Cited by (177)
Dietary effects on biomarkers of growth, stress, and welfare of diploid and triploid Atlantic salmon (Salmo salar) during parr-smolt transformation
2022, Aquaculture Reports
Triploidy is induced in Atlantic salmon (Salmo salar) to produce sterile fish for genetic containment and to hinder early sexual maturation in farmed fish, but it can have unwanted negative effects on growth, health, and welfare. However, the growth and welfare of triploid fish may be improved by adjusting the rearing environment, feeding conditions and diets. This study evaluated physiological changes and used a suite of biomarkers to assess the potential impact of diet on growth and welfare of diploid and triploid salmon during the parr-smolt transformation. Diploids and triploids, held at low temperature, were fed a standard salmon feed or one with hydrolyzed fish proteins thought to be suitable for triploid Atlantic salmon. Fish muscle was collected monthly from October to December (2454–3044 degree-days post-start feeding, ddPSF) for analysis of biomarkers, and the progress of the parr-smolt transformation was monitored using a seawater challenge test. Real-Time PCR and radioimmunoassay were used to assess growth and stress response biomarkers (expression of genes of the GH-IGF axis and HSP70; cortisol concentrations), and oxidative stress biomarkers of lipids (MDA) and proteins (AOPP) were assayed. Changes in the biomarkers were related to sampling time rather than being associated with diet or ploidy, and the changes were compatible with the progression of the parr-smolt transformation. Growth and expressions of the biomarkers in triploid Atlantic salmon were similar to those of their diploid counterparts, and there was no evidence that the rearing conditions employed in the study resulted in stress responses being elicited. Overall, the physiological indicators and biomarkers employed in this study did not point to there being any dietary effects on performance and welfare of diploid and triploid salmon that were undergoing parr-smolt transformation.
Differential effects of two seawater transfer regimes on the hypoosmoregulatory adaptation, hormonal response, feed efficiency, and growth performance of juvenile steelhead trout
2022, Aquaculture Reports
The differential effects of two seawater (SW) transfer regimes on the hypoosmoregulation, hormonal response, feed efficiency, and growth performance of 50g juvenile steelhead trout (Oncorhynchus mykiss) were determined to better understand the chronic responses to two salinity increase regimes. The fish reared in freshwater (FW) were exposed to either FW (control) or SW (32 ppt) via two regimes. In the first regime, the fish were exposed to a daily increase in salinity of 11 ppt and transferred to 32 ppt on the 3rd day (3DSW), and in the second regime, the fish were exposed to 20 ppt on the 1st day, which was followed by a daily 2 ppt increase, and transferred to 32 ppt on the 7th day (7DSW). Subsequently, an 8-week growth trial was conducted. At the end of the trial, the body weight of the control fish was higher than that of the 3DSW and 7DSW while the specific growth rate of the control was higher than that of the 3DSW but not significantly different from that of the 7DSW. Similarly, the feed efficiencies of the control were not different from that of the 7DSW but were higher than that of the 3DSW. The results on the plasma Na+ and Cl levels, osmolality, and gill Na+/K+ ATPase activity indicated that steelhead in the 3DSW and 7DSW developed high hypoosmoregulatory ability at weeks 4 and 8. Kidney Na+/K+-ATPase activity increased in the 7DSW and 3DSW groups at week 4. Circulating growth hormone and insulin-like growth factor I levels in the 7DSW group were elevated at week 4, whereas the cortisol level was not changed. Our results suggest that the 7DSW but not the 3DSW alleviated the chronic effect of osmotic stress on the growth rate and feed efficiency of 50g steelhead trout following SW transfer.
