Microplastic and nanoplastic pollution in aquatic environments is a topic of emerging concern due to the internalization, retention time and effects of these particles in aquatic biota. Bivalves are ...considered bioindicators due to their wide distribution, sessile behaviour, occupation of ecological niches and ability to filter a large water volume. The study of microplastics and nanoplastics in bivalves has revealed the uptake mechanisms, internalization, distribution and depuration of these particles as well as their effects on physiological parameters, morphological alterations, immunotoxicity and changes in gene expression and proteomic profiles. In this review, we examine the primary characteristics of microplastics and nanoplastics (type of material, size, coating, density, additives and shapes) involved in their possible toxicity in bivalves. Furthermore, secondary characteristics such as the suspension media, aggregation stage and adsorption of persistent pollutants were also recorded to assess the impact of these materials on bivalves. Here, we have highlighted the efforts exerted thus far and the remaining gaps in understanding the extent of microplastic and nanoplastic impacts on bivalves on the basis of laboratory experiments and mesocosm bioassays and in the field. Furthermore, further microplastic and nanoplastic toxicological studies are proposed to facilitate the realistic assessment of environmental risk.
Display omitted
•Bivalves ingest microplastics with bias according to plastic and species features.•Comparison effort between field and laboratory has been reviewed.•Uptake, translocation, internalization and depuration are related to plastic characteristics.•Effects from molecular to physiological levels have been detailed according to plastic characteristics.•Lack of knowledge and further research are discussed.
The contamination of the aquatic environment by plastic nanoparticles is becoming a major concern due to their potential adverse effects in aquatic biota. Therefore, in-depth knowledge of their ...uptake, trafficking and effects at cellular and systemic levels is essential to understand their potential impacts for aquatic species. In this work, zebrafish (Danio rerio) was used as a model and our aims were: i) to determine the distribution, uptake, trafficking, degradation and genotoxicity of polystyrene (PS) NPs of different sizes in a zebrafish cell line; ii) to study PS NPs accumulation, migration of immune cells and genotoxicity in larvae exposed to PS NPs; and iii) to assess how PS NPs condition the survival of zebrafish larvae exposed to a pathogen and/or how they impact the resistance of an immunodeficient zebrafish. Our results revealed that the cellular distribution differed depending on the particle size: the 50 nm PS NPs were more homogeneously distributed in the cytoplasm and the 1 μM PS NPs more agglomerated. The main endocytic mechanisms for the uptake of NPs were dynamin-dependent internalization for the 50 nm NPs and phagocytosis for the 1 μm nanoparticles. In both cases, degradation in lysosomes was the main fate of the PS NPs, which generated alkalinisation and modified cathepsin genes expression. These effects at cellular level agree with the results in vivo, since lysosomal alkalization increases oxidative stress and vice versa. Nanoparticles mainly accumulated in the gut, where they triggered reactive oxygen species, decreased expression of the antioxidant gene catalase and induced migration of immune cells. Finally, although PS NPs did not induce mortality in wild-type larvae, immunodeficient and infected larvae had decreased survival upon exposure to PS NPs. This fact could be explained by the mechanical disruption and/or the oxidative damage caused by these NPs that increase their susceptibility to pathogens.
Display omitted
•The impact of PS NPs was studied at the cellular, molecular and systemic levels.•The distribution and uptake of PS NPs in the ZF4 cell line were size dependent.•PS NPs colocalized with lysosomes and raised the pH of these organelles.•In vivo, PS NPs accumulated mainly in the gut and induced leukocyte migration.•PS NPs decreased the survival of immunosuppressed or infected larvae.
Display omitted
•The accumulation of PS NPs in M. galloprovincialis tissues was size-dependent.•Translocation to the hemolymph was higher for 50 nm PS NPs.•The uptake of PS NPs into hemocytes was ...controlled by different endocytic pathways.•Hemocytes exposed to PS NPs had their motility and immune function compromised.•Myt C was downmodulated after PS NPs and V. splendidus exposure, but not phagocytosis.
