The effects of the herbicide atrazine on freshwater snails

Overhauling the ecotoxicological impact of synthetic pesticides using plants' natural products: a focus on Zanthoxylum metabolites

The reduction in agricultural production due to the negative impact of insects and weeds, as well as the health and economic burden associated with vector-borne diseases, has promoted the wide use of chemicals that control these "enemies." However, the use of these synthetic chemicals has been recognized to elicit negative impacts on the environment as well as the health and wellbeing of man. In this study, we presented an overview of recent updates on the environmental and health impacts of synthetic pesticides against agro-pest and disease vectors while exhaustive reviewing the potentials of natural plant products from Zanthoxylum species (Rutaceae) as sustainable alternatives. This study is expected to spur further research on exploiting these plants and their chemicals as safe and effective pesticide entities to minimize the impact of their chemical and synthetic counterparts on health and the environment.

Using freshwater snail Biomphalaria glabrata (Say, 1818) as a biological model for ecotoxicology studies: a systematic review

Over time, a growing increase in human pollutants in the aquatic environment has been observed. The global presence of residues in water bodies reinforces the need to develop improved methods to detect them and evaluate their ecotoxicological effects in aquatic environments. Thus, this study aimed to present the main assays using Biomphalaria glabrata as a biological model for ecotoxicological studies. We performed a systematic literature review with data published up to June 2022 on the Web of Science, SCOPUS, Science Direct, PubMed, and SciELO databases. Thirty studies were selected for this review after screening. Biomphalaria glabrata has been studied as an ecotoxicological model for different substances through toxicity, embryotoxicity, cytotoxicity, genotoxicity, and bioaccumulation assays. Studies evaluating the impact of B. glabrata exposure to several substances have reported effects on their offspring, as well as toxicity and behavioral and reproductive effects. This review presents various assays using B. glabrata as a biological model for ecotoxicological studies. The use of a representative species of ecosystems from tropical regions is a necessary tool for tropical environmental monitoring. It was observed that the freshwater snail B. glabrata was effective for the evaluation of the ecotoxicity of several types of chemical substances, but further studies are needed to standardize the model.

Investigating the Effects of Pesticides on Ramshorn Snails (Planorbella [Helisoma] trivolvis) Infected with Echinostoma spp

Globally, parasite-induced diseases in humans and wildlife are on the rise, and pesticide pollution may be a contributing factor. Echinostoma spp. trematode parasites are prominent in North America, and they use ramshorn snails (Planorbella [Helisoma] trivolvis) as intermediate hosts. We investigated the impact of chronic exposure to 1 of 5 pesticide treatments (control, or 50 μg/L of atrazine, glyphosate, carbaryl, or malathion) on uninfected and Echinostoma-infected snails for 41 d in the laboratory. We recorded snail mortality, the number of egg masses laid, change in mass, and behavior. Chronic exposure to atrazine, carbaryl, and malathion significantly decreased snail survival, whereas parasite infection status or exposure to glyphosate did not. Pesticide and parasite treatments did not influence growth or behavior, but parasite infection caused complete reproductive failure in snail hosts. Our results indicated that the direct effects of pesticides could threaten snail populations in natural environments and disrupt host-parasite dynamics.  Environ Toxicol Chem 2021;40:2755-2763. © 2021 SETAC.

Reproductive toxicity due to herbicide exposure in freshwater organisms

Excessively used pesticides in agricultural areas are spilled into aquatic environments, wherein they are suspended or sedimented. Owing to climate change, herbicides are the fastest growing sector of the pesticide industry and are detected in surface water, groundwater, and sediments near agricultural areas. In freshwater, organisms, including mussels, snails, frogs, and fish, are exposed to various types and concentrations of herbicides. Invertebrates are sensitive to herbicide exposure because their defense systems are incomplete. At the top of the food chain in freshwater ecosystems, fish show high bioaccumulation of herbicides. Herbicide exposure causes reproductive toxicity and population declines in freshwater organisms and further contamination of fish used for consumption poses a risk to human health. In addition, it is important to understand how environmental factors are physiologically processed and assess their impacts on reproductive parameters, such as gonadosomatic index and steroid hormone levels. Zebrafish is a good model for examining the effects of herbicides such as atrazine and glyphosate on embryonic development in freshwater fish. This review describes the occurrence and role of herbicides in freshwater environments and their potential implications for the reproduction and embryonic development of freshwater organisms.