Regulation of thyroid hormones and branchial iodothyronine deiodinases during freshwater acclimation in tilapia
2021, Molecular and Cellular Endocrinology
Euryhaline fishes are capable of maintaining osmotic homeostasis in a wide range of environmental salinities. Several pleiotropic hormones, including prolactin, growth hormone, and thyroid hormones (THs) are mediators of salinity acclimation. It is unclear, however, the extent to which THs and the pituitary-thyroid axis promote the adaptive responses of key osmoregulatory organs to freshwater (FW) environments. In the current study, we characterized circulating thyroxine (T4) and 3-3’-5-triiodothyronine (T3) levels in parallel with the outer ring deiodination (ORD) activities of deiodinases (dios) and mRNA expression of dio1, dio2, and dio3 in gill during the acclimation of Mozambique tilapia (Oreochromis mossambicus) to FW. Tilapia transferred from seawater (SW) to FW exhibited reduced plasma T4 and T3 levels at 6h. These reductions coincided with an increase in branchial dio2-like activity and decreased branchial dio1 gene expression. To assess whether dios respond to osmotic conditions and/or systemic signals, gill filaments were exposed to osmolalities ranging from 280 to 450 mOsm/kg in an in vitro incubation system. Gene expression of branchial dio1, dio2, and dio3 was not directly affected by extracellular osmotic conditions. Lastly, we observed that dio1 and dio2 expression was stimulated by thyroid-stimulating hormone in hypophysectomized tilapia, suggesting that branchial TH metabolism is regulated by systemic signals. Our collective findings suggest that THs are involved in the FW acclimation of Mozambique tilapia through their interactions with branchial deiodinases that modulate their activities in a key osmoregulatory organ.
Testing of NKA expression by mobile real time PCR is an efficient indicator of smoltification status of farmed Atlantic salmon
Citation Excerpt :
Driven by the endocrine system salmon parr adapt into SW ready smolts through a number of morphological, physiological, behavioural and biochemical changes (Hoar, 1976; Folmar and Dickhoff, 1980; Barron, 1986; McCormick and Saunders, 1987; Dickhoff et al., 1997; McCormick, 2001; Ebbesson et al., 2008; McCormick et al., 2009, Stefansson et al., 2012). Studies on endocrine factors concluded that growth hormones (GH), thyroid hormone (Prunet et al., 1989; McCormick, 1995, 1996, 2001, 2013; Agustsson et al., 2001; Ebbesson et al., 2008; Bjornsson et al., 2011), insulin like growth factor (IGFI) (McCormick, 1995, 1996, 2001; Dickhoff et al., 1997; Agustsson et al., 2001) and cortisol (McCormick, 1996, 2001; McCormick et al., 2000, Kiilerich et al., 2007, Ebbesson et al., 2008) play a significant role in osmoregulation in salmon by inducing development of iononcytes in the gill epithelia switching the function from an ion absorbing to an ion secreting role. McCormick and Saunders (1987) suggested that the transport protein Sodium Potassium ATPase (NKA) is responsible for salt regulation and seawater acclimation in salmon.
Assessment of seawater readiness of freshwater salmon smolts is a crucial husbandry step with economic implications in salmon aquaculture but current methods rely on delayed centralised enzymic activity measurement. The efficiency of a qRT-PCR assay for sodium potassium ATPase (NKA) α1a mRNA was tested in a 3-year study on 19 hatcheries across Scotland incorporating environmental factors such as temperature and metal contamination. The NKA qRT-PCR assay was transferred to a mobile laboratory and on-site testing was carried out at 3 hatchery sites. For the first two years standard enzymatic and gene expression assays had similar success rates in detecting smoltification (NKA activity 60%, qRT-PCR 57%). In the third year, all but one site were determined as sea water ready by qRT-PCR but only at 4 by enzymatic testing. On site testing with mobile qRT-PCR was successfully performed on four farm sites. Altogether, high sensitivity was shown for the in lab (98.9%, SE 0.24) and mobile (93.43%, SE 0.119) assays when tested using a quantitative RNA standard. Some indication for obscured smoltification assay results due to environmental increased heavy metal contamination was observed.
Our results prove it is possible to test a smoltification marker on site and provide results on the day of testing during the smolt period allowing for informed decisions on seawater transfer.
Effects of long-term cortisol treatment on growth and osmoregulation of Atlantic salmon and brook trout
2021, General and Comparative Endocrinology
Citation Excerpt :
Many studies in salmonids and other teleost species have addressed the effects of cortisol on NKA activity in gills, indicating that this ion transport protein is directly regulated by cortisol (Arjona et al., 2011; Laiz-Carrión et al., 2002; Mancera and McCormick, 1999; McCormick, 1995; McCormick et al., 2013). Cortisol promotes seawater acclimation of teleosts by stimulating the development of seawater-type gill ionocytes, gill NKA activity, and other ion transporters involved in salt secretion, resulting in increased salinity tolerance (Madsen, 1990; Madsen et al., 1995; McCormick, 1995, 1996; McCormick et al., 2013; Shaughnessy and McCormick, 2018). In the present study, gill NKA activity of Atlantic salmon was elevated by cortisol treatment after 14 and 30 days of treatment, consistent with previous studies noted above.
