Saline Acclimation Research Articles

The effect of chlorpyrifos on salinity acclimation of juvenile rainbow trout (Oncorhynchus mykiss)

As a part of their unique life cycle, most salmonids undergo a transition from fresh water to salt water requiring various adjustments in metabolism, osmoregulation and ion regulation. Exposure to pesticides may affect the acclimation of juvenile salmonids to salt water during downstream migration to estuaries. Using the Caspian Sea as a model waterbody, the present study aimed to determine how the toxicity of the organophosphate pesticide chlorpyrifos (CPF) impacts saline acclimation of rainbow trout (Oncorhynchus mykiss). We pre-exposed 4-month-old fish to nominal concentrations of 0, 20, 40, 80, 160 μg/L of CPF for seven days, and then gradually to salinity (12 ppt) for another seven days. Mortality, levels of cortisol, T3 and T4 in serum, and expression of genes involved in gill ion transport (Na+/K+ATPase α1a and α1b) and liver xenobiotic detoxification (Glutathione-S-Transferase pi, GST) were measured at day fourteen. Cortisol concentrations in serum were not changed by CPF exposure in freshwater, but serum T3 increased up to three fold relative to controls in freshwater. Following salinity acclimation, T3 and T4 concentrations in the serum were both increased up to 2.5 and 8.8 fold in animals treated with CPF followed by saltwater. Na+/K + ATPase α1a and α1b mRNA in gill were unchanged by CPF treatment in freshwater but trended higher in CPF-treated animals after salinity acclimation. Hepatic mRNA of GST was significantly increased following exposure to CPF but was unchanged after saltwater exposure. Although saltwater treatment reduced the acute lethality of CPF, changes in T3/T4 suggest sublethal impacts may occur in CPF-treated fish after they acclimate to Caspian seawater.

Metabolic cost of osmoregulation in a hypertonic environment in the invasive African clawed frog Xenopus laevis.

ABSTRACTStudies of aquatic invertebrates reveal that salinity affects feeding and growth rates, reproduction, survival, and diversity. Little is known, however, about how salinity impacts the energy budget of vertebrates and amphibians in particular. The few studies focused on this topic in vertebrates suggest that the ingestion of salts and the resulting osmoregulatory activity is energetically expensive. We analyzed the effect of saline acclimation on standard metabolic rates (SMR) and the activities of metabolic enzymes of internal organs and osmoregulatory variables (plasma osmolality and urea plasma level) in females of Xenopus laevis by means of acclimating individuals to an isosmotic (235 mOsm NaCl; ISO group) and hyper-osmotic (340 mOsm NaCl; HYP group) environment for 40 days. After acclimation, we found that total and mass-specific SMR was approximately 80% higher in the HYP group than those found in the ISO group. These changes were accompanied by higher citrate synthase activities in liver and heart in the HYP group than in the ISO group. Furthermore, we found a significant and positive correlation between metabolic rates and plasma urea, and citrate synthase activity in liver and heart. These results support the notion that the cost of osmoregulation is probably common in most animal species and suggest the existence of a functional association between metabolic rates and the adjustments in osmoregulatory physiology, such as blood distribution and urea synthesis.

Produced Water Treatment with Simultaneous Bioenergy Production Using Novel Bioelectrochemical Systems

The present study investigated the biological treatment of produced water in a microbial electrochemical cell (MXC). The main objectives were to develop a novel spiral microbial electrochemical cell (SMXC) and test its performance for produced water treatment under highly saline conditions (salinity>200000ppm). The bioelectrochemical performance of the system was also evaluated in terms of power and hydrogen production over time. The comparatively inexpensive material and ease of application increased the feasibility of the SMXC configuration for produced water treatment. Optimal SMXC performance as a microbial fuel cell was achieved at a maximum open circuit potential of 330mV, maximum power density of 0.65mWm−3, and internal resistance of 110kΩ. Hydrogen gas was generated in a SMXC as a microbial electrolysis cell at a rate of 400ml-H2m−3day−1 and showed a total hydrogen recovery of 0.18%. A consequential reduction in the organic content of produced water (about 90%) indicates efficient biological treatment without costly saline acclimation.

