Na+/K+-ATPase expression

In this study we assessed the influence of three different environmental salinities (5, 15 and 31 psu during 90 days) on growth, osmoregulation, energy metabolism and digestive capacity in juveniles of the Notothenioid fish Eleginops maclovinus. At the end of experimental time samples of plasma, liver, gill, intestine, kidney, skeletal muscle, stomach and pyloric caeca were obtained. Growth, weight gain, hepatosomatic index and specific growth rate increased at 15 and 31 psu and were lower at 5 psu salinity. Gill Na ? , K ?-ATPase (NKA) activity presented a ''U-shaped'' relationship respect to salinity, with its minimum rates at 15 psu, while this activity correlated negatively with salinity at both anterior and posterior intestinal portions. No significant changes in NKA activity were observed in kidney or mid intestine. Large changes in plasma, metabolite levels and enzymatic activities related to energy metabolism in liver, gill, intestine, kidney and muscle were generally found in the groups exposed to 5 and 31 psu compared to the 15 psu group. Only the pepsin activity (digestive enzymes) assessed enhanced with environmental salinity, while pyloric caeca trypsin/ chymotrypsin ratio decreased. This study suggests that juvenile of E. maclovinus presents greater growth near its iso-osmotic point (15 psu) and hyperosmotic environment (31 psu). Acclimation to low salinity increased the osmoregulatory expenditure as seen by the gill and anterior intestine results, while at high salinity, branchial osmoregulatory activity was also enhanced. This requires the mobilization of lipid stores and amino acids, thereby holding the growth of fish back. The subsequent reallocation of energy sources was not sufficient to maintain the growth rate

The meagre (Argyrosomus regius), a farmed fish in Mediterranean countries, seasonally migrates from offshore areas to estuaries for reproduction. During the first two years of life, the meagre evidences a certain grade of euryhalinity by staying in brackish waters close to the shore. The aim of the present study was to establish if fingerling growth in brackish water is improved compared to seawater, where current culture procedures are conducted. Three-month-old fingerlings were maintained for 45 days under two different salinity regimens (12 and 39 ppt). Several growth parameters as well as osmoregulatory and metabolic variables were assessed. Specific growth rate and hepatosomatic index values revealed that fingerlings performed better in brackish waters (12 ppt) compared to 39 ppt. This study contributes to optimizing meagre rearing conditions, thereby supporting the role of A. regius in aquaculture diversification.

Inanga (Galaxias maculatus) is an amphidromous fish, capable of moving freely between waters of different salinities. The impact of environmental salinity on inanga physiology was investigated by examining ionic and osmotic regulation, nitrogen excretion, oxygen metabolism and energy expenditure. After 16 days of acclimation to salinities ranging from freshwater to 43, inanga showed only minor changes in plasma osmolality and no significant changes in metabolic rate or calculated energy expenditure, underlining their high salinity tolerance. Decreases in ammonia excretion at salinities close to the isosmotic point, and variation in oxygen to nitrogen ratios did, however, suggest changes in fuel use. Partitioning studies isolating the head from the body indicated that there was no trade-off between oxygen consumption and nitrogen excretion functions in the gills of inanga with salinity. Although extra-branchial epithelia (i.e. skin and/or kidney) were significant contributors to both gas exchange and ammonia excretion (e.g.~35% of ammonia excretion was extra-branchial), these contributions were independent of salinity. These data suggest that inanga do not incur significant physiological costs following acclimation to a wide range of environmental salinities, but that there may be subtle physiological advantages to inhabiting salinities close to their isosmotic point.

Anadromy is a distinctive life-history strategy in fishes that has evolved independently many times. In an evolutionary context, the benefits of anadromy for a species or population must outweigh the costs and risks associated with the habitat switch. The migration of fish across the freshwater-ocean boundary coincides with potentially energetically costly osmoregulatory modifications occurring at numerous levels of biological organization. By integrating whole animal and sub-cellular metabolic measurements, this study presents significant findings demonstrating how an anadromous salmonid (i.e. rainbow trout, Oncorhynchus mykiss) is able to transform from a hyper- to hypo-osmoregulatory state without incurring significant increases in whole animal oxygen consumption rate. Instead, underlying metabolic mechanisms that fuel the osmoregulatory machinery at the organ level (i.e. intestine) are modulated, as mitochondrial coupling and anaerobic metabolism are increased to satisfy the ele...

An inverse and unusual relationship was found between preferred temperature and acclimation temperature in the bullseye puffer, Sphoeroides annulatus. The final preferendum temperature (PT) was 26.8 1C. The critical thermal maxima (CTMax) were 37.7, 38.8, 40.0, 40.8 and 41.3 1C where the temperatures of acclimation were 19, 22, 25, 28 and 31 1C 7 1 1C, respectively, and the endpoint of CTMax was loss of the righting response. The acclimation response ratio presented an interval of 0.22-0.38; these values are in agreement with results for other subtropical and tropical fishes. The temperature significantly affected the oxygen consumption of bullseye puffer juveniles. The oxygen consumption rate (OCR) increased significantly with an increment in the temperature from 19 to 31 1C. The range of the temperature coefficient Q 10 in bullseye puffer individuals was lowest between 25 and 28 1C, at 1.37. The optimal temperature for growth was 26 1C. The results of this study will be useful for optimizing the culture of bullseye puffer juveniles in controlled conditions.

The energy allocation from food consumption (C) to fecal losses (F), routine oxygen consumption (Rr), ammonia excretion (U) and body mass production (P) was assessed in juveniles of Centropomus parallelus acclimated for 15 and 30 days to 5, 20 and 30 salinities, and temperature of 21º C. Oxygen consumption and ammonia excretion were linear related to fish wet weight and differences were significant either between salinities and acclimation periods. The body mass production suggests this salinity range as better conditions for rearing C. parallelus at this stage of life cycle. The energy balance as food consumption ranged from: 101.86 to 105.43%; 79.85 to 92.90%; 91.16 to 111.66%, at salinities 5, 20 and 30, respectively. This energy balance was comprised with metabolic maintenance that expended from 40 to 70% and with 20 to 42% saved as body mass production, in accordance to the salinity and period of acclimation. The energy lost as feces and ammonia excretion represented ca. of 8.7...

