Effect of Benzophenone-3 to Acetylcholinesterase and Antioxidant System in Zebrafish (Danio rerio) Embryos.

Benzophenone-3 (BP-3) is one of the most used UV filters. The present study aimed to evaluate the toxic effects of BP-3 during embryo stages of zebrafish four hours post-fertilization (4hpf). Embryos were exposed to 0, 1, and 10 µg L-1 of BP-3 for 72 h. We investigated biochemical and molecular biomarkers of neurotoxicity (AChE) and the antioxidant system (gene expression of catalase, CAT, superoxide dismutase, SOD, glutathione peroxidase, GPX, the concentration of total glutathione, GSH, and lipid hydroperoxides, LPO). Results indicated that the acute exposure to BP-3 in zebrafish embryos did not show significant differences in survival, hatching rate, or antioxidant system biomarkers. In contrast, there were significant differences associated with AChE gene expression and activity.

Comparing Sediment Microbiomes in Contaminated and Pristine Wetlands along the Coast of Yucatan.

Microbial communities are important players in coastal sediments for the functioning of the ecosystem and the regulation of biogeochemical cycles. They also have great potential as indicators of environmental perturbations. To assess how microbial communities can change their composition and abundance along coastal areas, we analyzed the composition of the microbiome of four locations of the Yucatan Peninsula using 16S rRNA gene amplicon sequencing. To this end, sediment from two conserved (El Palmar and Bocas de Dzilam) and two contaminated locations (Sisal and Progreso) from the coast northwest of the Yucatan Peninsula in three different years, 2017, 2018 and 2019, were sampled and sequenced. Microbial communities were found to be significantly different between the locations. The most noticeable difference was the greater relative abundance of Planctomycetes present at the conserved locations, versus FBP group found with greater abundance in contaminated locations. In addition to the difference in taxonomic groups composition, there is a variation in evenness, which results in the samples of Bocas de Dzilam and Progreso being grouped separately from those obtained in El Palmar and Sisal. We also carry out the functional prediction of the metabolic capacities of the microbial communities analyzed, identifying differences in their functional profiles. Our results indicate that landscape of the coastal microbiome of Yucatan sediment shows changes along the coastline, reflecting the constant dynamics of coastal environments and their impact on microbial diversity.

A vibriosis outbreak in the Pacific white shrimp, Litopenaeus vannamei reared in biofloc and clear seawater.

In May and June 2015, moderate and severe lesions were observed in Litopenaeus vannamei reared in clear seawater while, at the same time, lesions in shrimp reared in biofloc were considerably fewer. The signs of disease included anorexia, lethargy, melanization, expanded chromatophores, luminescence and necrotic areas in the uropods, suggesting a possible vibriosis. However, lesions observed in shrimp reared in biofloc disappeared after a certain time and without mortality in tanks, whereas mortality and severe signs continued to be observed in shrimp reared in clear seawater. To treat the possible vibriosis, oxytetracycline was administered only in clear seawater tanks, but the results were not successful. Bacterial cultures from hepatopancreas tissues of shrimp from both rearing systems confirmed a vibriosis outbreak only in the clear seawater system. Subsequently, Vibrio harveyi, Vibrio rotiferianus, Photobacterium sp. and Photobacterium damselae were identified from bacterial culture previously isolated for both rearing systems by molecular methods. Shewanella sp. was isolated and identified only in biofloc. To understand the possible pathogenicity and resistance mechanisms of the Vibiro strains for both rearing systems, pathogenicity (toxR) and oxytetracycline resistance-related genes (tet(B), tet(D), tet(G)) were determined. Although these genes were expressed for both rearing systems, biofloc proved to have the ability to control the development of the disease, in comparison to clear water, where the vibriosis was evident regardless of the administration of oxytetracycline as a treatment.

Partial Gene Sequencing of CYP1A, Vitellogenin, and Metallothionein in Mosquitofish Gambusia yucatana and Gambusia sexradiata.