MOLECULAR IDENTIFICATION OF JUVENILE NEOECHINORHYNCHUS SPP. (PHYLUM: ACANTHOCEPHALA) INFECTING OSTRACOD AND SNAIL HOSTS PROVIDES INSIGHT INTO ACANTHOCEPHALAN HOST USE

The role of invertebrates in some acanthocephalan life cycles is unclear because juvenile acanthocephalans are difficult to identify to species using morphology. Most reports suggest acanthocephalans from turtle definitive hosts use ostracods as intermediate hosts and snails as paratenic hosts. However, laboratory studies of the life cycle suggest that ostracods and snails are both required hosts in the life cycle. To elucidate the role of ostracods and snails in acanthocephalan life cycles better, we collected 558 freshwater snails of 2 species, including Planorbella cf. Planorbella trivolvis and Physa acuta, from 23 wetlands in Oklahoma, U.S.A., and examined them for acanthocephalan infections. Additionally, we examined 37,208 ostracods of 4 species, Physocypria sp. (morphotype 1), Cypridopsis sp., Stenocypris sp., and Physocypria sp. (morphotype 2) for juvenile acanthocephalans from 2 wetlands in Oklahoma. Juvenile acanthocephalans were morphologically characterized, and the complete internal transcribed spacer (ITS) region of nuclear rDNA was sequenced from acanthocephalans infecting 11 ostracod and 13 snail hosts. We also sampled 10 red-eared slider turtles, Trachemys scripta elegans, and 1 common map turtle, Graptemys geographica, collected from Oklahoma, Arkansas, and Texas and recovered 1,854 adult acanthocephalans of 4 species. The ITS of 17 adult acanthocephalans of 4 species from turtle hosts were sequenced and compared to juvenile acanthocephalan sequences from ostracod and snail hosts from this study and GenBank to determine conspecificity. Of the 23 locations sampled for snails, 7 (30%) were positive for juvenile acanthocephalans in the genus Neoechinorhynchus. The overall prevalence and mean intensity of acanthocephalans in Planorbella cf. P. trivolvis and P. acuta were 20% and 2 (1-6) and 2% and 1 (1), respectively. In contrast, only 1 of 4 species of ostracods, Physocypria sp. (morphotype 1), was infected with larval/juvenile Neoechinorhynchus spp. with an overall prevalence of 0.1% and a mean intensity of 1 (1-2). Although 4 species of acanthocephalans infected turtle definitive hosts, including Neoechinorhynchus chrysemydis, Neoechinorhynchus emydis, Neoechinorhynchus emyditoides, and Neoechinorhynchus pseudemydis, all the ITS sequences from cystacanths infecting snail hosts were conspecific with N. emydis. In contrast, the ITS sequences from larval/juvenile acanthocephalans from ostracods were conspecific with 2 species of acanthocephalans from turtles (N. emydis and N. pseudemydis) and 1 species of acanthocephalan from fish (Neoechinorhynchus cylindratus). These results indicate that N. emydis infects freshwater snails, whereas other species of Neoechinorhynchus appear not to infect snail hosts. We document new ostracod and snail hosts for Neoechinorhynchus species, including the first report of an ostracod host for N. pseudemydis, and we provide novel molecular barcodes that can be used to determine larva, juvenile, and adult conspecificity of Neoechinorhynchus species.

