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BACKGROUND: Wild pigs (Sus scrofa) are an invasive and destructive species throughout many regions of the world. A sodium nitrite (SN) toxic bait is currently used in Australia and being developed for use in the US and other countries to combat the increasing populations of wild pigs. In the US, efforts to modify the Australian SN‐toxic bait and baiting strategy have focused on reducing issues with non‐target animals accessing the SN‐toxic bait spilled outside of bait stations by wild pigs. We tested and compared modifications for efficacy (with wild pigs) and hazards (with non‐targets) in north‐central Texas, US during summer (July 2021) and winter (March 2023) seasons. RESULTS: During both seasons we found that visitation to the bait sites declined 94–99% after deploying the SN‐toxic bait, and we found a total of 106 dead wild pigs, indicating considerable lethality for the local population. Prior to deploying the SN‐toxic bait, Global Positioning System (GPS)‐collared wild pigs were more likely to cease visiting bait sites during summer when foraging resources were abundant. Farrowing decreased visitation to bait sites during the winter. We observed no dead non‐targets during summer; winter results showed an average of 5.2 dead migrating birds per bait site (primarily Dark‐eye juncos [Junco hyemalis]) from consuming SN‐toxic bait spilled by wild pigs. The presence and winter‐foraging behaviors of migrating birds appeared to increase hazards for those species. CONCLUSION: The current formulation of SN‐toxic bait was effective at removing wild pigs during both seasons, however it is clear that different baiting strategies may be required in winter when migrating birds are present. Baiting wild pigs prior to farrowing during the winter, and during drier summers, may further improve efficacy of the bait. Reducing hazards to non‐targets could be achieved by refining the SN‐toxic bait or modifying bait stations to decrease the potential for spillage, decreasing environmental persistence if spilled, or decreasing attractiveness to migrating birds. © 2024 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Background: In 2018, a sodium nitrite (SN)‐based toxic bait for invasive wild pigs (hereafter wild pigs; Sus scrofa), was evaluated to determine its effectiveness in reducing local wild pig populations in Texas. Localized population reductions of >70% were achieved, but spillage of bait outside wild pig‐specific feeders (bait stations) caused by feeding wild pigs resulted in the deaths of non‐target animals. To evaluate risks to non‐target animals, we tested whether bait presentation influenced the total amount of bait spilled by wild pigs and estimated the associated risk to non‐target species. Results: We found that bait spilled outside bait stations could be reduced by >90% when compacted in trays, as opposed to being manually crumbled into pieces. We documented a mean spill rate of 0.913 g of bait per wild pig. Conservative risk assessments for nine non‐target species for which SN toxicity data exist indicate that there is relatively low risk of lethal exposure, apart from zebra finches (Taeniopygia guttata) and white mice. Our results indicate that there may be enough spilled bait per feeding wild pig to kill 9.5 or 3.5 individuals of these species, respectively. Other species assessed range from 0.002 to 0.406 potential mortalities per wild pig. Conclusion: We demonstrated that the amount of bait spilled by wild pigs during feeding and the associated risk to non‐target animals can be minimized by presenting the bait compacted in trays within bait stations. We recommend that baits be tightly compacted and secured in bait stations to minimize risks to non‐target animals from spilled bait by wild pigs. © 2023 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the effect of tartaric acid (TTA) on Madin–Darby canine kidney (MDCK) cells compared to human kidney (HK)‐2 cells. Secondarily, to evaluate the effects of probenecid, an organic anion transporter (OAT)‐1 inhibitor, as well as human (h)OAT‐4 transfection into MDCK cells to prevent TTA‐induced cytotoxicity through decreasing accumulation via OAT‐1 uptake inhibition or increasing OAT‐4‐mediated TTA efflux. Design: Seventy‐two‐hour TTA concentration response and inhibitor studies in immortalized cell lines. Setting: School of Pharmacy biomedical research laboratory and tissue culture facility. Animals/Samples: MDCK and HK‐2 immortalized cell lines. Interventions: Both cell lines were treated with increasing concentrations of TTA for 72 hours. Additionally, MDCK cells were co‐incubated with TTA and increasing concentrations of probenecid or had been transfected with hOAT‐4 and subsequently treated with TTA for 72 hours. Measurements and Main Results: Media and samples were collected and lactate dehydrogenase (LDH) release was measured. LDH release was measured to assess TTA‐induced cytotoxicity after 72 hours. LDH was not significantly increased in the HK‐2 cells at any concentration but was significantly increased in the MDCK cells from 10 to 100 mM. LDH concentrations were significantly decreased (61%) in MDCK cells incubated with 50 mM TTA and probenecid when compared to TTA alone. hOAT‐4 MDCK cell transfection also significantly reduced LDH release (57%) when comparing the transfected MDCK cells to the nontransfected MDCK cells treated with 50 mM TTA. Conclusions: TTA is a species‐specific nephrotoxicant in dogs due to an interspecies difference in OAT‐4 expression. Inhibiting TTA uptake in MDCK cells in vitro using the OAT‐specific inhibitor, probenecid, prevents TTA‐induced cytotoxicity. [ABSTRACT FROM AUTHOR]

