Teratogenicity and embryotoxicity in aquatic organisms after pesticide exposure and the role of oxidative stress

Biomicroplastics versus conventional microplastics: An insight on the toxicity of these polymers in dragonfly larvae

The toxicological safety of products developed as alternative for conventional plastics (i.e., petroleum derivatives) inevitably demands conducting (eco)toxicological studies. Thus, the aim of the current study was to evaluate the biochemical toxicity of polyethylene microplastics (PE MPs) (representative of conventional MPs) and polylactic acid biomicroplastics (PLA BioMPs) in Aphylla williamsoni larvae used as experimental models. Animals subjected to short exposure to both pollutants (48 h), at environmentally relevant concentration (6 mg/L). At the end of the experiment, different toxicity biomarkers were evaluated. To assess the possible impact of pollutants on the nutritional status of the animals, the total protein, total soluble carbohydrate and triglyceride levels were determined. However, we did not observe differences between the groups, which suggests that PE MPs and PLA BioMPs did not affect the animals' energy metabolism, inducing them to a nutritional deficit. However, larvae exposed to PLA BioMPs have shown increased nitrite and lipid peroxidation levels, which supports the hypothesis that these pollutants increase oxidative stress processes in the animals evaluated, which can affect the animals' physiological homeostasis from different changes. In addition, the decrease in superoxide dismutase activity and of total thiols levels, in these same animals, is suggestive of the impact of PLA BioMPs on the antioxidant defenses, causing a REDOX imbalance, never before reported. On the other hand, decreased AChE activity was only observed in larvae exposed to PLA BioMPs, which demonstrates the anticholinergic activity of the tested polymers; the consequences of which include changes in different neurophysiological functions. Thus, the current study has helped improving the scientific knowledge about impacts caused by PLA BioMPs on freshwater ecosystems, as well as corroborated assertions about the risks posed by such biopolymers on these environments.

Congenital Malformations in Sea Turtles: Puzzling Interplay between Genes and Environment

Simple Summary

Congenital malformations can lead to embryonic mortality in many species, and sea turtles are no exception. Genetic and/or environmental alterations occur during early development in the embryo, and may produce aberrant phenotypes, many of which are incompatible with life. Causes of malformations are multifactorial; genetic factors may include mutations, chromosomal aberrations, and inbreeding effects, whereas non-genetic factors may include nutrition, hyperthermia, low moisture, radiation, and contamination. It is possible to monitor and control some of these factors (such as temperature and humidity) in nesting beaches, and toxic compounds in feeding areas, which can be transferred to the embryo through their lipophilic properties. In this review, we describe possible causes of different types of malformations observed in sea turtle embryos, as well as some actions that may help reduce embryonic mortality.

Abstract

The completion of embryonic development depends, in part, on the interplay between genetic factors and environmental conditions, and any alteration during development may affect embryonic genetic and epigenetic regulatory pathways leading to congenital malformations, which are mostly incompatible with life. Oviparous reptiles, such as sea turtles, that produce numerous eggs in a clutch that is buried on the beach provide an opportunity to study embryonic mortality associated with malformations that occur at different times during development, or that prevent the hatchling from emerging from the nest. In sea turtles, the presence of congenital malformations frequently leads to mortality. A few years ago, a detailed study was performed on external congenital malformations in three species of sea turtles from the Mexican Pacific and Caribbean coasts, the hawksbill turtle, Eretmochelys imbricata (n = 23,559 eggs), the green turtle, Chelonia mydas (n = 17,690 eggs), and the olive ridley, Lepidochelys olivacea (n = 20,257 eggs), finding 63 types of congenital malformations, of which 38 were new reports. Of the three species, the olive ridley showed a higher incidence of severe anomalies in the craniofacial region (49%), indicating alterations of early developmental pathways; however, several malformations were also observed in the body, including defects in the carapace (45%) and limbs (33%), as well as pigmentation disorders (20%), indicating that deviations occurred during the middle and later stages of development. Although intrinsic factors (i.e., genetic mutations or epigenetic modifications) are difficult to monitor in the field, some environmental factors (such as the incubation temperature, humidity, and probably the status of feeding areas) are, to some extent, less difficult to monitor and/or control. In this review, we describe the aetiology of different malformations observed in sea turtle embryos, and provide some actions that can reduce embryonic mortality.

Risk factors for major external structural birth defects among children in Kiambu County, Kenya: a case-control study

Background: Although major external structural birth defects continue to occur globally, the greatest burden is shouldered by resource-constrained countries with no surveillance systems. To our knowledge, many studies have been published on risk factors for major external structural birth defects, however, limited studies have been published in developing countries. The objective of this study was to identify risk factors for major external structural birth defects among children in Kiambu County, Kenya.

Methods: A hospital-based case-control study was used to identify the risk factors for major external structural birth defects. A structured questionnaire was used to gather information retrospectively on maternal exposure to environmental teratogens, multifactorial inheritance, and sociodemographic-environmental factors during the study participants' last pregnancies. 

Descriptive analyses (means, standard deviations, medians, and ranges) were used to summarize continuous variables, whereas categorical variables were summarized as proportions and percentages in frequency tables. Afterward, logistic regression analyses were conducted to estimate the effects of the predictors on the odds of major external structural birth defects in the country.

Results: Women who conceived when residing in Ruiru sub-county (adjusted odds ratio [aOR]: 5.28; 95% CI; 1.68-16.58; P<0.01), and Kiambu sub-county (aOR: 0.27; 95% CI; 0.076-0.95; P=0.04), and preceding siblings with history of birth defects (aOR: 7.65; 95% CI; 1.46-40.01; P=0.02) were identified as the significant predictors of major external structural birth defects in the county.

