Effects In Rainbow Trout Research Articles

Testing the detoxification power of black cumin oil (Nigella sativa) over cypermethrin insecticide effects in rainbow trout (Oncorhynchus mykiss) at multiple scales

This study investigated the curative effect of black cumin oil (Nigella sativa, NS), which is a phytotherapeutic agent against to cypermethrin (CYP), which is known to have adverse effects on rainbow trout (Oncorhynchus mykiss)’s behavioral changes, oxidative stress-mediated neurotoxicity, hematotoxicity and hepatotoxicity parameters. At the end of the trial period; (i) evaluation of critical swimming speed (Ucrit) (ii) hematology indices [white blood cell (WBC), red blood cell (RBC), hemoglobin (Hgb), hematocrit (Hct), mean cell volume (MCV), mean cell hemoglobin) (MCH), mean cell hemoglobin concentration (MCHC)] (iii) Elucidation of the mechanism of functional damage in brain tissue of O. mykiss by neurological parameter [acetylcholinesterase (AChE)] (iv) Evaluation of oxidative damage in oxidative stress-mediated neurotoxicity and hepatotoxicity in liver, gill and brain tissue of O. mykiss with antioxidant enzymes [(Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), Glutathione (GSH)] and [(detection by means of malondialdehyde (MDA)] (v) Obtaining applicable data in the toxicological field using a multi-biomarker approach to investigate the modulation of NS administration via target markers in the physiological pathway of O. mykiss were aimed. As a result of CYP application, it was determined that the Ucrit value of O. mykiss decreased significantly. It was determined that the changes in the values of RBC, Hgb and Hct, which are among the hematology parameters examined in the blood tissue, were statistically significant (p < 0.05). It was determined that WBC value was inhibited by CYP application and NS tried to make a positive contribution to WBC. It was determined that the AChE activity of O. mykiss in the brain tissue had a statistically significant inhibition in the CYP-treated group (p < 0.05). SOD, CAT, GPx, enzyme activities were found to be inhibited by CYP application and were statistically significant (p < 0.05). Acute toxicity of CYP was determined by antioxidant enzyme biomarkers in gill tissue. In the results obtained; While inhibitions were determined in SOD, CAT, GPx activities compared to the control group, an induction occurred in MDA value. NS administration was noted to be an important modulator of the SOD-CAT system against CYP exposure at both concentrations. Thus, it can be said that it indirectly functions as an effective antioxidant through the NS receptor protein and structurally stimulates the synthesis and activity of antioxidative enzymes under oxidative stress.

Comparative analysis of nutritional and transcriptional regulation of hacd1 in large yellow croaker (Larimichthys crocea) and rainbow trout (Oncorhynchus mykiss).

3-hydroxyacyl-CoA dehydratases 1 (Hacd1) is a critical enzyme in long-chain polyunsaturated fatty acids (LC-PUFA) biosynthesis. The difference in expression of hacd1 might account for the stronger capacity of LC-PUFA biosynthesis in freshwater fish than in marine fish, but little is known about fish hacd1. Therefore, this study compared the responses of large yellow croaker and rainbow trout hacd1 to different oil sources or fatty acids, and also examined transcriptional regulation of this gene. In this study, hacd1 was highly expressed in the liver of large yellow croaker and rainbow trout, which is the main organ for LC-PUFA biosynthesis. Therefore, we cloned the hacd1 coding sequence, with a phylogenetic analysis showing that this gene is evolutionarily conserved. Its localization to the endoplasmic reticulum (ER), likely also indicates a conserved structure and function. The expression of hacd1 in the liver was significantly decreased after the substitution of soybean oil (SO) for fish oil but was not significantly affected after palm oil (PO) substitution. Linoleic acid (LA) incubation significantly promoted hacd1 expression in primary hepatocytes of large yellow croaker and eicosapentaenoic acid (EPA) incubation significantly promoted hacd1 expression in primary hepatocytes of rainbow trout. Transcription factors STAT4, C/EBPα, C/EBPβ, HNF1, HSF3 and FOXP3 were identified in both large yellow croaker and rainbow trout. HNF1 had a stronger activation effect in rainbow trout than in large yellow croaker. FOXP3 inhibited hacd1 promoter activity in large yellow croaker but had no effect in rainbow trout. Therefore, the differences between HNF1 and FOXP3 affected the expression of hacd1 in the liver thus being responsible for the high capacity of LC-PUFA biosynthesis in rainbow trout.

