a major component of variability in phenotypic responses, although it is largely overlooked in typical toxicity tests. Thus the potential range of responses inherent to genetic diversity is rarely considered. Therefore, to account for intraspecific variations in sensitivity, our design involved eight clonal lines of D. pulex stemming from distinct natural populations or commercial strains. Clones exhibited strong variation in their responses, with median lethal concentration (LC50) values ranging from 0.10 to 1.84 mg/L for the mixture CMIT/MIT, and from 0.68 to 2.84 mg/L for MIT alone. These intraspecific ranges of LC50 values challenge the use of single clones of daphnids in standard ecotoxicological tests and the predictions based on their results. The present study brings new evidence that assessing ecological risk of chemicals while ignoring genotype diversity is neither ecologically relevant, nor a representative evaluation of the diversity of potential adverse outcomes. Environ Toxicol Chem 2023;42:805-814. © 2023 SETAC.

Cardiotoxicity and neurobehavioral effects induced by acrylamide in Daphnia magna

Acrylamide has neurotoxic and/or cardiotoxic effects on humans however available information regarding the neuro- and cardiotoxicity currently is very limited for freshwater organism models. Using three distinct techniques, thus, we investigated the neuro- and cardiotoxic effects of acrylamide in the freshwater invertebrate model, Daphnia magna. We exposed D. magna to acrylamide at concentrations of 0.3, 2.7, and 11.1 mg/L for 48 h alongside a control group. We then conducted physiological (thoracic limb activity and heart rate) and behavioral tests (including distance moved, velocity, turn angle, moving duration, the distance between subjects, and body contact frequency), as well as gene transcription analyses (related to cardiomyopathy, the serotonergic synapse, neuroactive ligand-receptor interactions, the GABAergic synapse, and acetylcholine receptors). After acrylamide exposure, the thoracic limb activity and heart rates of D. magna showed time- and dose dependent inhibition. From low to high exposure concentrations, both heart rates and thoracic limb activity were decreased. Additionally, the distance between subjects and body contact frequencies was significantly reduced. At the gene transcription level, acrylamide significantly altered the transcription of five genes related to cardiomyopathy and eight genes related to the serotonergic synapse, neuroactive ligand-receptor interactions, and the GABAergic synapse. The signs of hindered neural and cardiac functions were shown in D. magna. This suggests that acrylamide exposure leads to cardiotoxicity and neurobehavior defects in D. magna. Because cardiotoxicity and neurobehavioral changes may cause an ecological imbalance via predation of D. magna, acrylamide may also be considered a threat to freshwater ecosystem.

Adaptation to urban environments

Despite widespread evidence of urban evolution, the adaptive nature of these changes is often unclear. We review different phenotypic and molecular lines of evidence used for assessing urban adaptation, discussing the benefits and limitations of each approach, and rare examples of their integration. We then provide a synthesis of local adaptation to urban and rural environments. These data were drawn from phenotypic reciprocal transplant studies, the majority of which focus on insects and other arthropods. Broadly, we found support for local adaptation to urban and rural environments. However, there was asymmetry in the evidence for local adaptation depending on population of origin, with urban adaptation being less prevalent than rural adaptation, suggesting many urban populations are still adapting to urban environments. Further, the general patterns were underlain by considerable variation among study systems; we discuss how environmental heterogeneity and costs of adaptation might explain system-specific variation in urban-rural local adaptation. We then look to the future of urban adaptation research, considering the magnitude and direction of adaptation in context of different agents of selection including urban heat islands, chemical pollutants, and biotic interactions.