Transcriptome Profiling and Molecular Pathway Analysis of Genes in Association with Salinity Adaptation in Nile Tilapia Oreochromis niloticus.

Nile tilapia Oreochromis niloticus is a freshwater fish but can tolerate a wide range of salinities. The mechanism of salinity adaptation at the molecular level was studied using RNA-Seq to explore the molecular pathways in fish exposed to 0, 8, or 16 (practical salinity unit, psu). Based on the change of gene expressions, the differential genes unions from freshwater to saline water were classified into three categories. In the constant change category (1), steroid biosynthesis, steroid hormone biosynthesis, fat digestion and absorption, complement and coagulation cascades were significantly affected by salinity indicating the pivotal roles of sterol-related pathways in response to salinity stress. In the change-then-stable category (2), ribosomes, oxidative phosphorylation, signaling pathways for peroxisome proliferator activated receptors, and fat digestion and absorption changed significantly with increasing salinity, showing sensitivity to salinity variation in the environment and a responding threshold to salinity change. In the stable-then-change category (3), protein export, protein processing in endoplasmic reticulum, tight junction, thyroid hormone synthesis, antigen processing and presentation, glycolysis/gluconeogenesis and glycosaminoglycan biosynthesis—keratan sulfate were the significantly changed pathways, suggesting that these pathways were less sensitive to salinity variation. This study reveals fundamental mechanism of the molecular response to salinity adaptation in O. niloticus, and provides a general guidance to understand saline acclimation in O. niloticus.

Compensatory Adjustment in Chloride Cells During Salinity Adaptation in Mud Crab, Scylla serrata

Capacity acclimation is a measurement of understanding the degree of adaptation that take place in physiological activities or biological functions in altered environmental conditions. Precht and Prosser in different ways classified capacity acclimation due to alterations of environmental temperature with respect to various physiological processes in a variety of organisms. We hypothesized that the same may be applied to understand the degree of adaptation in various physiological processes of organisms due to change in the salinity or any other environmental parameters. In order to understand the adaptive capability or the degree of compensation in different saline environment in some of the physiological processes of chloride cells, the chloride cells from 1 psu and or 35 psu acclimated crabs were cultured further in vitro, in L-15 media maintained with 12 psu salinity for another 5 h without any mortality. Rate of ion transport across the chloride cell membrane, and the activity of ion transporting enzyme were recorded. Over compensation or perfect compensation in the transport rate of K+, Na+ and Ca++ ions, due to hypo saline as well as hyper saline acclimation, clearly indicates their role in maintaining the homeostasis in osmoregulatory processes during salinity adaptation. On the other hand, inverse compensation or partial compensation in the transport rate of Cl− ions and the activity of ATPases indicate about their involvement in adjusting the osmoregulatory processes in altered saline environment rather that contributing to adaptability processes during change in the environmental salinity.

Saline acclimation of striped mojarra Eugerres plumieri (Cuvier 1830) and optimal dosage of carp pituitary extract (CPE) to induce spawning