Plastic litter is an issue of global concern. In this work Mytilus galloprovincialis was used to study the distribution and effects of polystyrene nanoplastics (PS NPs) of different sizes (50 nm, 100 nm and 1 μm) on immune cells. Internalization and translocation of NPs to hemolymph were carried out by in vivo experiments, while endocytic routes and effects of PS NPs on hemocytes were studied in vitro. The smallest PS NPs tested were detected in the digestive gland and muscle. A fast and size-dependent translocation of PS NPs to the hemolymph was recorded after 3 h of exposure. The internalization rate of 50 nm PS NPs was lower when caveolae and clathrin endocytosis pathways were inhibited. On the other hand, the internalization of larger particles decreased when phagocytosis was inhibited. The hemocytes exposed to NPs had changes in motility, apoptosis, ROS and phagocytic capacity. However, they showed resilience when were infected with bacteria after PS NP exposure being able to recover their phagocytic capacity although the expression of the antimicrobial peptide Myticin C was reduced. Our findings show for the first time the translocation of PS NPs into hemocytes and how their effects trigger the loss of its functional parameters.
Apoptosis is a type of programmed cell death that produces changes in cell morphology and in biochemical intracellular processes without inflammatory reactions. The components of the apoptotic ...pathways are conserved throughout evolution. Caspases are key molecules involved in the transduction of the death signal and are responsible for many of the biochemical and morphological changes associated with apoptosis. Nowadays, It is known that caspases are activated through two major apoptotic pathways (the extrinsic or death receptor pathway and the intrinsic or mitochondrial pathway), but there are also evidences of at least other alternative pathway (the perforin/granzyme pathway). Apoptosis in mollusks seems to be similar in complexity to apoptosis in vertebrates but also has unique features maybe related to their recurrent exposure to environmental changes, pollutants, pathogens and also related to the sedentary nature of some stages in the life cycle of mollusks bivalves and gastropods. As in other animals, apoptotic process is involved in the maintenance of tissue homeostasis and also constitutes an important immune response that can be triggered by a variety of stimuli, including cytokines, hormones, toxic insults, viruses, and protozoan parasites. The main goal of this work is to present the current knowledge of the molecular mechanisms of apoptosis in mollusks and to highlight those steps that need further study.
Display omitted
•Apoptosis in mollusks is similar in complexity to apoptosis in vertebrates.•It has unique features related to the response to environmental changes and pathogens.•The complex apoptotic process could be related to the mollusks ecological success.•This knowledge allow us to develop new tools for the evaluation of genotoxic risk.
This paper presents a novel bioinspired algorithm to tackle complex optimization problems: the coral reefs optimization (CRO) algorithm. The CRO algorithm artificially simulates a coral reef, where ...different corals (namely, solutions to the optimization problem considered) grow and reproduce in coral colonies, fighting by choking out other corals for space in the reef. This fight for space, along with the specific characteristics of the corals' reproduction, produces a robust metaheuristic algorithm shown to be powerful for solving hard optimization problems. In this research the CRO algorithm is tested in several continuous and discrete benchmark problems, as well as in practical application scenarios (i.e., optimum mobile network deployment and off-shore wind farm design). The obtained results confirm the excellent performance of the proposed algorithm and open line of research for further application of the algorithm to real-world problems.
Zebrafish (Danio rerio), largely used as a model for studying developmental processes, has also emerged as a valuable system for modelling human inflammatory diseases. However, in a context where ...even mice have been questioned as a valid model for these analysis, a systematic study evaluating the reproducibility of human and mammalian inflammatory diseases in zebrafish is still lacking. In this report, we characterize the transcriptomic regulation to lipopolysaccharide in adult zebrafish kidney, liver, and muscle tissues using microarrays and demonstrate how the zebrafish genomic responses can effectively reproduce the mammalian inflammatory process induced by acute endotoxin stress. We provide evidence that immune signaling pathways and single gene expression is well conserved throughout evolution and that the zebrafish and mammal acute genomic responses after lipopolysaccharide stimulation are highly correlated despite the differential susceptibility between species to that compound. Therefore, we formally confirm that zebrafish inflammatory models are suited to study the basic mechanisms of inflammation in human inflammatory diseases, with great translational impact potential.
P. dicentrarchi is one of the most threatening pathogens for turbot aquaculture. This protozoan ciliate is a causative agent of scuticociliatosis, which is a disease with important economic ...consequences for the sector. Neither vaccines nor therapeutic treatments are commercially available to combat this infection. Numerous antimicrobial peptides (AMPs) have demonstrated broad-spectrum activity against bacteria, viruses, fungi, parasites and even tumor cells; an example is Nk-lysin (Nkl), which is an AMP belonging to the saposin-like protein (SAPLIP) family with an ability to interact with biological membranes. Following the recent characterization of turbot Nkl, an expression plasmid encoding Nkl was constructed and an anti-Nkl polyclonal antibody was successfully tested. Using these tools, we demonstrated that although infection did not clearly affect nkl mRNA expression, it induced changes at the protein level. Turbot Nkl had the ability to inhibit proliferation of the P. dicentrarchi parasite both in vivo and in vitro. Moreover, a shortened peptide containing the active core of turbot Nkl (Nkl71-100) was synthesized and showed high antiparasitic activity with a direct effect on parasite viability that probably occurred via membrane disruption. Therefore, the nkl gene may be a good candidate for genetic breeding selection of fish, and either the encoded peptide or its shortened analog is a promising antiparasitic treatment in aquaculture.