The energy allocation from food consumption (C) to fecal losses (F), routine oxygen consumption (Rr), ammonia excretion (U) and body mass production (P) was assessed in juveniles of Centropomus parallelus acclimated for 15 and 30 days to 5, 20 and 30 salinities, and temperature of 21º C. Oxygen consumption and ammonia excretion were linear related to fish wet weight and differences were significant either between salinities and acclimation periods. The body mass production suggests this salinity range as better conditions for rearing C. parallelus at this stage of life cycle. The energy balance as food consumption ranged from: 101.86 to 105.43%; 79.85 to 92.90%; 91.16 to 111.66%, at salinities 5, 20 and 30, respectively. This energy balance was comprised with metabolic maintenance that expended from 40 to 70% and with 20 to 42% saved as body mass production, in accordance to the salinity and period of acclimation. The energy lost as feces and ammonia excretion represented ca. of 8.7...

The meagre (Argyrosomus regius), a farmed fish in Mediterranean countries, seasonally migrates from offshore areas to estuaries for reproduction. During the first two years of life, the meagre evidences a certain grade of euryhalinity by staying in brackish waters close to the shore. The aim of the present study was to establish if fingerling growth in brackish water is improved compared to seawater, where current culture procedures are conducted. Three-month-old fingerlings were maintained for 45 days under two different salinity regimens (12 and 39 ppt). Several growth parameters as well as osmoregulatory and metabolic variables were assessed. Specific growth rate and hepatosomatic index values revealed that fingerlings performed better in brackish waters (12 ppt) compared to 39 ppt. This study contributes to optimizing meagre rearing conditions, thereby supporting the role of A. regius in aquaculture diversification.

An inverse and unusual relationship was found between preferred temperature and acclimation temperature in the bullseye puffer, Sphoeroides annulatus. The final preferendum temperature (PT) was 26.8 1C. The critical thermal maxima (CTMax) were 37.7, 38.8, 40.0, 40.8 and 41.3 1C where the temperatures of acclimation were 19, 22, 25, 28 and 31 1C 7 1 1C, respectively, and the endpoint of CTMax was loss of the righting response. The acclimation response ratio presented an interval of 0.22-0.38; these values are in agreement with results for other subtropical and tropical fishes. The temperature significantly affected the oxygen consumption of bullseye puffer juveniles. The oxygen consumption rate (OCR) increased significantly with an increment in the temperature from 19 to 31 1C. The range of the temperature coefficient Q 10 in bullseye puffer individuals was lowest between 25 and 28 1C, at 1.37. The optimal temperature for growth was 26 1C. The results of this study will be useful for optimizing the culture of bullseye puffer juveniles in controlled conditions.

Anemia is one of the most common cause of malnutrition, has a major community health significance affecting adolescent girls, women and children worldwide. Anemia highly prevalent among adolescent girls of Indian population mainly from lower socioeconomic status. This study was done with the intention of finding an efficient substitute in the form of non-haem iron of vegetable origin in drumstick leaves by administering as supplementation to treat anemia. Randomized clinical trial design was used in this study, the target group consisted adolescent girls with mild and moderate anemia. 12 (Experimental n=6, Control n=6) adolescent girls with their hemoglobin level between 9-12 gm/dl were selected as samples. Intervention was started with one tea spoon (about 5gm) dried drumstick leaves powder supplementation once a day with meals for 30 days to the experimental group. At the end of intervention, the posttest hemoglobin level was assessed. The result revealed that the subject showed a significant improvement in Hb level at (p<0.001 level), drumstick leaves powder had significantly improved mean Hb levels in the posttest from (10.7167±0.25) to (11.1000±0.32) gm/dl.

The euryhaline milkfish (Chanos chanos) is an excellent subject for studies of the physiological and behavioral processes involved in salinity adaptation. In this study, energy partitioning for metabolism, activity and growth, maximal activity performance and blood osmotic concentrations were assessed at two activity levels in juvenile milkfish fed equal rations and maintained at a relatively constant temperature (26±2 °C) and at salinities (15, 35 and 55 ‰) that represented a wide range of osmoregulatory challenges. Changes in the measured parameters were not consistently related to the magnitude of the trans-integumentary osmotic gradients. Routine oxygen consumption rates were high in 35 ‰ salinity (mean ±1 S.E.M. 167±8 mg O2 kg−1 h−1) and comparably low in 15 and 55 ‰ salinity (133±6 and 127±3 mg O2 kg−1 h−1, respectively). Routine activity levels (relative swimming velocity) were highest in 35 ‰ salinity (0.96±0.04 L s−1), where L is standard length, intermediate in 15 ‰ salini...

Background Salinity is an ecological factor with considerable importance for teleosts. A change in salinity can alter the osmotic pressure between medium and body fluid, causing osmoregulation directly in teleosts. Na +-K +-ATPase (NKA) is a membrane-spanning enzyme that actively transports Na + out of ionocytes and K + into ionocytes; this enzyme maintains osmotic equilibrium by providing a driving force for other ion-transporting systems (

Routine oxygen consumption rates ofjuvenile spot, Leiostornus xanthurus, were measured over a range of temperatures, salinities and fish weights. As predicted, QO, increased with temperature and decreased with body weight. However, QO, decreased with decreasing salinity and did not show the expected minimum at isosmotic concentrations. The data are best described by the relationship: log,, QO, (mg 0, g-' h-')=0.129 log,, salinity (oh)+ 1.604 log,, temperature (" C)-0.140 log,, (g)-2'767.

Tilapia were acclimated to the water source which had 8 precipitation (ppt) of salinity in the experimental unit before the experiment started and then, they were transfered to five different saltwater (SW) treatments: SW (8 ppt), 50% SW (12 ppt), 100% SW (16 ppt), 150% SW (20 ppt), and 200% SW (24 ppt). The objectives of this study were; to investigate the effects of five different salinities on specific growth rate (SGR), weight gain (WG), food intake (FI) and survival of tilapia in the long term trial (30 days) and find out how salinity affects muscle water content, hematosomatic index (HSI), and blood chemistry (sodium, chloride, potassium, glucose, total protein and triglycerides) in the short term trial (6 to 12 h). In the long-term trial, six fish were stocked in each aquarium. They were fed with commercial feed (Bagcı trout) to satiation twice a day and individually weighed at ten-days interval. Growth rate was highest in the 50% SW (SGR 0.95 ± 0.18% per day); there was no significant difference among the first three treatments. Growth rate was lowest in 200% SW (SGR 0.23 ± 0.08% per day). Weight gain and food intake showed identical results as SGR. Survival was high in the first three groups (72.2 ±1 9.2 to 100.0 ± 0.0) but it was lowest in the 200% SW treatment (22.2±19.2%). In the short-term trial, six tilapia were placed per aquarium. They were exposed to SW, 50, 100, 150 and 200% SW treatments and the fish were gradually acclimated to salt water. Blood samples were taken to analyse plasma sodium, chloride, potassium, total protein and triglycerides. Liver and muscle samples were collected for HSI and moisture values. Plasma sodium chloride increased in parallel with salinity rise. Total protein and triglycerides significantly reduced as salinity increased. Glucose and potassium were not altered significantly. HSI and muscle water content decreased when salinity concentration was elevated. Blood chemistry demonstrated that isosmotic water concentration was between 8 and 12 ppt. Salinity did not affect HSI and moisture until it reached as much as 16 ppt (100% SW). The results show that the optimum condition for farming blue tilapia, Oreochromis aureus, both with respect to growth rate and metabolic parameters is at salinities lower than 12 ppt. This is an important finding for the tilapia industry.

