Effects of different LED light spectra on rainbow trout (Oncorhynchus mykiss): in vivo evaluation of the antioxidant status

Melatonin injection and red light irradiation affect the antioxidant response and cell damage in disk abalone (Haliotis discus hannai) exposed to high water temperatures

The effects of red light-emitting diode (LED) light irradiation (630 nm, 0.5 W/m2) and melatonin (10-8 and 10-7 M) on oxidative stress and physiological responses in abalones exposed to high temperatures (28°C) were investigated. Changes in messenger RNA (mRNA) expressions of melatonin receptor (MT-R), heat shock protein 70 (HSP70), and antioxidant enzymes, as well as alterations in H2O2 levels in the hemolymph, were examined. The results revealed that high-temperature-stressed abalones treated with melatonin injections or exposed to red LED light showed a significant increase in MT-R mRNA expression, while HSP70 mRNA expression decreased. Notably, HSP70 mRNA expression levels in the red LED light-irradiated group were similar to those in the group injected with 10-8 M melatonin after 24 h exposure. Abalones treated with melatonin at 20°C or irradiated with red LED light exhibited decreased H2O2 levels and reduced antioxidant enzyme mRNA expression compared with those of the control group. However, the high-temperature environment induced oxidative stress in abalones, leading to increased antioxidant enzyme mRNA expression compared with that under 20°C conditions. Moreover, abalones exposed to high-temperature stress exhibited hepatopancreatic DNA damage, which was attenuated by melatonin treatment or red LED light irradiation. Hence, red LED light reduces oxidative stress, boosts antioxidant enzymes, and alleviates DNA damage in high-temperature-stressed abalones, akin to 10-8 M melatonin treatment. Therefore, considering the practical challenges of continuous melatonin administration to abalones, utilizing red LED light emerges as a practical, effective alternative to protect abalones from oxidative stress compared to 10-8 M melatonin treatment.

Sensitivity of different organs and tissues as biomarkers of oxidative stress in juvenile tambaqui (Colossoma macropomum) submitted to fasting

The present study was conducted to evaluate the effects of fasting on responses of oxidative biomarkers and antioxidant defenses using different organs and tissues of Colossoma macropomum. The fish were divided into two groups: fed (control) and fasting (7 days). After 7 days, the fish were sampled for assessment of oxidative stress biomarkers (MDA-lipid peroxidation and PCO-protein carbonyl) and antioxidant defenses (SOD-superoxide dismutase; CAT-catalase; GPX-glutathione peroxidase; and GST-glutathione-S -transferase) in the liver, intestine, gills, muscle, brain, and plasma. The results showed an increase in MDA, PCO, SOD, and GPX concentrations in the liver and intestine of fasting fish. In contrast, in the branchial tissue, there was a reduction in the activity of SOD and CAT enzymes in fasting fish. There was also a reduction in CAT activity in the muscle of fasting fish, while in the brain, there were no changes in oxidative stress biomarkers. Plasma showed a relatively low antioxidant response. In conclusion, our results confirm that a 7-day fasting period induced tissue-specific antioxidant responses, but the increase in antioxidant responses was only for the SOD and GPX enzymes of the liver and intestine. Additionally, the liver and intestine were the most responsive tissues, whereas the plasma was the least sensitive to oxidative stress.

Light-specific wavelengths differentially affect the exploration rate, opercular beat, skin color change, opsin transcripts, and the oxi-redox system of the longsnout seahorse Hippocampus reidi

Light is a strong stimulus for the sensory and endocrine systems. The opsins constitute a large family of proteins that can respond to specific light wavelengths. Hippocampus reidi is a near-threatened seahorse that has a diverse color pattern and sexual dimorphism. Over the years, H. reidi's unique characteristics, coupled with its high demand and over-exploitation for the aquarium trade, have raised concerns about its conservation, primarily due to their significant impact on wild populations. Here, we characterized chromatophore types in juvenile and adult H. reidi in captivity, and the effects of specific light wavelengths with the same irradiance (1.20 mW/cm2) on color change, growth, and survival rate. The xanthophores and melanophores were the major components of H. reidi pigmentation with differences in density and distribution between life stages and sexes. In the eye and skin of juveniles, the yellow (585 nm) wavelength induced a substantial increase in melanin levels compared to the individuals kept under white light (WL), blue (442 nm), or red (650 nm) wavelengths. In addition, blue and yellow wavelengths led to a higher juvenile mortality rate in comparison to the other treatments. Adult seahorses showed a rhythmic color change over 24 h, the highest reflectance values were obtained in the light phase, representing a daytime skin lightening for individuals under WL, blue and yellow wavelength, with changes in the acrophase. The yellow wavelength was more effective on juvenile seahorse pigmentation, while the blue wavelength exerted a stronger effect on the regulation of adult physiological color change. Dramatic changes in the opsin mRNA levels were life stage-dependent, which may infer ontogenetic opsin functions throughout seahorses' development. Exposure to specific wavelengths differentially affected the opsins mRNA levels in the skin and eyes of juveniles. In the juveniles, skin transcripts of visual (rh1, rh2, and lws) and non-visual opsins (opn3 and opn4x) were higher in individuals under yellow light. While in the juvenile's eyes, only rh1 and rh2 had increased transcripts influenced by yellow light; the lws and opn3 mRNA levels were higher in juveniles' eyes under WL. Prolonged exposure to yellow wavelength stimulates a robust increase in the antioxidant enzymes sod1 and sod2 mRNA levels. Our findings indicate that changes in the visible light spectrum alter physiological processes at different stages of life in H. reidi and may serve as the basis for a broader discussion about the implications of artificial light for aquatic species in captivity.

