Heterotrophic microbiota of intestinal mucosa in Parasalmo mykiss (Walbaum, 1792): Age-related differences

The present study aimed to evaluate the effect of various diets on growth performance in rainbow trout, Parasalmo mykiss (Walbaum, 1792). The eight months feeding experiment in fish farm in Ladoga lake (Republic of Karelia, Russia) was conducted to investigate the effects of different diets on growth rate in three genetically similar and homogeneous groups of juvenile rainbow trout aged 1+ (initial body weight, 110 g). Three commercial diets often used in fish farms in the North-West region of Russia and with different levels of protein and structural lipids and fatty acids were used. From March to November groups 1 and 2 were fed commercial diets 1 and 2, respectively. In late June group 2 was randomly divided into two groups (groups 2 and 3). Group 2 was continued to feed diet 2 when group 3 was fed diet 3. The contents of dietary protein, lipids and fatty acids were analyzed. In addition, at the third week of each month of experiment the body weight, body length and mortality of fish were measured (50 fishes from each group). The dynamic of growth in length and weight of rainbow trout was depended on the fish feeding schedule. Weight gain and growth rate in three groups of fish were different. The overall results of this study established that feeding a diet with high level dietary protein, structural lipids (phospholipids, cholesterin) and ω3 polyunsaturated fatty acids (diets 1and 3) leads to high growth rate of rainbow trout (groups 1 and 3, respectively).

The occurrence of Hexamita salmonis Moore, 1922 and Loma salmonae Putz, Hoffman and Dunbar, 1965 was investigated at 10 sites on the R. Itchen (five for brown trout only, three for rainbow trout only, and two for both brown trout and rainbow trout) and at three of its nine fish farms (two for rainbow trout, one for brown trout). Hexamita salmonis was recorded in brown trout from three river sites and the farm, and in rainbow trout from both farms and four river sites. Prevalence of Hexamita salmonis in farmed rainbow trout was higher than in farmed brown trout and was consistent with the former species being more susceptible to infection. H. salmonis was at significantly higher prevalence in rainbow trout from farm no. 5 than farm no. 2 for three size classes of fish. In wild brown trout and feral rainbow trout, the highest prevalences of H. salmonis were recorded at sites in the vicinity of farm no. 2. This distribution was consistent with an area of naturally high infection levels, and with infected fish unintentionally released from farm no. 2 serving as a source of infection, the infection subsequently becoming established in the river fish. Loma salmonae was recorded in wild brown trout and in rainbow trout from both farms. This appears to be the first recording of this parasite from British salmonids and also the first recording of the parasite from brown trout. The distribution of the parasite (particularly the prevalence being higher at farm no. 2 than farm no. 5) was consistent with it being introduced into the R. Itchen via rainbow trout from farm no. 2 (and probably no. 3) much of whose stock derived from imported Californian ‘Shasta’ rainbow trout.

Sulfur (S) is an essential nutrient for plant growth, influencing not only crop yields but also the composition and function of soil microbial communities. However, the differential effects of S fertilization on abundant and rare taxa in agricultural soils remain poorly understood. This study investigates the impact of different S fertilizer types on maize yield and the structure and stability of soil microbial communities, with a particular focus on abundant and rare taxa. S fertilization led to significant increases maize yield on two typical soils (black soil and sandy soil) (5.3–24.3%) and altered soil properties, including reducing pH (0.04–0.20) and increasing the available sulfur (AS) content (3.8–8.0 mg kg−1), with ammonium sulfate having a more pronounced effect than elemental sulfur. Microbial analysis revealed distinct impacts on the diversity and community structure of both abundant and rare taxa. Elemental sulfur reduced the alpha diversity of abundant taxa more than ammonium sulfate, while NMDS indicated significant shifts in community structures, particularly among abundant taxa. Network analysis showed that S fertilization decreased the complexity of microbial interactions among rare taxa, with ammonium sulfate leading to simpler networks and elemental sulfur resulting in higher modularity. SEM highlighted that the diversity of rare taxa played a crucial role in influencing maize yield, alongside direct effects from soil properties such as AS and SAR (aryl sulfatase). Functional predictions demonstrated that amino acid metabolism and xenobiotic biodegradation and metabolism pathways were enriched in rare taxa, suggesting significant implications for soil health and crop productivity. This study provides new insights into the roles of abundant and rare bacterial taxa under S fertilization, emphasizing their importance in optimizing fertilization strategies for enhanced crop yield in specific soil types.

