Special Issue "Behavioral Impairment in Aquatic Organisms Exposed to Neurotoxic Pollutants"

A special issue of Toxics (ISSN 2305-6304). This special issue belongs to the section "Ecotoxicology".

Deadline for manuscript submissions: 31 July 2021.

Special Issue Editors

Dr. Demetrio Raldúa
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Guest Editor
Department Environmental Chemistry, IDAEA-CSIC, Jordi Girona 18, 08034 Barcelona, Spain
Interests: fish neurotoxicology; zebrafish model; fish developmental neurotoxicology
Special Issues and Collections in MDPI journals
Dr. Carlos Barata
E-Mail
Guest Editor
Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Jordi Girona 18, 08034 Barcelona, Spain
Interests: analytical chemistry; aquatic toxicology; environmental risk assessment; toxicogenomics
Dr. Melissa Faria
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Guest Editor
Institute for Environmental Assessment and Water Research (IDAEA-CSIC), Jordi Girona 18, 08034 Barcelona, Spain
Interests: toxicology; biomarkers; environmental science; biological science; behaviour and neurotoxicity

Special Issue Information

Dear Colleagues,

It has been estimated that up to 30,000 of commercially used chemicals may have neurotoxic potential. Neuroactive chemicals, including neurotoxic pesticides, pharmaceuticals, and illicit drugs, are the largest group of micropollutants present in European rivers, where nearly 30% of all detected chemicals were linked to neurotoxicity. Furthermore, neurotoxic actions of environmental contaminants on non-target species have been determined. It is suspected that such actions include changes in the behavior of organisms. For example, environmental pollutants such as trace metals and organic toxicants have been reported to increase fish susceptibility to predation, antidepressant drug altered sex mating behavior in fish, phototaxis and feeding in amphipods, cladocerans and worms, altered mobility of snails, memory, cognitive function, and the ability to camouflage in cuttlefish at environmental relevant concentrations.

This Special Issue on “Behavioral Impairment in Aquatic Organisms Exposed to Neurotoxic Pollutants” aims to highlight research on behavioral analysis in aquatic organisms using automated image analysis systems. Studies that anchor behavioral impairment with molecular markers, and also with population level effects will be preferred. Research addressing exposure to environmental relevant concentrations of pollutants will receive priority. Methodological studies developing new tools for the automated behavioral analysis in aquatic organisms are also encouraged.

Authors are invited and welcome to submit original research papers, reviews, and short communications.

Dr. Demetrio Raldúa
Dr. Carlos Barata
Dr. Melissa Faria
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Toxics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Behavioral analysis
  • Neuroactive chemicals
  • Neurotoxicity
  • Neuroendocrine disruption
  • Environmental relevant concentrations
  • Aquatic organisms

Published Papers (5 papers)

