Generation Larvae Research Articles

Diluted concentrations of methamphetamine in surface water induce behavior disorder, transgenerational toxicity, and ecosystem-level consequences of fish

Methamphetamine (METH) has been recognized as an emerging organic contaminant as it was widely detected in the aquatic environment via wastewater effluent discharge. However, the ecological hazard posed by METH at environmentally relevant concentrations was remained unclear. In this study, adult medaka fish were exposed to METH at environmental levels (0.05, 0.2, 0.5, 5 μg L−1) and high level (25 and 100 μg L−1) for 90 days to investigate its effect on ecologically behavioral functions, histopathology, bioconcentration, and transgenerational toxicity. The significant increase of locomotion activity, total distance, and max velocity of adult medaka were observed at low METH levels (0.2–0.5 μg L−1), while it markedly decreased at high levels (25–100 μg L−1). This effect may increase the predation risk of the fish. The significant alteration on the relative expressions of the genes (cacna1c, oxtr, erk1, and c-fos), as well as the contents of the proteins (oxytocin (OXT) and protein kinase A (PKA)) involved in Voltage Dependent Calcium Channel (VDCC) and Mitogen-Activated Protein Kinase (MAPK) signaling channel induced by METH could partly elucidate the underlying mechanisms of the changes of the behavioral traits. METH could induce obvious minimal gliosis, neuronal loss, and necrotic in brain tissues. Additionally, the significant increase of hepatic-somatic index (HSI) of male medaka at 0.2–5 μg L−1 groups, and the decrease of female medaka at 100 μg L−1 group indicated male fish was more susceptible to METH. Nephric-somatic index (NSI) of medaka markedly declined induced by METH at 0.05–100 μg L−1. The bioconcentration factor (BCF) (0.4–5.8) in medaka fish revealed the bioconcentration potential of METH in fish. This study for the first time demonstrated METH could induced the development defects of larvae in F1 generation at environmentally relevant concentrations, thereby resulting in a significant decrease in the capacity of fish to produce offspring. Meanwhile, the RQ values (>1) of METH in river in China, USA, and Australia showed a high teratogenic risk level, suggesting the ecosystem-levels consequence posed by METH should be concerned.

CHANGES IN SUSCEPTIBILITIES TO INSECTICIDES IN MUSCA DOMESTICA UNDER SELECTION WITH FIPRONIL

New knowledge about resistance and cross-resistance to insecticides of different chemical classes in insects is crucial for correct and effective pest management. This paper reports changes in the susceptibility to insecticides of different chemical classes in the first generations of houseflies Musca domestica L. when they were selected with fipronil. The selection of M. domestica was carried out by feeding adult insects with sugar containing fipronil in a dose that causes the 40–60% mortality of insects. The susceptibility of adults and larvae to insecticides was evaluated by the resistance ratio (RR). In the fipronil-selected strain of M. domestica, the susceptibility to fipronil was unchanged in adults in 3–5 generations and increased in larvae in the fifth generation (RR = 0.5). The susceptibility to deltamethrin decreased in adults of the fourth generation and in larvae of the fifth generation, and the RR was 4.5 and 4.3, respectively, that may suggest the development of cross-resistance in the future. The susceptibility to chlorfenapyr was reduced in adults of fipronil-selected flies of the fourth generation (RR = 1.9). The susceptibility to ivermectin increased in adults of fipronil-selected flies (RR = 0.67) and in larvae of the fifth generation (RR = 0.5). The susceptibility to acetamiprid in the fipronil-selected strain and the laboratory (unselected) strain of M. domestica did not differ. The results are useful for the development of insecticide resistance management programs.

Microsclerotial Granular Formulation of the Entomopathogenic Fungus Metarhizium brunneum and Its Combinations With Hydrogel and Imidacloprid Against the Annual Bluegrass Weevil (Coleoptera: Curculionidae).