Cortisol is the final product of the hypothalamic-pituitary-interrenal (HPI) axis and acts as a gluco- and mineralo-corticoid in fish. Long-term elevations of cortisol have been linked to reduced growth in fishes, but the mechanism(s) and relative sensitivities of species are still unclear. We carried out experiments to examine the relative effects of cortisol on growth and gill NKA activity in two salmonids: Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis). Treatment with intraperitoneal cortisol implants for 30days resulted in reduced growth in both species, but with greater sensitivity to cortisol in brook trout. Gill NKA activity was strongly upregulated by cortisol in Atlantic salmon, and weakly upregulated in brook trout but with no statistically significant effect. Cortisol treatment resulted in reduced plasma levels of insulin-like growth factor I and increased plasma growth hormone levels in Atlantic salmon. Our results demonstrate that there are species differences in the sensitivity of growth and osmoregulation to cortisol, even among species in the same family (Salmonidae).
Dynamics of BK channel expression in gills during smoltification of Atlantic Salmon under farm conditions
Smoltification is a crucial step in the aquaculture of Atlantic salmon. Currently, the Na+/K+ ATPase (NKA) test is used to determine whether fish have adapted to seawater when moved from freshwater. The mortality rate of unadapted fish in Chile is ~10% after smoltification. During this period, BK channel expression decreases in gills after two weeks in saline water under laboratory conditions. However, these findings have not yet been tested on an industrial scale. We characterized the changes in mRNA levels of BK channels in gills from Salmo salar during smoltification using salmon farming protocols and compare these results against gill NKA activity and found a significant decrease in expression of BK channel transcripts during the smolt stage. We also characterized the dynamic of the BK channel expression (mRNA) versus NKA activity by using transcriptomic and RT-PCR analyses under an industrial setting. BK channels are involved in a variety of physiological processes, and our results indicate that BK potassium channel expression in gills could form the basis of a new complementary test to determine the level of smoltification more precisely.
Recommended articles (6)
Microbial community dynamics in semi-commercial RAS for production of Atlantic salmon post-smolts at different salinities
Aquacultural Engineering, Volume 78, Part A, 2017, pp. 42-49
Fish live in close contact with microbes in their surrounding water. For cultivated marine fish larvae, stable microbial environments, characterized by slow-growing, K-selected bacteria, have been found to improve growth and survival. Compared to flow-through systems, recirculating aquaculture systems (RAS) offer a better possibility for obtaining microbial stability in the rearing water. However, the microbial ecology in RAS is complex and little studied, and to optimize the microbial water quality more knowledge is needed on microbial community dynamics and interactions between microbes and fish. In the present study we investigated microbial community dynamics in three large-scale RAS, operated with different salinities (12, 22 and 32ppt), for production of Atlantic salmon post-smolts. We focused on the stability of microbial communities over time in the bioreactors and the fish tanks, and compared the microbial communities within and between the three RAS. The study showed that: 1) The microbial community of the water was similar between the compartments of each RAS at the same time point, 2) The microbial communities of the water (and to a lesser extent the biofilm) within each system underwent large changes over time, 3) The microbiota of biofilm and water differed significantly within each system, 4) Biofilm community profiles were more similar between RAS than the water community profiles, and 5) Salinity structured the microbial community composition. The present study provides new knowledge on how the microbiota in RAS varies with time and how it is influenced by environmental factors.
Salinity and temperature variations reflecting on cellular PCNA, IGF-I and II expressions, body growth and muscle cellularity of a freshwater fish larvae
General and Comparative Endocrinology, Volume 202, 2014, pp. 50-58
The present study assessed the influence of salinity and temperature on body growth and on muscle cellularity of Lophiosilurus alexaxdri vitelinic larvae. Slightly salted environments negatively influenced body growth of freshwater fish larvae and we observed that those conditions notably act as an environmental influencer on muscle growth and on local expression of hypertrophia and hypeplasia markers (IGFs and PCNA). Furthermore, we could see that salinity tolerance for NaCl 4gl−1 diminishes with increasing temperature, evidenced by variation in body and muscle growth, and by irregular morphology of the lateral skeletal muscle of larvae. We saw that an increase of both PCNA and autocrine IGF-II are correlated to an increase in fibre numbers and fibre diameter as the temperature increases and salinity diminishes. On the other hand, autocrine IGF-I follows the opposite way to the other biological parameters assessed, increasing as salinity increases and temperature diminishes, showing that this protein did not participate in muscle cellularity, but participating in molecular/cellular repair. Therefore, slightly salted environments may provide adverse conditions that cause some obstacles to somatic growth of this species, suggesting some osmotic expenditure with a salinity increment.