The Effect of Rainbow Trout (Oncorhynchus mykiss) Collagen Incorporated with Exo-Polysaccharides Derived from Rhodotorula mucilaginosa sp. on Burn Healing.

Burn is one of the physically debilitating injuries that can be potentially fatal; therefore, providing appropriate coverage in order to reduce possible mortality risk and accelerate wound healing is mandatory. In this study, collagen/exo-polysaccharide (Col/EPS 1-3%) scaffolds are synthesized from rainbow trout (Oncorhynchus mykiss) skins incorporated with Rhodotorula mucilaginosa sp. GUMS16, respectively, for promoting Grade 3 burn wound healing. Physicochemical characterizations and, consequently, biological properties of the Col/EPS scaffolds are tested. The results show that the presence of EPS does not affect the minimum porosity dimensions, while raising the EPS amount significantly reduces the maximum porosity dimensions. Thermogravimetric analysis (TGA), FTIR, and tensile property results confirm the successful incorporation of the EPS into Col scaffolds. Furthermore,the biological results show that the increasing EPS does not affect Col biodegradability and cell viability, and the use of Col/EPS 1% on rat models displays a faster healing rate. Finally, histopathological examination reveals that the Col/EPS 1% treatment accelerates wound healing, through greater re-epithelialization and dermal remodeling, more abundant fibroblast cells and Col accumulation. These findings suggest that Col/EPS 1% promotes dermal wound healing via antioxidant and anti-inflammatory activities, which can be a potential medical process in the treatment of burn wounds.

Involvement of Mechanistic Target of Rapamycin (mTOR) in Valine Orexigenic Effects in Rainbow Trout.

This study was aimed at clarifying the importance of a mechanistic target of rapamycin (mTOR) in the central orexigenic effect of valine in fish. For this, rainbow trout (Oncorhynchus mykiss) were intracerebroventricularly (ICV) injected with valine alone or in the presence of rapamycin as the mTOR inhibitor, and two experiments were performed. In the first experiment, we evaluated feed intake levels. In the second experiment, we evaluated in the hypothalamus and telencephalon the following: (1) the phosphorylation status of mTOR and its downstream effectors ribosomal protein S6 and p70 S6 kinase 1 (S6K1), (2) the abundance and phosphorylation status of transcription factors involved in appetite regulation, and (3) the mRNA levels of key neuropeptides associated with homeostatic regulation of feed intake in fish. Rising central levels of valine clearly resulted in an orexigenic response in rainbow trout. This response occurred in parallel with mTOR activation in both the hypothalamus and telencephalon, as supported by depressant changes in proteins involved in mTOR signalling (S6 and S6K1). Also, these changes disappeared in the presence of rapamycin. However, it is not clear which precise mechanisms link the activation of mTOR and the alteration in feed intake levels since we did not observe changes in mRNA levels of appetite-regulatory neuropeptides as well as in the phosphorylation status and levels of integrative proteins.

Comprehensive proteomic analysis to elucidate the anti-heat stress effects of nano-selenium in rainbow trout (Oncorhynchus mykiss)