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Research

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Article
Pharmacological Modulation of Serotonin Levels in Zebrafish Larvae: Lessons for Identifying Environmental Neurotoxicants Targeting the Serotonergic System
Toxics 2021, 9(6), 118; https://doi.org/10.3390/toxics9060118 - 25 May 2021
Viewed by 342
Abstract
This study examines the effects of acute pharmacological modulation of the serotonergic system over zebrafish larvae’s cognitive, basic, and defense locomotor behaviors, using a medium to high throughput screening assay. Furthermore, the relationship between behavior, enzyme activity related to neurotransmitter metabolism, neurotransmitter levels, [...] Read more.
This study examines the effects of acute pharmacological modulation of the serotonergic system over zebrafish larvae’s cognitive, basic, and defense locomotor behaviors, using a medium to high throughput screening assay. Furthermore, the relationship between behavior, enzyme activity related to neurotransmitter metabolism, neurotransmitter levels, and gene expression was also determined. Modulation of larvae serotonergic system was accomplished by 24 h exposure to single and opposite pharmacodynamics co-exposure to three model psychopharmaceuticals with antagonistic and agonistic serotonin signaling properties: 2.5 mM 4-Chloro-DL-phenylalanine (PCPA) and 5 µM deprenyl and 0.5 µM fluoxetine, respectively. Similar behavioral outcome was observed for deprenyl and fluoxetine, which was reflected as hypolocomotion, decrease in larvae defensive responses, and cognitive impairment. Contrarily, PCPA induced hyperlocomotion and increase in larvae escape response. Deprenyl exposure effects were more pronounced at a lower level of organization than fluoxetine, with complete inhibition of monoamine oxidase (MAO) activity, dramatic increase of 5-HT and dopamine (DA) levels, and downregulation of serotonin synthesis and transporter genes. PCPA showed mainly effects over serotonin and dopamine’s main degradation metabolites. Finally, co-exposure between agonistic and antagonist serotonin signaling drugs reviled full recovery of zebrafish impaired locomotor and defense responses, 5-HT synthesis gene expression, and partial recovery of 5-HT levels. The findings of this study suggest that zebrafish larvae can be highly sensitive and a useful vertebrate model for short-term exposure to serotonin signaling changes. Full article
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Article
Assessing Combined Effects for Mixtures of Similar and Dissimilar Acting Neuroactive Substances on Zebrafish Embryo Movement
Toxics 2021, 9(5), 104; https://doi.org/10.3390/toxics9050104 - 06 May 2021
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Abstract
Risk assessment of chemicals is usually conducted for individual chemicals whereas mixtures of chemicals occur in the environment. Considering that neuroactive chemicals are a group of contaminants that dominate the environment, it is then imperative to understand the combined effects of mixtures. The [...] Read more.
Risk assessment of chemicals is usually conducted for individual chemicals whereas mixtures of chemicals occur in the environment. Considering that neuroactive chemicals are a group of contaminants that dominate the environment, it is then imperative to understand the combined effects of mixtures. The commonly used models to predict mixture effects, namely concentration addition (CA) and independent action (IA), are thought to be suitable for mixtures of similarly or dissimilarly acting components, respectively. For mixture toxicity prediction, one important challenge is to clarify whether to group neuroactive substances based on similar mechanisms of action, e.g., same molecular target or rather similar toxicological response, e.g., hyper- or hypoactivity (effect direction). We addressed this by using the spontaneous tail coiling (STC) of zebrafish embryos, which represents the earliest observable motor activity in the developing neural network, as a model to elucidate the link between the mechanism of action and toxicological response. Our objective was to answer the following two questions: (1) Can the mixture models CA or IA be used to predict combined effects for neuroactive chemical mixtures when the components share a similar mode of action (i.e., hyper- or hypoactivity) but show different mechanism of action? (2) Will a mixture of chemicals where the components show opposing effect directions result in an antagonistic combined effect? Results indicate that mixture toxicity of chemicals such as propafenone and abamectin as well as chlorpyrifos and hexaconazole that are known to show different mechanisms of action but similar effect directions were predictable using CA and IA models. This could be interpreted with the convergence of effects on the neural level leading to either a collective activation or inhibition of synapses. We also found antagonistic effects for mixtures containing substances with opposing effect direction. Finally, we discuss how the STC may be used to amend risk assessment. Full article
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Article
High-Throughput Screening of Psychotropic Compounds: Impacts on Swimming Behaviours in Artemia franciscana
Toxics 2021, 9(3), 64; https://doi.org/10.3390/toxics9030064 - 17 Mar 2021
Viewed by 737
Abstract
Animal behaviour is becoming increasingly popular as an endpoint in ecotoxicology due to its increased sensitivity and speed compared to traditional endpoints. However, the widespread use of animal behaviours in environmental risk assessment is currently hindered by a lack of optimisation and standardisation [...] Read more.
Animal behaviour is becoming increasingly popular as an endpoint in ecotoxicology due to its increased sensitivity and speed compared to traditional endpoints. However, the widespread use of animal behaviours in environmental risk assessment is currently hindered by a lack of optimisation and standardisation of behavioural assays for model species. In this study, assays to assess swimming speed were developed for a model crustacean species, the brine shrimp Artemia franciscana. Preliminary works were performed to determine optimal arena size for this species, and weather lux used in the experiments had an impact on the animals phototactic response. Swimming speed was significantly lower in the smallest arena, whilst no difference was observed between the two larger arenas, suggesting that the small arena was limiting swimming ability. No significant difference was observed in attraction to light between high and low light intensities. Arena size had a significant impact on phototaxis behaviours. Large arenas resulted in animals spending more time in the light side of the arena compared to medium and small, irrespective of light intensity. The swimming speed assay was then used to expose specimens to a range of psychotropic compounds with varying modes of action. Results indicate that swimming speed provides a valid measure of the impacts of behaviour modulating compounds on A. franciscana. The psychotropic compounds tested varied in their impacts on animal behaviour. Fluoxetine resulted in increased swimming speed as has been found in other crustacean species, whilst oxazepam, venlafaxine and amitriptyline had no significant impacts on the behaviours measured. The results from this study suggest a simple, fast, high throughput assay for A. franciscana and gains insight on the impacts of a range of psychotropic compounds on the swimming behaviours of a model crustacean species used in ecotoxicology studies. Full article
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Article
Teratogenic, Oxidative Stress and Behavioural Outcomes of Three Fungicides of Natural Origin (Equisetum arvense, Mimosa tenuiflora, Thymol) on Zebrafish (Danio rerio)
Toxics 2021, 9(1), 8; https://doi.org/10.3390/toxics9010008 - 09 Jan 2021
Cited by 1 | Viewed by 727
Abstract
The improper use of synthetic fungicides has raised public concerns related to environmental pollution and animal health. Over the years, plant-derived antifungals have been investigated as safer alternatives, although little scientific evidence of its neurodevelopmental effects exist. The main objective of this study [...] Read more.
The improper use of synthetic fungicides has raised public concerns related to environmental pollution and animal health. Over the years, plant-derived antifungals have been investigated as safer alternatives, although little scientific evidence of its neurodevelopmental effects exist. The main objective of this study was to explore the effects of three alternative natural extracts (Equisetum arvense, Mimosa tenuiflora, Thymol) with antifungal properties during the early development of zebrafish by evaluating different teratogenic, oxidative stress and behavioural outcomes. Following the determination of the 96 h-LC50, exposure to sublethal concentrations showed the safety profile of both E. arvense and M. tenuiflora. However, following 96-h exposure to Thymol, increased lethality, pericardial oedema, yolk and eye deformations, and decreased body length were observed. The reduced and oxidized glutathione (GSH:GSSG) ratio was increased, and the glutathione-s-transferase activity in the group exposed to the highest Thymol concentration. Overall, these results support a more reducing environment associated with possible effects at the cellular proliferation level. In addition, the disruption of behavioural states (fear- and anxiety-like disorders) were noted, pointing to alterations in the c-Jun N-terminal kinase developmental signalling pathway, although further studies are required to explore this rationale. Notwithstanding, the results provide direct evidence of the teratogenic effects of Thymol, which might have consequences for non-target species. Full article
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Review