BACKGROUND: Wild pigs (Sus scrofa) cause widespread environmental and economic damage, and as a result are subjected to extensive control. Current management strategies have proven insufficient, and there is growing interest in use of toxicants to control invasive populations of this species. In 2017 a low‐dose warfarin bait was federally approved for use in controlling wild pigs in the United States. However, no states have allowed use of this bait due to unanswered questions regarding welfare concerns, field efficacy, and non‐target impacts. RESULTS: All captive wild pigs fed 0.005% warfarin baits in no choice feeding trials succumbed in an average of 8 days from exposure. Behavioral symptoms of warfarin exposure included vomiting, external bleeding, abnormal breathing, incoordination, and limping. Postmortem examinations revealed hemorrhaging in organs and muscles, particularly the legs, gastrointestinal tract, and abdomen. Warfarin residues in tissues averaged 1.0 mg kg‐1 for muscle, 3.9 mg kg‐1 for liver, and 2.8 mg kg‐1 for small intestines. Field testing revealed wild pigs required extensive training to access bait within pig‐specific bait stations, and once acclimated, exhibited reluctance to consume toxic baits, resulting in no mortalities across two separate field deployments of toxic bait. CONCLUSION: Our results suggest wild pigs are susceptible to low‐dose warfarin, and warfarin residues in pig tissues postmortem are generally low. However, although warfarin‐based baits are currently approved for use by the US Environmental Protection Agency, further improvements to pig‐specific bait delivery systems and bait palatability are needed, as well as additional research to quantify efficacy, cost, and non‐target impacts prior to widespread implementation. © 2021 Society of Chemical Industry. This article has been contributed to by US Government employees and their work is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

BACKGROUND: Wild pigs (Sus scrofa) are a destructive invasive species throughout many regions of the world. In 2018, a field evaluation of an early prototype of a sodium nitrite (SN) toxic bait in the United States revealed wild pigs dropped large amounts of the toxic bait outside the pig-specific bait stations while feeding, and thus subsequent hazards for non-target animals. We modified the SN-toxic bait formulation, the design of the bait station, and the baiting strategy to reduce dropped bait. We tested the modifications in Queensland, Australia (December 2018), Alabama, USA (August 2019), and Texas, USA (March 2020) under differing climatic and seasonal conditions for one night. RESULTS: Cumulatively we found 161 carcasses of all age classes of wild pigs using systematic transects. Remote camera indices indicated high lethality for wild pigs, achieving population reductions of 76.3 to 90.4%. Wild pigs dropped only small particles of SN-toxic bait (average = 55.5 g per bait site), which represented a 19-fold decrease from the previous trial. Despite this reduction, we found three Australian ravens (Corvus coronoides) in Queensland, two Virginia opossums (Didelphis virginiana) in Alabama, and 35 granivorous-passerine birds (mostly dark-eyed juncos [Junco hyemalis]) in Texas dead from consuming the dropped bait. We did not detect any population-level effects for those species. CONCLUSION: Our modifications were effective at reducing populations of wild pigs, but the deaths of non-target species require further steps to minimize these hazards. Next steps will include evaluating various deterrent devices for birds the morning after SN-toxic bait has been offered. [ABSTRACT FROM AUTHOR]