Because of the continuous intensification of global warming, extreme climate fluctuations, and high-density farming, cold-water rainbow trout (Oncorhynchus mykiss) are exposed to conditions of heat stress, which has severely impacted their survival and yield. Nano-selenium (nano-Se) shows higher biological activity and lower toxicity and has emerged as an ideal and ecological Se formulation. Herein rainbow trout were fed either a basal diet (control group) or basal diet plus 5 mg/kg nano-Se (treatment group). Samples were collected before (18 °C for 9 days; CG18, Se18) and after (24 °C for 8 h; CG24, Se24) heat stress. The DIA/SWATH approach was then applied to compare changes at the proteome level. We found 223 and 269 differentially abundant proteins in the CG18-CG24 and Se18-Se24 groups, respectively, which mainly included apoptosis-, heat stress-, and lipid-related proteins. In comparison with the CG18-CG24 group, the Se18-Se24 group showed higher abundance of molecular chaperone, such as Hsp70, Hsp90a.1, Hspa8, Hsp30, DNAJA4, Dnajb1, Bag2 and Ahsa1; on nano-Se supplementation, the heat stress-induced decline in the abundance of the selenoprotein MsrB2 was partially restored. Furthermore, nano-Se supplementation downregulated the abundance of lipid-related (CYP51, EBP, DHCR7, DHCR24, and APOB) and pro-apoptotic (caspase-8 and Bad) proteins. Protein–protein interaction analyses suggested that nano-Se inhibits apoptosis by upregulating the expression of Hsp70, Hsp90a.1, Hspa8, and Dnajb1; further, Hsp70/Hspa8 and MsrB2 appear to play a synergistic role in antioxidant defense under heat stress. Overall, our findings provide novel insights into nano-Se-mediated tolerance of heat stress, demonstrating that nano-Se exerts its anti-heat stress effects in rainbow trout by promoting protein repair, enhancing recovery of antioxidant enzyme activity, and alleviating lipid metabolism and apoptosis.

Intracellular taurine deficiency impairs cardiac contractility in rainbow trout (Oncorhynchus mykiss) without affecting aerobic performance.

Taurine is a non-proteinogenic sulfonic acid found in high concentrations inside vertebrate cardiomyocytes and its movement across the sarcolemmal membrane is critical for cell volume regulation. Taurine deficiency is rare in mammals, where it impairs cardiac contractility and leads to congestive heart failure. In fish, cardiac taurine levels vary substantially between species and can decrease by up to 60% in response to environmental change but its contribution to cardiac function is understudied. We addressed this gap in knowledge by generating a taurine-deficient rainbow trout (Oncorhynchus mykiss) model using a feed enriched with 3% β-alanine to inhibit cellular taurine uptake. Cardiac taurine was reduced by 17% after 4weeks with no effect on growth or condition factor. Taurine deficiency did not affect routine or maximum rates of O2 consumption, aerobic scope, or critical swimming speed in whole animals but cardiac contractility was significantly impaired. In isometrically contracting ventricular strip preparations, the force-frequency and extracellular Ca2+-sensitivity relationships were both shifted downward and maximum pacing frequency was significantly lower in β-alanine fed trout. Cardiac taurine deficiency reduces sarcoplasmic reticular Ca2+-ATPase activity in mammals and our results are consistent with such an effect in rainbow trout. Our data indicate that intracellular taurine contributes to the regulation of cardiac contractility in rainbow trout. Aerobic performance was unaffected in β-alanine-fed animals, but further study is needed to determine if more significant natural reductions in taurine may constrain performance under certain environmental conditions.

The effect of rainbow trout (Oncorhynchus mykiss) invasions on native fish communities in the subtropical Blyde River, Mpumalanga province, South Africa

This study investigated the effects of rainbow trout (Oncorhynchus mykiss) invasion on native fish communities in the upper Blyde River catchment. A fish survey was undertaken between September 2017 and October 2018 from 11 sites in the Blyde and Treur Rivers using electrofishing and fyke nets. Differences in species composition, relative abundance, and community structure among sites were tested using multivariate analysis. A total of ten fish species were captured. There were significant differences in composition and abundance between fish communities that could be attributed to O. mykiss invasion and variation in habitats. Populations of native species that historically occurred throughout the upper catchment, such as Enteromius treurensis, were greatly reduced and fragmented in the presence of O. mykiss. However, instream migration barriers such as waterfalls have prevented upstream migration of O. mykiss, and these invasion-free areas have remnant populations of native fishes that appear to be largely intact. This finding is consistent with other studies that have shown that introduced alien predatory fish can have a significant effect on fish communities and highlighted the need to prevent human-facilitated introductions in biodiversity sensitive areas, such as mountain headwater streams, that are inhabited by endemic and range-restricted minnows.

