首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
The effects of the Na+/K+ and Mg2+/Ca2+ ratios in saline groundwaters on Na+-K+-ATPase activity, survival and growth of Marsupenaeus japonicus postlarvae were investigated. The results indicate that the Na+-K+-ATPase activity, survival rate and weight gain of postlarvae were significantly affected by the Na+/K+ and Mg2+/Ca2+ ratios (P < 0.05). The Na+-K+-ATPase activity of postlarvae, in every treatment, changed corresponding to Na+/K+ and Mg2+/Ca2+ ratios, and came to a stable level after 24 h. There was a negative relation between Na+-K+-ATPase activity and Na+/K+ ratio, while there was a positive relation between Na+-K+-ATPase activity and Mg2+/Ca2+ ratio. Compared with seawater (the Na+/K+ and Mg2+/Ca2+ ratios are 27.8 and 4.64 respectively), the Na+-K+-ATPase activity of the Na+/K+ ratio 30 treatment showed no significant difference, while the Mg2+/Ca2+ ratio 4.5 treatment showed distinct difference. The survival rates and weight gain of postlarvae increased markedly when the suitable amount of K+ and Ca2+ was added to test water, and arrived at their maximum in the Na+/K+ ratio 20-30 or Mg2+/Ca2+ ratio 4.5 treatment, having no significant difference compared with normal seawater. Therefore, considering the Na+/K+, Mg2+/Ca2+ ratios and the absolute concentration of Mg2+, Ca2+ in the experimental saline groundwaters applied to Marsupenaeus japonicus farming, it should be modulated to around 30, 4.5 and 1312 mg/l, 291 mg/l, respectively.  相似文献   

2.
Metamorphic responses of pediveliger larvae of Mytilus galloprovincialis to different ions were investigated through a series of bioassays. Effects of tetraethylammonium chloride (TEA) on inductive effects of these above ions were also investigated. Excess ions including Li+, Cs+, Rb+ and Ca2+ induced larval metamorphosis at 10?3 M to 5 × 10?2 M in 24‐h exposure assays. In continuous exposure assays, only excess Ca2+ showed inductive activity and induced 25% metamorphosis at 5 × 10?2 M. Larval responses to Li+ and Rb+were inhibited by TEA, while induction of metamorphosis by Cs+and Ca2+ was independent of the presence of TEA. Thus, these ions used can be useful inducers of larval metamorphosis for application in the aquaculture industry. The finding provides new insights on the biochemical mechanism controlling larval metamorphosis in this species.  相似文献   

3.
We investigated the effect of exposure to low salinity water on plasma ion regulation and survival rates in artificially wounded devil stinger Inimicus japonicus. All fishes survived in 33% seawater (SW), while survival rate in 100% SW was 5.1% at 24 h. In 100% SW, plasma Na+, K+, Mg2+, and Ca2+ concentrations significantly increased to 238?±?49.9, 9.6?±?2.4, 15.1?±?3.5 and 5.0?±?0.7 mmol/l at 6 h, respectively; the gill Na+/K+–ATPase (NKA) activity was almost stable, although only one fish survived to 24 h. In 33% SW, plasma Na+ and K+ concentrations remained at the same level, and plasma Mg2+ and Ca2+ concentrations gradually increased to 16.2?±?0.7 and 4.5?±?0.2 mmol/l until 24 h, respectively. The NKA activity significantly increased to 5.1?±?1.1 µmol ADP/mg protein per h at 6 h. A positive correlation was observed between the wound surface area against body weight and the plasma ion concentrations, although no difference was observed in the restoration rate of the wounded area between 100 and 33% SW. These results indicate that exposure of wounded fish to low salinity water improves survivability by favoring plasma ion regulation without influencing the restoration rate.  相似文献   

4.
This study investigated the effect of 0.25–5 mM K+, Ca2+, and Mg2+ on sperm motility in the perch, Perca fluviatilis. In 75 mM NaCl, the used motility-activating solution, motility rate, and swimming velocity decreased within the first 4 min after activation, and the rate of locally motile sperm increased. Thereafter, the motility parameters remained constant for periods >20 min. Based on the decrease in sperm motility, two types of semen samples could be distinguished. Semen samples of type I retained a high motility rate of >65 % after 20 min, and the rate of locally motile sperm was <20 %. In semen samples of type II, the motility rate decreased to values <30 % after 20 min, and the rate of locally motile sperm exceeded >50 %. Ca2+ and Mg2+ concentrations of 0.25–0.5 mM had no effect on the sperm motility parameters 10 s after activation, while 0.25 mM K+ increased the swimming velocity. K+, Ca2+, and Mg2+ concentrations ≥1.5 mM had suppressive effects on the sperm motility 10 s after activation. No differences were found between the two semen types. Twenty minutes after activation, type I semen was not affected by the tested cations. On the contrary, 0.25–2.5 mM K+, 0.25 mM Mg2+, and 0.25–2.5 mM Ca2+ significantly increased the sperm motility rate and/or sperm velocity of type II semen. Therefore, supplementation of saline solution with cations might stabilize the motility of perch sperm, which can be a benefit for experimental purposes and for specific handling procedures in aquaculture.  相似文献   