External stressors, especially environmental toxicants can disturb biological homeostasis and thus lead to adverse health effects. However, there is limited understanding of how cells directly exposed to stressors transmit the signals to cells indirectly in contact with stressors. Extracellular vesicles (EVs) are receiving increasing attention as signal transductors between various types of cells in organisms. Cargo in EVs, including RNAs, proteins, lipids, and other signal molecules can be transferred between cells and become critical determining factors of intercellular communication. EVs can be a powerful mediator of environmental stimuli. It has been shown that external stressors reshape the secretion of EVs, modify the composition of EVs, and thus influence the mediating function of EVs. These abnormal EVs can lead to dysfunction of recipient cells, and even the pathogenesis of diseases. In this review, we first summarized current knowledge about the responses of EVs to external stimuli, including chemicals and chemical mixtures. Then we explained how these altered EVs regulate signal pathways in recipient cells, thus mediating physio‐pathological responses in detail. The most up‐to‐date evidence from molecular, cellular, animal and human levels was synthesized to systematically address the mediating roles of EVs. EVs can be regarded as a bridge to link external stressors and internal response. Further toxicological and molecular epidemiological studies are expected to provide further insight into the roles of EVs in toxicology. The gaps in the engulfment of toxicants into EVs are listed as the priority to be solved in future studies. The minireviews analyzed and detailed the current understanding of the roles of extracellular vesicles (EVs) in the toxicology of environmental pollutants. General knowledge of EVs was first summarized. The way and results of literature searching were then elucidated.Six types of environmental pollutants were introduced with regard to their effects through EVs. The orders were heavy metals, organic chemicals, nanomaterials, alcohol, and finally chemical mixtures. The pathways of pollutants‐donor cells‐EVs‐recipient cells‐phenotype were addressed. [ABSTRACT FROM AUTHOR]

Objective: To describe a serious adverse event of gastrointestinal obstruction requiring surgery following routine administration of multiple doses of activated charcoal (AC) granules, which were prescribed for carprofen toxicosis. Case Summary: A 2‐year‐old female neutered Airedale Terrier presented for ingestion of 207 mg/kg of carprofen. Decontamination was initiated with apomorphine to induce emesis. Along with additional supportive care, the dog received an initial dose of 75 mL of AC suspension containing sorbitol by mouth (15.6 g of AC, or 0.6 g/kg), followed by 50 g of AC granules every 8 hours for 4 additional doses. While hospitalized, the dog experienced clinical signs, including vomiting and black diarrhea, as well as bloodwork changes including mild to moderate elevations in kidney and liver enzymes. Given clinical improvement after 72 hours of hospitalization, the patient was discharged for monitoring and ongoing care at home. Two days later, the patient presented again for nausea, dark diarrhea with frank blood, and panting. Abdominal ultrasound showed findings suspicious for partially obstructive foreign material or atypical impacted fecal material partially occluding the distal ileum. Despite medical management overnight, recheck ultrasound the following day demonstrated persistent obstruction with ileal foreign material. Exploratory laparotomy and enterotomy revealed moderate distension and obstruction of the distal ileum with black granular foreign material consistent with charcoal granules. The patient remained in hospital for supportive care for 4 days following the procedure, and all clinical signs were resolved at the time of discharge. New or Unique Information Provided: This report documents a serious adverse event of gastrointestinal obstruction associated with routine multidose AC administration, which has been occasionally reported in people but not in dogs. The potential for this complication should be taken into account when prescribing multiple doses of AC granules. [ABSTRACT FROM AUTHOR]