•The turbot nkl gene is not modulated during infection with P. dicentrarchi.•Changes in the number of Nkl-positive cells are observed after infection.•Nkl is released into the peritoneal exudate during infection with P. dicentrarchi.•Nkl and a synthetic shorter peptide have antiparasitic activity.•Nkl reduces parasite viability via membrane disruption.
Display omitted
•A specific diagnosis of Perkinsus olseni was obtained with a new qPCR assay.•The results of the real-time PCR assay were sensitive and reproducible.•No false negatives were obtained ...with the qPCR assay compared with traditional methods.•Gill tissue provided more accurate qPCR results than those of hemolymph samples.
Perkinsus olseni is a protozoan parasite that infects a wide variety of molluscs worldwide, causing economic losses in the aquaculture sector. In the present study, a quantitative PCR (qPCR) assay was developed for the detection and quantification of P. olseni in clam gill tissue and hemolymph (Ruditapes philippinarum and R. decussatus), and the results were compared with those of the standard diagnostic methods recommended by the O.I.E. (World Organisation for Animal Health): Ray's fluid thioglycollate culture method (RFTM), a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay and histopathology. The efficiency, sensitivity and reproducibility of the newly described qPCR assay were also determined. The highest prevalence was detected using the qPCR assay, and the strongest linear correlation was obtained between the RFTM infection levels and the threshold cycle (Ct) number from the gill tissue. Although better results were obtained from gill than from the hemolymph in the qPCR assays, especially with lower infection levels of the parasite, a significant linear correlation was observed between Ct values from the gill and hemolymph. The qPCR assay that was developed in this study showed high sensitivity, specificity and reproducibility for the detection and quantification of P. olseni.
► Zebrafish IL-6 was identified using the synteny between human and zebrafish genome. ► The expression of IL-6 and the IL-6 receptor complex, IL-6R and gp130, was studied. ► Their expression was ...modulated by immunostimulation. ► The genes were expressed at early ages mainly in the head, epidermis and neuromasts.
Interleukin-6 (IL-6) is one of the most pleiotropic cytokines due to its importance in both innate and adaptive immune responses and other physiological processes. In this study, we identified the zebrafish (Danio rerio) IL-6 homologue by investigating the synteny between the human (Homo sapiens), the fugu (Takifugu rubripes) and the zebrafish genome. Although zebrafish IL-6 showed a low sequence homology with other IL-6 sequences in other species, it presented a high structural similarity to human IL-6. We also analysed IL-6 expression in several different tissues, along with analysis of the expression of the genes that form the IL-6 receptor complex, IL-6R and gp130. After treatment with bacterial or viral stimuli, zebrafish IL-6 expression was modulated in a manner similar to that of other proinflammatory molecules, such as IL-1β and TNF-α. The expression of IL-6, IL-6R and gp130 was also studied during the ontogeny of zebrafish larvae using quantitative PCR and in situ hybridisation. Our results indicated that the transcripts were detected very early, increased during the first week of life and were predominantly expressed in the head, epidermis and neuromasts of the anterior and posterior lateral line system, suggesting their involvement in the normal development of these tissues.
In this paper a novel evolutionary algorithm for optimal positioning of wind turbines in wind farms is proposed. A realistic model for the wind farm is considered in the optimization process, which ...includes orography, shape of the wind farm, simulation of the wind speed and direction, and costs of installation, connection and road construction among wind turbines. Regarding the solution of the problem, this paper introduces a greedy heuristic algorithm which is able to obtain a reasonable initial solution for the problem. This heuristic is then used to seed the initial population of the evolutionary algorithm, improving its performance. It is shown that the proposed seeded evolutionary approach is able to obtain very good solutions to this problem, which maximize the economical benefit which can be obtained from the wind farm.
► This paper presents a novel hybrid evolutionary algorithm with heuristics for optimal wind turbines layout in wind farms. ► A novel optimization model which takes into account wind farm shape, orography and new costs is proposed. ► Experiments in different scenarios have shown the good performance of the proposed algorithm.
PDF