Yersinia ruckeri, Serovar I or Hagerman strain, has been isolated from the first outbreak of enteric redmouth disease in Switzerland.The disease occurred in rainbow trout Salmo gairdneri Richardson.Relevant epizootiological data are discussed.

The differences between luminal microbiota (LM) and mucosal microbiota (MAM) were little known, especially in duodenum. In this study, LM and MAM in colon and duodenum of mice were investigated through 16S rRNA high-throughput sequencing. The lowest bacterial diversity and evenness were observed in duodenal LM (D_LM), followed by duodenal MAM (D_MAM). Meanwhile, the bacterial diversity and evenness were obviously increased in D_MAM than these in D_LM, while no significant difference was observed between colonic MAM (C_MAM) and colonic LM (C_LM). PCoA analysis also showed that bacterial communities of LM and MAM in duodenum were completely separated, while these in colon overlapped partly. The ratio of Firmicutes to Bacteroidetes (F/B) in D_MAM was significantly higher than that in D_LM. Lactobacillus was largely enriched and was the characteristic bacteria in D_LM. The characteristic bacteria in D_MAM were Turicibacter, Parasutterella, Marvinbryantia and Bifidobacterium, while in C_LM they were Ruminiclostridium_6, Ruminiclostridium_9, Ruminococcaceae_UCG_007 and Lachnospiraceae_UCG_010, and in C_MAM they were Lachnospiraceae_NK4A136, Mucispirillum, Alistipes, Ruminiclostridium and Odoribacter. The networks showed that more interactions existed in colonic microbiota (24 nodes and 74 edges) than in duodenal microbiota (17 nodes and 29 edges). The 16S rDNA function prediction results indicated that bigger differences of function exist between LM and MAM in duodenum than these in colon. In conclusion, microbiota from intestinal luminal content and mucosa were different both in colon and in duodenum, and bacteria in colon interacted with each other much more closely than those in duodenum.

Rainbow trout (Oncorhynchus mykiss) farming is one of the major aquacultures in Turkey. Some conditions in fish farming can induce oxidative stress leading to the deterioration in properties such as appearance/color, texture, and flavor in fish meat. This situation may cause the consumer not to prefer edible fish. Although there are some studies on the impacts of light intensity on fish welfare, the changes in the antioxidant enzyme activities have not been elucidated. In the current study, it was intended to examine in rainbow trout how cultivating under different wavelengths affects the antioxidant enzymes and acetylcholine esterase (AChE) activity, because its activity is associated with oxidative stress, and also the determination of which light is suitable for fish welfare was aimed. Rainbow trout larvae were grown under four lights with different wavelengths: natural sunlight and incandescent long-wave (red light), medium-wave (green light), and short-wave (blue light) LED light. The experiment lasted for 64days. Biochemical assays were carried on in the brain, gill, and liver of rainbow trout. Antioxidant enzymes and AChE activity, which play an important role in the central nervous system, were assayed. In gill tissues, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glucose 6 phosphate dehydrogenase (G6PD), glutathione reductase (GR), glutathione S-transferase (GST), and AChE activities increased under all three light wavelengths. In the liver, while activities of antioxidant enzymes and AChE decreased in red light, all of them increased in blue and green light. In the brain, GPx, GST, G6PD, and SOD activities were reduced but AChE activity did not alter under all three light sources. In conclusion, light sources with different spectral structures caused important changes in the activities of antioxidant enzymes in rainbow trout. On this basis, it may be thought that this may be a response to the changing redox status of a cell. Based on our results, blue light sources may be suggested for fish welfare in rainbow trout culture, and providing fish welfare by changing light sources can be easy and cheap in fish farming.