Ground characteristics in the Yucatan Peninsula make recovery and treatment of wastewater very expensive. This situation has contributed to an increase of pollutants in the aquifer. Unfortunately, studies related to the effects of those pollutants in native organisms are scarce. The aim of this work was to obtain partial sequences of widely known genes used as biomarkers of pollutant effect in Gambusia yucatana and Gambusia sexradiata. The studied genes were: cytochrome P450 1A (CYP1A); vitellogenin (VTG); metallothionein (MT), and two housekeeping genes, 18S and ß-actin. From reported sequences of Gambusia affinis, primers were designed and amplification was done in the local Gambusia species exposed for 48 h to gasoline (100 µL/L, stirred for 24 h pre-exposure). Preliminary results revealed partial sequences of all genes with an approximate average length of 200 bp. BLAST analysis of found sequences indicated a minimum of 97% identity with reported sequences for G. affinis or Gambusia holbrooki showing great similarity.

Impacts of oxidative stress on acetylcholinesterase transcription, and activity in embryos of zebrafish (Danio rerio) following Chlorpyrifos exposure.

Organophosphate pesticides cause irreversible inhibition of AChE which leads to neuronal overstimulation and death. Thus, dogma indicates that the target of OP pesticides is AChE, but many authors postulate that these compounds also disturb cellular redox processes, and change the activities of antioxidant enzymes. Interestingly, it has also been reported that oxidative stress plays also a role in the regulation and activity of AChE. The aims of this study were to determine the effects of the antioxidant, vitamin C (VC), the oxidant, t-butyl hydroperoxide (tBOOH) and the organophosphate Chlorpyrifos (CPF), on AChE gene transcription and activity in zebrafish embryos after 72h exposure. In addition, oxidative stress was evaluated by measuring antioxidant enzymes activities and transcription, and quantification of total glutathione. Apical effects on the development of zebrafish embryos were also measured. With the exception of AChE inhibition and enhanced gene expression, limited effects of CPF on oxidative stress and apical endpoints were found at this developmental stage. Addition of VC had little effect on oxidative stress or AChE, but increased pericardial area and heartbeat rate through an unknown mechanism. TBOOH diminished AChE gene expression and activity, and caused oxidative stress when administered alone. However, in combination with CPF, only reductions in AChE activity were observed with no significant changes in oxidative stress suggesting the adverse apical endpoints in the embryos may have been due to AChE inhibition by CPF rather than oxidative stress. These results give additional evidence to support the role of prooxidants in AChE activity and expression.

Evaluation of the estrogenic and oxidative stress effects of the UV filter 3-benzophenone in zebrafish (Danio rerio) eleuthero-embryos.

Personal care products have been detected in superficial waters, representing an environmental risk to the biota. Some studies indicated that 3-benzophenone (3BP) alters hormones, inducing vitellogenesis and having adverse effects on fish reproduction. Other studies have reported generation of free radicals and changes in antioxidant enzymes. Therefore, the aim of the present study was to test acute exposure to 3BP at concentrations within and beyond that found environmentally to provide important toxicological information regarding this chemical. We evaluated the effect of 3BP on vitellogenin 1 (VTG1) gene expression and the transcription of the enzymes catalase (CAT), superoxide dismutase (SOD) or glutathione peroxidase (GPx), which are involved in cellular redox balance. Zebrafish eluthero-embryos (168hpf) were exposed to 1,10, 100, 1000µg/L 3BP, in addition to a negative control and a 0.1% ethanol control for 48h. The results of our study indicated a positive significant correlation between exposure concentrations and VTG1 expression (r=0.986, p=0.0028) but only 1000µg/L 3BP produced a significant increase from control. Acute exposure showed no significant differences in transcription levels of CAT, SOD or GPx at the tested conditions. Nevertheless, a trend toward increase in GPx expression was observed as a positive significant correlation (r=0.928, p=0.017) was noted.