Anadromy is a distinctive life-history strategy in fishes that has evolved independently many times. In an evolutionary context, the benefits of anadromy for a species or population must outweigh the costs and risks associated with the habitat switch. The migration of fish across the freshwater-ocean boundary coincides with potentially energetically costly osmoregulatory modifications occurring at numerous levels of biological organization. By integrating whole animal and sub-cellular metabolic measurements, this study presents significant findings demonstrating how an anadromous salmonid (i.e. rainbow trout, Oncorhynchus mykiss) is able to transform from a hyper- to hypo-osmoregulatory state without incurring significant increases in whole animal oxygen consumption rate. Instead, underlying metabolic mechanisms that fuel the osmoregulatory machinery at the organ level (i.e. intestine) are modulated, as mitochondrial coupling and anaerobic metabolism are increased to satisfy the ele...

Objectives: This study aims to study some hematologic parameters, here, the packed cell volume (PCV), the red blood cell (RBC) count, hemoglobin concentration (HC) and white blood cell (WBC) count in residents of Offa in Kwara state, Nigeria. Methods: Blood samples of healthy male and female Offa indigenes were analyzed for RBC count, PCV, HC and WBC count. Results: The mean HC was 14.6 and 13.71 g/dl of blood, for both males and females respectively, while the mean PCV was 43.1% and 40.4% for both males and females, respectively. The mean RBC count for males was 5.45 x 166 cells per mm3 while that of females was 4.55 x 106 / mm3. Conclusion: All values investigated were lower than that for Caucasians. The probable causes of the differences between the above values as compared to those of the western world were also discussed. Bangladesh Journal of Medical Science Vol. 12 No. 02 April’13 Page 180-185 DOI: http://dx.doi.org/10.3329/bjms.v12i2.14947

Persian sturgeon, Acipenser persicus juveniles are annually produced and released (2-3g body weight) to the estuaries surrounding the southern parts of the Caspian Sea by hatchery centers. However, juveniles cannot withstand the salinity stress and the majority of them die before entering the Caspian Sea. In order to improve the salinity acclimation in Persian sturgeon juveniles weighing less than 2 g (1.62 ± 0.27 g; 7.4 ± 0.58 cm), the fish were treated with cortisol bath method using three different concentrations; 3, 5 and 7 mg L-1 for 24 h in freshwater. The fish were then directly transferred from freshwater to the Caspian Sea water (11‰) and sampled after 1, 4 and 9 days post-transfer. Daily mortality was recorded. Plasma osmolality, changes in the abundance and size of the Na+-K+-ATPase immunoreactive fluorescence chloride cells within the gill epithelium of the juveniles were determined. In spite of lower mortality in fish treated with higher concentrations of cortisol, plas...

Persian sturgeon, Acipenser persicus juveniles are annually produced and released (2-3g body weight) to the estuaries surrounding the southern parts of the Caspian Sea by hatchery centers. However, juveniles cannot withstand the salinity stress and the majority of them die before entering the Caspian Sea. In order to improve the salinity acclimation in Persian sturgeon juveniles weighing less than 2 g (1.62 ± 0.27 g; 7.4 ± 0.58 cm), the fish were treated with cortisol bath method using three different concentrations; 3, 5 and 7 mg L-1 for 24 h in freshwater. The fish were then directly transferred from freshwater to the Caspian Sea water (11‰) and sampled after 1, 4 and 9 days post-transfer. Daily mortality was recorded. Plasma osmolality, changes in the abundance and size of the Na +-K +-ATPase immunoreactive fluorescence chloride cells within the gill epithelium of the juveniles were determined. In spite of lower mortality in fish treated with higher concentrations of cortisol, plasma osmolality, chloride cells number and size in treated fish exhibited the same trends as the control (untreated) fish after 9-day post-transfer. In conclusion, cortisol treatment alone, is not directly implicated in osmoregulation and had no effect on Persian sturgeon juveniles to improve their salinity tolerance.

A physiological study was performed to explore the effects in Sphoeroides annulatus (Jenyns 1842) juveniles of exposure to different salinities 10, 17, 23, 29, 35 and 41& on oxygen consumption rate (OCR), ammonium excretion rate (AER), the oxygen-nitrogen atomic ratio (O:N), osmoregulation and Na + /K +-ATPase expression. The OCR values ranged from 27.9 to 30.9 mg O 2 h À1 kg À1 , displaying a Type 1 response pattern Kinne (1977). AER ranged from 0.60 to 0.69 mg NH þ 4 h À1 kg À1 , and O:N values were from 53.12 to 59.26, indicating that the puffers use proteins and lipids as an energy-substrate. Osmoregulation in S. annulatus was hyposmotic in salinities of 23, 29, 35 and 41& and hyperosmotic in a salinity of 10&. The isosmotic point of the bullseye puffer was 356 mmol kg À1 (10.5&). The enzyme expression analysis indicates that the fish acclimated to 41& had the highest Na + /K +-ATPase expression level, whereas, the lowest expression level was found close to the isosmotic point. Na + /K +-ATPase expression in the gills was found to have a U-shaped relationship with environmental salinity. We conclude that the bullseye puffer is strongly euryhaline and can be cultivated in a wide range of environments that has important economic implications.