Aerially delivered toxic baits have proven effective for landscape‐level control of numerous invasive vertebrate populations with major benefits for conservation and ecosystem function, but this technique has not been broadly adapted for control of invasive reptiles. Nonnative brown treesnakes (Boiga irregularis) on the Pacific island of Guam have caused severe ecological and economic damage and pose an invasion risk on other islands, making them a high‐profile candidate for application of aerial baiting methods. Although terrestrial applications of traps, toxicants, and hand‐removal are standard brown treesnake management practices, these methods are not cost‐effective for control in the island's large tracts of remote, rugged forest. In 2016, the first major in situ evaluation of a helicopter‐borne automated aerial bait delivery system applied snake‐targeted toxic baits at an effective rate of approximately 120 baits/ha over a 110‐ha forested test plot on Guam. We evaluated the extent and duration of the suppressive effect of this toxic bait application on brown treesnakes by measuring nontoxic bait take rates as a proxy index of relative snake abundance before and after toxic bait application in a treatment plot and surrounding reference area. We placed 4,420 nontoxic baits in random transects at georeferenced locations, from 1 month before until nearly 12 months after toxic bait application, allowing temporal analysis of the suppressive effect and spatial analysis of treatment plot reinvasion. Over the first 30 days after toxic bait application, average nontoxic bait take rate in the treatment plot was 41.2% lower than the pre‐application rate, and there was no immediate decrease in bait take in the reference area. Reduced snake activity was still evident nearly 12 months after bait application. Roads forming a portion of the treatment boundary appeared to slow snake movement between treated area and surrounding untreated area. Trail cameras monitoring a subset of bait tubes showed that 97.5% of baits removed were taken by snakes rather than nontarget species. We indexed rodent abundance in the treatment plot and reference area, and found no indication of a rodent population increase following toxic bait application. Our results show that automated aerial bait applications can suppress brown treesnake abundance over a large area and that reinvasion from surrounding untreated habitat occurs over several months. We anticipate that repeated bait applications could achieve and maintain greatly reduced brown treesnake abundance on a landscape scale, potentially improving biosecurity and enabling experimental reintroduction of native birds extirpated by brown treesnake predation. Published 2019. This article is a U.S. Government work and is in the public domain in the USA. The Journal of Wildlife Management published by Wiley Periodicals, Inc. on behalf of The Wildlife Society. Methods have been developed for the automated manufacturing and aerial delivery of toxic baits for control of invasive brown treesnakes on Guam. This study follows the extent and duration of brown treesnake suppression before and out to a year after an experimental aerial bait application in comparison to surrounding untreated forest. [ABSTRACT FROM AUTHOR]

BACKGROUND: Insect pheromones and host volatiles are important for pest control due to their high efficiency and low potential for environmental pollution. The functions of myrtenol, myrtanol and myrtenal in pest–host interactions are unknown. This study aimed to determine the presence of myrtenol, myrtanol and myrtenal in newly emerged and emerged stages of Dendroctonus armandi, and in infected and healthy Pinus armandi, and to identify their roles in tree protection and pest management based on electroantennography (EAG), Y‐tube and toxicity experiments. RESULTS: Gas chromatographic and mass spectrometry (GC–MS) analyses, EAG, Y‐tube and toxicity assays revealed the following: (1) myrtenol was found in P. armandi phloem and did not exhibit significant toxicity towards D. armandi; (2) myrtanol was produced by infected P. armandi after D. armandi invasion and had significant toxicity towards D. armandi, especially females; and (3) myrtenal might represent an aggregation pheromone produced by female D. armandi to exert aggregation effects on other females, to help them overcome the resistance of P. armandi jointly and ensure a successful invasion, females remained in an aggregation state from leaving the host to mating in a new host. CONCLUSION: These findings suggest that myrtanol as a repellent has potential for the protection of P. armandi and that myrtenal could be used to trap and disorient D. armandi. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

