Pyriproxyfen induces lethal and sublethal effects on biological traits and demographic growth parameters in Musca domestica

Musca domestica is a global insect-pest of human beings and animal agriculture. Pyriproxyfen, a juvenile hormone analog, has shown its potential for effective management of M. domestica. However, lethal and sublethal effects of pyriproxyfen on biological traits and demographic growth parameters of M. domestica are still unknown. The present study investigated the effects of lethal and sublethal concentrations on different biological traits of M. domestica for two generations i.e., exposed parents (F0) and their offspring (F1). Concentration-response bioassays revealed that concentrations of pyriproxyfen that caused 50% (LC₅₀), 25% (LC₂₅), 10% (LC₁₀) and 2% (LC₂) mortality of M. domestica were estimated as 0.12, 0.06, 0.03 and 0.01 μg/g, respectively. In the F0 generation, exposure of 3^rd instar larvae to these concentrations resulted in a reduced pupation rate, lengthened pupal stage duration, light weight pupae and reduction in adult emergence in a concentration-dependent manner. In the case of F1 generation, similar trend was observed for pupation rate, pupal stage duration, and total developmental period (i.e., egg to adult); however, pupal weight was affected at LC₁₀, LC₂₅, LC₅₀ levels, and adult emergence at only LC₂₅ and LC₅₀ levels. The values of demographic growth parameters, analyzed through age-stage, two-sex life table theory, were significantly decreased at all the levels of pyriproxyfen compared with control. This study highlights that pyriproxyfen has the potential to suppress the population of M. domestica through its lethal and sublethal effects and presents an empirical basis from which to consider management decisions for chemical control in the field.

     

Lethal and sublethal effects of azadirachtin on the bumblebee Bombus terrestris (Hymenoptera: Apidae)

Ecotoxicology - Azadirachtin is a biorational insecticide commonly reported as selective to a range of beneficial insects. Nonetheless, only few studies have been carried out with pollinators,...     

Sublethal and transgenerational effects of spinetoram on the biological traits of Plutella xylostella (L.) (Lepidoptera: Plutellidae)

Spinetoram, a spinosyn insecticide is used to manage lepidopteran pests, including diamondback moth, Plutella xylostella. In addition to determining the lethal effects, identifying low and/or sublethal effects of an insecticide is crucial to understanding the total impact of an insecticide. We assessed the low lethal and sublethal effects of spinetoram on two successive generations of P. xylostella. The initial bioassay results showed that spinetoram exhibited high toxicity against P. xylostella with an LC₅₀ of 0.114 mg L⁻¹ after 48 h exposure. The low lethal (LC₂₅) and sublethal (LC₁₀) concentrations of spinetoram showed significant reduction in pupation rate, pupal weight and adult emergence. The fecundity of F₁ generation was significantly lower in LC₂₅ (117.85 eggs/female) and LC₁₀ (121.34 eggs/female) treated group than untreated control (145.32 eggs/female). The intrinsic rates of increase (r) was significantly lower (r = 0.1984 day⁻¹) in spinetoram treated P. xylostella F₁ progeny compared to untreated control (r = 0.2394 day⁻¹). Our results suggest that LC₁₀ and LC₂₅ concentration of spinetoram might affect P. xylostella population growth by reducing its survival, development, and reproduction.

     

Assessment of the effects of lethal and sublethal exposure to dinotefuran on the wheat aphid Rhopalosiphum padi (Linnaeus)

Ecotoxicology - The wheat aphid Rhopalosiphum padi (Linnaeus) (Hemiptera: Aphididae) is a devastating pest of wheat crops worldwide. Dinotefuran, a novel neonicotinoid insecticide, has been used to...     

Medetomidine as a candidate antifoulant: sublethal effects on juvenile turbot (Psetta maxima L.)