We determined the potential of the entomopathogenic fungus Metarhizium brunneum Petch (Hypocreales: Clavicipitaceae) F52 strain, and of a microsclerotial formulation, for the control of the annual bluegrass weevil, Listronotus maculicollis Kirby, which is a major pest of golf course turf in eastern North America with widespread insecticide resistance. Under laboratory conditions in Petri dishes with moist sand, the microsclerotia (23-46 kg granules/ha) caused high rates of mortality (85-100%) and infection (67-80%) in annual bluegrass weevil adults, but these levels did not occur until after 9 d at constant 26°C and 12-15 d at 14 h at 23°C and 10 h at 17°C. Production of viable conidia was marginally higher at the higher temperature regime (7.3 vs. 5.2 × 109 per gram of granules). Application of microsclerotia did not provide significant control and infection of adults in pots with grass in the greenhouse. In field trials targeting spring generation larvae, microsclerotia application (50-100 kg granules/ha) was ineffective, and coapplication of hydrogel to stabilize soil moisture did not increase larval control. A liquid M. brunneum F52 conidial formulation (4.75-9.5 × 1013 colony forming units/ha) provided up to 51% control. Combinations of M. brunneum F52 with the neonicotinoid insecticide imidacloprid provided additive control with up to 70% control with the conidial formulation. Field efficacy was probably limited by suboptimal temperatures for the fungus, and future tests need to examine whether higher control rates can be achieved in applications targeting the summer generation larvae.

Larval Response to Parental Low pH Exposure in the Pacific Oyster Crassostrea gigas

As negative effects of ocean acidification are experienced by coastal ecosystems, there is a growing trend to investigate the effect ocean acidification has on multiple generations. Parental exposure to ocean acidification has been shown to induce larval carryover effects, but whether acute exposure to a stressor as an adult can influence the larval generation long after the stress has been removed has yet to be tested. To assess how a temporary exposure to experimental ocean acidification affects the ecologically and commercially relevant Pacific oyster Crassostrea gigas, adult oysters were exposed to either low pH (7.31 ± 0.02) or ambient pH (7.82 ± 0.02) conditions for 7 wk. Oysters were then held for 8 wk in ambient conditions, and subsequently reproductively conditioned for 4 wk at ambient pH. After conditioning, the oysters were strip-spawned to create four families based on maternal and paternal ocean acidification exposure. The number of D-hinge larvae was counted 18 h postfertilization. A sex-specific brood stock response was observed, where female exposure to low pH conditions resulted in fewer D-hinge larvae. This study demonstrates that the effects of ocean acidification can last beyond the time from when the environmental perturbation is experienced. Broadening the understanding of environmental memory will be valuable when considering organismal ability to persist in the face of environmental change.

Heritable natural variation of light/dark preference in an outbred zebrafish population

Anxiety is a fear-like response to stimuli perceived to be threatening. Excessive or uncontrollable anxiety is a debilitating psychiatric disorder which affects many people throughout their lifetime. In unravelling the complex genetic and environmental regulations of anxiety-like phenotypes, models measuring the natural dark avoidance of larval zebrafish have shed light on the individual variation and heritability of this anxiety-related trait. Using the light/dark choice paradigm and selective breeding, this study aims to validate previous findings of the variable (VDA) and strong dark aversion (SDA) heritability in AB-WT larval zebrafish using the outbred zebrafish strain EK, which offers more genetic diversity to aid in future molecular mapping efforts. 190 larvae (6 days post fertilization [dpf] and 7 dpf) were tested across four trials and divided into variable (VDA), medium (MDA) and strong (SDA) dark aversion for further in-crosses. VDA and MDA larvae became more explorative with time, whereas SDA larvae rarely left the preferred light zone. The SDA and VDA in-crosses significantly increased the respective phenotypes in the second generation of larvae, whereas VDA × MDA inter-crosses did not. For the second-generation SDA cohort, dark aversion correlated with increased thigmotaxis, which reinforces SDA as an anxiety-like phenotype. Our finding that the dark aversion trait and SDA and VDA phenotypes are heritable in an outbred zebrafish population lays an important foundation for future studies of genetic underpinnings using whole-genome mapping methods. This conserved fear/anxiety-like response in a highly accessible model organism also allows for further pharmacological and behavioral studies to elucidate the etiology of anxiety and the search for novel therapeutics for anxiety disorders.