Cyanotoxins within and Outside of Microcystis aeruginosa Cause Adverse Effects in Rainbow Trout (Oncorhynchus mykiss).

The global expansion of toxic Microcystis blooms, and production of cyanotoxins including microcystins, are an increasing risk to freshwater fish. Differentiating intracellular and extracellular microcystin toxicity pathways (i.e., within and outside of cyanobacterial cells) in fish is necessary to assess the severity of risks to populations that encounter harmful algal blooms in pre-to-postsenescent stages. To address this, adult and juvenile Rainbow Trout (Oncorhynchus mykiss) were, respectively, exposed for 96 h to intracellular and extracellular microcystins (0, 20, and 100 μg L-1) produced by Microcystis aeruginosa. Fish were dissected at 24 h intervals for histopathology, targeted microcystin quantification, and nontargeted proteomics. Rainbow Trout accumulated intracellular and extracellular microcystins in all tissues within 24 h, with greater accumulation in the extracellular state. Proteomics revealed intracellular and extracellular microcystins caused sublethal toxicity by significantly dysregulating proteins linked to the cytoskeletal structure, stress responses, and DNA repair in all tissues. Pyruvate metabolism in livers, anion binding in kidneys, and myopathy in muscles were also significantly impacted. Histopathology corroborated these findings with evidence of necrosis, apoptosis, and hemorrhage at similar severity in both microcystin treatments. We demonstrate that sublethal concentrations of intracellular and extracellular microcystins cause adverse effects in Rainbow Trout after short-term exposure.

PHARMACOKINETIC, PHARMACODYNAMIC, AND TOXICOLOGY STUDY OF ROBENACOXIB IN RAINBOW TROUT (ONCORHYNCHUS MYKISS).

Postoperative antinociception control in fish is currently suboptimal, as commonly used antiinflammatory drugs last for only a few hours at tested temperatures. Therefore, long-acting anti-inflammatory drugs, such as robenacoxib, could improve the welfare of fish. The pharmacokinetics, duration of antinociceptive action, and potential adverse effects of robenacoxib were evaluated through two prospective randomized blinded trials in rainbow trout (Oncorhynchus mykiss). Six healthy rainbow trout received a single IM administration of robenacoxib (2 mg/kg), and two control fish received the same volume of saline IM. Blood samples were collected at predetermined time points for 5 d. Plasma robenacoxib concentrations were measured using high-performance liquid chromatography-high-resolution hybrid orbitrap mass spectrometry and noncompartmental pharmacokinetic analysis. Ten additional rainbow trout received an intralabial injection of 0.05 ml of 2% acetic acid following a previously validated nociceptive model. The treated group (n = 6) received 2 mg/kg of robenacoxib IM and the control group (n = 4) received an equivalent volume of saline IM. The behavior, appetite, and opercular rate of the fish were evaluated every hour for 5 h, then once daily for 3 d. All 12 treated trout and 6 controls underwent histopathologic evaluation. Average maximum plasma concentration (Cmax) was 329.9 ± 137.3 ng/ml observed at 2.1 ± 0.7 h (Tmax) and terminal half-life was 12.6 ± 2.27 h. Plasma concentrations described as antinociceptive in domestic carnivores were measured for 3-4 d. This dose was associated with a significant decrease in rocking behavior (P = 0.017). No adverse effects were detected clinically nor on histopathology. Robenacoxib administered IM at 2 mg/kg appears to be safe and may provide an antinociceptive effect in rainbow trout. This study presents a new therapeutic option to provide long-lasting antinociception in rainbow trout.