BACKGROUND: An international effort to develop an acute and humane toxic bait for invasive wild pigs (Sus scrofa) is underway to curtail their expansion. We evaluated the ability to expose a population of wild pigs to a simulated toxic bait (i.e., placebo bait containing a biomarker, rhodamine B, in lieu of the toxic ingredient) to gain insight on potential population reduction. We used 28 GPS‐collars and sampled 428 wild pigs to examine their vibrissae for evidence of consuming the bait. RESULTS: We estimated that 91% of wild pigs within 0.75 km of bait sites (total area = 16.8 km2) consumed the simulated toxic bait, exposing them to possible lethal effects. Bait sites spaced 0.75–1.5 km apart achieved optimal delivery of the bait, but wild pigs ranging ≥ 3 km away were susceptible. Use of wild pig‐specific bait stations resulted in no non‐target species directly accessing the bait. CONCLUSION: Results demonstrate the potential for exposing a large proportion of wild pigs to a toxic bait in similar ecosystems. Toxic baits may be an effective tool for reducing wild pig populations especially if used as part of an integrated pest management strategy. Investigation of risks associated with a field‐deployment of the toxic bait is needed. © 2018 Society of Chemical Industry A new toxic bait is under development to curtail invasive wild pigs in the USA and Australia. Proper baiting strategy can expose most wild pigs in a large population to this bait. [ABSTRACT FROM AUTHOR]

BACKGROUND: Invasive wild pigs damage agriculture, property, and natural ecosystems. To curtail damage, an effective and humane toxic bait containing microencapsulated sodium nitrite is under development. Strategies for delivering the toxic bait are needed to establish adequate spacing of bait sites, and for simultaneously accustoming wild pigs to the novel bait and wild pig‐specific bait stations designed to exclude non‐target species. RESULTS: We monitored movements of 32 Global Positioning System (GPS)‐collared wild pigs relative to 41 bait sites containing placebo bait. Among the bait sites, we compared three experimental baiting strategies (and a control) to evaluate which strategy led to the most wild pigs accessing the placebo bait inside bait stations. We found that bait sites should be spaced 0.5–1 km apart to maximize opportunities for all wild pigs to find and utilize the bait sites. Baiting strategies that allowed ≥ 15 days for accustoming wild pigs to bait stations were most effective and resulted in nearly 90% of wild pigs accessing the placebo bait inside the bait stations. Bait stations excluded all non‐target animals, except one instance with a raccoon (Procyon lotor). CONCLUSION: These results demonstrate the potential for toxic bait to be an effective tool for reducing populations of wild pigs with minimal risks to non‐target species, if optimized delivery procedures are followed. © 2018 Society of Chemical Industry Strategies are needed for safe and efficient delivery of toxic bait to control damage by wild pigs. We present refined strategies for maximizing access to bait stations by wild pigs. [ABSTRACT FROM AUTHOR]

