Acute Lethal Effects Research Articles

Alien toxic toads suppress individual growth and phenotypic development of native predatory salamanders.

Alien species can influence populations of native species through individual-level effects such as predation, competition, and poisoning. For alien species that possess strong defensive chemicals, poisoning is one of the most powerful mechanisms of individual-level effects on native biota. Although toxic alien species could potentially negatively affect survival (lethal effects) or life history traits (sub-lethal effects) of native predators via poisoning, previous studies have mainly focused on acute lethal effects. Thus, delayed effects on predator life history traits have been largely overlooked. To fill this knowledge gap, we conducted laboratory and field experiments to investigate whether toxic alien prey (hatchlings and tadpoles of an invasive toad, Bufo formosus) affect the survival and/or growth and development of a native predatory salamander (larvae of Hynobius retardatus) on Hokkaido, Japan. The laboratory experiment revealed that consumption of a single toad hatchling exerted non-lethal effects on salamanders, but suppressed both salamander growth and development of an ecological phenotype (broad-gape) normally induced by environmental conditions. Furthermore, the field experiment in a natural pond showed that the presence of toad hatchlings and tadpoles resulted in reduced salamander growth (smaller body size) and lower survival of salamanders in the later larval period. The results of the laboratory and field experiments are complementary evidence of the life history impacts of the toxic alien toad on native salamanders. Thus, the poisoning effects of toxic alien species can affect the life history of native predators even if they do not exert acute lethality.

A test method for assessing chronic oral toxicity of a pesticide to solitary nesting orchard bees, Osmia spp. (Hymenoptera: Megachilidae).

Orchard bees of the genus Osmia Panzer are important pollinators of fruit trees in various regions of the world, with some species commercially available in the United States and Europe. In addition to their pollination services, Osmia lignaria, Osmia cornifrons, Osmia bicornis, and Osmia cornuta have been identified as potential model species for solitary bees in pesticide risk assessment and have been used for the development of new methods to test acute lethal effects via contact and oral routes of exposure. Our goal was to expand the available methodology to characterize the toxicity of pesticides for these solitary bees through a chronic oral test for adult bees. Chronic oral toxicity of pesticides to orchard bees has been reported, but methods differ among research groups. In our study, O. lignaria, O. cornifrons, O. bicornis, and O. cornuta female bees had access to sucrose solution ad libitum in separate, species-specific 10-day tests. Mean body mass, mean daily consumption, and survival differed among the studied bee species. The dose-response test design was validated with dimethoate, a reference toxic compound, and chronic toxicity endpoints were estimated for the 4 Osmia species. The median lethal daily doses normalized by weight for O. lignaria, O. bicornis, O. cornuta, and O. cornifrons were within the same order of magnitude at 0.23, 0.26, 0.49, and 0.61 µg dimethoate/g bee/day, respectively. The methodology described here was aligned as much as possible with the available honey bee and bumble bee standard methods to facilitate the comparison of chronic toxicity profiles among bee species.

Exposure to sublethal levels of insecticide-fungicide mixtures affect reproductive success and population growth rates in the solitary bee Osmia cornuta

In agricultural environments, bees are routinely exposed to combinations of pesticides. For the most part, exposure to these pesticide mixtures does not result in acute lethal effects, but we know very little about potential sublethal effects and their consequences on reproductive success and population dynamics. In this study, we orally exposed newly emerged females of the solitary bee Osmia cornuta to environmentally-relevant levels of acetamiprid (a cyano-substituted neonicotinoid insecticide) singly and in combination with tebuconazole (a sterol-biosynthesis inhibitor (SBI) fungicide). The amount of feeding solution consumed during the exposure phase was lowest in bees exposed to the pesticide mixture. Following exposure, females were individually marked and released into oilseed rape field cages to monitor their nesting performance and assess their reproductive success. The nesting performance and reproductive success of bees exposed to the fungicide or the insecticide alone were similar to those of control bees and resulted in a 1.3-1.7 net population increases. By contrast, bees exposed to the pesticide mixture showed lower establishment, shortened nesting period, and reduced fecundity. Together, these effects led to a 0.5-0.6 population decrease. Female establishment and shortened nesting period were the main population bottlenecks. We found no effects of the pesticide mixture on nest provisioning rate, offspring body weight or sex ratio. Our study shows how sublethal pesticide exposure may affect several components of bee reproductive success and, ultimately, population growth. Our results calls for a rethinking of pollinator risk assessment schemes, which should target not only single compounds but also combinations of compounds likely to co-occur in agricultural environments.