Background-Enhanced late inward Na current (I Na-L) modulates action potential duration (APD) and plays a key role in the genesis of early and delayed afterdepolarizations (EADs & DADs) and triggered activity. Objectives-To define the influence of selective block of the I Na-L on EAD-& DAD-mediated triggered ventricular tachycardia and fibrillation (VT & VF) in intact hearts using (GS967), a selective and potent (IC 50 =0.13±0.01 μM) blocker of the I Na-L. Methods-VT/VF were induced either by local aconitine injection (50 μg) in the LV muscle of adult (3-4 months) male rats (N=21) or by arterial perfusion of 0.1 mM H 2 O 2 in aged male rats (24-26 months, N=16). The LV epicardial surface of the isolated-perfused hearts was optically mapped using fluorescent voltage-sensitive dye, and microelectrode recordings of APs were made adjacent to the aconitine injection site. The suppressive and preventive effects of GS967 (1 μM) against EAD/DAD-mediated VT/VF were then determined. Results-Aconitine induced VT in all 13 hearts studied. Activation map (N=6) showed that the VT was initiated by a focal activity arising from the aconitine injection site (CLs of 84±12) that degenerated to VF (CL=52±8 ms) within a few seconds. VF was maintained by multifocal activity with occasional incomplete reentrant wavefronts. Administration of GS967 suppressed the VT/VF in 10 out of 13 hearts (P<0.001). Pre-exposure to GS967 for 15 min prior to aconitine injection prevented the initiation of VT/VF in 5 of 8 additional hearts (P<0.02). The VF reoccurred within 10 min upon washout of GS967. Microelectrode recordings (N=7) showed that the VT/VF was initiated by EAD-and DAD-mediated triggered activity at CL of 86±14ms (NS from VT CL) that preceded the VF. GS967 shortened the AP duration (APD), flattened the slope of the dynamic APD restitution curve and reduced APD dispersion from 42±12 ms to 8±3 ms (P<0.01). H 2 O 2

The gills of teleost fishes are responsible both for gas exchangein respiration and salt transport in osmoregulation (JOBLING,  1995; ZADUNAISKY, 1996; PERRY, 1997; VAN DER HEIJDEN et al., 1997; EVANS et al., 1999; EVANS et al., 2005). In marine teleosts the gill epithelium secretes salt mainly through chloride cells (JOBLING, 1995; ZADUNAISKY, 1996; PERRY, 1997; VAN DER HEIJDEN et al., 1997; FERNANDES et al., 1998; EVANS et al., 2005). These cells are typically located between secondary lamellae at their insertion in the gill filament (inter-lamellar region) or in the gill filament itself (LAURENT & DUNEL, 1980; PERRY, 1997; FERNANDES et al., 1998; EVANS et al., 2005). These cells are rounded, display abundant mitochondria, a tubular system of endomembranes, sub-apical vesicles, and extensive intercellular junctional complexes (LAURENT…

The marine-estuarine species of pufferfishes Sphoeroides testudineus and S. greeleyi are very efficient osmoregulators. However, they differ with respect to their tolerance of salinity reduction. During low tide S. testudineus remains in diluted estuarine waters, whereas S. greeleyi returns to seawater (SW). The hypothesis tested here was that the short-term mobilization of metabolic substrates stored in their main osmoregulatory organs would correlate with this differential tolerance. Fishes exposed to 5‰ (for 6 h) were compared to those kept in 35‰. Branchial and renal contents of triglycerides, protein and glycogen were evaluated, and total ATPase activity accounted for the tissues&#39; metabolism. Plasma osmolality, chloride and glucose, hematocrit, and muscle water content were also measured. Total triacylglycerol content was higher in S. greeleyi than in S. testudineus in both salinities and in both organs. Kidney glycogen contents were higher in S. greeleyi than in S. testudi...

2q often hypo-regulated 20-35‰. In contrast, Mg was strongly hypo-regulated in all salinities. According to their distribution records in nature, S. greeleyi was less able to tolerate strong sea water dilution, showing mortality after 5 days in 5‰ water. These estuarine pufferfishes are thus efficient regulators of plasma ionic concentrations in diluted sea water, as expected from their occupation of estuaries. The experiments have supported the distribution records of both species in the estuarine complex and resident estuarine species were thus characterized with respect to their osmoregulatory capacities.

Persian sturgeon, Acipenser persicus juveniles are annually produced and released (2-3g body weight) to the estuaries surrounding the southern parts of the Caspian Sea by hatchery centers. However, juveniles cannot withstand the salinity stress and the majority of them die before entering the Caspian Sea. In order to improve the salinity acclimation in Persian sturgeon juveniles weighing less than 2 g (1.62 ± 0.27 g; 7.4 ± 0.58 cm), the fish were treated with cortisol bath method using three different concentrations; 3, 5 and 7 mg L-1 for 24 h in freshwater. The fish were then directly transferred from freshwater to the Caspian Sea water (11‰) and sampled after 1, 4 and 9 days post-transfer. Daily mortality was recorded. Plasma osmolality, changes in the abundance and size of the Na+-K+-ATPase immunoreactive fluorescence chloride cells within the gill epithelium of the juveniles were determined. In spite of lower mortality in fish treated with higher concentrations of cortisol, plas...

Background-Enhanced late inward Na current (I Na-L) modulates action potential duration (APD) and plays a key role in the genesis of early and delayed afterdepolarizations (EADs & DADs) and triggered activity. Objectives-To define the influence of selective block of the I Na-L on EAD-& DAD-mediated triggered ventricular tachycardia and fibrillation (VT & VF) in intact hearts using (GS967), a selective and potent (IC 50 =0.13±0.01 μM) blocker of the I Na-L. Methods-VT/VF were induced either by local aconitine injection (50 μg) in the LV muscle of adult (3-4 months) male rats (N=21) or by arterial perfusion of 0.1 mM H 2 O 2 in aged male rats (24-26 months, N=16). The LV epicardial surface of the isolated-perfused hearts was optically mapped using fluorescent voltage-sensitive dye, and microelectrode recordings of APs were made adjacent to the aconitine injection site. The suppressive and preventive effects of GS967 (1 μM) against EAD/DAD-mediated VT/VF were then determined. Results-Aconitine induced VT in all 13 hearts studied. Activation map (N=6) showed that the VT was initiated by a focal activity arising from the aconitine injection site (CLs of 84±12) that degenerated to VF (CL=52±8 ms) within a few seconds. VF was maintained by multifocal activity with occasional incomplete reentrant wavefronts. Administration of GS967 suppressed the VT/VF in 10 out of 13 hearts (P<0.001). Pre-exposure to GS967 for 15 min prior to aconitine injection prevented the initiation of VT/VF in 5 of 8 additional hearts (P<0.02). The VF reoccurred within 10 min upon washout of GS967. Microelectrode recordings (N=7) showed that the VT/VF was initiated by EAD-and DAD-mediated triggered activity at CL of 86±14ms (NS from VT CL) that preceded the VF. GS967 shortened the AP duration (APD), flattened the slope of the dynamic APD restitution curve and reduced APD dispersion from 42±12 ms to 8±3 ms (P<0.01). H 2 O 2