Effects of sucrose supplementation and generation on life‐history traits of Bracon cephi and Bracon lissogaster, parasitoids of the wheat stem sawfly

AbstractKnowledge of the life‐history traits that influence the reproductive success of parasitoids could provide useful information to enhance their effectiveness as biological control agents. The wheat stem sawfly Cephus cinctus Norton (Hymenoptera: Cephidae) is a major pest of wheat in the Northern Great Plains of North America. The bivoltine, sympatric and specialist parasitoids Bracon cephi (Gahan) and Bracon lissogaster Muesebeck (Hymenoptera: Braconidae) are the only species known to attack C. cinctus in wheat. In the present study, we quantify the body size, longevity, egg load and egg volume of B. cephi and B. lissogaster aiming to test whether these life‐history traits differ among adult females developing from overwintering and summer generation larvae. We also investigate the effect of sucrose supplementation on the same reproductive parameters. The results obtained show no differences between life‐history traits of B. cephi developing from the overwintering and summer generations. By contrast, the egg load of B. lissogaster is significantly different between generations, with overwintered females producing 1.2‐fold more eggs than summer individuals. Sucrose feeding has a strong positive effect on life‐history traits of both parasitoid species and generations. The longevity of sucrose‐fed females of B. cephi is increased three‐fold, whereas the survival of B. lissogaster is increased almost nine‐fold. Females of B. cephi treated with sucrose have four‐fold more mature eggs, whereas the egg load of B. lissogaster is increased 1.15‐ to 1.25‐fold with sugar feeding. Only B. cephi females increase egg volume with sucrose. The present study provides valuable insights on the life‐history and nutritional requirements of these two important parasitoid species.

Survei Entomologis dan Status Kerentanan Larva Aedes aegypti terhadap Insektisida Organofosfat di Desa Banguntapan Yogyakarta

Aedes aegypti is a vector of many arboviruses. Information of the breeding site of this vector is important for preventing many diseases and for design intervention programs. This study was to determine the breeding place of Ae. aegypti, type of water-holding container and susceptibility for organophosphate insecticide in Banguntapan village. Design of this research was cross-sectional study that located in Banguntapan village from November 2016 until January 2017 on 400 houses. All water holding container that present in and around houses were inspected for the presence of Ae. aegypti with single larvae method. Susceptibility test using bioassay and biochemist test was applied on F1 generation larvae. Risk indicator of the entomological survey was the free larvae index (FLI), house index, container index and breteau index. A total 696 container were inspected, of which 149 containers were positive Ae. aegypti, with FLI 73%, HI 27%, BI of 33%, CI 18.14% and PI of 17.5%. The most common breeding habitats for larvae were bathtub, bucket, plant’s pot, birds drinking pot. Susceptibility status to temephos was susceptible, whiles for organophosphate insecticide was medium resistance. Banguntapan village was a high potential for arbovirus transmission and bathtub is the most potential breeding place for Ae. aegypti mosquitoes.

Correction to Influence of Thuja Essential Oil on Untreated Larvae and F1 Generation Larvae of Galleria mellonella Irradiated with Gamma Radiation

Correction to Influence of Thuja Essential Oil on Untreated Larvae and F1 Generation Larvae of Galleria mellonella Irradiated with Gamma Radiation

Zebrafish breeding program: genetic parameters estimates for growth traits.

The objective of this study was to evaluate the genetic parameters of two generations of zebrafish breeding program. The base population was formed by crossing individuals of six commercial stocks of zebrafish, resulting in a nucleus with 60 families. Two generations were evaluated, with a total of 780 and 781 individuals for the first and second generation, respectively. The selection was made based on the mean genetic value of each family, followed by mass selection of the breeders. Mathematical models that considered the fixed (age, density in the larval stage, sex, and generation) and random (animal additive genetics, common to full-sibs, and residual) effects were evaluated using BLUPF90 program family. Weight and total length were used as response variables. Total length was the best selection criterion because it had a higher heritability (0.30) than weight (0.22). There was a high common to full-sib effect, especially in the first generation of animals. For second-generation data, the heritability was 0.26 for total length, as well as a lower common to full-sib effect for length. The best model obtained for this evaluation was considering all effects, being age and density as first and second polynomial, respectively. The genetic and phenotypic correlations for weight and length were 0.87 and 0.75, respectively. These results indicate that genetic breeding using total length as the selection criterion may produce a larger and heavier zebrafish strain.