In vitro assessment of some probiotic properties and inhibitory activity against Yersinia ruckeri of bacteria isolated from rainbow trout Oncorhynchus mykiss (Walbaum)

In the present study, we isolated bacteria from intestines of healthy rainbow trout, screened for their probiotic properties, and inhibitory activity against Y. ruckeri. A total of 21 out of 541 isolates from the intestine of adult rainbow trout (∼ 200–350 g), showed inhibition zones around at least one Y. ruckeri strains tested. Six of them were selected due to their ability to inhibit all the pathogenic strains on solid medium. They were identified as B. amyloliquefaciens 131and Paenibacillus spp (code 134, 1cc, 1d, 1k, and 2cc). Excluding the isolate 1k, selected strains were able to inhibit Y. ruckeri strains at 22 and 15 ± 0.5 °C when they were simultaneously cocultured, however, they did not show inhibition at 12 ± 0.5 °C. A pre incubation process of the selected strains for 24 h prior to co-culture with strains of Y. ruckeri enabled them to inhibit target pathogens at the lowest temperature tested. Furthermore, probiotic candidates survived to high concentrations of rainbow trout bile salts and acidic conditions. Selected bacteria were also able to produce amylolitic, proteolytic and lipolytic enzymes and showed variable hydrophobic values. Biosafety assays, performed by oral and intraperitoneal infection using B. amyloliquefaciens 131 and Paenibacillus spp (code 134, 1cc, 1d, 1k, and 2cc), showed no pathogenic effect in rainbow trout during 20-day experiment. Therefore, selected strains showed potential characteristics that are required to be evaluated in vivo for their possible subsequent use as probiotics in rainbow trout aquaculture.

Genistein Induces Adipogenic and Autophagic Effects in Rainbow Trout (Oncorhynchus mykiss) Adipose Tissue: In Vitro and In Vivo Models.

Soybeans are one of the most used alternative dietary ingredients in aquafeeds. However, they contain phytoestrogens like genistein (GE), which can have an impact on fish metabolism and health. This study aimed to investigate the in vitro and in vivo effects of GE on lipid metabolism, apoptosis, and autophagy in rainbow trout (Oncorhynchus mykiss). Primary cultured preadipocytes were incubated with GE at different concentrations, 10 or 100 μM, and 1 μM 17β-estradiol (E2). Furthermore, juveniles received an intraperitoneal injection of GE at 5 or 50 µg/g body weight, or E2 at 5 µg/g. In vitro, GE 100 μM increased lipid accumulation and reduced cell viability, apparently involving an autophagic process, indicated by the higher LC3-II protein levels, and higher lc3b and cathepsin d transcript levels achieved after GE 10 μM. In vivo, GE 50 µg/g upregulated the gene expression of fatty acid synthase (fas) and glyceraldehyde-3-phosphate dehydrogenase in adipose tissue, suggesting enhanced lipogenesis, whereas it increased hormone-sensitive lipase in liver, indicating a lipolytic response. Besides, autophagy-related genes increased in the tissues analyzed mainly after GE 50 µg/g treatment. Overall, these findings suggest that an elevated GE administration could lead to impaired adipocyte viability and lipid metabolism dysregulation in rainbow trout.

Effect of quorum quenching bacteria on growth, virulence factors and biofilm formation of Yersinia ruckeri invitro and an invivo evaluation of their probiotic effect in rainbow trout.

Five N-acyl homoserine lactone-degrading bacteria (quorum quenching (QQ) strains) were selected to evaluate their impacts on growth, virulence factors and biofilm formation in Yersinia ruckeri invitro. No difference was observed among the growth pattern of Y.ruckeri in monoculture and coculture with the QQ strains. To investigate the regulation of virulence factors by quorum sensing in Y.ruckeri, cultures were supplemented with 3oxo-C8-HSL. The results indicated that swimming motility and biofilm formation are positively regulated by QS (p<0.05), whereas caseinase, phospholipase and haemolysin productions are not influenced by 3oxo-C8-HSL (p>0.05). The QQs were able to decrease swimming motility and biofilm formation in Y.ruckeri. QQ bacteria were supplemented to trout feed at 108 CFU/g (for 40days). Their probiotic effect was verified by Y.ruckeri challenge either by immersion or injection in trout. All strains could significantly increase fish survival with Bacillus thuringiensis and Citrobacter gillenii showing the highest and lowest relative percentage survival (RPS) values (respectively, 85% and 38%). Besides, there was no difference between the RPS values by either immersion or injection challenge expect for B.thuringiensis. The putative involvement of the QQ capacity in the protection against Yersinia is discussed.