The energy allocation from food consumption (C) to fecal losses (F), routine oxygen consumption (Rr), ammonia excretion (U) and body mass production (P) was assessed in juveniles of Centropomus parallelus acclimated for 15 and 30 days to 5, 20 and 30 salinities, and temperature of 21º C. Oxygen consumption and ammonia excretion were linear related to fish wet weight and differences were significant either between salinities and acclimation periods. The body mass production suggests this salinity range as better conditions for rearing C. parallelus at this stage of life cycle. The energy balance as food consumption ranged from: 101.86 to 105.43%; 79.85 to 92.90%; 91.16 to 111.66%, at salinities 5, 20 and 30, respectively. This energy balance was comprised with metabolic maintenance that expended from 40 to 70% and with 20 to 42% saved as body mass production, in accordance to the salinity and period of acclimation. The energy lost as feces and ammonia excretion represented ca. of 8.7...

The energy allocation from food consumption (C) to fecal losses (F), routine oxygen consumption (Rr), ammonia excretion (U) and body mass production (P) was assessed in juveniles of Centropomus parallelus acclimated for 15 and 30 days to 5, 20 and 30 salinities, and temperature of 21º C. Oxygen consumption and ammonia excretion were linear related to fish wet weight and differences were significant either between salinities and acclimation periods. The body mass production suggests this salinity range as better conditions for rearing C. parallelus at this stage of life cycle. The energy balance as food consumption ranged from: 101.86 to 105.43%; 79.85 to 92.90%; 91.16 to 111.66%, at salinities 5, 20 and 30, respectively. This energy balance was comprised with metabolic maintenance that expended from 40 to 70% and with 20 to 42% saved as body mass production, in accordance to the salinity and period of acclimation. The energy lost as feces and ammonia excretion represented ca. of 8.7...

Aim: Hypokalaemia is associated with a lethal form of ventricular tachycardia (VT), torsade de pointes, through pathophysiological mechanisms requiring clarification. Methods: Left ventricular endocardial and epicardial monophasic action potentials were compared in isolated mouse hearts paced from the right ventricular epicardium perfused with hypokalaemic (3 and 4 mm [K + ] o) solutions. Corresponding K + currents were compared in whole-cell patchclamped epicardial and endocardial myocytes. Results: Hypokalaemia prolonged epicardial action potential durations (APD) from mean APD 90 s of 37.2 AE 1.7 ms (n ¼ 7) to 58.4 AE 4.1 ms (n ¼ 7) and 66.7 AE 2.1 ms (n ¼ 11) at 5.2, 4 and 3 mm [K + ] o respectively. Endocardial APD 90 s correspondingly increased from 51.6 AE 1.9 ms (n ¼ 7) to 62.8 AE 2.8 ms (n ¼ 7) and 62.9 AE 5.9 ms (n ¼ 11) giving reductions in endocardial-epicardial differences, DAPD 90 , from 14.4 AE 2.6 to 4.4 AE 5.0 and)3.4 AE 6.0 ms respectively. Early afterdepolarizations (EADs) occurred in epicardia in three of seven spontaneously beating hearts at 4 mm [K + ] o with triggered beats followed by episodes of non-sustained VT in nine of 11 preparations at 3 mm. Programmed electrical stimulation never induced arrhythmic events in preparations perfused with normokalemic solutions yet induced VT in two of seven and nine of 11 preparations at 4 and 3 mm [K + ] o respectively. Early outward K + current correspondingly fell from 73.46 AE 8.45 to 61.16AE6.14 pA/pF in isolated epicardial but not endocardial myocytes (n ¼ 9) (3 mm [K + ] o). Conclusions: Hypokalaemic mouse hearts recapitulate the clinical arrhythmogenic phenotype, demonstrating EADs and triggered beats that might initiate VT on the one hand and reduced transmural dispersion of repolarization reflected in DAPD 90 suggesting arrhythmogenic substrate on the other. Keywords arrhythmogenesis, hypokalaemia, mouse heart. Cardiac K + channels govern a range of important physiological functions that include heart rate and action potential (AP) waveform and duration (Tamargo et al. 2004). In particular, cardiac AP repolarization is regulated by a variety of K + channel currents that include the transient outward current, I to , the rapidly activating delayed rectifier current, I Kr , and the inwardly rectifying current, I K1. Reductions in outward

Background-Enhanced late inward Na current (I Na-L) modulates action potential duration (APD) and plays a key role in the genesis of early and delayed afterdepolarizations (EADs & DADs) and triggered activity. Objectives-To define the influence of selective block of the I Na-L on EAD-& DAD-mediated triggered ventricular tachycardia and fibrillation (VT & VF) in intact hearts using (GS967), a selective and potent (IC 50 =0.13±0.01 μM) blocker of the I Na-L. Methods-VT/VF were induced either by local aconitine injection (50 μg) in the LV muscle of adult (3-4 months) male rats (N=21) or by arterial perfusion of 0.1 mM H 2 O 2 in aged male rats (24-26 months, N=16). The LV epicardial surface of the isolated-perfused hearts was optically mapped using fluorescent voltage-sensitive dye, and microelectrode recordings of APs were made adjacent to the aconitine injection site. The suppressive and preventive effects of GS967 (1 μM) against EAD/DAD-mediated VT/VF were then determined. Results-Aconitine induced VT in all 13 hearts studied. Activation map (N=6) showed that the VT was initiated by a focal activity arising from the aconitine injection site (CLs of 84±12) that degenerated to VF (CL=52±8 ms) within a few seconds. VF was maintained by multifocal activity with occasional incomplete reentrant wavefronts. Administration of GS967 suppressed the VT/VF in 10 out of 13 hearts (P<0.001). Pre-exposure to GS967 for 15 min prior to aconitine injection prevented the initiation of VT/VF in 5 of 8 additional hearts (P<0.02). The VF reoccurred within 10 min upon washout of GS967. Microelectrode recordings (N=7) showed that the VT/VF was initiated by EAD-and DAD-mediated triggered activity at CL of 86±14ms (NS from VT CL) that preceded the VF. GS967 shortened the AP duration (APD), flattened the slope of the dynamic APD restitution curve and reduced APD dispersion from 42±12 ms to 8±3 ms (P<0.01). H 2 O 2