Eco-symbiotic system constructed and purified effect for wastewater treatment

In order to reduce and deal with domestic sewage from the source, Eco-Symbiotic system (ESS) was built to investigate the biological symbiosis, output of biological organisms and purification of sewage under natural condition. The results showed that the ESS provided good growth for biological symbiosis. Three generation larvae were bred by three guppy couples, and water spinach were harvested 6 times with a total of 4304g in the test period. The ESS has strong buffering capacity, for the stable pH value (7.35-7.75), and the high removal rate of total phosphorus (TP, 89.2%) and total nitrogen (TN, 71.3%). The effluent can reach A level of Urban Sewage Treatment Plant Pollutant Discharge Standards (GB18918-2002). The ESS is a type of treatment to reduce sewage emissions from where the pollution started, improving the utilization of water resources, so it has broader application prospects.

Influence of Thuja Essential Oil on Untreated Larvae and F1 Generation Larvae of Galleria mellonella Irradiated with Gamma Radiation

The objective of the current study was to determine the fumigant toxicity of Thuja essential oil against 3rd and 5th instar larvae of the greater wax moth, Galleria mellonella. Thuja essential oil was extracted from unripe fruits of Thuja orientalis plant by water distillation. The mortality of larvae at the end of larval period, pupation and adult emergence were tested at different concentrations of Thuja oil after a 24h exposure period ranging from 5 to 25µL for 3rd instar larvae and 80µL for 5th instar. The combined effect of Thuja essential oil and larvae resulting from parents irradiated as pupae of G.mellonella with 80Gy was investigated. The results demonstrated that the mortality increased by increasing oil concentration. The percent mortality of 3rd instar larvae reached 100% when exposed to a higher concentration of Thuja oil (25µL) after 24h, while in the case of 5th instar larvae the mortality was 73.3% at (80µL). Larvae of both instars resulting from parents of G. mellonella irradiated as pupae with 80Gy and exposed to the same concentrations of Thuja oil vapor became more susceptible to the oil as a result of the combined effect of the two agents. The LC50 and LC90 values for each experiment were calculated. The tested plant oil prolonged the larval - pupal periods and reduced both pupation percentage of adult emergence.

Gonadal impairment and parental transfer of tris (2-butoxyethyl) phosphate in zebrafish after long-term exposure to environmentally relevant concentrations

Tris (2-butoxyethyl) phosphate (TBOEP) is a ubiquitous environmental contaminant due to its overuse. TBOEP has been found to cause reproductive toxicity and endocrine disruption during acute toxic experiment. In this study, we examined the effects of TBOEP on growth in initial generation (F0) zebrafish and transgenerational effects on growth of first generation (F1) larvae after parental long-term exposure (120 d) to environmentally relevant concentrations (0, 0.1, 1, 10 and 100 μg/L). Exposure to TBOEP resulted in significantly less growth as measured by body length, body weight and gonadosomatic index (GSI) in F0 females but not F0 males. Furthermore, the bioaccumulation of TBOEP in gonad, the alteration of the gene transcriptions in the hypothalamic-pituitary-gonadal (HPG) axis, and the delay in gonadal development in both female and male zebrafish were demonstrated. In addition, the residues of TBOEP were detected in F1 larvae after parental exposure, resulting in lower survival and shorter body length, as well as faster heart rate. And no significant changes in gene expressions along the growth hormone/insulin-like growth factor (GH/IGF) axis and the hypothalamic-pituitary-thyroid (HPT) axis were found in F1 larvae. In conclusion, these results indicated that long-term parental exposure to environmentally relevant concentrations of TBOEP could inhibit the development of progeny by parental gonadal impairment and by TBOEP transfer to offspring, instead of gene transcription in GH/IGF and HPT axes.