Intramuscular infiltration of a local anesthetic, lidocaine, does not result in adverse behavioural side effects in rainbow trout

Fish are a useful animal model for research, but our improvement in some aspects of their welfare has not kept pace with their increased popularity for this use. For example, researchers rarely use analgesics. We evaluated the side effects of lidocaine, a local anesthetic widely used in human and veterinary medicine. We infiltrated lidocaine on each side of the dorsal fin (total 20 mg/kg) of young rainbow trout (15 fish per group) compared with infiltration with an equal volume of saline. We monitored behaviour of individual trout during the 4-hour trial. Food was presented 5 times during the trial (30 min, 1 h, 2 h, 3 h, 4 h after infiltration) and we analyzed behaviour for 1 minute before and after food presentation. Behaviour of Saline-Infiltrated trout compared with trout that received no infiltration showed that infiltration in and of itself had no statistically significant effects on trout behaviour. However, there were many statistically significant effects of Lidocaine-Infiltrated trout compared with Saline-Infiltrated trout; none of the side-effects were adverse.

Rainbow trout (Oncorhynchus mykiss) immune response towards a recombinant vaccine targeting the parasitic ciliate Ichthyophthirius multifiliis.

The protective effect in rainbow trout (Oncorhynchus mykiss) of an experimental subunit vaccine targeting antigens in the parasite Ichthyophthirius multifiliis has been evaluated and compared to effects elicited by a classical parasite homogenate vaccine. Three recombinant parasite proteins (two produced in E.coli and one in insect cells) were combined and injected i.p., and subsequently, protection and antibody responses were analysed. Both the experimental and the benchmark vaccine induced partial but significant protection against I.multifiliis when compared to control fish. Specific antibody responses of vaccinated trout (subunit vaccine) were raised against one neurohypophysial n-terminal domain protein #10 of three recombinant proteins, whereas the benchmark vaccine group showed specific antibody production against all three recombinant proteins. The immunogenic parasite protein #10 may be a potential vaccine candidate supplementing the protective I-antigen in future vaccine trials.

Rainbow trout effects on zooplankton in the reproductive area of the critically endangered hooded grebe

AbstractAquaculture in arid Patagonia is potentially affecting the hooded grebe (Podiceps gallardoi), a critically endangered endemic waterbird. Exotic rainbow trout (Oncorhynchus mykiss) were stocked from 1994 in naturally fishless lakes, the primary reproductive habitat of this grebe.Trout and grebes are visual predators, whose diets overlap. Consequently, trout could reduce the abundance of prey of the hooded grebe.This study compared the size distribution and abundance of the pelagic zooplankton fraction preyed upon by trout in four fishless lakes and three lakes stocked with trout, including vegetated and unvegetated lakes.The mean size ofDaphniaspp. was 45% and 35% larger in fishless lakes than in stocked lakes, for unvegetated and vegetated lakes, respectively.Boeckellaspp. were larger in fishless than in stocked vegetated lakes.Fishless and stocked lakes had highly contrasting biomasses of large pelagic crustaceans. Amphipods were absent from the water column of all stocked lakes analysed, and were abundant in fishless lakes.Parabroteas sarsiwas absent from the two large unvegetated lakes, stocked with trout.These shifts in the abundance and size spectrum of the zooplankton may reflect competition between trout and hooded grebe, affecting the survival of the latter species.The current conservation status of this rare aquatic bird demands the application of management tools to reduce the detrimental effects of aquaculture on their primary reproductive habitat.Copyright © 2016 John Wiley &amp; Sons, Ltd.