The main objective of the current study was to determine an optimal dosage of commercial carp pituitary extract (CPE) of the conventional heteroplastic hypophysation technique to induce spawning in the wild caught striped mojarra broodstock Eugerres plumieri under laboratory conditions. We also describe trials testing saline acclimation regimes (changes from 10‰ to 30‰) prior to hormonal induction. For saline acclimation, three treatments were performed: first and second treatments began 1-day after conditioning of broodstock fish with a total duration of the saline changes lasting 1-day and 2-days, respectively. The third treatment began 30-days after conditioning with a 7-day saline regime. After reaching 30‰, all fish from the first and second treatments died after the fourth and ninth days, respectively; while the fishes in the third treatment survived more than two years. These fish remain on public exhibit in the “Mundo Marino” Aquarium, Santa Marta, Colombia. Four treatments of hormonal induction were tested on females using a total concentration of 5-mg of CPE per kg of body weight: first, second and third treatments were applied in two hormonal doses that corresponded to 10%–90%, 30%–70% and 40%–60%, respectively, with time intervals between doses of 14-h for the first and second treatment and of 12-h for the third treatment. The fourth treatment was applied in four hormonal doses that it corresponded to 20%–20%–30%–30% with 12-h time intervals between doses. Only the fishes of the fourth treatment resisted the induction, continued to live and reached spawning artificially. Water temperature remained at 28 ± 1°C and at 30‰ salinity during the study. The “dry” method of fertilization was used. The fertilized eggs were incubated at 30‰ and 35‰ salinities. These eggs reached the Morula early stage, but were later attacked by protozoan. These results suggest that fast changes of saline and limited hormonal dosages do not offer effective results in Eugerres plumieri. This work provided fundamental procedures for the culture and maintenance of live broodstock for striped mojarra in saltwater and/or coastal lagoon habitats and provides an effective and viable dosage of CPE for artificial spawning and commercial production in this species.

Influences of sex and saline intake on diurnal changes in plasma melatonin and osmoregulatory hormones of Pekin ducks ( Anas platyrhynchos)

Melatonin (MT) inhibits salt gland secretion of Pekin ducks [Ching, A.C.T., Hughes, M.R., Poon, A.M.S., Pang, S.F., 1999. Melatonin receptors and melatonin inhibition of duck salt gland secretion. Gen. Comp. Endocrinol. 116, 229–240]. The present study examined simultaneous diurnal changes in plasma concentrations of MT and four osmoregulatory hormones of Pekin ducks to assess the possible interactions among these hormones that might contribute to inhibition of extrarenal salt secretion. The study compared diurnal changes in freshwater (FW) and saline-acclimated (SA) male and female ducks. We hypothesized plasma concentrations of osmoregulatory hormones: (1) differ between sexes (partially accepted); (2) vary diurnally (accepted, influenced by sex and treatment); (3) are correlated with MT (partially accepted); and their diurnal variation is affected by (4) sex (partially accepted); and (5) saline acclimation (partially accepted). We compared body mass, plasma osmolality (Osm pl), plasma volume, concentrations of plasma ions, and arginine vasotocin (AVT), angiotensin II (AII), prolactin, (PRL), and aldosterone (ALDO), in relation to plasma melatonin (MT). At night body mass increased in FW ducks and decreased in SA ducks. This likely reflects the higher plasma PRL concentration of female ducks and its middark increase only in SA ducks. Plasma volume increased at night in all but FW males. Plasma sodium and osmolality were higher in SA ducks and did not vary diurnally in either FW or SA ducks. Midday MT did not differ between males and females or between FW and SA ducks; at middark, all ducks, except FW females, increased MT. Midday AVT was higher in SA ducks. Only FW ducks increased AVT at middark. Changes in AVT and MT were positively correlated in males and negatively correlated in females. Males had higher AII and, at night, AII increased in SA ducks and decreased in FW ducks. AVT and AII were negatively correlated. ALDO was highly correlated with AII and unaffected by sex, saline, or time. At night, only AVT was elevated in FW ducks, while MT, AII, and PRL were elevated in SA ducks. FW and SA ducks appear to follow different, but equally effective, hormonal strategies to maintain osmotic homeostasis at night. We conclude that the effect of MT on salt gland secretion is probably a direct effect. These may be influenced by gender.