Medetomidine is proposed as a candidate antifouling compound proven effective against barnacles. It is routinely used as a sedative in veterinary medicine. It is therefore important to also investigate possible adverse effects on non-target organisms. Thus, sublethal effects on two different ages of juvenile turbot (Psetta maxima) exposed to a wide concentration range of medetomidine (0.063-420nM) were assessed after exposure under semistatic as well as flow-through conditions, for a maximum of 96h. Effects on respiration frequency and amount of oxygen consumed were assessed, as well as the ability of turbot to adapt to a dark background. A significant decrease was seen both in respiration frequency with a lowest observed effect concentration (LOEC) of 2.1nM as well as in amount of oxygen consumed (LOEC=420nM) and colour adaptation (LOEC=4.2nM). Colour adaptation was also evaluated in a short exposure experiment, 1h, where significant effects were observed (LOEC=2.1nM). Reversibility, when fish were incubated in clean seawater following exposure, was seen for all observed effects. Ecological relevance of the observed effects is discussed.     

Lethal and sublethal effects of toxicants on bumble bee populations: a modelling approach

Ecotoxicology - Pollinator decline worldwide is well-documented; globally, chemical pesticides (especially the class of pesticides known as neonicotinoids) have been implicated in hymenopteran...     

Evaluation of cytotoxic effects of fipronil on ovaries of semi-engorged Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) tick female

The ovary of the Rhipicephalus sanguineus dog tick female is structurally formed by oocytes in five different stages of development (from I to V) and attached to the gonad by the pedicel. The present study evaluated possible toxic effects of the acaricide fipronil (Frontline) on ovaries of semi-engorged ticks. Sixty partially fed females of R. sanguineus tick were distributed into four groups of 15 specimens each: I--non-treated; II, III and IV--treated with 1, 5 and 10 ppm of fipronil, respectively. The acaricide induced structural changes in the oocytes of individuals of the different treated groups ranging from the presence of a few small vacuoles to cellular death. In conclusion, germinative cells of semi-engorged R. sanguineus tick female are affected by different concentrations of fipronil leading to the reduction of tick fertility.     

Acute and sublethal effects of organotin compounds on aquatic biota: an interpretative literature evaluation

The objectives of this review were to: (1) collect, synthesize, and interpret acute and sublethal organotin toxicity data in both freshwater and estuarine-marine ecosystems; (2) present environmental water column and sediment concentrations of organotin compounds in both freshwater and estuarine-marine systems to facilitate interpretation of toxicity data; and (3) identify deficiencies in available data to recommend areas of future research for assessing ecological effects of organotin compounds in aquatic systems. The following recommendations are suggested: (1) evaluation of the bioavailability of organotin compounds in aquatic systems; (2) assessment of the relationship between physicochemical characteristics of organotin compounds and subsequent toxicity effects on aquatic organisms; (3) determination of organotin effects on food chains; (4) evaluation of the specific mechanisms and modes of toxicity for organotin compounds with aquatic biotia; (5) evaluations of the adaptive responses of aquatic biota to organotins; (6) measurement of organotin concentrations in testing chambers throughout toxicity tests using peer-reviewed analytical techniques (nominal concentrations can provide misleading data); (7) assessment of long-term "low level" exposures of organotin compounds on histological, histochemical, behavioral, and physiological responses of aquatic biota; and (8) toxicity assessment of plasticizer organotin compounds to aquatic biota.     

Effects of abamectin exposure on male fertility in rats: Potential role of oxidative stress-mediated poly(ADP-ribose) polymerase (PARP) activation

Despite the known adverse effects of abamectin pesticide, little is known about its action on male fertility. To explore the effects of exposure to abamectin on male fertility and its mechanism, low (1 mg/kg/day) and high dose (4 mg/kg/day) abamectin were applied to male rats by oral gavage for 1 week and for 6 weeks. Weight of testes, serum reproductive hormone levels, sperm dynamics and histopathology of testes were used to evaluate the reproductive efficiency of abamectin-exposed rats. Abamectin level was determined at high concentrations in plasma and testicular tissues of male rats exposed to this pesticide. The testes weights of animals and serum testosterone concentrations did not show any significant changes after abamectin exposure. Abamectin administration was associated with decreased sperm count and motility and increased seminiferous tubule damage. In addition, significant elevations in the 4-hydroxy-2-nonenal (4-HNE)-modified proteins and poly(ADP-ribose) (PAR) expression, as markers for oxidative stress and poly(ADP-ribose) polymerase (PARP) activation, were observed in testes of rats exposed to abamectin. These results showed that abamectin exposure induces testicular damage and affects sperm dynamics. Oxidative stress-mediated PARP activation might be one of the possible mechanism(s) underlying testicular damage induced by abamectin.     