Lethal and behavioral effects of semi-purified microcystins, Micropeptin and apolar compounds from cyanobacteria on freshwater microcrustacean Thamnocephalus platyurus

The mass proliferation of cyanobacteria, episodes known as blooms, is a concern worldwide. One of the most critical aspects during these blooms is the production of toxic secondary metabolites that are not limited to the four cyanotoxins recognized by the World Health Organization. These metabolites comprise a wide range of structurally diverse compounds that possess bioactive functions. Potential human and ecosystem health risks posed by these metabolites and co-produced mixtures remain largely unknown. We studied acute lethal and sublethal effects measured as impaired mobility on the freshwater microcrustaceans Thamnocephalus platyurus for metabolite mixtures from two cyanobacterial strains, a microcystin (MC) producer and a non-MC producer. Both cyanobacterial extracts, from the MC-producer and non-MC-producer, caused acute toxicity with LC50 (24 h) values of 0.50 and 2.55 mgdw_biomass/mL, respectively, and decreased locomotor activity. Evaluating the contribution of different cyanopeptides revealed that the Micropeptin-K139-dominated fraction from the MC-producer extract contributed significantly to mortality and locomotor impairment of the microcrustaceans, with potential mixture effect with other cyanopeptolins present in this fraction. In the non-MC-producer extract, compounds present in the apolar fraction contributed mainly to mortality, locomotor impairment, and morphological changes in the antennae of the microcrustacean. No lethal or sublethal effects were observed in the fractions dominated by other cyanopetides (Cyanopeptolin 959, Nostoginin BN741). Our findings contribute to the growing body of research indicating that cyanobacterial metabolites beyond traditional cyanotoxins cause detrimental effects. This underscores the importance of toxicological assessments of such compounds, also at sublethal levels.

Congener-specific fate and impact of microcystins in the soil-earthworm system

Microcystins (MCs) have a significant influence on aquatic ecosystems, but little is known about their terrestrial fate and impact. Here, we investigated the fate of two MCs (MC-LR and MC-RR) in the soil-earthworm system, with consideration of their congener-specific impact on earthworm health, soil bacteria, and soil metabolome. Although MCs had little acute lethal effect on earthworms, they caused obvious growth inhibition and setae rupture. Relative to MC-RR, MC-LR exhibited higher bioaccumulation and the resulting dermal lesions and deformation of longitudinal muscles. While the incorporation of both MCs into soils stimulated pathogenic bacteria and depressed oxidative stress tolerant bacteria, the response among soil nitrification and glutathione metabolism differed between the two congeners. The dissipation kinetics of MCs obeyed the first-order model. Earthworms stimulated soil N-cycling enzyme activities, increased the abundance of MC-degrading bacteria, and promoted bacterial metabolic functions related to glutathione metabolism, xenobiotics biodegradation, and metabolism of amino acids that comprise MCs, which accelerated the dissipation of MC-LR and MC-RR by 227% and 82%, respectively. These results provide evidence of significant congener differences in the terrestrial fate and impact of MCs, which will enable a better understanding of their role in mediating soil functions and ecosystem services.