This study was carried out to determine the effects of gradual salinity increase on osmoregulatory ability of the Caspian roach Rutilus caspicus, under conditions which mimic stocking conditions of hatchery-raised fish. Initially, 30 juvenile fish (mean ± s.d. 3•20 ± 0•34 g) were transferred to 20 l circular tanks, in which salinities were changed in a stepwise fashion, from 0 to 5, 10 or 15 at 48 h intervals. The fish at salinity 15 were held for an additional 48 h at this salinity. Forty-eight hours after salinity transfer, survival rate, haematocrit, plasma Cl − , Na + and K + concentrations, osmolality and gill Na + /K +-ATPase (NKA) activity were measured. The only effect of exposure to 5 was a significant reduction in haematocrit compared to the freshwater control group. Exposure to salinity 10 raised haematocrit, Cl − and Na + concentrations and osmolality. At 48 h exposure to salinity 15, haematocrit, Cl − and Na + concentrations and osmolality were significantly higher than freshwater controls, and gill NKA activity was significantly lower, but the effect on NKA was no longer evident at 96 h exposure. There were no effects on survival. These results indicate that R. caspicus juveniles experience an initial non-lethal iono-osmotic perturbation following salinity increase but can adapt to brackish water at salinity 15.

Background: Sequel to the diverse diseases resulting in muscle mass degeneration and its key role in the prognosis of the diseases. For instance, currently, only resistance exercise can be used to promote recovery of mass/strength following disuse atrophy. But in contrast, many patients are unable or unwilling to exercise at a sufficient intensity to promote muscle growth. It would therefore be of great advantage to develop natural compounds that counteract the negative effects of skeletal muscle degenerative diseases especially in the form of therapeutic feed). The present study was aimed at elucidating the mechanism by which M. oleifera ameliorates skeletal muscle degeneration caused by malnutrition. Methods: The experimental animals were malnourished with low protein iso-caloric diets for four weeks after which they were treated with 25% M. oleifera leafbased diet, vitamin E supplemented feed and soy bean based-diet for another four weeks. Results: There was a significant reduction in the activity of calcium ATPase in the skeletal muscle of animals induced with skeletal muscle degeneration. However, this activity was significantly increased following treatments with the most significant increase observed in the skeletal muscle of animals treated with M. Oleifera leaf based diet followed by those fed with vitamin E supplemented diet. Conclusions: In summary, the study revealed that the mechanism by which M. oleifera leaf corrects muscle degeneration caused by PEM might be by increasing calcium ATPase activity and/ or its synthesis and by preventing oxidative stress due to its antioxidant properties.

Besides commercial aquaculture another major aim of sturgeon culture is in support of restocking programmes. Identifying the appropriate size, age and location for release of post-larvae or fingerlings is very important to achieve success. We investigated the potential acclimation ability of Acipenser persicus post larvae (245 ± 21.53 mg) to abrupt changes of salinity. Reared postlarvae (salinity 0.5) were exposed, either abruptly or gradually to brackish water (salinities: 2, 4, 6, 8, and approximately 12.5) for 5 days (120 h). Daily survival rate, gill chloride cell counts, and variation in glomeruli size were measured during exposure periods in both trails. These parameters were compared at the start and end of each trial. No mortality was observed during gradual adaptation to brackish water while chloride cell counts differed significantly (P < 0.05) at 6 ppt vs 12 ppt. In the gradual exposure trial, glomeruli sizes displayed a reduction with salinity increase from 8 to 12, this result was observed again between 96 and 120 h exposure to (12.5) in the abrupt exposure trial. In addition, post-larvae exposed to a gradual salinity increase had significantly higher final weights than those exposed to an abrupt salinity increase. Based on our result, it seems that A. persicus post-larvae exhibit some acclimation ability to gradual salinity change.

The objective of this study was to investigate the influence of size on salinity tolerance in 1 year old juvenile white sturgeon. Two sizes of sturgeon (10 and 30 g) from the same spawning event (thus reducing confounding effects of genetic make-up and size) and reared in the same environment were exposed to a salinity of 0, 8, 16, 24, or 32 ppt for up to 120 h. Both 10 and 30 g fish exhibited N 93% mortality within 24 h after transfer to 24 or 32 ppt, regardless of whether they were transferred directly from freshwater (FW) or following a 48 h pre-treatment period at 16 ppt. Direct transfer from FW to 16 ppt was associated with 25 to 30% mortality, indicating that these fish have some ability to tolerate large changes in salinity for up to 5 days at this stage. Following exposure to 8 and 16 ppt, an elevation in plasma osmolarity, [Na + ], and [Cl -] was observed between 24 and 72 h in both 10 and 30 g sturgeon, but plasma ions and osmolarity in surviving fish at 120 h were not significantly different between groups held at 0, 8, and 16 ppt. Despite being unprepared for either direct or stepwise transfer to salinities of 24 ppt or greater, size confers some ionoregulatory advantage, as mortality occurred more slowly and the degree of ionoregulatory perturbation was less in 30 g than 10 g fish over the course of the exposures. It is not known whether the apparent advantage of size is related to a size-dependent development of ionoregulatory capacity or due to social status which can also influence ionoregulatory capacity, but age and genetic differences did not likely contribute to this size effect.

The effect of salinity on survival, growth and activity of digestive enzymes was evaluated in the fat snook (Centropomus parallelus). Juveniles of 76 days after hatching (0.35 g) were reared at 5, 15 and 35 ppt, in triplicate, for 50 days, at 0.6 fish/l. Snook presented excellent survival (N 93.3%) at 5, 15 and 35 ppt, demonstrating the euryhalinity of the species. At the end of the experiment, no differences in weight and specific-growth rates (mean 1.8%/day) were observed, however, total and standard length values were higher at 15 ppt when compared to those at 5 ppt (P N 0.05). The best results in food conversion ratio (1.3) and digestive enzymes activity were obtained at 15 ppt. The activity of total alkaline proteinase was significantly affected at this salinity (0.124 ± 0.006 Δ absorbance 366 nm /min/ml/mg protein), being twofold and six-fold higher, compared to 35 and 5 ppt, respectively. The activity of total amylase was higher at 15 and 35 ppt (mean 0.016 ± 0.001 μmol reducing sugar/min/ml/mg protein), compared to 5 ppt (P b 0.05). Results indicate that fat snook reared at 15 ppt presented a higher potential for a more efficient digestibility and nutrient absorption, especially proteins. Additionally, at this salinity, the energetic demand for osmoregulation is probably reduced by the isosmotic medium, leading to growth enhancement. In terms of production costs, feeding expenses can be lowered at this salinity due to a better food conversion ratio.