BACKGROUND An acute and orally delivered toxic bait containing micro-encapsulated sodium nitrite (MESN), is under development to provide a novel and humane technology to help curtail damage caused by invasive wild pigs ( Sus scrofa). We evaluated potential secondary risks for non-target species by: testing whether four different types of micro-encapsulation coatings could reduce vomiting by invasive wild pigs, testing the levels of residual sodium nitrite (SN) in tissues of invasive wild pigs, testing the environmental persistence of SN in vomitus, and conducting a risk assessment for scavengers. RESULTS Micro-encapsulation coatings did not affect the frequency of vomiting. We identified no risk of secondary poisoning for non-target scavengers that consume muscle, eyes, and livers of invasive wild pig carcasses because residual SN from the toxic bait was not detected in those tissues. The risk of secondary poisoning from consuming vomitus appeared low because ∼90% of the SN was metabolized or broken down prior to vomiting, and continued to degrade after being exposed to the environment. Secondary poisoning could occur for common scavengers that consume approximately ≥15% of their daily dietary requirements of digestive tract tissues or undigested bait from carcasses of invasive wild pigs in a rapid, single-feeding event. The likelihood of this occurring in a natural setting is unknown. The digestive tracts of poisoned invasive wild pigs contained an average of ∼4.35 mg/g of residual SN. CONCLUSION Data from this study suggest no risks of secondary poisoning for non-target species (including humans) that consume muscle, liver, or eyes of invasive wild pigs poisoned with a MESN toxic bait. More species-specific testing for scavengers that consume digestive tract tissues and undigested bait is needed to reduce uncertainty about these potential risks. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Objective To determine the effectiveness of xylazine for the induction of emesis in cats that were suspected of ingesting potentially toxic substances or foreign objects. Design Retrospective study. Setting Private emergency and specialty referral hospital. Animals Forty-eight client-owned cats that were administered xylazine to induce emesis for decontamination of a toxic substance or expulsion of an ingested foreign object. Interventions None. Measurements and Main Results The medical records of 48 cats presenting for known or suspected ingestion of foreign material that underwent decontamination with xylazine were reviewed. Signalment, material ingested, dose and route of xylazine administration, success of emesis and recovery of foreign material ingested, use of a reversal agent, and adverse effects were noted. The induction of emesis was successful in 29/48 (60%) of cats. Sedation was the most common adverse effect and was noted in 15/48 (31%) of patients. Conclusions Xylazine is safe and reasonably effective at inducing emesis in cats. [ABSTRACT FROM AUTHOR]

BACKGROUND Secondary toxicity in mammals and birds that consume animals containing residues of anticoagulant rodenticides represents a persistent conflict between conservation, agriculture and environmental contamination. Chlorophacinone residues in black-tailed prairie dogs ( Cynomys ludovicianus) represent a secondary exposure hazard to predatory and scavenging avian and mammalian species in the Central Plains of the United States, especially considering efforts to re-establish black-footed ferrets ( Mustela nigripes). Rozol® Prairie Dog Bait (chlorophacinone 0.005%) is registered to control black-tailed prairie dogs in ten states throughout the midwestern and western United States. RESULTS We fed Rozol Prairie Dog Bait to captive black-tailed prairie dogs for 2 days and analyzed their livers and whole bodies (without livers) for chlorophacinone residue on days 3, 5, 7, 9, 11, 14, 18 and 27 post-exposure. We found the greatest levels of residues in livers ( = 5.499 mg kg−1) and whole bodies ( = 1.281 mg kg−1) on day 3. Residues in both tissues declined rapidly over time, with estimated half-lives of approximately 6 days post-exposure. However, a risk assessment of secondary toxicity to non-target mammals indicated acute risks for mammalian species up to 27 days post-exposure and negligible risks for birds. CONCLUSION The results suggest that the greatest risk of secondary toxicity occurs ≤14 days post-application of Rozol Prairie Dog Bait and declines thereafter. This corresponds to the time when chlorophacinone residues are high, and prairie dogs exhibit signs of intoxication and are perhaps most susceptible to predation and scavenging. These results confirm that Rozol Prairie Dog Bait should not be used in areas where black-footed ferrets or other sensitive species occur. Published 2015. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Coking wastewater contributes approximately 5% of the total discharge volume of industrial wastewaters every year in China. The toxicity of coking wastewater to aquatic organisms is still unknown. The authors evaluated the toxicity of wastewater from different treatment stages in a coking wastewater treatment plant, South China, using 5 test species belonging to different trophic levels: luminous bacteria, green alga, a crustacean, duckweed, and zebrafish embryos. The raw influent displayed the highest toxicity to the test species, with toxic units ranging from 16.2 to 1176. The toxicity in the wastewater was then gradually removed by sequential primary treatment, biological fluidized-bed treatment, and secondary clarifier treatment. The toxic unit of the final effluent was reduced to 2.26 for the green alga ( Pseudokirchneriella subcapitata) and to 0 for the other 4 organisms. Quantitative analysis of metals and polycyclic aromatic hydrocarbons (PAHs) and qualitative scanning by gas chromatography-mass spectrometry showed the presence of a variety of pollutants in the coking wastewaters. Multivariate statistical analysis revealed that the toxicity in the coking wastewater was correlated to the chemical oxygen demand, total nitrogen, ammonia nitrogen, volatile phenols, sulfide, metals (Cr, As, Sb, Hg, Pb, and Ni), and ΣPAHs. Based on the results, it is required to set a safety emission limit value for the discharge of coking wastewater to protect aquatic organisms in the receiving water bodies. Environ Toxicol Chem 2014; 33:1967-1975. © 2014 SETAC [ABSTRACT FROM AUTHOR]