Occurrence of Flavobacterium psychrophilum in fish farms and fish-farming environments was studied using agar plate cultivation, the immunoflourescence antibody technique (IFAT) and nested PCR. Characteristics of 64 F. psychrophilum isolates from rainbow trout Oncorhynchus mykiss, fish farm rearing water, ovarian fluid and wild fish were serotyped, ribotyped and compared biochemically. Virulence of F. psychrophilum isolates from different sources was compared by injection into rainbow trout. Additionally, the number of F. psychrophilum cells shed by naturally infected rainbow trout was determined. F. psychrophilum was detected and isolated from skin mucus, skin lesions and internal organs of diseased rainbow trout and from fish without clinical disease. The pathogen was also present in wild perch Perca fluviatilis, roach Rutilus rutilus, and ovarian fluids of farmed rainbow trout brood fish. Isolates were biochemically homogenous, excluding the capability to degrade elastin. Five different agglutination patterns with different antisera against F. psychrophilum were found among the isolates studied. Although several different ribopatterns were found (ClaI: 12 ribopatterns and HaeIII: 9 ribopatterns), ribotype A was the most dominant. Farmed rainbow trout brood fish carried a broad-spectrum of serologically and genetically different F. psychrophilum in ovarian fluids. Virulence of the tested isolates in rainbow trout varied and naturally infected rainbow trout shed 10(4) to 10(8) cells fish(-1) h(-1) of F. psychrophilum into the surrounding water.

Observations on Red Mark Syndrome in juvenile rainbow trout farmed in RAS system.

Rainbow trout (Oncorhynchus mykiss) infections are the most important risk factor causing losses in fish farming industry. The aim of the present study was to identify and determine the frequency of bacterial pathogens Streptococcus iniae, S. parauberis, Lactococcus garvieae, L. lactis, Flavobacterium branchiophilum, F. psychrophilum and Yersinia ruckeri in diseased rainbow trout samples collected from different fish farms in Zanjan, Iran. A total of 103 individual diseased rainbow trout including 412 organ samples of liver, kidney, gills and eye organs were collected from 17 fish farms. Overall, 92 (89.3%) out of 103 rainbow trout were positive for the presence of at least one tested pathogen. According to culture and biochemical tests, 199 (48.3%) bacterial isolates were detected. However, molecular analysis confirmed 92.4% (184/199) of isolates. The most common isolated pathogen was L. garvieae (56.3%, 112/199), followed by S. iniae (11.5%, 23/199), F. branchiophilum (9.5%, 19/199) and Y. ruckeri (9.1%, 18/199). Lactococcus lactis and F. psychrophilum were detected with lowest frequency (2.5%, 5/199). Considering the high frequency of bacterial infections in our study, it seems that appropriate surveillance and control measures are essential to prevent the emergence and transmission of bacterial pathogens in rainbow trout farms.

Broad environmental adaptation of abundant microbial taxa in Robinia pseudoacacia forests during long-term vegetation restoration

Strategies for regulating the intensity of different cyanobacterial blooms: Insights from the dynamics and stability of bacterioplankton communities