Effects of Cadmium Ingestion on Plasma and Osmoregulatory Hormone Concentrations in Male and Female Pekin Ducks

Effects of ingested cadmium (Cd) on body mass and plasma, urine, salt-gland secretion, and osmoregulatory hormone concentrations were assessed in male and female Pekin ducks, Anas platyrhynchos, acclimated to 450 mM NaCl over 6 wk and then held an additional 13 wk on 300 mM NaCl (prolonged saline exposure). Groups of six birds ate diets containing 0 (control), 50 (low-Cd diet), or 300 (high Cd diet) w g Cd/g food. Ducks that ingested Cd, especially females, lost body mass. Cadmium ingestion did not affect salt-gland secretion concentration. Control males had higher plasma osmolality and lower relative plasma volume. These increased in both sexes during saline acclimation. The high-Cd diet suppressed the increase in plasma osmolality in both sexes, but a rise in relative plasma volume occurred only in females. Following prolonged exposure to saline, plasma osmolality and relative plasma volume were reduced in control ducks but further elevated in ducks on the high-Cd diet. Cadmium ingestion suppressed the increase in urine osmolality that occurred in control ducks during saline acclimation. Neither saline acclimation nor Cd ingestion affected plasma concentrations of arginine vasotocin or prolactin. Arginine vasotocin was not correlated with plasma osmolality; prolactin was negatively correlated with plasma osmolality, but only in males. Cadmium suppressed the increase in angiotensin II that occurred at higher salinities in control and low-Cd males. This study examined the effects of gradually increasing body cadmium content on osmotic homeos-tasis. Cadmium affected plasma and urine, but not salt-gland secretion, concentrations and some of these responses were sexually disparate. Cadmium did not affect osmoregulatory hormones (arginine vasotocin and prolactin) by which observed changes in plasma concentration might have been influenced.

Effect of saline acclimation on body water and sodium compartmentalization in Pekin ducks (Anas platyrhynchos)

The compartmentalization of body fluids was measured in individual Pekin ducks ( Anas platyrhynchos) drinking freshwater and after sequential acclimation to 300 mM NaCl and 400 mM NaCl. Total body water, extracellular fluid volume, plasma volume and exchangeable sodium pool were measured using (3)H(2)O, [(14)C]-polyethylene glycol, Evans Blue dye, and (22)Na dilution, respectively. Following acclimation to 300 mM NaCl, body mass decreased, but total body water and total exchangeable sodium pool were unaltered. Na and water were redistributed from the extracellular fluid (interstitial fluid) compartment into the intracellular fluid compartment. Following further acclimation to 400 mM NaCl, body mass, total body water and intracellular fluid volume decreased, but exchangeable sodium pool and extracellular fluid volume were unchanged. Our results suggested that, when Pekin ducks drink high but tolerable salinities, they maintain total body water, but redistribute Na(+) and water from interstitial fluid to the intracellular fluid compartment. When stressed beyond their ability to maintain total body water, they lose water from the intracellular fluid.

Dopamine D 1 receptors in the gills of Chinese crab Eriocheir sinensis

Our investigations indicate the existence of binding sites for [ 3H]SCH23390 on crude membrane preparations in the anterior and posterior gills of the Chinese crab, Eriocheir sinensis acclimated to freshwater (FW) or seawater (SW). Maximum specific binding in the posterior gills is always higher than in the anterior gills, independent of saline acclimation. K d values are similar in the two regions, suggesting the same affinity of both types of gills for the ligand, either from FW or from SW crabs.

Effect of saline drinking water on the size and water content of the gut and other organs of male and female mallards

Ducks absorb imbibed Na+and water in the anterior gut and reabsorb Na+and water from urine refluxed into the hind gut. In Mallards (Anas platyrhynchos) this process is sexually disparate: males reflux and reabsorb more water, mainly in the ceca. We examined the effect of saline acclimation on the size of Mallard organs, especially the gut and other osmoregulatory organs (kidneys, salt glands) in both sexes. We tested and accept two hypotheses: (1) saline increases the mass of the Mallard hind gut and other osmoregulatory organs and (2) saline has a greater effect on the organs of males. Drinking saline did not affect the mass of body, kidney, heart, or liver, but increased the mass of the salt glands, ileum, and ceca. Increases in organ mass were greater in males than in females. Saline acclimation increased the length of the jejunum only in males and decreased the length of the esophagus and the length and mass of the proventriculus only in females. Our data suggest that the upper and lower gut segments may play somewhat different roles in ion and water transport in the two sexes.