Effect of carcass model on maggot distribution and thermal generation of two forensically important blowfly species, Chrysomya megacephala (Fabricius) and Chrysomya rufifacies (Macquart)

BackgroundAt feeding stage, blowfly larvae (Diptera: Calliphoridae) form aggregation to facilitate the breakdown of a human body after death. The aggregation structure of blowfly larvae could probably be different depending on fly species and food size. In forensic investigations, corpse size does not only affect the internal temperature after death, but it could also potentially influence the distribution, aggregation temperature, and species of flies that inhabit a corpse. However, there is no reference available to explain how these factors could affect maggot distribution pattern and thermal generation. The best way to answer this is by accessing blowfly aggregation on multiple forensic entomology animal models of different sizes. Thus, this research is a preliminary assessment to determine maggot aggregation structure and its thermal generation in three carcass species which are commonly used as a surrogate for human corpses in Malaysia.MethodologyFrequency of Chrysomya megacephala (Fabricius) and Chrysomya rufifacies (Macquart) aggregations at a different location in carcass was determined. Aggregation temperature, depth, perimeter, area, and volume of tightly packed aggregations were measured. These variables were compared to ambient temperature and relative humidity. Correlation analysis was performed to access any relationship between each variable.ResultsAggregation temperature was found strongly correlated to carcass temperature (r = 0.65, p < 0.05), moderately correlated to carcass ground temperature (r = 0.57, p < 0.05), and weakly correlated to aggregation depth (r = 0.21, p < 0.05), relative humidity (r = 0.06, p = 0.35), and ambient temperature (r = 0.01, p = 0.89). The rate of carcass loss was significantly influenced by carcass model (p < 0.05). The frequency of Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) aggregation was more in rat carcasses, while for rabbits and macaques, Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae) was more frequent. Aggregations of Chrysomya rufifacies were frequently observed located below carcasses while Chrysomya megacephala were observed mostly in the mouth and genitalia. Chrysomya rufifacies aggregations have produced higher temperature compared to Chrysomya megacephala.ConclusionCarcass model was proven to be a critical factor in larval aggregation distribution and temperature. Therefore, this preliminary study has pointed out the necessity of proper selection of animal model for forensic entomology study. Food source characteristics, particularly body size, could play a significant factor in larval aggregation distribution and thermal generation, therefore making this factor important when making postmortem interval (PMI) estimation based on larval growth.

Competition among Aedes aegypti larvae.

Adult Aedes aegypti mosquitoes are important vectors of human disease. The size of the adult female affects her success, fitness, and ability to transmit diseases. The size of the adults is determined during the aquatic larval stage. Competition among larvae for food influences the size of the pupa and thus the adult. In these experiments, the food level (mg/larva) and the density (larvae/vial) both affect intraspecific competition, which shows up as the interaction of the two factors. Furthermore, the total food per vial affects the nature of competition among the larvae, also apparent in the interaction of food and density. Male larvae are affected by the percent of males in the vial, but females are not. Seven biologically significant dependent variables were examined, and the data analyzed by multivariate analysis of variance to gain insight into the relationships among the variables and the effects of these factors on the larvae as they grew in small containers. Male and female larvae compete differently from one another for the particulate yeast cells in this experiment; female larvae outcompete males through larger size and by retaining cells within their gut at low total food levels. Under conditions of more intense competition, the pupal masses of both males and females are smaller, so the effect of competition is a reduced apparent food level. The age at pupation is also affected by food and density. Across the twenty treatment combinations of food/larva and larvae/vial, female larvae grew as though there were six different ecological environments while male larvae grew as though there were only four different environments. No interference competition was observed. Eradication efforts aimed at adult populations of this mosquito may inadvertently increase the size and robustness of the next generation of larvae, resulting in a subsequent adult population increase in the second generation.

Parental transfer of perfluorooctane sulfonate and ZnO nanoparticles chronic co-exposure and inhibition of growth in F1 offspring

Perfluorooctane sulfonate (PFOS) and ZnO nanoparticles (Nano-ZnO) are two kinds of environmental contaminants that have been frequently detected in natural waters. The potential joint toxicity of PFOS and nano-ZnO remains to be fully elucidated. The objective of this study was to evaluate co-exposure effects of PFOS and nano-ZnO on growth in initial generation (F0) zebrafish after chronic exposure and to examine possible parental transfer of PFOS and nano-ZnO transgenerational effects on the growth of first generation (F1) larvae. When zebrafish (2 h after incubation) were exposed to single- and co-exposure groups for 120 days, bioconcentration resulted in significantly less growth as measured by body length and body weight, higher mortality, and less spawning in the F0 generation. These effects were possibly due to the down-regulation of the expression of Vtg1 genes along with a sex hormone (T/E2) involved in the hypothalamus-pituitary-gonad (HPG) axis. Furthermore, after long-term exposure, less fertilization, less hatching, greater mortality and more malformation were found in the F1 generation. The down-regulation of genes and hormones might be responsible for transgenerational toxicity. This study suggested that chronic exposure to PFOS and nano-ZnO adversely impacts development, reproduction in the F0 generation, and offspring embryonic growth.

