Multi-biomarker Assessment in a Native Species Psalidodon eigenmanniorum Under Inorganic Mercury and Recovery Scenarios.

The increasing contamination of water bodies with mercury raises concerns about its possible effects on aquatic organisms. The combined use of several biomarkers allows researchers to study the impact of a chemical at different levels of biological organization. In the present work, we determined the response of histological (gills and liver), somatic (condition factor and hepato-somatic index), and behavioral (predator-prey relationship, through the presentation of a computer-animated image) biomarkers in the native species Psalidodon eigenmanniorum exposed to 100 µg L-1 of inorganic Hg (IHg) during 96 h. We also assessed whether there was a change in the biomarkers analyzed after 7 days in Hg-free water compared with those exposed to IHg. In exposed fish, IHg caused damage to the gills and liver tissues. The condition factor showed no difference between IHg-exposed organisms and control organisms, while the hepato-somatic index was lower in IHg-exposed fish. As for the behavioral analyses, it was observed that the presentation of a stimulus induced changes in the behavioral responses of fish exposed to IHg, which showed a heightened state of alertness with respect to control. On the other hand, after 7 days in Hg-free water, the organisms generally showed no changes in biomarkers compared with IHg-exposed fish. Our results contribute new data on IHg toxicity in a native species and provide information on the plasticity of damage to reverse itself. Furthermore, this work provides baseline information for environmental assessments in water bodies where mercury is present.

What types of enzyme activities are useful biomarkers of bifenthrin exposure on Chironomus sp. (Diptera, Chironomidae) larvae under laboratory and field-based microcosm conditions?

Bifenthrin is a second generation synthetic pyrethroid insecticide that is widely used in Australia and worldwide. It is frequently found in urban freshwater sediments at concentrations likely to impact biota as it is highly toxic to fish and macroinvertebrates, such as chironomids. Our main goal was to evaluate if oxidative stress and hydrolase enzymes are useful biomarkers of effect of synthetic pyrethroids exposure under different scenarios. Chironomus tepperi larvae (5 days old) were exposed to sub-lethal sediment concentrations of bifenthrin for 5 days under controlled laboratory conditions. A field-based microcosm exposure with bifenthrin-spiked sediments (using the same concentrations as the laboratory exposure) was carried out at a clean field site for four weeks to allow for colonization and development of resident chironomid larvae. At the end of both experiments, Chironomus larvae (C. tepperi in the laboratory exposures and C. oppositus in the microcosm exposures) were collected and oxidative stress enzymes (Glutathione-s-Transferase, Glutathione Reductase and Glutathione Peroxidase) and hydrolase enzymes (Acetylcholinesterase and Carboxylesterase) were measured. Only the Glutathione Peroxidase activity was significantly impacted in larvae from the laboratory exposure. On the contrary, significant changes were observed in all the measured enzymes from the field-based microcosm exposure. This is likely because exposure was throughout the whole life cycle, from egg mass to fourth instar, showing a more realistic exposure scenario. Furthermore, this is the first time that changes in oxidative stress and hydrolase enzymes have been shown to occur in Australian non-biting midges exposed under field-based microcosm conditions. Thus, this study demonstrated the usefulness of these enzymes as biomarkers of effect following bifenthrin exposure in microcosms. It also highlights the importance of using a range of different biochemical endpoints to get a more holistic understanding of pesticide effects and the pathways involved.

Dynamics of thymol dietary supplementation in quail (Coturnix japonica): Linking bioavailability, effects on egg yolk total fatty acids and performance traits.

Phytogenic additives such as thymol are encountering growing interest in the poultry industry. However, there are still questions concerning dynamics of their bioavailability, biological action, optimal dosage and duration of supplementation needed to achieve meaningful effects, as well as persistence of induced changes after supplement withdrawal. We studied the link between the dynamics of free thymol concentration and the changes in fatty acids composition in quail egg yolk, both during a month-long chronic dietary supplementation and after 3 weeks of supplement withdrawal (post-supplementation). Fifty, 85 days-old, female quail of homogeneous body weights (251±1g) in egg-laying peak were used. To evaluate potential dose-dependent effects, three increasing doses 2, 4, and 6.25 g of thymol/kg of feed (THY2, THY4 and THY6, respectively) and two controls were evaluated (n = 10). In parallel, we assessed the concomitant changes in free thymol excretion, potential liver histopathological changes, and birds´ performance traits. Egg yolk and droppings show a dose-dependent increase in THY concentration after 9 days of supplementation and a decrease after post-supplementation. In egg yolk, these changes were accompanied by reduced saturated fatty acid concentrations achieved by 28 days of supplementation in THY2 and 14 days of supplementation in THY4 and THY6. However, after post-supplementation the aforementioned effect disappeared in THY2 but not in THY4 and THY6. While THY2 failed to increase polyunsaturated fatty acids, THY4 and THY6 increased polyunsaturated fatty acids by day 14 of supplementation and remained increased after post-supplementation. Fatty acids changes induced by thymol are consistent with improved nutritional quality of eggs. No treatment effects were observed in liver histopathology and female performance. Findings suggest that both dose of thymol and duration of supplementation modulate thymol and fatty acids concentrations in egg yolk and thymol concentration in droppings. Furthermore, the persistence of those effects after post-supplementation period is also a dose-dependent phenomenon.