Effects of abamectin exposure on male fertility in rats: potential role of oxidative stress-mediated poly(ADP-ribose) polymerase (PARP) activation

Despite the known adverse effects of abamectin pesticide, little is known about its action on male fertility. To explore the effects of exposure to abamectin on male fertility and its mechanism, low (1 mg/kg/day) and high dose (4 mg/kg/day) abamectin were applied to male rats by oral gavage for 1 week and for 6 weeks. Weight of testes, serum reproductive hormone levels, sperm dynamics and histopathology of testes were used to evaluate the reproductive efficiency of abamectin-exposed rats. Abamectin level was determined at high concentrations in plasma and testicular tissues of male rats exposed to this pesticide. The testes weights of animals and serum testosterone concentrations did not show any significant changes after abamectin exposure. Abamectin administration was associated with decreased sperm count and motility and increased seminiferous tubule damage. In addition, significant elevations in the 4-hydroxy-2-nonenal (4-HNE)-modified proteins and poly(ADP-ribose) (PAR) expression, as markers for oxidative stress and poly(ADP-ribose) polymerase (PARP) activation, were observed in testes of rats exposed to abamectin. These results showed that abamectin exposure induces testicular damage and affects sperm dynamics. Oxidative stress-mediated PARP activation might be one of the possible mechanism(s) underlying testicular damage induced by abamectin.     

Cold storage effects on lethal and sublethal responses of Amphibalanus amphitrite Nauplii

Bioassays are extensively used in ecotoxicology and there is a constant need for even more sensitive, reliable and easy to rear and obtain model organisms. Larvae of the crustacean Amphibalanus amphitrite are a good ecotoxicological model, for their high sensitivity to a wide range of toxicants and emerging contaminants. A standardized protocol for this toxicity bioassay has been recently proposed. Nevertheless, a limit of this model organism is the lack of resting stages and the need to use larvae immediately after their release from adults, thus increasing laboratory efforts related to the maintenance of adults. The aim of this work is to verify if short-term cold storage of A. amphitrite larvae prior to use in ecotoxicological tests may affect the ecotoxicological responses of these organisms. Three end-points (mortality, immobilization and swimming speed alteration) were measured on nauplii after storing them at 4?±?1?°C for different times (24, 72 and 120?h) before bioassay set-up. Bioassays were set up using: (i) clean filtered natural sea water (0.22?µm FNSW), (ii) a reference toxicant (Cadmium Nitrate) and (iii) an environmental matrix (sediment elutriate). Results show that mortality, differently from the other two endpoints, was not affected by cold-storage. Even after 5 days of larvae storage at 4?±?1?°C before bioassay set up, mortality data were comparable to those obtained for non-cold-stored organisms. Moreover, larval sensitivity to the reference toxicant and sediment elutriate did not change. Regarding the other two end points, low cadmium concentrations significantly changed immobility and swimming activity in cold-stored nauplii compared to larvae used immediately after larval release. In conclusion, short-term cold storage of A. amphitrite nauplii before bioassay set up is an appropriate procedure in ecotoxicological testing if mortality is the endpoint to be considered for final evaluation.

     

Acute and sublethal effects of two insecticides on earthworms (Lumbricus terrestris L.) under laboratory conditions

Earthworms (Lumbricus terrestris L.) were exposed to commercial formulations of endosulfan and aldicarb for 2, 7, and 15 days, and the LC(10), LC(25), and LC(50) were determined. Worms were then exposed to LC(10), LC(25), and LC(50) concentrations of endosulfan and LC(10) and LC(25) concentrations of aldicarb. The growth rate and total protein content were determined and related to endosulfan and aldicarb residues in soil and earthworms. Aldicarb was more toxic than endosulfan under the experimental conditions. The residues of endosulfan and aldicarb caused a significant reduction in the growth rate and total protein content of earthworms. The residues of endosulfan and aldicarb were monitored in soil and earthworms after 2, 7, and 15 days of exposure. The residues remaining in the soil after the experiments ranged between 37.75% and 68.54% of the applied concentration for endosulfan and between 10.13% and 67.71% of the applied concentration for aldicarb. Small amounts of both insecticides were detected in worms, and accumulation was more important for endosulfan. This study proposes the use of growth rate and total protein content as biomarkers for contamination by endosulfan and aldicarb.     