Effects of caecal ligation and saline acclimation on plasma concentration and organ mass in male and female Pekin ducks, Anas platyrhynchos

The intestinal caeca reabsorb urinary sodium chloride (NaCl) and water (Rice and Skadhauge 1982). Free water may be generated if the reabsorbed NaCl is secreted via salt gland secretion (Schmidt-Nielsen et al. 1958). Therefore ceacal ligation should (a) reduce hingut NaCl and water reabsorption, (b) enhance the increase in plasma osmolality during saline acclimation, and (c) affect drakes more than ducks. Twelve Pekin drakes and 13 Pekin ducks, Anas platyrhynchos, were caecally ligated or sham operated before acclimation to 450 mmol · 1 NaCl. Body mass, hematocrit, plasma osmolality, and inonic concentrations of plasma, cloacal fluid, and salt gland secretion were measured after each increase in drinking water salinity. Osmoregulatory organ masses were determined. Caecal ligation did not effect plasma osmolality or ion concentrations of plasma, cloacal fluid, or salt gland secretion, but reduced salt gland size in ducks. Drakes and ducks drinking fresh water had the same hematocrit, plasma osmolality, and plasma concentrations of Na+ and Cl−. In both sexes exposure to 75 mmol · 1-1 NaCl significantly decreased plasma [Na+] and doubled cloacal fluid [Na+]. Exposure to 450 mmol · 1-1 NaCl decreased body mass and increased hematocrit, plasma [Na+], [Cl−], and plasma osmolality (more in drakes than in ducks); cloacal fluid osmolality nearly doubled compared to freshwater-adapted ducks, due mainly to osmolytes other than Na+ and Cl−. The [Cl−] in salt gland secretion only slightly exceeded drinking water [Cl−].

Effects of saline acclimation and cecal ligation on body water and water flux in male and female Pekin ducks

Total body water, mean daily water flux, and plasma ionic and osmotic concentrations were determined in sham-operated and cecally ligated male and female Pekin ducks, Anas platyrhynchos, drinking fresh water and after acclimation to 0.3 M NaCl. Body mass, hematocrit, plasma sodium concentration, and osmolality were unaffected by saline acclimation or cecal ligation. Total body water of ducks acclimated to fresh water was about 63% of body mass and increased to 73% of body mass in all groups acclimated to 0.3 M NaCl except ligated females. Mean daily water flux of male and female ducks acclimated to fresh water was the same and was not affected by cecal ligation. Drinking 0.3 M NaCl increased mean daily water flux by 70% in both sham-operated male (P < 0.05) and female ducks (P < 0.01), and 135% (P < 0.001) in cecally ligated males, but did not affect cecally ligated females. Thus, following saline acclimation, mean daily water flux was greater (P < 0.05) in cecally ligated males than in females.

Exchangeable sodium pool size and sodium turnover in freshwater- and saltwater-acclimated ducks and gulls