Fish is one of the best sources of protein and the consumption of fish provides polyunsaturated fatty acids (PUFA), liposoluble vitamins, and essential minerals for human health. However contrary to their known benefits, fish may pose potential risks to human health since they can accumulate substantial concentrations of heavy metals in their tissues. This research is aimed to evaluate the heavy metals contamination and human health risk in rainbow trout (Oncorhynchus mykiss) collected from different farms of Chaharmahal and Bakhtiari province in Iran. The Chaharmahal and Bakhtiari province is targeted due to this province is the largest coldwater fish production center. In the present research accumulation of four heavy metals such as lead (Pb), cobalt (Co), copper (Cu) and zinc (Zn) were investigated in farmed rainbow trout, collected from fish farming at eight cities in the province of Chaharmahal and Bakhtiari, Iran. Risk to human health by the intake of metal-contaminated rainbow trout fish have been evaluated by estimated daily intake (EDI), target hazard quotient (THQ), and hazard index (HI). Pb and Cu concentrations in rainbow trout muscle were above the safe limits of FAO, FAO/WHO, and WHO standards in all the fish farms, while Zn were lower than the permissible limits. The estimated daily intakes (EDI) and estimated weekly intakes (EWI) of all studied heavy metals (mg/day or week/bw-kg) via consumption of the rainbow trout by the consumers were well below the provisional tolerable daily intake (PTDI) and provisional tolerable weekly Intake (PTWI) set by FAO/WHO. Pb and Co THQ values indicated the absence of health risks through consumption of the studied fish species, but pose non carcinogenic risk for Cu and Zn (target hazard quotient (THQ) > 1). In general, aggregate effect, assessed by hazard index (HI), expressed health risk for consumption of rainbow trout for a life time of more than 70 years.

Distribution of Infectious Hematopoietic Necrosis (IHN) was studied in rainbow trout fish farms in Chaharmahal and Bakhtyari Province which is a major trout culture region in Iran. Overall 150 suspected rainbow trout fry with less than 3 g body weight from 30 fish farms in Chaharmahal and Bakhtyari Province, Iran, were studied and fishes of 10 hatcheries (33.3% of all studied farms) found to be infected with IHNV. Reverse transcriptase polymerase chain reaction (RT-PCR) was applied to the detection of infectious hematopoietic necrosis virus (IHNV) using primer pairs. The product of 371 bp was amplified from the RNA extracts of infected organs of suspected fish. DNA sequencing of the PCR products demonstrated specificity of the amplification. The RT-PCR was found to be a simple, highly specific and sensitive method allowing diagnosis of IHN in a short time. Key words: Reverse transcription-polymerase chain reaction (RT-PCR), IHN, rainbow trout.

Genetic polymorphism of complement component C3 in rainbow trout ( Oncorhynchus mykiss) and resistance to viral haemorrhagic septicaemia

Farmed rainbow trout require specific cold, freshwater habitations to maximize overall growth for future release and general production. The growth and development of muscle tissue in rainbow trout are critical factors in understanding and maximizing the production and quality of farmed fish. Unlike mammals, rainbow trout can undergo muscle hyperplasia and hypertrophy throughout its lifetime, which only adds to its muscle growth potential as a species. This study aimed to investigate the growth patterns and gene expression changes in red, pink, and white muscle tissue over time in farmed rainbow trout. Twenty rainbow trout were harvested at 6 and 7 mo of age from the Walhalla State Hatchery (SC), and red, pink, and white muscle samples were collected in RNAlater for RNA extraction and downstream gene expression analysis. General growth pattern changes were assessed through measurements of wet body weight, wet length, empty carcass weight, and filet weight, while gene expression changes were examined using quantitative polymerase chain reaction (RT-qPCR). Genes such as PAX7A, PAX7B, MYOG, MYOD, IGF1, and IGF2B were investigated to illuminate dynamic changes in the muscle tissue of rainbow trout. These genes are associated with myogenic regulatory factors involved in muscle growth and development. Water and ambient temperature were captured to monitor potential temperature effects. Wet weight (g) and left filet weight (g) increased (P < 0.05) over the 30-d period. PAX7A, PAX7B, and MYOG were all downregulated (P < 0.05) in red and pink muscle in comparison to the previous 30 d. White muscle displayed no differences (P > 0.05) in expression of PAX7A, PAX7B, and MYOG. IGF1 gene expression in red, pink and white muscle were downregulated (P < 0.05) over the 30 d. MYOD had a very low expression in comparison with other target genes during these age points. These findings highlight the dynamic nature of muscle growth in rainbow trout and the importance of red and pink muscle dynamics. Understanding the molecular mechanisms underlying muscle growth and gene expression changes over time can inform strategies to optimize fish growth and meat quality in aquaculture systems. Further investigation is needed to elucidate the specific regulatory pathways involved in muscle development and their potential applications in fish farming.