Liposomal- and CpG oligodeoxynucleotide-based vaccine formulations offer protection with reduced adverse effects in rainbow trout

Mass-scale, intraperitoneal administration of vaccines containing mineral oil-adjuvants, has been common practice in salmonid aquaculture since the early 1990’s. Introduced as a response to the threat of disruptive outbreaks of aquatic pathogens such as Aeromonas salmonicida subspecies salmonicida, the causative agent of furunculosis, such formulations have increased the survival rates and profitability of the farming of these species. Nevertheless, well-documented local adverse effects, including granulomatous inflammation with melanisation and adhesions of the peritoneal cavity, in addition to systemic effects, have also been observed. Here, aiming at exploring alternatives to mineral oil-adjuvanted furunculosis injection vaccines, three different vaccine formulations were designed and administered to rainbow trout (Onchorhynchus mykiss) fry. All three formulations were based on whole-cell A. salmonicida subspecies salmonicida bacterin, formulated with either Freund’s incomplete adjuvant (FIA), dimethyldioctadecylammonium/trehalose 6,6’dibehenate liposomes (CAF01), or CpG oligodeoxynucleotides. Non-vaccinated, TBSinjected and bacterin-injected groups were included as control groups. Following vaccination, fish were sampled in order to monitor the occurrence of adverse effects, as well as the development of the immunological reaction to each vaccine formulation. Finally, a waterborne challenge with A. salmonicida was performed to assess the protection obtained in each experimental group. Significant differences were observed with regards to the occurrence of adverse effects, both in individual scoring of adhesions and pigmentation, as well as in the combining Speilberg score, demonstrating a general reduction in adverse effects in the CpGand CAF01-group, compared to individuals injected with the FIA-formulation. When analyzing serum samples, significantly elevated antibody titers were seen in all three experimental formulations when compared to non-vaccinated controls, and finally a significant, uniform protective effect was seen in all three vaccine groups. While this is still an ongoing study, the combination of protection from infection along with the reduction in adverse effects achieved by the use of liposomal and nucleotide adjuvants in this study, is promising with respect to alternative, low-toxicity adjuvants in aquaculture.

Effect of rainbow trout (Oncorhynchus mykiss) seminal plasma on the post-thaw quality of ram semen cryopreserved in a soybean lecithin-based or egg yolk-based extender

The aim of the current study was to evaluate the effects of different concentrations of rainbow trout seminal plasma (RTSP) (0.1%, 1% and 10%) in extenders containing either egg yolk or lecithin for use in Awassi ram semen cryopreservation. Pooled sperm were diluted in a two-step dilution method to a final concentration of 1/5 (semen/extender) in egg yolk or lecithin extender containing no RTSP, 0.1%, 1% or 10% RTSP (v/v). Semen samples were assessed for sperm motility, plasma membrane integrity [hypoosmotic swelling test (HOST) and Hoechst 33258] and defective acrosomes [FITC-conjugated Pisum sativum agglutinin (PSA-FITC)] at the following five time points: after dilution with extender A; after equilibration; and post-thaw at 0h, 3h and 5h. Malondialdehyde (MDA) was examined only after thawing. Freezing and thawing procedures (dilution, equilibration and post-thaw incubation at 0h, 3h and 5h) negatively affected the motility (P<0.001) and acrosome integrity (P<0.001). Additionally, freezing and thawing negatively affected the plasma membrane integrity, as determined by the HOST and Hoechst 33258 (P<0.001). The extender group affected the motility (P<0.001) and the HOST results (P<0.001). Levels of MDA in the egg yolk extender with 1% RTSP group were significantly lower than in the lecithin control group (P<0.05). In conclusion, the egg yolk extender groups that were supplemented with 10% and 1% RTSP provided greater cryoprotective effects for semen survivability during 5h incubation than the other extender groups.