In euryhaline teleosts, osmoregulatory mechanisms vary with osmotic stresses, and heat shock proteins (HSPs) play a central role in maintaining cellular homeostasis. The present study aimed to investigate the expression and potential roles of HSP70 and HSP90 in the gills of seawater (SW)-and freshwater (FW)-acclimated milkfish (Chanos chanos). Four HSP genes, including Cchsc70 (heat shock cognate 70), Cchsp70, Cchsp90α, and Cchsp90β, were analyzed in milkfish gills. Among these genes, only the mRNA abundance of branchial Cchsp90α was significantly lower in the FW-acclimated than in the SW-acclimated milkfish. Immunoblotting showed no significant difference in the relative protein abundance of branchial HSP70 and HSP90 between the two groups. The time-course experiments (from SW to FW) showed that the protein abundance of HSP70 and HSP90 at the 3 h and 6 h post-transfer and then declined gradually. To further illustrate the potential osmoregulatory roles of HSP70 and HSP90, their interaction with Na + , K +-ATPase (NKA, the primary driving force for osmoregulation) was analyzed using co-immunoprecipitation. The results showed the interaction between HSP70, HSP90 and NKA after acclimation to SW or FW increased within 3 h; and then returned to normal levels within 7 days. To our knowledge, the present study was the first to demonstrate that the interaction between HSP70, HSP90 and NKA changes with hypotonic stress in euryhaline teleosts. Before the transfer, no interaction was detected. When transferred to FW from SW, the interaction of HSP70 and HSP90 with NKA were detected. The results suggested that HSP70 and HSP90 participated in the acute responses of osmoregulatory mechanisms to protect branchial NKA from hypotonic stress in milkfish.

Besides commercial aquaculture another major aim of sturgeon culture is in support of restocking programmes. Identifying the appropriate size, age and location for release of post-larvae or fingerlings is very important to achieve success. We investigated the potential acclimation ability of Acipenser persicus post larvae (245 ± 21.53 mg) to abrupt changes of salinity. Reared postlarvae (salinity 0.5) were exposed, either abruptly or gradually to brackish water (salinities: 2, 4, 6, 8, and approximately 12.5) for 5 days (120 h). Daily survival rate, gill chloride cell counts, and variation in glomeruli size were measured during exposure periods in both trails. These parameters were compared at the start and end of each trial. No mortality was observed during gradual adaptation to brackish water while chloride cell counts differed significantly (P < 0.05) at 6 ppt vs 12 ppt. In the gradual exposure trial, glomeruli sizes displayed a reduction with salinity increase from 8 to 12, this result was observed again between 96 and 120 h exposure to (12.5) in the abrupt exposure trial. In addition, post-larvae exposed to a gradual salinity increase had significantly higher final weights than those exposed to an abrupt salinity increase. Based on our result, it seems that A. persicus post-larvae exhibit some acclimation ability to gradual salinity change.

The effect of salinity on survival, growth and activity of digestive enzymes was evaluated in the fat snook (Centropomus parallelus). Juveniles of 76 days after hatching (0.35 g) were reared at 5, 15 and 35 ppt, in triplicate, for 50 days, at 0.6 fish/l. Snook presented excellent survival (N 93.3%) at 5, 15 and 35 ppt, demonstrating the euryhalinity of the species. At the end of the experiment, no differences in weight and specific-growth rates (mean 1.8%/day) were observed, however, total and standard length values were higher at 15 ppt when compared to those at 5 ppt (P N 0.05). The best results in food conversion ratio (1.3) and digestive enzymes activity were obtained at 15 ppt. The activity of total alkaline proteinase was significantly affected at this salinity (0.124 ± 0.006 Δ absorbance 366 nm /min/ml/mg protein), being twofold and six-fold higher, compared to 35 and 5 ppt, respectively. The activity of total amylase was higher at 15 and 35 ppt (mean 0.016 ± 0.001 μmol reducing sugar/min/ml/mg protein), compared to 5 ppt (P b 0.05). Results indicate that fat snook reared at 15 ppt presented a higher potential for a more efficient digestibility and nutrient absorption, especially proteins. Additionally, at this salinity, the energetic demand for osmoregulation is probably reduced by the isosmotic medium, leading to growth enhancement. In terms of production costs, feeding expenses can be lowered at this salinity due to a better food conversion ratio.

The size and number of chloride cells and serum ion concentrations in kutum, Rutillus frisii kutum Nordman, from brackish (Caspian Sea) and fresh water (Khoshkrood River) environments were studied to gain a better understanding of osmoregulation in this species. Twenty mature kutum specimens were collected from the Caspian Sea (Anzali coasts, 8.49 ppt salinity and 12.4°C temperature) and 20 specimens from Khoshkrood River (0.18 ppt salinity and 18°C temperature). Gill samples were analyzed histologically and concentrations of Na

Eff&s of temperature on aspects of ionic regulation in kidney and gills of Rut&s rut&s and Saluelinus a$inus were studied by a variety of techniques. 2. In the kidney tissue of coid acclimated R. rut&s, the maximal number of binding sites per mg protein (Bmax) and the activity of Na+, K+-ATPase, as well as tissue respiration increased significantly, whereas in S. alpinus no changes in these variables were observed. On the other hand, 86Rb+ efllux from kidney tissue was unaffected by temperature in R. rutiius, whereas it was about 60% lower in S. alpinus acclimated and measured at YC, than in specimens acclimated and measured at 15°C. 3. In both species, the activity of gill Na+, K+-ATPase was 1.5. to 2-fold higher in cold-acclimated than in warm-acclimated fish although Bmax decreased in R. r&us, but remained constant in S. alpinus. 4, Problems of ionic regulation are discussed with regard to differences in temperature sensitivity of passive flows and primary active transport of ions in the t&sues of poikilothermic animals. ~TRODU~ON Temperature plays a decisive role in the ionic regulation of poikilothe~s, one of the main reasons