Efficiently Controlled <i>Callosobruchus maculatus</i> (F.) (Fam. Bruchidae) by Ultraviolet Ray or Microwave Energy in Conjugation with Pirimiphos-Methyl

This study aimed to explore novel approaches for effectively managing Callosobruchus maculatus while ensuring minimal impact on human health and the environment. The investigation involved exposing the insects to ultraviolet rays (254 nm) for 24 hours, which did not directly cause mortality in adult C. maculatus but led to a significant reduction in their progeny by 10%. The reduction in progeny further increased when insects were pre-exposed to a sublethal dose of actellic at LC25, resulting in a reduction of 39%. Additionally, ultraviolet rays exhibited a significant ovicidal effect, with hatchability reduced to 26% compared to 73% in the control group. Microwave exposure at a low energy level for 4-6 minutes demonstrated a significant acute lethal effect, reduced progeny, and ovicidal action. Combining microwaves with actellic at LC25 slightly enhanced the lethal effect. In conclusion, this study unveils promising strategies for the effective management of Callosobruchus maculatus, highlighting the potential of ultraviolet rays and microwave energy, either alone or in combination with actellic, while emphasizing the importance of minimizing adverse impacts on both human health and the environment.

Quantification of inorganic anions in surface and drinking waters using ion chromatography

The Republic of Bulgaria regulates the quality of surface waters for drinking and domestic purposes, monitoring anions like F-, Cl-, Br-, I-, BrO3-, NO2-, NO3-, SO42-, PO43-, and SCN-. The presence of NO3- and NO2- in water is undesirable, as they have a harmful effect on human health. It is also well known that CN- as opposed to SCN- has acute toxic and lethal effects on living organisms including humans. In the present study, an instrumental method was developed and optimized for the separation and quantification of inorganic anions in surface and drinking water using ion chromatography. The analytical characteristics of the proposed instrumental method were determined. The oxidation of CN- to OCN- was investigated, and the optimal experimental conditions for the oxidation were established. The achieved low LOD and LOQ of the analyzed inorganic anions allows their detection and quantification in surface and drinking waters. The applicability of the proposed chromatographic method was determined in the analysis of surface and bottled waters. The analyzed anions in bottled waters were close to the label's values, only one spring water showed significant deviations.

Life stage-specific effects of tire particle leachates on the cosmopolitan planktonic copepod Acartia tonsa

Tire wear particles (TWP) are a major source of microplastics in the aquatic environment and the ecological impacts of their leachates are of major environmental concern. Among marine biota, copepods are the most abundant animals in the ocean and a main link between primary producers and higher trophic levels in the marine food webs. In this study, we determined the acute lethal and sublethal effects of tire particle leachates on different life stages of the cosmopolitan planktonic copepod Acartia tonsa. Median lethal concentration (LC50, 48h) ranged from 0.4 to 0.6gL-1 depending on the life stages, being nauplii and copepodites more sensitive to tire particle leachates than adults. The median effective concentration (EC50, 48h) for hatching was higher than 1gL-1, indicating a relatively low sensitivity of hatching to tire particle leachates. However, metamorphosis (from nauplius VI to copepodite I) was notably reduced by tire particle leachates with an EC50 (48h) of 0.23gL-1 and the absence of metamorphosis at 1gL-1, suggesting a strong developmental delay or endocrine disruption. Leachates also caused a significant decrease (10-22%) in the body length of nauplii and copepodites after exposure to TWP leachates (0.25 and 0.5gL-1). We tested a battery of enzymatic biomarkers in A. tonsa adult stages, but a sublethal concentration of 50mgL-1 of tire particle leachates did not cause a statistically significant effect on the measured enzymatic activities. Our results show that tire particle leachates can negatively impact the development, metamorphosis, and survival of planktonic copepods. More field data on concentrations of TWPs and the fate and persistence of their leached additives is needed for a better assessment of the risk of tire particle pollution on marine food webs.

Evaluation of Acute Toxicity and Antioxidant Response of Earthworm Exposed to a Lignin-Modified Crosslinked Hydrogel.