Changes in hemocytes of Biomphalaria glabrata infected with Echinostoma paraensei and exposed to glyphosate-based herbicide

The immune system of snails is highly sensitive to pollutants, which can suppress its immune response. We investigated the effects of exposure to the glyphosate-based herbicide Roundup® Original on the snail Biomphalaria glabrata infected by the platyhelminth Echinostoma paraensei by evaluating changes in the snail's internal defense system. Four cohorts were studied: control group, infected snails, snails treated with Roundup®, and snails infected and treated with Roundup®. The hemocyte viability was assessed, morphological differentiation of cells was observed and flow cytometry was performed to determine the morphology, viability and the lectin expression profiles. The frequencies of dead hemocytes were lower in the infected group and higher in both pesticide treated groups. Three cell types were identified: blast-like cells, hyalinocytes and granulocytes. The highest number of all types of hemocytes, as well as the highest number of dead cells, were observed in the infected, pesticide-treated group. The association between infection and herbicide exposure greatly increased the frequency of dead hemocytes, suggesting that this condition impairs the internal defense system of B. glabrata making the snails more vulnerable to parasitic infections.

Combining the assessment of apical endpoints and gene expression in the freshwater snail Physa acuta after exposure to reclaimed water

Post-treatment wastewater reuses are diverse. Recreational and environmental restoration uses of reclaimed water (RW) can be potentially harmful to aquatic organisms. In this work the freshwater snail Physa acuta was exposed to RW (100%) and its dilution (RW 50%). A simple laboratory mixture of three emerging pollutants was used to address the complex problem of mixture toxicity of RW. Hence fortified reclaimed water (FRW), obtained by adding fluoxetine (400 μg FLX/L), perfluorooctane sulphonic acid (90 μg PFOS/L) and methylparaben (9 μg MP/L), was tested at two dilution percentages: 100% and 50%. The effects of the laboratory mixture of FLX, PFOS and MP on the test medium were also studied. Long-lasting effects, together with early molecular responses, were assessed. Fecundity (cumulative egg production) over 21 days and the hatching of produced eggs (F1) after another 21-day embryonic exposure were monitored. The gene expression of three genes was analysed after 24 h of exposure: two endocrine-related nuclear receptors (ERR and RXR) and one stress protein gene (Hsp70). This reproduction test, with additional assessments of the F1 recovered eggs' hatching success, showed that both RW and FRW significantly reduced fecundity. F1 hatching was affected only by FRW. The gene expression results showed that the RXR response was strikingly similar to the fecundity response, which suggests that this nuclear receptor is involved in the reproductive pathways of gastropods. ERR remained virtually unaltered. Hsp70 was overexpressed by the laboratory mixture in the test medium, but no effect was observed in the fortification of RW. This opposite effect and lack of response for F1 hatching produced by the laboratory mixture in the test medium highlighted the difficulty of predicting mixture effects. The experimental approach allowed us to test the effects caused by RW on P. acuta at different biological organisation levels. Thus, the combination of molecular biomarkers and ecological relevant endpoints is a good strategy to test complex mixtures like RW as it provides a framework to link mechanisms of action and whole organism effects when it is almost impossible to detect the pollutant(s) that cause toxic effects.

New hairworm (Nematomorpha, Gordiida) species described from the Arizona Madrean Sky Islands

Gordiids, or freshwater hairworms, are members of the phylum Nematomorpha that use terrestrial definitive hosts (arthropods) and live as adults in rivers, lakes, or streams. The genus Paragordius consists of 18 species, one of which was described from the Nearctic in 1851. More than 150 years later, we are describing a second Paragordius species from a unique habitat within the Nearctic; the Madrean Sky Island complex. The Madrean Sky Islands are a series of isolated high mountains in northern Mexico and the southwestern United States (Arizona and New Mexico), and are well known for their high diversity and endemicity. The new species is described based on both molecular data (COI barcoding) and morphological characters of the eggs, larvae, cysts, and adults. Adult females have unique small oblong mounds present on the interior of the trifurcating lobes with randomly dispersed long hairs extending from the furrows between the mounds. Marked genetic differences support observed morphological differences. This species represents the second new hairworm to be described from the Madrean Sky Islands, and it may represent the first endemic hairworm from this biodiversity hotspot.

Enhanced atrazine degradation is widespread across the United States

BACKGROUND

Atrazine (ATZ) has been a key herbicide for annual weed control in corn, with both a soil and post-emergence vegetation application period. Although enhanced ATZ degradation in soil with a history of ATZ use has been reported, the extent and rate of degradation in the US Corn Belt is uncertain. We show that enhanced ATZ degradation exists across much of the country.