We have developed an oral bioassay to determine the toxicity of hydramethylnon to individual workers and queens of the Argentine ant, Linepithema humile. We fed seven concentrations of hydramethylnon in suspension to individual workers or queens, determined the amount of hydramethylnon ingested and evaluated the individual ants for mortality 14 days later. At concentrations ⩾0.37 g liter-1, the amount of liquid the queens ingested decreased dramatically, indicating that Argentine ant queens may detect hydramethylnon. Significantly larger volumes of the two highest concentrations of the hydramethylnon suspension were ingested by the workers, compared to the lower concentrations, suggesting that hydramethylnon may act as a feeding stimulant for the workers. Worker mortality was higher than queen mortality at the highest concentrations tested. The highest worker mortality resulted when the ants ingested 1.03 μg of hydramethylnon per mg of ant tissue. At the highest concentration (1.0 g liter-1) tested, workers ingested almost 12 times as much active ingredient per mg of body weight as did queens, suggesting that, in order to increase mortality of queens, multiple feedings must occur. [ABSTRACT FROM AUTHOR]

Abstract1. This paper approaches the phenomenon of hormesis (i.e. stimulatory effects occurring in response to low levels of exposure to agents that are harmful at high levels of exposure) from an evolutionary perspective and addresses three questions related to its occurrence and consequences: (1) Is the occurrence of hormesis to be expected on the basis of evolutionary arguments? (2) Considering selection as a driving force in the evolution of hormesis, is it likely that certain aspects of organism performance have a greater tendency than others to exhibit hormesis? (3) What are the practical implications of hormesis for ecological risk assessment? 2. Several hypotheses are presented to explain the observations of hormesis, and a literature review is used to assess the evidence for hormesis of various fitness-related traits. 3. To avoid statistical artefacts, it is essential that the underlying distribution of traits that appear to show hormesis be examined, particularly as many of them may be expected to deviate from normality. 4. The occurrence of hormesis of individual life-history traits can be explained as an evolutionary adaptation that acts to maintain fitness in a changing environment. 5. As a result of energetic trade-offs among life-history traits, not all traits are likely to exhibit hormesis simultaneously, and therefore overall fitness is not likely to be enhanced at low levels of exposure to toxic agents. Because toxic agents affect different traits in different directions and to different degrees, interpreting the ecological consequences of hormesis of any single trait is not possible without examining it in relation to overall effects on fitness. [ABSTRACT FROM AUTHOR]

An environmental survey of several rivers of the southern Huasteca area of Mexico revealed high concentrations of manganese (Mn) and the presence of DDT in the sediments and pore water. Therefore, acute (48-h) toxicities of Mn and DDT were assessed both independently and as a combination on 24-h-old neonates of Daphnia magna Strauss and Lecane quadridentata Ehrenberg. Daphnia magna showed high sensitivity to both toxicants, whereas L. quadridentata was highly resistant to DDT and less susceptible to Mn. For D. magna, the Mn and DDT coexposure was significantly more toxic than any of the singly tested compounds. When D. magna was exposed to sediment pore water, no association was found between the Mn content in the samples and the observed toxicity. Preliminary particle analysis of pore water showed different compounds of Mn, which apparently were not in bioavailable form. [ABSTRACT FROM AUTHOR]