Tissue-specific effects of acute aluminium exposure on the radiation-induced bystander effect in rainbow trout (Oncorhynchus mykiss, Walbaum)

Purpose: To investigate if aluminium (Al) modifies the rainbow trout response to radiation exposure and/or the induction of a radiation-induced bystander effect.Methods: Rainbow trout were exposed to 100 or 200 μg l−1 Al (for 3 h), a 0.5 Gy X-ray dose or Al followed immediately by irradiation. The exposed fish were then swum with completely untreated bystander fish. A human reporter cell clonogenic assay was used to determine whether Al exposure modified the effects of irradiation on the skin and gills from directly exposed fish and also the radiation-induced bystander effect in untreated fish.Results: Al exposure did not modify the response to direct irradiation by the skin, or the gill. Al did not modify the bystander effect in the skin. However Al did modify the bystander effect in the gill. Gills of bystander fish swum with fish exposed to 200 μg l−1 Al, followed by irradiation, caused a greater reduction in HPV-G cell survival than was caused by irradiation only. Interestingly Al exposure only also caused a bystander effect (reduced HPV-G survival) in the gill.Conclusion: This study shows that, in a multiple stressor scenario, the communication of radiation-induced stress signals is modified on a tissue-specific basis by acute Al exposure. Aside from the implications this has for radiological protection this response may also have potential for environmental monitoring where detection of the bystander effect could act as an indicator of radiation exposure when direct exposure responses are not evident.

Dietary inclusion of salmon testes meal from Alaskan seafood processing byproducts: Effects on growth and immune function of rainbow trout, Oncorhynchus mykiss (Walbaum)

Abstract This study investigated the growth and immune function effects following partial replacement of fish meal with dried testes meal from pink salmon ( Oncorhynchus gorbuscha ) testes collected from Alaskan seafood processing byproducts. It was hypothesized that the dietary nucleotide content of testes meal may provide an immunostimulatory effect in rainbow trout ( Oncorhynchus mykiss ). Three diets were formulated and used for this study; a commercial type control diet, a Macrogard diet, and an experimental diet containing 50 g kg − 1 testes meal. Triplicate groups of juvenile rainbow trout (8.65 ± 0.13 g fish − 1 ) were fed each diet for 12 weeks, at which time they were challenged with Flavobacterium psychrophilum (the causative agent of coldwater disease). No significant differences in feed conversion ratio or specific growth rates were observed. Kidney macrophage (phagocytic) activity was significantly (P

Developmental toxicity of PAH mixtures in fish early life stages. Part I: adverse effects in rainbow trout

A new gravel-contact assay using rainbow trout, Oncorhynchus mykiss, embryos was developed to assess the toxicity of polycyclic aromatic hydrocarbons (PAHs) and other hydrophobic compounds. Environmentally realistic exposure conditions were mimicked with a direct exposure of eyed rainbow trout embryos incubated onto chemical-spiked gravels until hatching at 10 °C. Several endpoints were recorded including survival, hatching delay, hatching success, biometry, developmental abnormalities, and DNA damage (comet and micronucleus assays). This bioassay was firstly tested with two model PAHs, fluoranthene and benzo[a]pyrene. Then, the method was applied to compare the toxicity of three PAH complex mixtures characterized by different PAH compositions: a pyrolytic extract from a PAH-contaminated sediment (Seine estuary, France) and two petrogenic extracts from Arabian Light and Erika oils, at two environmental concentrations, 3 and 10 μg g(-1) sum of PAHs. The degree and spectrum of toxicity were different according to the extract considered. Acute effects including embryo mortality and decreased hatching success were observed only for Erika oil extract. Arabian Light and pyrolytic extracts induced mainly sublethal effects including reduced larvae size and hemorrhages. Arabian Light and Erika extracts both induced repairable DNA damage as revealed by the comet assay versus the micronucleus assay. The concentration and proportion of methylphenanthrenes and methylanthracenes appeared to drive the toxicity of the three PAH fractions tested, featuring a toxic gradient as follows: pyrolytic < Arabian Light < Erika. The minimal concentration causing developmental defects was as low as 0.7 μg g(-1) sum of PAHs, indicating the high sensitivity of the assay and validating its use for toxicity assessment of particle-bound pollutants.