RESULTS

Soils from 15 of 16 surveyed states had enhanced ATZ degradation. The average ATZ half-life was only 2.3 days in ATZ history soils, compared with an average 14.5 days in soils with no previous ATZ use, meaning that ATZ degrades an average 6 times faster in soils with previous ATZ use.

CONCLUSION

When ATZ is used for several years, enhanced degradation will undoubtedly change the way ATZ is used in agronomic crops and also its ultimate environmental fate. © 2017 Society of Chemical Industry.

Derivation of predicted no-effect concentration and ecological risk for atrazine better based on reproductive fitness

Atrazine (ATZ) is an herbicide most commonly used in China and other regions of the world. It is reported toxic to aquatic organisms, and frequently occurs at relatively high concentrations. Currently, ATZ has been proved to affect reproduction of aquatic species at much lower levels. So it is controversial to perform ecological risk assessment using predicted no-effect concentrations (PENCs) derived from traditional endpoints, which fail to provide adequate protection to aquatic organisms. In this study, PNECs of ATZ were derived based on six endpoints of survival, growth, behavior, biochemistry, genetics and reproduction. The PNEC derived from reproductive lesion was 0.044μg ATZ L^-1, which was obviously lower than that derived from other endpoints. In addition, a tiered ecological risk assessment was conducted in the Taizi River based on six PNECs derived from six categories of toxicity endpoints. Results of these two methods of ecological risk assessment were consistent with each other, and the risk level of ATZ to aquatic organisms reached highest as taking reproductive fitness into account. The joint probability indicated that severe ecological risk rooting in reproduction might exist 93.9% and 99.9% of surface water in the Taizi River, while 5% threshold (HC₅) and 1% threshold (HC₁) were set up to protect aquatic organisms, respectively. We hope the present work could provide valuable information to manage and control ATZ pollution.

Atrazine reduces the transmission of an amphibian trematode by altering snail and ostracod host-parasite interactions

Trematodes are ubiquitous members of aquatic environments, have many functional roles in ecosystems, and can cause diseases in humans, livestock, and wild animals. Despite their importance and reports of parasite population declines, few studies have concurrently assessed the effects of aquatic contaminants on multiple hosts, multiple parasite life cycle stages, and on transmission-related host-parasite interactions. Here, we test the effects of environmentally relevant concentrations of the herbicide atrazine (0, 3, 30 μg/L) on the establishment and development of an amphibian trematode (Halipegus eccentricus) in a first-intermediate snail host (Physa acuta) and in a second-intermediate ostracod host (Cypridopsis sp.). Additionally, we test the interactive effects of atrazine and parasitism on snail and ostracod survival. Our results indicate that atrazine negatively affects trematode transmission by altering snail and ostracod host-parasite interactions. Although atrazine did not affect the survival of uninfected snails alone, atrazine acted synergistically with parasitism to reduce the longevity of infected snails. As a result, the number of cercariae (i.e., larval trematodes) produced by snails was 50.7 % (3 μg/L) and 14.9 % (30 μg/L) relative to controls. Atrazine exhibited direct negative effects on ostracod survival at 30 μg/L. However, when ostracods were also exposed to trematodes, the negative effects of atrazine on survival were diminished. Although infected ostracod survival remained high, trematode development was significantly reduced, resulting in reduced infectivity of metacercariae (i.e., nongravid adult cysts infective to definite host) to 32.2 % (3 μg/L) and 28.6 % (30 μg/L) relative to the controls. The combination of reduced cercaria production and reduced metacercarial infectivity in the 3 and 30 μg/L atrazine treatment groups reduced the net number of infective worms produced to 16.4 and 4.3 % (respectively) relative to the control. These results demonstrate the complex nature of pesticide effects on trematode infections and indicate that trematodes can affect their first- and second-intermediate hosts differently under different pesticide concentrations. Our work has broad implications for parasite transmission and conservation and provides a testable mechanism for understanding trematode population declines in contaminated wetlands.