Background-Hypokalemia is known to promote ventricular arrhythmias, especially in combination with class III antiarrhythmic drugs like dofetilide. Here, we evaluated the underlying molecular mechanisms. Methods and Results-Arrhythmias were recorded in isolated rabbit and rat hearts or patch-clamped ventricular myocytes exposed to hypokalemia (1.0-3.5 mmol/L) in the absence or presence of dofetilide (1 μmol/L). Spontaneous early afterdepolarizations (EADs) and ventricular tachycardia/fibrillation occurred in 50% of hearts at 2.7 mmol/L [K] in the absence of dofetilide and 3.3 mmol/L [K] in its presence. Pretreatment with the Ca-calmodulin kinase II (CaMKII) inhibitor KN-93, but not its inactive analogue KN-92, abolished EADs and hypokalemia-induced ventricular tachycardia/ fibrillation, as did the selective late Na current (I Na) blocker GS-967. In intact hearts, moderate hypokalemia (2.7 mmol/L) significantly increased tissue CaMKII activity. Computer modeling revealed that EAD generation by hypokalemia (with or without dofetilide) required Na-K pump inhibition to induce intracellular Na and Ca overload with consequent CaMKII activation enhancing late I Na and the L-type Ca current. K current suppression by hypokalemia and dofetilide alone in the absence of CaMKII activation were ineffective at causing EADs. Conclusions-We conclude that Na-K pump inhibition by even moderate hypokalemia plays a critical role in promoting EAD-mediated arrhythmias by inducing a positive feedback cycle activating CaMKII and enhancing late I Na. Class III antiarrhythmic drugs like dofetilide sensitize the heart to this positive feedback loop.

To quantify the salinity preference of juvenile green sturgeon Acipenser medirostris, two groups of A. medirostris [140 days post hatch (dph); total length (L T) 38•0-52•5 cm] were acclimated to either near fresh water (mean ± s.e. salinity = 3•2 ± 0•6) or full-strength salt water (34•1 ± 1•2) over 8 weeks. Following acclimation, the two groups were divided into experimental and control groups, where experimental A. medirostris from both freshwater and saltwater acclimations were individually introduced (200-220 dph) into a rectangular salinity-preference flume (maximum salinity gradient: 5-33). Control A. medirostris were presented with only their acclimation water (fresh water or salt water) on both sides of the flume. It was demonstrated that A. medirostris acclimated to both salt water and fresh water spent a significantly greater amount of time on the side of the testing area with the highest salinity concentration (P < 0•05 and P < 0•001, respectively) while control A. medirostris spent an equal amount of time on each side of the flume. These findings indicate that juvenile A. medirostris are not only capable of detecting salt water within the first year of their lives but perhaps are actively seeking out saline environments as they move through a watershed. Establishing A. medirostris salinity preferences provides a better understanding of the early life history of this threatened species, shedding light on possible outmigration timing.

As global change alters multiple environmental conditions, predicting species&#39; responses can be challenging without understanding how each environmental factor influences organismal performance. Approaches quantifying mechanistic relationships can greatly complement correlative field data, strengthening our abilities to forecast global change impacts. Substantial salinity increases are projected in the San Francisco Estuary, California, due to anthropogenic water diversion and climatic changes, where the critically endangered delta smelt (Hypomesus transpacificus) largely occurs in a low-salinity zone (LSZ), despite their ability to tolerate a much broader salinity range. In this study, we combined molecular and organismal measures to quantify the physiological mechanisms and sublethal responses involved in coping with salinity changes. Delta smelt utilize a suite of conserved molecular mechanisms to rapidly adjust their osmoregulatory physiology in response to salinity changes ...

Aquaculture in Europe aims to diversify and optimize fish farming. The meagre (Argyrosomus regius) arose as a promising species due to its fast growth rates and flesh quality. Thus, it is currently being produced in several Mediterranean countries, mainly in sea-cages and salt-marshes. However, although meagre naturally spend the first years of life in brackish waters, to date it is cultured in seawater. Here, we show that juveniles may not successfully face either freshwater or hyper-osmotic environments as high as 55 ppt salinity. We found that 55 ppt induced catabolism and mobilization of energy metabolites stored in the liver, probably to maintain its osmotic balance. Furthermore, we found that osmoregulatory tissues such as gills managed to maintain plasma osmolality levels without differences in meagre acclimated at 5, 12 and 39 ppt salinity. Our results demonstrate the euryhaline capacity of this species, highlighting that juveniles may be cultured in a wider range of salinit...

The population structure of Rutilus rutilus caspicus (Jakowlew, 1870) from two locations on the Iranian coastline and one location in Russia was investigated using microsatellite DNA markers. Genomic DNA from 90 specimens and seven loci with reasonable polymorphism were amplified using a PCR approach The results showed that the lowest mean number of alleles per locus (6.42) was observed in the Russian population and the highest (7) in the Gorgan Bay population. The observed heterozygosity in the Anzali Wetland (0.59) population was higher than the other populations in Iran (Gorgan Bay: 0.5) and Russia (0.52). Significant to highly significant deviations from Hardy-Weinberg expectations were found at more loci in Iranian populations than in the Russian. Population differentiation was modest among all populations. The highest and significant (0.044; p0.01) population differentiation (F st) value was between Iranian populations and Russian populations and the lowest and non-significant population differentiation (F st) value was between Iranian populations (0.012; p0.07). The estimated gene flow (N m) value between Iranian populations (Gorgan Bay and Anzali Wetland) across all the studied loci was the highest, while the N m value between Iranian and Russian population was the lowest.

Background Salinity is an ecological factor with considerable importance for teleosts. A change in salinity can alter the osmotic pressure between medium and body fluid, causing osmoregulation directly in teleosts. Na +-K +-ATPase (NKA) is a membrane-spanning enzyme that actively transports Na + out of ionocytes and K + into ionocytes; this enzyme maintains osmotic equilibrium by providing a driving force for other ion-transporting systems (

The effect of formalin exposure on subsequent saltwater tolerance was investigated in Caspian roach (Rutilus rutilus caspicus). Fish were subjected to 0 (control), 10, 15 and 25 ppm formalin over 0 (control), 12, 24 and 168 h (4×4 treatments; 6 tanks per treatment) as well as 25, 50, 100 and 150 ppm formalin over 0.5 and 1 h (4×2 treatments; 6 tanks per treatment). Thereafter, half of each treatment's tanks (3 tanks) were subjected to formalinfree freshwater and the rests were subjected to formalin-free saltwater (12 ppt NaCl) and mortality was recorded at 0, 72 and 168 h exposure. Results showed decrease in saltwaterinduced mortality with increase in formalin exposure from 12 to 168 h, particularly in fish exposed to 25 ppm formalin. However, increment in formalin exposure from 0.5 to 1 h caused increase in saltwater-induced mortality, particularly in formalin concentrations of 100 and 150 ppm. Increase in saltwater tolerance after 168 h formalin exposure might be due to adaptation mechanisms development or suppression in stress induced by formalin exposure. Decrease in saltwater tolerance after 1 h, compared to 0.5 h, formalin exposure might be due to cumulative effect of the two stressors (formalin and saltwater exposure).