Water temperature and oxygen: The effect of triploidy on performance and metabolism in farmed Atlantic salmon (Salmo salar L.) post-smolts
Aquaculture, Volume 473, 2017, pp. 1-12
The use of sterile triploids in Atlantic salmon aquaculture would mitigate the environmental risks associated with introgressive hybridization between escaped farmed and wild Atlantic salmon. However, production of farmed triploid salmon is limited due to reports of poorer growth and higher mortality when compared to diploids, in particular under sub-optimal environmental conditions. To address these concerns, we monitored triploid and diploid Atlantic salmon post-smolts at temperatures between 3 and 18°C and 100% oxygen saturation (O2 sat), and additional periods of 60% O2 sat (hypoxia) at 6 or 18°C, respectively. Feed intake and oxygen consumption rate were monitored throughout the experimental period. Muscle and blood samples were collected at 100 and 60% O2 sat at 6 and 18°C for analysis of white muscle energy phosphates (creatine phosphate, adenosine triphosphate) and carbohydrate fuels (glucose, glycogen) as well as blood clinical chemistry (whole blood: hematocrit; plasma: Na+, K+, Cl−, glucose, lactate, pH, triacylglycerol). Mortality was similar between ploidies, but higher in triploids compared to diploids during reduced O2 sat at 18°C. Compared to diploids, triploids had higher feed intake (% biomass) at ≤9°C, but lower feed intake at ≥15°C. Feed intake peaked at 12 and 15°C for triploids and diploids, respectively. Triploids progressively reduced feed intake with increasing temperature after peak feeding, indicating reduced scope for specific dynamic action with increasing water temperature. During hypoxia, triploids had lower feed intake than diploids at 6 and 18°C. The difference in feed intake was not associated with any ploidy effect on body weight gain or feed conversion ratio, but triploids had greater body length growth compared to diploids. At ≥15°C triploids consumed less oxygen than diploids. In the white musculature, the only observed difference between ploidies was a lower level of glycogen in triploids compared to diploids at 18°C and 100% O2 sat. In the blood plasma, the concentration of ions was lower and glucose level higher in triploids compared to diploids at 18°C and 60% O2 sat. The results of this study indicate that triploid Atlantic salmon post-smolts can substitute diploids, but are less tolerant to high seawater temperature and low O2 sat. For sea-cage farming of triploid salmon post-smolts, this would favour production areas with maximum temperatures of 15°C and sufficient oxygen.
This study demonstrates that triploid Atlantic salmon post-smolts have lower temperature optima for feeding and growth than diploids, a similar physiological response to high temperatures, but higher mortality under suboptimal conditions. Consequently triploid Atlantic salmon post-smolts may be well suited for commercial farming in geographical regions with moderate water temperatures in the summer and autumn months.
Tolerance and growth of the longsnout seahorse Hippocampus reidi at different salinities
Aquaculture, Volume 463, 2016, pp. 1-6
Hippocampus reidi is one of the most popular seahorse species in the aquarium trade. The commercial breeding of this species is an alternative to reducing the fishing pressure on natural populations. Two experiments with newly born juveniles were conducted in this study to assess salinity tolerance (Lethal Time for 50% of the population-LT50), survival and growth during the first 10days of life. A third experiment determined the isosmotic point of adults. The highest LT50 was observed at 10psu, followed by 15, 20, 25, 30, and 35psu, and the lowest LT50 was recorded at 5psu. A negative relationship between salinity and final weight and between salinity and final height was observed through the regressions performed, such that a decrease in salinity (until the lowest level analysed; 10psu) implied a higher growth in height and weight. The highest survival rates were observed between the salinities 10 and 25psu. The isosmotic point of the species was determined at 11.68psu (303.38mOsm/kg), which is in agreement with the salinity where the best salinity results were observed in the first two experiments. Using an intermediate salinity to produce H. reidi on a commercial scale would be advantageous because of survival and growth improvement in addition to requiring a lower seawater uptake and less cost for purchase artificial salt.