Tissue uptake, mortality, and sublethal effects of monomethylarsonic acid (MMA(V)) in nestling zebra finches (Taeniopygia guttata)

Monosodium methanearsonate (MSMA), an arsenic-based pesticide, has been used since the mid 1980s in attempts to suppress mountain pine beetle (Dendroctonus ponderosae) outbreaks in British Columbia, Canada. It was previously shown that cavity nesting forest birds forage and breed in MSMA-treated pine stands. The present study was designed to investigate the effects of ecologically relevant oral exposure to MSMA, including tissue distribution, growth parameters, and general health, including survival and immune function, of a model passerine, the zebra finch (Taeniopygia guttata). Nestling finches were orally dosed for 20 d from hatching to fledging with 4, 8, 12, 24, 36, or 72 microg/g bw/d of monomethylarsonic acid (MMA(V), which corresponds to MSMA at physiological pH). Preliminary trials showed complete mortality at 36 and 72 microg/g bw/d, and repeat trials also resulted in high mortality at 24 microg/g bw/d. Surviving nestlings showed dose-dependent trends in accumulation of arsenic in blood and specific tissues, and decreased tarsi and wing cord length upon fledging. There were no observed effects of dosing on measured immune function (phytohemagglutinin [PHA], hematocrit, and leukocrit). The data obtained suggest that passerine nestlings may be at risk of mortality and reduced growth due to exposure to MSMA under current environmental conditions.     

Lethal and sublethal effects of aniline and chlorinated anilines on zebrafish embryos and larvae

Environmental risk assessments show increased attention to the sublethal effects of chemicals on aquatic organisms. The Organization for Economic Cooperation and Development (OECD) established the “Fish, Short‐term Toxicity Test on Embryo and Sac‐fry Stages” (OECD test 212) to predict lethal effects. It is still unclear, however, whether this test can predict sublethal effects. Although their sublethal effects are still unknown, chlorinated anilines are widely used in various fields. The purpose of this study, therefore, is to investigate sublethal effects of chlorinated anilines using OECD test 212 with zebrafish, and to examine the correlation of several sublethal effects between embryo and larval stages. Embryos were exposed to aniline and nine chlorinated anilines until 8 days post‐fertilization. A delayed lethal effect was observed from three of the 10 anilines tested. In the control group, the swim bladder inflated after hatching, but there was no swim‐bladder inflation after exposure to the chlorinated anilines. Fertilized eggs exposed to lower concentrations of test chemicals showed effects during embryogenesis that did not affect mortality rates, such as changes in body curvature and edema. Our results show that chlorinated anilines induce not only lethal effects but also a variety of sublethal effects. Moreover, a detailed estimate of these effects requires study during both embryonic and larval stages. OECD test 212 may therefore prove useful as a method for screening chemicals for lethal and sublethal effects. Copyright © 2017 John Wiley & Sons, Ltd.     

Acute and sublethal effects of organophosphate insecticide chlorpyrifos on freshwater fish Oreochromis niloticus