Estimating acute mortality of Lepidoptera caused by the cultivation of insect-resistant Bt maize – The LepiX model

The cultivation of Bt maize, genetically modified to be resistant to insect pests, has led to intense scientific and political debate about its possible adverse impacts on biodiversity. To better address this question we developed an individual-based simulation model (LepiX). LepiX considers the temporal dynamics of maize pollen shedding and larval phenology, and pollen deposition on host plants related to distance from the maize field, in order to estimate mortality of lepidopteran larvae exposed to toxic Bt pollen. We employed a refined exposure analysis, comparison to previous approaches, using recent evidence on leaf pollen deposition and accounting for the spatial heterogeneity of pollen on leaves. Moreover, we used a stochastic approach, considering literature data on a minimum dataset for butterfly biology in combination with historic data on temporal pollen deposition to predict the coincidence between larval phenology and pollen deposition. Since conservation management actions may act at the level of the individual for protected species, LepiX, as an individual based spatially explicit model, is suited to assist both risk assessment and management measures based on threshold mortalities. We tested our model using Inachis io (Lepidoptera: Nymphalidae) as butterfly species and the cultivation of insect resistant MON810 maize. In accordance to predictions based on other models we identified mortality risks of I. io larvae for the second larval generation. An analysis of the sensitivity of input parameters stressed the importance of both the slope and the LC50 value of the dose-response curve as well as the earliest day of larval hatching. Using different published data to characterize the dose-response of MON810 pollen to I. io we revealed consequences due to uncertainties in ecotoxicological parameters and thus highlight the importance of key biological parameters for reliable estimates of effects, and decision making (e.g. isolation distances) in risk assessment.

Billbug (Coleoptera: Dryophthoridae: Sphenophorus spp.) Seasonal Biology and DNA-Based Life Stage Association in Indiana Turfgrass

Eleven species of billbugs (Coleoptera: Dryophthoridae: Sphenophorus spp. Schönherr) infest managed turfgrass in North America. However, the regional variation in species composition remains unresolved and the seasonal phenology of several species has not been well documented. The latter gap is largely due to the inability to identify the larval stage to species-a confounding problem with several sympatric insect species. We used field trapping (adults) and soil sampling (larvae and pupae) surveys along with a DNA-based life-stage association to characterize the biology of billbugs associated with turfgrass in the Midwestern United States. Pitfall trapping at four locations in Indiana revealed four billbug species: S. venatus Say, S. parvulus Gyllenhaal, S. minimus Hart, and S. inaequalis Say. Sphenophorus venatus was the most abundant species on warm-season turfgrass while S. parvulus was most abundant on cool-season turfgrass. Investigation of S. venatus seasonal biology revealed two overwintered life stages-larva and adult-which resulted in two overlapping cohorts and two larval generations. Degree-day models describing S. venatus activity were more accurate for first-generation adults and larvae than for overwintering life stages. Maximum-likelihood analyses provided the first molecular species identification of billbug larvae and direct evidence that S. venatus larvae are capable of overwintering above 40°N latitude. Findings clarify the utility of molecular markers (CO1, 18S, and ITS2) for describing billbug larval population dynamics and seasonal phenology in regions where several sympatric billbug species occur. These results support the development of sustainable management strategies based on billbug seasonal phenology in different regions of North America.

