Integrative Biomarker Indices in a Benthic Indicator Species Modiolus Modiolus (L.) Under a Simulated Oil Spill

The horse mussel Modiolus modiolus (L.) is a sentinel bivalve species used in monitoring programs to assess potential biological exposure to anthropogenic contaminants, including oil hydrocarbons, in benthic environments. In an aquariumbased experiment, these mussels were exposed to a simulated oil spill where crude oil at realistic concentrations (from low to high) interacted with an inert environment (seawater, gravel surface, etc.) and the biota. Using a combination of endpoints that included tissue contaminant load, protease activity, antioxidant enzyme activity, and low-molecular antioxidant profiles, we characterized M. modiolus responses to this simulated crude oil spill. Significant differences were observed in tissue protein reserves, protease activity, and oxidative stress markers including glutathione content and glutathione-S-transferase activity in the hepatopancreas and gill tissues of the bivalves treated with oil. Total concentrations of oil-derived polycyclic aromatic hydrocarbons in M. modiolus tissues were generally highest under the highest ambient oil concentration with much lower levels at the lowest. This general pattern does match the activity of protein quality control proteases but not the antioxidant enzyme activity profiles. Glutathione-S-transferase activity in bivalves showed decreased activity under the high compared to the lower oil load and oil-free animals, while glutathione content and calpain activity were positively correlated with oil uptake. The data suggest that these benthic organisms were exhibiting biological responses to the oil polycyclic aromatic hydrocarbons and support the bioindicator value of the species. Keywords: M. modiolus, oil spill, PAHs, integrative biomarker approach, protein quality control, GSH, GS

Growth-Related Dynamics of Muscle Protein Degradation in Reared Oncorhynchus Mykiss during Growing Season

Although temperature influence on the physiology of rainbow trout have been widely studied, there is little information about the responses of muscle growth and overall protein turnover to temperatures. Therefore, body growth rate and muscle protein turnover of cultivated rainbow trout (Oncorhynchus mykiss) of 0+ and 1+ year-classes were studied within a growing season since June to October. Fish grown on cages on a natural lake does not face with food shortage or other growth-retarding factors, and the environmental water temperature affects fish growth primarily. There were detected that water temperature increase in-season results in maximal growth increments and maximal protein turnover rate in trout muscles. Since protein synthesis recognized to be similar between individuals, high overall protein turnover rate depended on increased protein-degrading activities mostly relying on calpain system. Trout of different year classes significantly differs in growth rate and calpain activity coordinately decreasing with age while their temperature responses are quite similar. New data expands on aquaculture practice since based on our observations on coincidence of peak water temperatures (mid-summer) and increased muscle protease activities in trout we can recommend excluding this period for fish slaughter to avoid postmortem flesh deterioration and excessive fillet softening

Muscle Protease Activities in Salmo Trutta L. Inhabiting the Krivoi Ruchey River

The effects of size, age, and smoltification on muscle protein breakdown systems were studied in wild brown trout Salmo trutta L. inhabiting the Krivoi Ruchey River of the White Sea basin, Kola Peninsula. Activities of autophagy-related proteases including cathepsin B and D, calpains, and proteasome were assayed in the skeletal muscle of brown trout parr and smolt of different age group. Youngest fish group consisted of the most actively growing individuals possessed the higher rate of protein breakdown compared to older groups. Different patterns of muscle protein breakdown inherent to brown trout parr and smolts were shown to be associated with calpain system and cathepsin D activities. Thus, increased activity of these proteases in smoltifying individuals obviously results in amino acid accumulation that could be a mechanism of seawater tolerance required for seaward migration. This study is the first to show the age- and stage-related dynamics in protease activities in skeletal muscle of brown trout inhabiting the Krivoi Ruchey River. Growth- and smoltification-related patterns of protease activities were quite similar in brown trout from the Krivoi Ruchey River and previously studied rivers of the White Sea basin, however, some habitat-related differences were observed

Integrative Biomarker Indices in A Benthic Indicator Species Modiolus Modiolus (L.) Under A Simulated Oil Spill