Chlorpyrifos is a widely used organosphosphate insecticide in India. Residue of the insecticide is frequently detected in trace to moderate concentration in food grains and in surface water of different freshwater ecosystems of the country. In this study, 96?h LC₅₀ of the technical grade (94% a.i.) and commercial formulation (20% EC) of chlorpyrifos to freshwater fish Oreochromis niloticus were determined as 90.0 and 42.0?µg/L based on 2?h actual concentration of chlorpyrifos in water. About 96?h exposure to sublethal concentrations (0, 12.0 and 25.0?μg/L) of the commercial formulation (20% EC) of chlorpyrifos reduced the level of hepatic glycogen, activities of alkaline phosphatase, acetylcholinesterase, and catalase in liver and elevated the level of plasma glucose and activities of hepatic acid phosphatase, aspartate aminotransferase, and alanine aminotransferase in O. niloticus. About 28-day exposure to these sub-lethal concentrations caused anemia in fish, while 90 days exposure reduced growth of the fish and carcass concentration of crude protein and crude lipid as compared to control. It was concluded from this study that commercial formulation of chlorpyrifos (20% EC) was highly toxic to O. niloticus. Exposure to sub-lethal concentrations of the insecticide could induce oxidative stress and anemia resulting in reduced growth of the fish.     

Lethal and sublethal effects on the progeny of male rats treated with methadone

Fifteen male rats were treated with methadone-HCl (Meth) at 10 mg/kg sc per day for 12 days and an equal number received injections of sterile distilled water. Each male was caged with four untreated females each night. A necropsy was performed on male rats following the period of mating and the litter sizes, birth and weaning weights, and survival to 21 days (neonatal mortality) of their progeny were evaluated. METH-treated males had a reduction in body and seminal vesicle weights and in mating frequency, confirming prior studies. Progeny of METH-treated males (507 pups) were of lower average birth weight than the 276 controls. In addition, it was found that prior copulation had a differential effect, resulting in slightly heavier control pups but significantly decreased birth weights in the METH group. Neonatal mortality of the METH progeny was significantly increased, with 18.2% dead by 21 days compared to 9.5% of the controls (p < 0.01). The present data indicated that mortality was related in a complex fashion to number of drug exposures and previous sexual experience of the sire and that male offspring were particularly affected. Ponderal growth of survivors from litters with high neonatal death rates was inhibited, with females being significantly lighter at 75 and 132 days of age. Open-field defecation scores were significantly different at 2 but not at 4 months of age, but no differences in acquisition of a conditioned avoidance response were noted. No differences in litter size, neonatal mortality, or birth or weaning weights as a result of METH administration were found in the F₂ generation. These results, together with previous data from our laboratory, establish that there are lethal, sublethal, and possibly delayed effects on the progeny of male rats treated with methadone.     

Transgenerational consequences of adolescent morphine exposure in female rats: effects on anxiety-like behaviors and morphine sensitization in adult offspring

Rationale and objective Opiate abuse in adolescent girls has increased in the past decade; however, few animal studies have examined the potential consequences of opiate use occurring at this time. The purpose of the present study was to determine whether exposing female rats to morphine during the peripubertal period can alter the adult behavior of their offspring. Methods Beginning at 30 days of age, female rats were injected subcutaneously (s.c.) twice daily with either morphine sulfate or saline. The initial morphine dose of 2.5 mg/kg was increased by 2.5 mg/kg daily for a total of 20 days. Ten days after the final drug treatment, all subjects were mated. Their subsequent offspring were then tested as adults on the elevated plus maze, in a novel environment or were examined in a morphine locomotor sensitization paradigm. Results Adult female offspring of dams exposed to morphine during puberty spent less time in the open arms of the elevated plus maze and displayed decreased exploration in a novel environment. Female offspring also demonstrated a more rapid induction of morphine sensitization. Finally, male offspring demonstrated a significant enhancement in the expression of morphine sensitization. Conclusions Chronic morphine exposure during adolescence can have significant transgenerational effects on adult offspring. Future studies will be needed to determine how these changes are transferred to the offspring and whether these effects are specific to drug exposure that occurs during the peripubertal period. This work was supported by the National Institute on Health grant DA14613 awarded to E.M. Byrnes     

The influence of etofenprox on narrow clawed crayfish (Astacus leptodactylus Eschscholtz, 1823): Acute toxicity and sublethal effects on histology,hemolymph parameters,and total hemocyte counts