The exchangeable sodium pool size and its turnover rate were determined in ducks, Anas platyrhynchos, and gulls, Larus glaucescens, acclimated to freshwater and subsequently to 2/3 seawater. Saline acclimation led to a significant reduction in body mass in ducks but not gulls. Exchangeable body sodium per unit wet body mass was significantly greater for gulls (43 mmol∙kg−1) than for ducks (30 mmol∙kg−1) drinking freshwater. It was not significantly different between saltwater-acclimated ducks (48 mmol∙kg−1) and gulls (44 mmol∙kg−1). Saline drinking increased the sodium pool of ducks but not gulls. Similarly, the sodium flux per unit body mass was significantly higher for freshwater gulls (4.2 mmol∙kg−1∙day−1) than for ducks (2.1 mmol∙kg−1∙day−1). It was not significantly different between saltwater gulls (19 mmol∙kg−1∙day−1) and ducks (21 mmol∙kg−1∙days−1). Saline acclimation increased sodium flux by a factor of 4.5 for gulls and 10.4 for ducks. Freshwater-acclimated gulls had significantly higher levels of plasma sodium, chloride, and osmolality than did ducks. Saline acclimation increased the plasma osmolality of both species and the sodium and chloride concentrations of the plasma of ducks, and it decreased the hematocrit of ducks. Hematocrit and plasma osmotic and ionic concentrations were similar for saline-acclimated gulls and ducks.

Saline acclimation and water and sodium transport across avian small intestine

The uptake of sodium and water across everted sacs of the jejunum and ileum of Pekin ducklings, nestling Glaucous-winged gulls, and adult Japanese quail was measured in both freshwater- and saltwater-acclimated birds to assess the importance of the avian small intestine in salt and water balance after a salt load. The jejunum and ileum together were divided into segments I-V in ducklings and gulls and segments I-IV in Japanese quail. Acclimation to sodium chloride solutions increased the uptake of sodium and water, per unit dry weight of tissue, across segments II and IV in larger ducklings, although no significant differences were observed in smaller ducklings. Sodium and water transport were significantly greater across the posterior region of the small intestine of saltwater-acclimated gulls. In Japanese quail acclimated to sodium chloride solutions, mean values for sodium and water uptake were decreased, compared with fresh-water-acclimated birds, but were not statistically significantly different. Increased uptake of water and sodium after saline acclimation appears to be correlated with the presence of functional salt glands.

Salinity Adaptation in the Salamander Batrachoseps

ABSTRACT Batrachoseps attenuatus and B. major were successfully acclimated to 600 m-osmol NaCl and 400 m-osmol sucrose solutions. Accumulation of sodium and an increased rate of synthesis of urea provide substantial increases in plasma concentrations of these solutes. Sodium concentrations in excess of 230 mM and urea concentrations in excess of 200 mm indicate that these are the two major solutes (plus anions) responsible for elevation of osmotic concentration in Batrachoseps. Batrachoseps exhibits a water balance response upon dehydration (greater than twofold increase in cutaneous uptake, 50% reduction in urine production). Urine production, estimated from bladder contents, was significantly reduced in salamanders acclimated to sucrose solutions compared to animals acclimated to tap water or saline of equivalent osmotic concentration. Plasma urea concentration was equivalent to urine urea concentration when Batrachoseps was kept in tap water and during short term saline acclimation. After long term saline acclimation, urine urea concentration was one-fourth the plasma urea concentration.

Effects of saline acclimation on plasma electrolytes, urea excretion, and hepatic urea biosynthesis in a freshwater stingray, Potamotrygon sp. garman, 1877

1. 1. Freshwater stingrays, Potamotrygon sp., were slowly acclimated to 40% sea water. 2. 2. Saline acclimation had no significant effect on the rate of urea biosynthesis. 3. 3. Rates of urea excretion were low and did not differ significantly in freshwater and saline acclimated rays. Total ammonia- n + urea- n was excreted primarily as ammonia- n in both groups. 4. 4. The rate of simultaneous total-body clearance of urea- 14C and thiourea- 14C in saline acclimated rays did not indicate that saline acclimation was accompanied by renal conservation of urea. 5. 5. Hematocrits and plasma urea concns did not differ significantly in fresh water and saline acclimated rays. 6. 6. Plasma sodium and chloride concns were significantly increased by saline acclimation.

Osmotic regulation and urea metabolism in the lemon shark Negaprion brevirostris.

Osmotic regulation and urea metabolism in the lemon shark Negaprion brevirostris.