Leptin stimulates hepatic growth hormone receptor and insulin-like growth factor gene expression in a teleost fish, the hybrid striped bass
General and Comparative Endocrinology, Volume 229, 2016, pp. 84-91
Leptin is an anorexigenic peptide hormone that circulates as an indicator of adiposity in mammals, and functions to maintain energy homeostasis by balancing feeding and energy expenditure. In fish, leptin tends to be predominantly expressed in the liver, another important energy storing tissue, rather than in fat depots as it is in mammals. The liver also produces the majority of circulating insulin-like growth factors (IGFs), which comprise the mitogenic component of the growth hormone (GH)-IGF endocrine growth axis. Based on similar regulatory patterns of leptin and IGFs that we have documented in previous studies on hybrid striped bass (HSB: Morone saxatilis×Morone chrysops), and considering the co-localization of these peptides in the liver, we hypothesized that leptin might regulate the endocrine growth axis in a manner that helps coordinate somatic growth with energy availability. Using a HSB hepatocyte culture system to simulate autocrine or paracrine exposure that might occur within the liver, this study examines the potential for leptin to modulate metabolism and growth through regulation of IGF gene expression directly, or indirectly through the regulation of GH receptors (GHR), which mediate GH-induced IGF expression. First, we verified that GH (50nM) has a classical stimulatory effect on IGF-1 and additionally show it stimulates IGF-2 transcription in hepatocytes. Leptin (5 and/or 50nM) directly stimulated in vitro GHR2 gene expression within 8h of exposure, and both GHR1 and GHR2 as well as IGF-1 and IGF-2 gene expression after 24h. Cells were then co-incubated with submaximal concentrations of leptin and GH (25nM each) to test if they had a synergistic effect on IGF gene expression, possibly through increased GH sensitivity following GHR upregulation by leptin. In combination, however, the treatments only had an additive effect on stimulating IGF-1 mRNA despite their capacity to increase GHR mRNA abundance. This suggests that leptin’s stimulatory effect on GHRs may be limited to enhancing transcription or mRNA stability rather than inducing full translation of functional receptors, at least within a 24-h time frame. Finally, leptin was injected IP (100ng/g and 1μg/gBW) to test the in vivo regulation of hepatic IGF-1 and GHR1 gene expression. The 100ng/g BW leptin dose significantly upregulated in vivo IGF-1 mRNA levels relative to controls after 24h of fasting, but neither dosage was effective at regulating GHR1 gene expression. These studies suggest that stimulation of growth axis component transcripts by leptin may be an important mechanism for coordinating somatic growth with nutritional state in these and perhaps other fish or vertebrates, and represent the first evidence of leptin regulating GHRs in vertebrates.
Water salinity and postprandial effects on transcription of peptide and amino acid transporters in the kidney of Mozambique tilapia (Oreochromis mossambicus)
Aquaculture, Volume 536, 2021, Article 736384
Preservation of amino acids is highly important, as these are vital nutrients that support many physiological and biochemical processes. During fish osmoregulation, the kidney reabsorbs amino acids and short peptides that are filtered from the blood into the nephron. However, little is known about reabsorption systems in teleost kidney. To identify transporters involved in this process, we examined by PCR the expression of eight genes, coding to peptide and amino acid transporters, as well as of two ion transport systems, in the kidney of the euryhaline Mozambique tilapia (Oreochromis mossambicus). We found that three amino acid transporters (slc1a5, ASCT2; slc7a9, b0,+AT; slc6a19, B0AT) and one peptide transporter (slc15a2, PepT2) were expressed in the kidney, as were the two ion transporters VHA and NHE3 (coded by atp6v1a and slc9a3, respectively). Next, to investigate transcriptional interactions of these transporters with osmoregulation and nutritional status, we compared by qPCR expression levels in fish acclimated to either fresh or saltwater and at three time points after feeding (6, 24, 72h). Significant effect of salinity was detected on the expression of ASCT2 and VHA, whereas time after feeding affected PepT2 and VHA transcripts. Interactions between salinity and feeding significantly affected NHE3 transcription. PepT2 expression was an order of magnitude higher than free amino acid transporters, indicating the importance of peptide reabsorption in the kidney of Mozambique tilapia. Immunofluorescence staining of PepT2 showed an apical staining while, b0,+AT antibody stained the basolateral membrane of the nephrons epithelial cells. The two transporters expression were found in separates segment of the nephrons. These results reveal specific transporters involved in kidney reabsorption of amino acids and short peptides and their response to the fish osmotic and nutritional status.
Copyright © 1996 Academic Press. All rights reserved.