The acute and sublethal effects of etofenprox, a nonester pyrethroid, was determined in narrow‐clawed crayfish (Astacus leptodactylus Eschscholtz, 1823). Semistatic bioassay procedures were followed in both experiments, and the 24, 48, 72, and 96 h LC₅₀ values (with 95% confidence limits) of technical etofenprox for crayfish were calculated as 0.68, 0.61, 0.45, and 0.41 µg/L, respectively based on Finney's probit analysis. Two concentrations of etofenprox (0.04 and 0.1 µg/L) were tested to determine sublethal effects due to 96 hours exposure. After exposure to sublethal etofenprox, hemolymph glucose, and lactate levels increased while total hemocyte counts and sodium levels decreased (p < 0.05). Hemolymph calcium, potassium, magnesium, and chloride concentrations did not change significantly. Histological alterations were evident in the gills and hepatopancreas after exposure to sublethal etofenprox concentrations. Lamellar hyperplasia and lining in the afferent and efferent branchial vessels were recorded in gills; whilst tubule necrosis was obvious in hepatopancreas. Etofenprox was found to be very highly toxic to crayfish, a nontarget organism. Exposure to sublethal concentrations for 96 h affected circulating hemocytes and hemolymph stress parameters via histological response, to compansate for the adverse effects of etofenprox. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 887–894, 2015.     

Direct and indirect effects of sublethal toxicant exposure on population dynamics of freshwater rotifers: a modeling approach

Ecotoxicological assessments commonly consider the direct effects of anthropogenic toxicants on the survival, growth, and reproduction of organisms. However, toxicants also may have indirect effects on aquatic communities by altering species interactions such as predation and competition. Such indirect effects are often mediated by changes in animal behavior, and contribute to uncertainty in predicting the environmental effects of toxicants. In an attempt to better understand indirect effects, a modeling approach was used to simulate the population dynamics of the predatory rotifer Asplanchna girodi and six prey species of herbivorous rotifers in response to sublethal concentrations (110, 190 or 330 mg/l) of pentachlorophenol (PCP). Simulations were performed assuming three different toxicant effect scenarios: behavioral toxicity alone, reproductive toxicity alone, or both behavioral and reproductive toxicity. Population growth rates (G(r)), maximum population densities (D(max)), and the percent of carrying capacity at D(max) (%K) were calculated for A. girodi and each prey species for each effect scenario and toxicant concentration. Similar qualitative results were obtained regardless of which prey species was exploited by A. girodi. Toxicant effects on predator and prey population densities appeared to be the dominant cause of both direct and indirect toxicant effects, and behavioral toxicity was a redundant endpoint relative to reproductive toxicity. These results suggest that assessing toxicant effects on the population growth of individual species may provide sufficient data to predict toxicant effects on species interactions as well.     

Transgenerational reproductive toxicity of 2,4,6-trinitrotoluene (TNT) and its metabolite 4-ADNT in Caenorhabditis elegans

2,4,6-trinitrotoluene (TNT) as an energetic compound widely used in military applications has aroused great concerns in recent years due to its large-scale contamination in soil and water; however, its toxicity is still largely unknown. In this study, we investigated the reproductive toxicity and the transgenerational effects of TNT on Caenorhabditis elegans (C. elegans). Our data showed that exposure to TNT at concentrations ranging from 10 to 100 ng/mL resulted in decreasing the lifespan, brood size, number of oocytes and eggs in uterus, while increasing the number of germ cell apoptosis in C. elegans. The apoptotic effects of TNT were blocked in mutants of cep-1 (w40), egl-1 (n487), and hus-1 (op241), indicating conserved genotoxic response genes was involved in mediating TNT-induced germ cell apoptosis. Parental exposure to TNT significantly increased the germ cell apoptosis from P0 to F2 generation, but the toxicity faded away in F3 and F4 generations. Furthermore, TNT was rapidly metabolized in P0, and the accumulation of 4-aminodinitrotoluene (4-ADNT), the main metabolite of TNT in C. elegans, showed a significant decrease from P0 to F1 and a slow decrease in the subsequent generations. Our results demonstrated that ingested TNT can cause severe transgenerational reproductive toxicity and be rapidly converted to 4-ADNT in the nematodes. These data provided basis for future studies on the effects of energetic compounds across generations.