Hydrogels are polymers of great importance due to their multiple applications, which have led to an exponential increase in their production. However, once they have fulfilled their function, they become waste and their ecotoxicological effects are unknown. The aim of the present study was to evaluate the acute toxicity and total antioxidant capacity of the earthworm (Eisenia fetida) exposed to a terpolymeric hydrogel (acrylic acid, acrylamide, and 2-acrylamido-2-methyl-1-propane-sulfonic acid) crosslinked with modified kraft lignin. Four different amounts of hydrogel per unit area were evaluated (0.0924, 0.1848, 0.9242, and 1.848 mg hydrogel/cm2) plus a control, and three replicates were performed for each group. Starting from the amount of 0.1848 mg hydrogel/cm2, the earthworms showed physiological and behavioral alterations; at higher amounts, 0.9242 and 1.848 mg hydrogel/cm2, more acute signs were observed with mortality rates of 51.7% and 100%, respectively. On the other hand, the antioxidant activity assay showed that the higher the hydrogel exposure amount, the higher the oxidative stress, as evidenced by lower antioxidant activity (67.09% inhibition of the ABTS●+ radical). Therefore, we concluded that the lignin-modified hydrogel generated oxidative stress and acute lethal toxic effects in Eisenia fetida.

Evaluating the Sublethal Effects of Origanum vulgare Essential Oil and Carvacrol on the Biological Characteristics of Culex pipiens biotype molestus (Diptera: Culicidae).

Culex pipiens is a mosquito species complex spread worldwide that poses a serious threat to human health as the primary vector of West Nile virus. Its control is mainly based on larvicidal applications with synthetic insecticides on mosquito breeding sites. However, the excessive use of synthetic larvicides may provoke mosquito resistance issues and negative side effects to the aquatic environment and human health. Plant-derived essential oils, including those from the Lamiaceae family, can be eco-friendly alternative larvicidal agents causing acute larval toxicity and/or growth inhibitory effects on the developmental stages of mosquitoes through different modes of action. In the current laboratory study, we evaluated the sublethal effects of carvacrol-rich oregano essential oil and pure carvacrol on Cx. pipiens biotype molestus, the autogenous member of the Cx. pipiens species complex, after the exposure of 3rd-4th instar larvae to LC50 concentrations. The short-term (24 h) larvicidal treatment with the sublethal concentrations of both tested materials exhibited an acute lethal effect on the exposed larvae as well as significant delayed mortality for surviving larvae and pupae. Larvicidal treatment with carvacrol reduced the longevity of the emerged males. In addition, the morphological abnormalities that were observed at the larval and pupal stage along with failed adult emergence indicate the potential growth inhibitory properties of the tested bioinsecticides. Our findings suggest that carvacrol and carvacrol-rich oregano oil are effective plant-based larvicides at doses lower than the acute lethal ones, thus promoting an environmentally friendly and more affordable perspective for their use against the WNV vector Cx. pipiens biotype molestus.

Oral exposure to thiacloprid-based pesticide (Calypso SC480) causes physical poisoning symptoms and impairs the cognitive abilities of bumble bees

BackgroundPesticides are identified as one of the major reasons for the global pollinator decline. However, the sublethal effects of pesticide residue levels found in pollen and nectar on pollinators have been studied little. The aim of our research was to study whether oral exposure to the thiacloprid levels found in pollen and nectar affect the learning and long-term memory of bumble bees. We tested the effects of two exposure levels of thiacloprid-based pesticide (Calypso SC480) on buff-tailed bumble bee (Bombus terrestris) in laboratory utilizing a learning performance and memory tasks designed to be difficult enough to reveal large variations across the individuals.ResultsThe lower exposure level of the thiacloprid-based pesticide impaired the bees’ learning performance but not long-term memory compared to the untreated controls. The higher exposure level caused severe acute symptoms, due to which we were not able to test the learning and memory.ConclusionsOur results show that oral exposure to a thiacloprid-based pesticide, calculated based on residue levels found in pollen and nectar, not only causes sublethal effects but also acute lethal effects on bumble bees. Our study underlines an urgent demand for better understanding of pesticide residues in the environment, and of the effects of those residue levels on pollinators. These findings fill the gap in the existing knowledge and help the scientific community and policymakers to enhance the sustainable use of pesticides.

Toxicological Comparison of Pesticide Active Substances Approved for Conventional vs. Organic Agriculture in Europe.