This study compares lethal and sublethal responses of Daphnia magna Straus exposed to fenvalerate continuously (21 d) and as a pulse (24 h). Survival was reduced more severely in the continuous- than in the pulse-exposure regime. Complete mortality occurred at 1 µg/L for continuous exposure and at 3.2 µg/L for pulse exposure. Regarding reproductive endpoints, fenvalerate delayed the age at first reproduction. At the beginning of the reproductive phase (day 10), this delay resulted in a reduction of the neonates per living female at similar concentrations in both exposure regimes (0.3 and 0.1 µg/L for continuous and pulse exposure, respectively). The population growth rate was inhibited in continuous and pulse exposure at 0.3 and 0.6 µg/ L, respectively. However, the effects of fenvalerate in the pulse exposure were transient. After 21 d, a recovery to values close to the controls occurred with respect to the total neonates per female and the population growth rate over a broad range of concentrations from 0.1 up to 1 µg/L. In contrast, no substantial recovery occurred in the continuous-exposure regime. [ABSTRACT FROM AUTHOR]

Negative interaction between individuals is a distinctive feature ofpopulations. The question is addressed whether the population response to toxicants (e.g., the pyrethroid pesticide fenvalerate) is altered by the strength of negative intraspecific interaction. Larvae of the trichopteran Limnephilus lunatus Curtis were exposed for 1 h to fenvalerate, then larval survival and adult emergence were monitored inoutdoor stream microcosms over eight months. Degree of interaction was varied by changing larval densities. No survival was observed after 15 d at 100 mug/L. Survival decreased slightly at 10 mug/L when strong interaction was present. Survival in the range of 0.001 to 1 mug/L was similar to that in the control, regardless of the strength of interaction. In contrast, chronic effects differed widely according tothe degree of interaction. Weak interaction resulted in high survival of controls, a lowest-observed-effect concentration (LOEC) (mortality) of 0.1 mug/L, a delay in development at 0.001 to 0.01 mug/L, and reduced weight of adults from 0.01 mug/L on. Strong interaction resulted in low survival of controls, a LOEC (mortality) of 100 mug/L, anda delay in development at 0.1 mug/L. The suggestion was made that these differences in chronic effects are caused by a toxicant-induced reduction of negative intraspecific interaction at high concentrations(>1 mug/L). Hence, direct effects of the toxicant are partly compensated because of indirect reduction of negative interaction compared to the control. Interaction is not decreased at low concentrations (<0.1 mug/L) and, thus, effects of the toxicant are not compensated. Accordingly, the response to toxicants at the population level when negative interaction is present differs from the response at individual level. [ABSTRACT FROM AUTHOR]

Within the scope of bioassay-directed identification of dioxin-like toxicants in complex environmental samples, EC50based and fixed-effect-level-based 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity equivalents (TEQs) were compared to assess 7-ethoxyresorufin-O-deethylase (EROD) inducing potency of sediment fractions using the rainbow trout liver cell line RTL-W1 as bioassay system. Toxicity equivalents onthe basis of fixed effect levels are suggested in order to minimize interpretation problems due to the superposition of enzyme-inducing and enzyme-inhibiting effects. Bioassay-directed fractionation of a contaminated sediment extract in the industrial region of Bitterfeld (Germany) based on fixed-effect-level TEQs indicated high dioxin-like activity in the lipophilic sediment fractions containing the prototypic arylhydrocarbon receptor (AhR) agonists polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). However, only a small part of the EROD induction could be attributed to the PCBs and PAHs that were analyzed. Significant EROD induction occurred also with some of the more polar fractions. [ABSTRACT FROM AUTHOR]