The horse mussel Modiolus modiolus (L.) is a sentinel bivalve species used in monitoring programs to assess potential biological exposure to anthropogenic contaminants, including oil hydrocarbons, in benthic environments. In an aquariumbased experiment, these mussels were exposed to a simulated oil spill where crude oil at realistic concentrations (from low to high) interacted with an inert environment (seawater, gravel surface, etc.) and the biota. Using a combination of endpoints that included tissue contaminant load, protease activity, antioxidant enzyme activity, and low-molecular antioxidant profiles, we characterized M. modiolus responses to this simulated crude oil spill. Significant differences were observed in tissue protein reserves, protease activity, and oxidative stress markers including glutathione content and glutathione-S-transferase activity in the hepatopancreas and gill tissues of the bivalves treated with oil. Total concentrations of oil-derived polycyclic aromatic hydrocarbons in M. modiolus tissues were generally highest under the highest ambient oil concentration with much lower levels at the lowest. This general pattern does match the activity of protein quality control proteases but not the antioxidant enzyme activity profiles. Glutathione-S-transferase activity in bivalves showed decreased activity under the high compared to the lower oil load and oil-free animals, while glutathione content and calpain activity were positively correlated with oil uptake. The data suggest that these benthic organisms were exhibiting biological responses to the oil polycyclic aromatic hydrocarbons and support the bioindicator value of the species. Keywords: M. modiolus, oil spill, PAHs, integrative biomarker approach, protein quality control, GSH, GS

Taxifolin Modulates Transcriptomic Response to Heat Stress in Rainbow Trout, <i>Oncorhynchus mykiss</i>

Taxifolin is a natural flavonoid known for its antioxidant, anti-inflammatory, and antiproliferative effects on animals. In this work, we have studied the effect of this compound on rainbow trout, Oncorhynchus mykiss, a major object of aquaculture, under slowly increasing ambient temperature and Gyrodactylus flatworm infection. Transcriptomic profiling of liver samples performed by using the Illumina HiSeq 2500 sequencing platform shows that a combined taxifolin/heat treatment, unlike heat treatment alone, downregulates the production of isopentenyl diphosphate, likely affecting the production of cholesterol and other sterols. Taxifolin treatment also modulates multiple apoptosis regulators and affects the expression of HSPs in response to increasing temperature. On the other hand, the expression of antioxidant enzymes in response to heat is not significantly affected by taxifolin. As for the Gyrodactylus infection, the parasite load is not affected by taxifolin treatment, although it was lower in the high-temperature group. Parasite load also did not induce a statistically significant transcriptomic response within the no heat/no taxifolin group

Survival, Growth Performance, and Hepatic Antioxidant and Lipid Profiles in Infected Rainbow Trout (<i>Oncorhynchus mykiss</i>) Fed a Diet Supplemented with Dihydroquercetin and Arabinogalactan

Natural feed supplements have been shown to improve fish viability, health, and growth, and the ability to withstand multiple stressors related to intensive cultivation. We assumed that a dietary mix of plant-origin substances, such as dihydroquercetin, a flavonoid with antioxidative, anti-inflammatory, and antimicrobial properties, and arabinogalactan, a polysaccharide with immunomodulating activity, would promote fish stress resistance and expected it to have a protective effect against infectious diseases. Farmed rainbow trout fish, Oncorhynchus mykiss, received either a standard diet or a diet supplemented with 25 mg/kg of dihydroquercetin and 50 mg/kg of arabinogalactan during a feeding season, from June to November. The fish in the control and experimental groups were sampled twice a month (eight samplings in total) for growth variable estimations and tissue sampling. The hepatic antioxidant status was assessed via the quantification of molecular antioxidants, such as reduced glutathione and alpha-tocopherol rates, as well as the enzyme activity rates of peroxidase, catalase, and glutathione-S-transferase. The lipid and fatty acid compositions of the feed and fish liver were analyzed using thin-layer and high-performance liquid chromatography. The viability, size, and biochemical indices of the fish responded to the growth physiology, environmental variables such as the dissolved oxygen content and water temperature, and sporadic factors. Due to an outbreak of a natural bacterial infection in the fish stock followed by antibiotic treatment, a higher mortality rate was observed in the fish that received a standard diet compared to those fed supplemented feed. In the postinfection period, reduced dietary 18:2n-6 and 18:3n-3 fatty acid assimilation contents were detected in the fish that received the standard diet in contrast to the supplemented diet. By the end of the feeding season, an impaired antioxidant response, including reduced glutathione S-transferase activity and glutathione content, and a shift in the composition of membrane lipids, such as sterols, 18:1n-7 fatty acid, and phospholipids, were also revealed in fish fed the standard diet. Dietary supplementation with plant-origin substances, such as dihydroquercetin and arabinogalactan, decreases lethality in fish stocks, presumably though the stimulation of natural resistance in farmed fish, thereby increasing the economic efficacy during fish production. From the sustainable aquaculture perspective, natural additives also diminish the anthropogenic transformation of aquaculture-bearing water bodies and their ecosystems