There is much debate about whether the (mostly synthetic) pesticide active substances (AS) in conventional agriculture have different non-target effects than the natural AS in organic agriculture. We evaluated the official EU pesticide database to compare 256 AS that may only be used on conventional farmland with 134 AS that are permitted on organic farmland. As a benchmark, we used (i) the hazard classifications of the Globally Harmonized System (GHS), and (ii) the dietary and occupational health-based guidance values, which were established in the authorization procedure. Our comparison showed that 55% of the AS used only in conventional agriculture contained health or environmental hazard statements, but only 3% did of the AS authorized for organic agriculture. Warnings about possible harm to the unborn child, suspected carcinogenicity, or acute lethal effects were found in 16% of the AS used in conventional agriculture, but none were found in organic agriculture. Furthermore, the establishment of health-based guidance values for dietary and non-dietary exposures were relevant by the European authorities for 93% of conventional AS, but only for 7% of organic AS. We, therefore, encourage policies and strategies to reduce the use and risk of pesticides, and to strengthen organic farming in order to protect biodiversity and maintain food security.

Effects of acute and chronic bendiocarb exposure during early life stages of the pond snail (Lymnaea stagnalis)

ABSTRACT Environmental pollution is a global concern, and anthropogenic activities have contaminated natural water sources. Pesticides are one of the most recognised pollutants worldwide. Carbamates are a widely used pesticide family, and bendiocarb is a broad-spectrum carbamate insecticide detected in surface and groundwater. In the present work, acute lethal and chronic effects of bendiocarb on the early life stages of freshwater snail Lymnaea stagnalis were investigated. 24-h LC50 of bendiocarb on L. stagnalis embryos and juveniles was estimated at 20.39 (18.30–22.71) mg/L and 38.35 (29.58–52.89) mg/L, respectively. Chronic tests were conducted for 21-d to evaluate the potential effects of the environmentally realistic concentrations of bendiocarb (5 and 100 µg/L) on the embryos. Mortality, development, growth (embryo: egg ratio and shell height), heart rate, and hatching success were investigated. The test results showed that mortality, developmental progression, embryo: egg ratio, shell height measurements and cumulative hatching rate were not significantly impaired by chronic bendiocarb exposure compared to the control. However, bendiocarb induced increased heart rate in the exposed snails.

Commercial Fungicide Toxic Effects on Terrestrial Non-Target Species Might Be Underestimated When Based Solely on Active Ingredient Toxicity and Standard Earthworm Tests.

The ecosystem services provided by earthworms are lost when land management reduces their populations, hence, the importance of thorough assessments of management effects on this group. The present study aimed to: (1) review the possible influence of other ingredients within the formulations of two commercial fungicides; (2) assess the sublethal effects of these commercial fungicides on Eisenia fetida; and (3) assess the acute lethal effects of one commercial fungicide on both Glossoscolex rione and E. fetida. Examining all components of the studied commercial formulations revealed that alongside the toxic active ingredients are other ingredients that are equally as or more toxic than the former and may even be in higher concentrations. The inhibition concentration of 10% of E. fetida’s progeny (IC10) was estimated at 133 mg kg−1 for PROSARO® and 1544 mg kg−1 for SWING PLUS®. Both fungicides showed an effect of hormesis on the progeny. In this first toxicity study with G. rione, it was found that this species is more sensitive to PROSARO® than E. fetida, with preliminary 14 day-lethal concentrations of 285 mg kg−1 for the former and >1000 mg kg−1 for the latter.