Effects of Various LED Light Spectra on Growth, Gonadal Development, and Growth-/Reproduction-Related Hormones in the Juvenile Red Spotted Grouper, Epinephelus akaara

The light spectrum is a key environmental cue involved in growth and reproduction in teleosts. This study investigated the effects of exposure on juvenile red spotted grouper exposed to white (control), red (590 nm), blue (480 nm), and green (520 nm) light-emitting diodes (LEDs) (12 h light:12 h dark) for two months. The body weight (BW), total length (TL), condition factor (CF), weight gain rate (WGR), gonadosomatic index (GSI), and hepatosomatic index (HSI) were assessed. Gonadal development was observed. The gene expression of growth-related hormones, such as growth hormone (GH), pre-pro-somatostatin-I (PSS-I), neuropeptide Y (NPY), and CCK, and of reproduction-related hormones, such as Kiss1, Kiss2, GPR54, sbGnRH, FSHβ, and LHβ, was analyzed. The results showed that the fish in the white LED group exhibited the best BW, TL, CF, WGR, and HSI after one or two months. The fish exposed to white LEDs showed the best growth after two months, but no significant differences in GH levels were detected. Contrarily, the expression levels of the PSS-I significantly increased (p < 0.05) in fish from the white group, suggesting the complex regulation of GH production and the limited effects of PSS-I on the inhibition of GH synthesis and somatic growth. The significantly increased NPY levels in the four LED groups (p < 0.05) indicated that these four LED spectra were effective in stimulating food intake and energy homeostasis. After two months, the gonads developed from chromatin nucleolar-stage oocytes to perinucleolar-stage oocytes in the four LED groups. The gene expression of Kiss2 and GPR54 in the four LED groups and of sbGnRH in the white and blue LED groups significantly increased when compared to that in the initial group (p < 0.05), while there were no significant differences in FSHβ and LHβ expression in the four LED groups. These results suggest that FSH and LH may not play important roles in gonadal development in juvenile red spotted grouper that are exposed to these four LED spectra.

Transcriptomic and metabolomic integration to assess the response of gilthead sea bream (Sparus aurata) exposed to the most used insect repellent: DEET

DEET is one of the most frequently detected insect repellents in the environment reaching concentrations of several μg L^-1 in surface water. There is scarce information available regarding its mode of action in non-target organisms. Here, we have used an integrated metabolomic and transcriptomic approach to elucidate the possible adverse effects of DEET exposure in the marine fish gilthead sea bream (Sparus aurata). Individuals were exposed at an environmentally relevant concentration of DEET (10 μg L^-1) for 22 days in a continuous flow-through system. Transcriptomic analysis revealed 250 differentially expressed genes in liver, while metabolomic analysis identified 190 differentially modulated features in liver and 98 in plasma. Multi-omic data integration and visualization allowed elucidation of the modes of action of DEET exposure, including: energy depletion through the disruption of carbohydrate and amino acids metabolisms, oxidative stress leading to DNA damage, lipid peroxidation, and damage to cell membrane and apoptosis. Activation of xenobiotic pathway as well as the inmune-inflammatory reaction was evidenced in the present work.

Can high- and low-temperature thermal stress modulate the antioxidant defense response of Astyanax lacustris brain?

Change in temperature of aquatic environment have impacts on the physiology of fish, especially in the brain, which is a vital organ and prone to oxidative damage. Astyanax lacustris is a freshwater fish that play an important role in the food market and has been increasingly used in fish farms, besides environmental monitoring studies. Therefore, this study aimed to evaluate the responses of antioxidant biomarkers and products of the oxidative process in the brains A. lacustris subjected to thermal shock. The specimens were obtained from artificial farming lakes and subjected to shock induced by exposure to high (31 °C ± 0.5) and low (15 °C ± 0.5) temperature for 2, 6, 12, 24, 48, 72 and 96 h; control group were maintained at 23 °C ± 0.5. At 31 °C, glutathione-related enzymes were more responsive, suggested by the change activity of GPx and G6PDH enzymes, in addition to GSH levels. At 15 °C, enzymes of the first line of defense were more active, evidenced by the change CAT activity. No significant changes were detected in the levels of ROS, LPO and PCO. These results indicate that the brains of A. lacustris have an efficient antioxidant defense system with the ability to acclimatize to the temperatures tested.

Multi-Approach Assessment for Stress Evaluation in Rainbow Trout Females, Oncorhynchus mykiss (Walbaum, 1792) from Three Different Farms during the Summer Season

Blood biochemistry parameters are valuable tools for monitoring fish health. Their baseline values are still undefined for a multitude of farmed fish species. In this study, changes in the blood profile of rainbow trout females (Oncorhynchus mykiss) from three farms were investigated using different biomarkers during the summer season. In the given context, the main water physicochemical parameters were investigated and twelve biochemical parameters were measured from blood samples of rainbow trout reared in the Fiad, Șoimul de Jos, and Strâmba farms. We selected these farms because the genetic background of the rainbow trout is the same, with all studied specimens coming from the Fiad farm, which has an incubation station. Forty-five samples were collected monthly (May to August) throughout summer to observe the changes in the blood profile of rainbow trout. Principal component analysis showed a clear separation both among the studied farms and months. Furthermore, significant correlations (p < 0.05) between the majority of the biochemical parameters were found, indicating that the environmental parameters can influence several blood parameters at the same time. The present study provides several useful norms for assessing the welfare of rainbow trout, indicating that the relationships among different parameters are important factors in interpreting the blood biochemical profiles.