Conclusions: These findings pointed to MESBDs of genetic, multifactorial inheritance, and sociodemographic-environmental etiology. Thus, we recommend regional defect-specific surveillance programs, public health preventive measures, and treatment strategies to understand the epidemiology and economic burden of these defects in Kenya. We specifically recommend the integration of clinical genetic services with routine reproductive health services because of potential maternal genetic predisposition in the region.

Polyvinyl chloride microplastics induce growth inhibition and oxidative stress in Cyprinus carpio var. larvae

The occurrence and accumulation of microplastics in wildlife and humans have become a serious global scale concern over the last decade. To evaluate the potential toxic effects of PVC (polyvinyl chloride) microplastics in freshwater fish larvae, we conducted chronic 30-day and 60-day dietary exposure using Cyprinus carpio var. larvae. We exposed the larvae to four treatments with different microplastic concentrations (10%, 20%, and 30%) using food rationed diets, in conjunction with a non-plastic control. The results indicated that microplastics significantly inhibited weight gain and growth under all PVC treatments, compared to the control group. SOD (superoxide dismutase) and CAT (catalase) activities were analyzed, and an inverse relationship between them was observed. The activities of GPx (glutathione peroxidase) initially ascended and then descended with increased PVC concentrations following 30 days of exposure. A dose dependent downtrend was observed after 60 days of exposure. Malondialdehyde (MDA) levels were significantly reduced upon exposure to different concentrations of microplastics in various tissues. Altered antioxidant-related gene expression was observed in the livers of larvae exposed to the PVC microplastics. The transcription of CYP1A and GSTa initially increased, and then decreased under higher microplastics concentrations following 30 days of exposure. Furthermore, histological studies revealed cytoplasmic vacuolation in the liver under exposure to 20% and 30% microplastics. This investigation provided basic toxicological data toward elucidating and quantifying the impacts of PVC microplastics on freshwater organisms.

Developmental Toxicity of Diethylnitrosamine in Zebrafish Embryos/Juveniles Related to Excessive Oxidative Stress

Diethylnitrosamine (DEN) is present in food, water, and daily supplies and is regarded as a toxicant of carcinogenicity. The developmental toxicity of DEN has been rarely reported as yet. In this study, zebrafish were exposed to different concentrations of DEN at 6 h post-fertilization (hpf) to access embryonic toxicity of the compound. The results show that DEN resulted in negative effects of hatching rate, heartbeat, body length, and spontaneous movement. Deformities, including notochord malformation, pericardium edema, embryonic membrane turbidity, tail hypoplasia, yolk sac deformity, and growth retardation, happened during exposure period. Moreover, production of reactive oxygen species (ROS) significantly increased after DEN treatment. Then, alterations of the expression level of oxidative stress-related genes were observed in our results. To our knowledge, this is the first study concerning the effect of DEN on zebrafish. And from the information of our research, we speculated that development toxicity of DEN should be related to the excessive oxidative stress.

Comparative embryotoxicity of phenanthrene and alkyl-phenanthrene to marine medaka (Oryzias melastigma)

Alkylated polycyclic aromatic hydrocarbons (alkyl-PAHs) are the predominant form of PAHs in oil, comprising 85-95% of total PAHs. However, little attention has been paid to these chemicals in ecological risk assessment of marine oil spill. A comparative study of the toxic effects of phenanthrene and retene (7-isopropyl-1-methylphenanthrene, an alkyl-phenanthrene) on the early life stage of marine medaka (Oryzias melastigma) was conducted. Results showed that retene was significantly more toxic than phenanthrene, and marine medaka could be more sensitive to retene than some freshwater fishes. Retene had a higher excretion rate than phenanthrene during the larvae stage. Both of compounds resulted in developmental malformation of marine medaka embryos, with phenanthrene affecting on peripheral vascular system and yolk sac, while retene affecting on cardiac tissues. The toxicity of phenanthrene might be mainly related to its anesthetic effects, and that of retene might be related to the CYP1A-mediated toxicity of its metabolites.

Wildlife ecotoxicology of pesticides: can we track effects to the population level and beyond?

During the past 50 years, the human population has more than doubled and global agricultural production has similarly risen. However, the productive arable area has increased by just 10%; thus the increased use of pesticides has been a consequence of the demands of human population growth, and its impact has reached global significance. Although we often know a pesticide's mode of action in the target species, we still largely do not understand the full impact of unintended side effects on wildlife, particularly at higher levels of biological organization: populations, communities, and ecosystems. In these times of regional and global species declines, we are challenged with the task of causally linking knowledge about the molecular actions of pesticides to their possible interference with biological processes, in order to develop reliable predictions about the consequences of pesticide use, and misuse, in a rapidly changing world.

Toxic effects of deltamethrin and λ-cyhalothrin on Xenopus laevis tadpoles

This study evaluates the toxic effects of deltamethrin and λ-cyhalothrin on Xenopus laevis tadpoles after 168 h of exposure. The LC(50) of deltamethrin and λ-cyhalothrin at 168 h was calculated as the μg of active ingredient per liter (μg AI/L). According to these values, the LC(50) was 6.26 and 3.94 μg AI/L for deltamethrin and λ-cyhalothrin, respectively. Several enzymes were studied for early signs of intoxication following exposure to the pesticides for 24 h. Glutathione-S-transferase,carboxylesterase, and lactate dehydrogenase were inhibited by λ-cyhalothrin, and both pesticides inhibited acid phosphatase and aspartate aminotransferase. In contrast, acetylcholinesterase was activated by deltamethrin. The results suggest that X. laevis is sensitive to the pyrethroids that were tested, and the enzyme responses suggest that they are potential biomarkers for evaluating the toxic effect of pyrethroids on amphibians in environmental conditions.