Chronic and Acute Effects of Imidacloprid on a Simulated BEEHAVE Honeybee Colony

Honeybees (Apis mellifera) are important pollinators for wild plants as well as for crops, but honeybee performance is threatened by several stressors including varroa mites, gaps in foraging supply, and pesticides. The consequences of bee colony longtime exposure to multiple stressors are not well understood. The vast number of possible stressor combinations and necessary study duration require research comprising field, laboratory, and simulation experiments. We simulated long-term exposure of a honeybee colony to the insecticide imidacloprid and to varroa mites carrying the deformed wing virus in landscapes with different temporal gaps in resource availability as single stressors and in combinations. Furthermore, we put a strong emphasis on chronic lethal, acute sublethal, and acute lethal effects of imidacloprid on honeybees. We have chosen conservative published values to parameterize our model (e.g., highest reported imidacloprid contamination). As expected, combinations of stressors had a stronger negative effect on bee performance than each single stressor alone, and effect sizes were larger after 3 years of exposure than after the first year. Imidacloprid-caused reduction in bee performance was almost exclusively due to chronic lethal effects because the thresholds for acute effects were rarely met in simulations. In addition, honeybee colony extinctions were observed by the last day of the first year but more pronounced on the last days of the second and third simulation year. In conclusion, our study highlights the need for more long-term studies on chronic lethal effects of pesticides on honeybees. Environ Toxicol Chem 2022;41:2318-2327. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Effect of insecticides on biological attributes of the egg parasitoid Telenomus remus (Hymenoptera: Platygastridae)

ABSTRACT The egg parasitoid Telenomus remus (Hymenoptera: Platygastridae) is one of the most important natural enemies of Spodoptera frugiperda (Lepidoptera: Noctuidae). The application of chemical insecticides is the main strategy to control this insect pest, although it can affect T. remus and harm integrated pest management (IPM) programmes. This study evaluated the acute lethal (mortality) and sublethal (parasitism and emergence rate, sex ratio, and longevity) effects caused by chlorfenapyr, spinosad, and thiamethoxam + lambda-cyhalothrin by tarsal contact on T. remus adults. The lethal concentration (LC50) of the insecticides showed that thiamethoxam + lambda-cyhalothrin had the highest lethal toxicity on T. remus adults. However, sublethal effects on the F0 generation showed that all insecticides (chlorfenapyr, spinosad, and thiamethoxam + lambda-cyhalothrin) were classified as innocuous, without significant differences in the parasitism rate, emergence rate, and sex ratio compared to the control. Nevertheless, the risk quotient (RQ, mg ai L−1) classified the insecticides thiamethoxam + lambda-cyhalothrin and chlorfenapyr as toxic to T. remus. In contrast, spinosad was classified as slightly to moderately toxic. Also, thiamethoxam + lambda-cyhalothrin, chlorfenapyr, and spinosad did not affect the biological development of T. remus. These results can be used as a basis for integrating chemical and biological control to manage S. frugiperda in an attempt to preserve natural enemies in the field.

Crushed Capsicum chacoense Hunz Fruits: A Food Native Resource of Paraguay with Antioxidant and Anthelmintic Activity.

The nutritional composition and toxicity of native plants with food potential like Capsicum chacoense are important for the safe use of populations and could be used as a source for searching for new drug candidates. Infections produced by parasites such as helminths are a public health concern for many countries. The drugs used for treating these diseases are few, and the emergence of resistance is a risk. In this work, the nutritional composition, acute toxicity, antioxidant activity, and anthelmintic activity of crushed C. chacoense fruits were evaluated. The composition was analyzed by standard procedures. Antioxidant activity was evaluated using the ABTS radical and the total phenolic compound (TPC) tests. The toxicity was evaluated on Swiss albino mice by the single-DL50-dose procedure. The anthelmintic activity was tested against Eisenia foetida. The samples presented high levels of dietary fiber (47.05-49.19 g/100 g), proteins (14.43-15.60 g/100 g), and potassium (1708-1733 mg/100 g). In the samples, the absence of acute lethal effects in doses lower than 2000 mg/kg was observed. A rich composition of TPC (517.26-543.32 mg GAE/100 g sample), total carotenoids (125.72-239.57 mg/kg), β-carotene (3.29-5.60 mg/kg), and good TAC was observed (154-158 mM TEAC/g SMTC). The methanolic extracts at the doses tested (2.5 to 40 mg/mL) showed good anthelmintic activity. The presence of alkaloids was demonstrated in the methanolic extract, consistent with the levels of capsaicin (131.85 and 98.80 mg/100 g) and dihydrocapsaicin (80.75 and 63.68 mg/100 g), with significant statistical differences between samples (p < 0.05). These results show that through the chemical composition of this underutilized native resource and good fruit processing procedures, the C. chacoense fruits have a great nutraceutical potential of interest for the food and pharmaceutical industries.