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Review
Not Only Toxic but Repellent: What Can Organisms’ Responses Tell Us about Contamination and What Are the Ecological Consequences When They Flee from an Environment?
Toxics 2020, 8(4), 118; https://doi.org/10.3390/toxics8040118 - 12 Dec 2020
Cited by 1 | Viewed by 959
Abstract
The ability of aquatic organisms to sense the surrounding environment chemically and interpret such signals correctly is crucial for their ecological niche and survival. Although it is an oversimplification of the ecological interactions, we could consider that a significant part of the decisions [...] Read more.
The ability of aquatic organisms to sense the surrounding environment chemically and interpret such signals correctly is crucial for their ecological niche and survival. Although it is an oversimplification of the ecological interactions, we could consider that a significant part of the decisions taken by organisms are, to some extent, chemically driven. Accordingly, chemical contamination might interfere in the way organisms behave and interact with the environment. Just as any environmental factor, contamination can make a habitat less attractive or even unsuitable to accommodate life, conditioning to some degree the decision of organisms to stay in, or move from, an ecosystem. If we consider that contamination is not always spatially homogeneous and that many organisms can avoid it, the ability of contaminants to repel organisms should also be of concern. Thus, in this critical review, we have discussed the dual role of contamination: toxicity (disruption of the physiological and behavioral homeostasis) vs. repellency (contamination-driven changes in spatial distribution/habitat selection). The discussion is centered on methodologies (forced exposure against non-forced multi-compartmented exposure systems) and conceptual improvements (individual stress due to the toxic effects caused by a continuous exposure against contamination-driven spatial distribution). Finally, we propose an approach in which Stress and Landscape Ecology could be integrated with each other to improve our understanding of the threat contaminants represent to aquatic ecosystems. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Psychoactive drugs in the aquatic environment: are they of concern?
Authors: Luigi Margiotta-Casaluci; John P. Sumpter
Affiliation: Brunel University London, UK

Title: A transient exposure to sub-lethal concentrations of a pesticide mixture (chlorpyrifos-difenoconazole) caused different responses in fish species from different trophic levels of the same community
Authors: Sergei Redondo-López; Ana C. León; Katherine Jiménez; Karla Solano; Kinndle Blanco-Peña; Freylan Mena
Affiliation: Instituto Regional de Estudios en Sustancias Tóxicas / Central American Institute for Studies on Toxic Substances (IRET
Abstract: Pesticide contamination of aquatic ecosystems is a major concern in agricultural landscapes. The improvement of ecotoxicological methods should address the assessments of pesticide mixtures and the early effects caused in biota by exposure to sub-lethal concentrations. A multi-level biomarker approach was used to assess the effects of a transient exposure to a pesticide mixture on two freshwater mesoamerican fish species. Fish, Parachromis dovii, and Poecilia gillii were shortly (48h) exposed to a mixture of sublethal concentrations of chlorpyrifos (5 µg/L) and difenoconazole (325 µg/L). Transcriptomic induction of cyp1A, as well as EROD and GST activities, were measured as biotransformation-related biomarkers. ChE activity was assessed as a neurotoxic effect biomarker. Resting metabolic rate (RMR) was measured as a physiological biomarker, and the movement of fish in a dark-light environment was assessed as a behavior biomarker. The exposure to the pesticides had different effects on the fish: P. gillii had evident induction of biotransformation phase I, with significant induction of cyp1A transcription and increased EROD activity, accompanied by ChE inhibition in muscle and an increased permanence in the light side of the dark-light environment. On the other hand, P. dovii only showed a significant induction of cyp1A, without significant evidence of neurotoxicity or changes in behavior. None of the species showed physiological changes after the exposure. This rapid, multi-level evaluation, applied to two fish species that share the environment and a predator-prey relationship, demonstrated that a short, sub-lethal exposure to widely used pesticides has the potential to cause impairment in the trophic structure of the community.

 

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