Reduced genetic diversity of freshwater amphipods in rivers with increased levels of anthropogenic organic micropollutants

Anthropogenic chemicals in freshwater environments contribute majorly to ecosystem degradation and biodiversity decline. In particular anthropogenic organic micropollutants (AOM), a diverse group of compounds, including pesticides, pharmaceuticals, and industrial chemicals, can significantly impact freshwater organisms. AOM were found to impact genetic diversity of freshwater species; however, to which degree AOM cause changes in population genetic structure and allelic richness of freshwater macroinvertebrates remains poorly understood. Here, the impact of AOM on genetic diversity of the common amphipod Gammarus pulex (Linnaeus, 1758) (clade E) was investigated on a regional scale. The site‐specific AOM levels and their toxic potentials were determined in water and G. pulex tissue sample extracts for 34 sites along six rivers in central Germany impacted by wastewater effluents and agricultural run‐off. Population genetic parameters were determined for G. pulex from the sampling sites by genotyping 16 microsatellite loci. Genetic differentiation among G. pulex from the studied rivers was found to be associated with geographic distance between sites and to differences in site‐specific concentrations of AOM. The genetic diversity parameters of G. pulex were found to be related to the site‐specific AOM levels. Allelic richness was significantly negatively correlated with levels of AOM in G. pulex tissue (p < 0.003) and was reduced by up to 22% at sites with increased levels of AOM, despite a positive relationship of allelic richness and the presence of waste‐water effluent. In addition, the inbreeding coefficient of G. pulex from sites with toxic AOM levels was up to 2.5 times higher than that of G. pulex from more pristine sites. These results indicate that AOM levels commonly found in European rivers significantly contribute to changes in the genetic diversity of an ecologically relevant indicator species.

A Theory of City Biogeography and the Origin of Urban Species

Many of the choices humans make with regard to infrastructure, urban planning and other phenomena have impacts that will last thousands of years. This can readily be seen in modern cities in which contemporary streets run along street grids that were laid out thousands of years prior or even in which ancient viaducts still play a role. However, rarely do evolutionary biologists explicitly consider the future of life likely to be associated with the decisions we are making today. Here, we consider the evolutionary future of species in cities with a focus on the origin of lineages and species. We do so by adjusting evolutionary predictions from the theory of island biogeography so as to correspond to the unique features of cities as islands. Specifically, the species endemic to cities tend to be associated with the gray habitats in cities. Those habitats tend to be dominated by human bodies, pet bodies and stored food. It is among such species where the origin of new lineages is most likely, although most research on evolution in cities has focused on green habitats. We conclude by considering a range of scenarios for the far future and their implications for the origin of lineages and species.

Novel genetic sex markers reveal unexpected lack of, and similar susceptibility to, sex reversal in free-living common toads in both natural and anthropogenic habitats

Anthropogenic environmental changes are affecting biodiversity and microevolution worldwide. Ectothermic vertebrates are especially vulnerable, since environmental changes can disrupt their sexual development and cause sex reversal, a mismatch between genetic and phenotypic sex. This can potentially lead to sex-ratio distortion and population decline. Despite these implications, we have scarce empirical knowledge on the incidence of sex reversal in nature. Populations in anthropogenic environments may be exposed to sex-reversing stimuli more frequently, which may lead to higher sex-reversal rate, or alternatively, these populations may adapt to resist sex reversal. We developed PCR-based genetic sex markers for the common toad (Bufo bufo) to assess the prevalence of sex reversal in wild populations living in natural, agricultural and urban habitats, and the susceptibility of the same populations to two ubiquitous estrogenic pollutants in a common-garden experiment. We found negligible sex-reversal frequency in free-living adults despite the presence of various endocrine-disrupting pollutants in their breeding ponds. Individuals from different habitat types showed similar susceptibility to sex reversal in the laboratory: all genetic males developed female phenotype when exposed to 1 µg/L 17α-ethinylestradiol (EE2) during larval development, whereas no sex reversal occurred in response to 1 ng/L EE2 and a glyphosate-based herbicide with 3 µg/L or 3 mg/L glyphosate. The latter results do not support that populations in anthropogenic habitats would have either increased propensity for or higher tolerance to chemically induced sex reversal. Thus, the extremely low sex-reversal frequency in wild toads compared to other ectothermic vertebrates studied before might indicate idiosyncratic, potentially species-specific resistance to sex reversal.