Children and Parents' Awareness Regarding Potential Hazards Derived from the Use of Chemical Products in Greece.

Over the last decades, human activities prompted the high production and widespread use of household chemical products, leading to daily exposure of humans to several chemicals. The objective of this study was to investigate the frequency of chemicals’ use by children and parents in Greece and estimate the level of risk awareness and understanding among them. A total of 575 parents and children were asked to answer an anonymous, closed-ended, validated, and self-administered questionnaire. One-third of the children and almost half of the parents participating in the study believed that commonly used chemical products do not pose any risk to human health or to the environment, despite the product labelling. The majority of both children (61.8%) and parents (70.6%) were informed about product safety via the product labelling. Around 20% in both groups could not differentiate between systemic toxicity and acute lethal effects depicted by pictograms on the label and milder hazards, such as skin irritation. Moreover, the information on hazard and precautionary statements appearing on the label was very poorly perceived. Therefore, as both children and parents seem not to clearly identify the hazards and risks arising from the use of everyday chemical products, targeted awareness policies should be implemented to support the safe use of household products.

Responses of the ecological characteristics and antioxidant enzyme activities in Rotaria rotatoria to UV-B radiation

UV-B radiation is an increasing threat to aquatic organisms and also a potential driving force for zooplankton population dynamics. To explore the ecological effects of UVR on rotifers and the responses of antioxidant system against UVR, the acute lethal effects, the life history strategies, population growth, and antioxidant enzyme activities were assessed in the Bdelloid Rotaria rotatoria after exposure to UV-B radiation. The results indicated that the persistence of tolerance in rotifer to stress was playing a more vital role than the radiation dose in survival. The larger the culture volume, the weaker the lethal effect. Rotifers prolonged their first reproductive time and shortened their reproductive period and longevity with the increasing of radiation dose, and the fecundity was significant inhibited by UV-B radiation. These responses can be taken as energy trade-off to retard their mortality. The population density of the rotifers increased at the lowest dose of radiation and then descended with the increasing of UVR dose, and this pattern was also corroborated by detecting the content of SOD and CAT, which suggested that hormesis also applies to R. rotatoria under UV-B radiation stress. The enzyme SOD has higher level of content and more sensitive to low UVR than CAT.

Stream Salamanders are Relatively Tolerant of Salty Streams.

The application of road salt as a deicing agent is common, but investigations of potential negative effects of salt runoff on stream salamanders have been limited. Additionally, modern stormwater management practices should influence the delivery of salt ions to streams. We used data loggers in streams draining watersheds with and without stormwater management ponds and acute 96-h LC50 tests to investigate exposure of, and road salt toxicity among, two widespread salamanders in the Eastern USA, northern dusky salamanders (Desmognathus fuscus) and northern two-lined salamanders (Eurycea bislineata). In streams below stormwater ponds, base levels of conductivity were elevated throughout the year and elevated Cl- levels led to more frequent acute and chronic exceedances of U.S. Environmental Protection Agency ambient water quality criteria for Cl- when compared to streams draining watersheds with no stormwater management ponds. However, five of the six streams studied had exceedance frequencies suggesting Cl- associated with road salt application represented a persistent threat to aquatic life. Larval stream salamanders were relatively tolerant of salt, not exhibiting any lethal effects over a 96-h period until chloride levels exceeded 5000mg/L for both species, and concentrations in streams rarely exceeded these levels and only for very short periods of time. Our results suggest road salts are not having acute lethal effects on salamanders in the streams we studied, but exceedance of U.S. Environmental Protection Agency ambient water quality standards for Cl- suggest the potential for sublethal and indirect effects of Cl- on salamander populations that require further study.