Host plant exodus and larval wandering behaviour in a butterfly: diapause generation larvae wander for longer periods than do non‐diapause generation larvae

1. Prior to pupation, lepidopteran larvae enter a wandering phase lasting up to 30 h before choosing a pupation site. Because stillness is important for concealment, this behaviour calls for an adaptive explanation.2. The explanation most likely relates to the need to find a suitable pupation substrate, especially in terms of shelter from predation, and given that many predators and parasitoids use host plants as prey‐location cues, mortality probably decreases with distance from the host plant. Hence, remaining on the host includes a long‐term risk, while moving away from the host introduces an increased risk during locomotion.3. Bivoltine species that overwinter in the pupal stage produce two kinds of pupae; non‐diapausing pupae from which adults emerge after 1–2 weeks, or diapausing pupae that overwinter with adults emerging after 8–10 months.4. Given the hypothesis of distance‐from‐host‐plant‐related predation, this should select for phenotypic plasticity with larvae in the diapausing generation having a longer wandering phase than larvae under direct development, if there is a trade‐off between mortality during the wandering phase and accumulated mortality during winter.5. Here this prediction is tested by studying the duration of the wandering period in larvae of the partially bivoltine swallowtail butterfly, Papilio machaon, under both developmental pathways.6. The results are in agreement with the predictions and show that the larval wandering phase is approximately twice as long under diapause development. The authors suggest that the longer duration of the wandering phase in the diapause generation is a general phenomenon in Lepidoptera.

Differential DNA methylation at conserved non-genic elements and evidence for transgenerational inheritance following developmental exposure to mono(2-ethylhexyl) phthalate and 5-azacytidine in zebrafish

BackgroundExposure to environmental stressors during development may lead to latent and transgenerational adverse health effects. To understand the role of DNA methylation in these effects, we used zebrafish as a vertebrate model to investigate heritable changes in DNA methylation following chemical-induced stress during early development. We exposed zebrafish embryos to non-embryotoxic concentrations of the biologically active phthalate metabolite mono(2-ethylhexyl) phthalate (MEHP, 30 µM) and the DNA methyltransferase 1 inhibitor 5-azacytidine (5AC, 10 µM). Direct, latent and transgenerational effects on DNA methylation were assessed using global, genome-wide and locus-specific DNA methylation analyses.ResultsFollowing direct exposure in zebrafish embryos from 0 to 6 days post-fertilization, genome-wide analysis revealed a multitude of differentially methylated regions, strongly enriched at conserved non-genic elements for both compounds. Pathways involved in adipogenesis were enriched with the putative obesogenic compound MEHP. Exposure to 5AC resulted in enrichment of pathways involved in embryonic development and transgenerational effects on larval body length. Locus-specific methylation analysis of 10 differentially methylated sites revealed six of these loci differentially methylated in sperm sampled from adult zebrafish exposed during development to 5AC, and in first and second generation larvae. With MEHP, consistent changes were found at 2 specific loci in first and second generation larvae.ConclusionsOur results suggest a functional role for DNA methylation on cis-regulatory conserved elements following developmental exposure to compounds. Effects on these regions are potentially transferred to subsequent generations.

Parental transfer of tris(1,3-dichloro-2-propyl) phosphate and transgenerational inhibition of growth of zebrafish exposed to environmentally relevant concentrations

Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) is a re-emerging environmental contaminant that has been frequently detected at sub-ppb (<μg/L) concentrations in natural waters. The objective of this study was to evaluate effects of TDCIPP on growth in initial generation (F0) zebrafish after chronic exposure to environmentally relevant concentrations, and to examine possible parental transfer of TDCIPP and transgenerational effects on growth of first generation (F1) larvae. When zebrafish (1-month old) were exposed to 580 or 7500 ng TDCIPP/L for 240 days, bioconcentration resulted in significantly less growth as measured by body length, body mass, brain-somatic index (BSI) and hepatic-somatic index (HSI) in F0 females but not F0 males. These effects were possibly due to down-regulation of expression of genes along the growth hormone/insulin-like growth factor (GH/IGF) axis. Furthermore, residues of TDCIPP were detected in F1 eggs after exposure of parents, which resulted in less survival, body length and heart rate in F1 individuals. Down-regulation of genes in the GH/IGF axis (e.g., gh, igf1) might be responsible for transgenerational toxicity. This study provides the first known evidence that exposure of zebrafish to environmentally relevant concentrations of TDCIPP during development can inhibit growth of offspring, which were not exposed directly to TDCIPP.