Dynamics of thymol dietary supplementation in quail (Coturnix japonica): Dataset on thymol bioavailability, egg yolk fatty acids profile and performance traits.

Dietary supplementation with thymol (2-isopropyl-5-methylphenol) has been proposed as a strategy to improve modern intensive poultry production. Moreover, its antioxidant properties and potential beneficial influence on lipid metabolism have fostered current research focusing on enhancing nutritional quality of meat and egg products. In general, studies have focused on the overall effects of dietary supplementation once the supplementation protocol has finished and using only one potential dose, without actually measuring bioactive compounds' concentration in the diet supplied or target tissues. Herein, we provide a unique dataset of the dynamics of thymol bioavailability and biological action, optimal dosage and duration of supplementation needed to achieve meaningful effects, as well as persistence of induced changes after chronic supplement withdrawal. Specifically, during a month-long supplementation period, 5 sampling points were evaluated separated by at least 1 week. Then, a last sampling point was studied after a 3-week withdrawal period. Three increasing doses of dietary thymol were used, and approximately 80 variables assessed. The measured variables were associated with free thymol concentration in feed, egg yolk and droppings, feed and egg yolk fatty acids profile (saturated, unsaturated, and polyunsaturated fatty acids), performance traits (body weight, feed intake, egg laying rate, egg physical characteristics), general welfare quality assessment (plumage state) and liver histopathology. The data can provide insights on the link between the dynamics of free thymol concentration and the changes in fatty acids profile in quail egg yolk, both during chronic thymol dietary supplementation and after supplement withdrawal. The comprehensive approach used herein for studying thymol supplementation outcome could help understanding the scope of its effects on a whole organism level.

Endosulfan acute toxicity and histomorphological alterations in Jenynsia multidentata (Anablepidae, Cyprinodontiformes).

Toxicity tests using adult specimens of Jenynsia multidentata were carried out during 96 hours in order to determine the lethal concentration (LC50) of endosulfan. Histological alterations were determined in gills and liver. Gill damage was quantified as secondary lamellae thickness. The 96 hr LC50 values were significantly different between males (0.719 microg x L(-1)) and females (1.317 microg x L(-1)). The sex difference was attributed to the dimorphism in the lipid content in females (2.16%) and males (1.79%). Histological alterations in gills included hypertrophy and lifting of the epithelium of the secondary lamellae and aneurisms. These alterations caused a significant increase of the secondary lamellae thickness in treatment versus control fish. Finally, reversible histological alterations (such as hydropic degeneration and dilation of sinusoids) were observed in the liver of exposed fish as well as an irreversible change such as necrosis at the highest concentrations.

LAF1 ubiquitination by COP1 controls photomorphogenesis and is stimulated by SPA1.

Far-red light regulates many aspects of seedling development, such as inhibition of hypocotyl elongation and the promotion of greening, acting in part through phytochrome A (phyA). The RING motif protein COP1 is also important because cop1 mutants exhibit constitutive photomorphogenesis in darkness. COP1 is present in the nucleus in darkness but is gradually relocated to the cytoplasm upon illumination. Here we show that COP1 functions as an E3 ligase ubiquitinating both itself and the myb transcription activator LAF1, which is required for complete phyA responses. In transgenic plants, inducible COP1 overexpression leads to a decrease in LAF1 concentrations, but is blocked by the proteasome inhibitor MG132. The coiled-coil domain of SPA1, a negative regulator of phyA signalling, has no effect on COP1 auto-ubiquitination but facilitates LAF1 ubiquitination at low COP1 concentrations. These results indicate that, in darkness, COP1 functions as a repressor of photomorphogenesis by promoting the ubiquitin-mediated proteolysis of a subset of positive regulators, including LAF1. After the activation of phyA, SPA1 stimulates the E3 activity of residual nuclear COP1 to ubiquitinate LAF1, thereby desensitizing phyA signals.