5.
The Monaco shrimp Lysmata seticaudata (Risso, 1816) is a marine ornamental species whose ecology and biology, as well as its larval culture has previously been addressed. The objective of the study was to predict and improve productivity of this species rearing protocol through modelling. The models developed intend to help aquaculturists to maximize survival to postlarva, decrease larval duration and increase synchronism of metamorphosis and newly metamorphosed postlarvae size by manipulating temperature, diet, first feeding period and stocking density.The models developed allow us to conclude that the L. seticaudata rearing protocol productivity can be improved by raising larvae at a density of 40 larvae L− 1 and fed newly hatched Artemia nauplii since hatching to zoea V, and with Algamac 2000™ enriched Artemia metanauplii from zoea V to metamorphosis to postlarvae.By providing more productive protocols to aquaculturists, destructive practices and wild collection may be reduced.  相似文献   

6.
Branchial activities of Na+,K+-ATPase (ouabain sensitive), Mg2+ ATPase (ouabain insensitive) and kinetic analysis of high and low affinity Ca2+ ATPase were measured inAnguilla anguilla that had been acclimated to demineralized water (DW, Ca < 10 M), freshwater (FW, Ca = 2 mM), and Low calcium freshwater (L-Ca, Ca = 0.9 mM). Na+,K+-ATPase activity decreased while ouabain insensitive activity increased when ambient Ca2+ decreased. Two kinetic forms of Ca2+ ATPase could be resolved in each environmental condition. The stimulation coefficients of both sites or enzymes were not affected by ambient Ca2+ concentrations. The maximal velocity of both the high and the low affinity Ca2+ ATPase was increased when external Ca2+ was decreased during acclimation. The low affinity Ca2+ ATPase and the Mg2+ stimulated enzyme could be a non specific enzyme accepting either Ca2+ or Mg2+. Results are compared with previous results in the literature and in relation to the branchial morphology and ionic exchanges in fish.  相似文献   

7.
Two experiments over 21 days were conducted to assess the effect of different ionic profiles (mainly K+) of inland saline water (ISW) on the survival, growth, osmoregulation and moisture content of juvenile greenlip abalone Haliotis laevigata. In experiment I, the juveniles were cultured in five different water types: ocean water (OW) as a control, inland saline water (ISW or ISW K+0), ISW fortified with 33%, 66% and 100% K+ as in OW (ISW K+33, ISW K+66 and ISW K+100 respectively). In experiment II, five different culture media, 100% OW(control), 75% OW mixed with 25% ISW (ISW25), 50% OW mixed with 50% ISW (ISW50), 25% OW mixed with 75% ISW (ISW75) and 100% ISW (ISW or ISW100), were tested. Within 21 days, all of the abalone in ISW (ISW K+0 and ISW100; Na+/K+ ratio of 111 L?1) died compared with 100% survival in OW. One‐hundred per cent K+ fortification of ISW increased the specific growth rate (SGR) and serum osmolality of the surviving juveniles. The 96 h acute LC50 value was between ISW50 and ISW75. The increased proportion of ISW in OW resulted in significantly (P<0.05) lower survival, SGR and serum osmolality of juveniles. The moisture content of the juveniles was not influenced by any water type. The results suggested that abalone cannot survive in raw ISW, but survival can increase when it is fortified with K+ and ionic ratios of ISW are brought closer to OW by mixing it with OW. Furthermore, abalone survival is influenced by other ions in ISW besides K+.  相似文献   

8.
Increase in salinity of inland water sources is adversely affecting aquatic and terrestrial ecosystems around the world including Australia. Inland saline water (ISW) with similar ionic profile to ocean water has potential for culturing marine species. Gracilaria species are commercially important as they are a source of agar. One of the native species Gracilaria cliftonii has been reported for high agar yield of 52%dw. The aim of this research was to investigate the feasibility of culturing G. cliftonii in different ionic profiles of ISW under laboratory conditions. The growth rate of G. cliftonii under different ionic profiles ranged from 0.9 to 2.5 %day−1. Gracilaria cliftonii carbohydrate content decreased while protein content increased in culture conditions when compared to natural populations. Agar yield, gel strength and melting point decreased while gelling temperature and sulphate content increased in culture conditions when compared to natural populations. Strong correlation (R 2 > 0.8, P < 0.05) was observed between K+, Na+, Ca2+, and Mg2+ content in tissue and water indicating ionic regulation by G. cliftonii. This research provides basic information and presents supportive arguments for G. cliftonii as a potential species for inland saline water aquaculture.  相似文献   

9.
Reuse of fish effluent for the culture of marine shrimp, such as Pacific white shrimp, Litopenaeus vannamei, could provide an opportunity for the US shrimp farming industry to ease constraints (e.g., environmental concerns and high production costs) that have limited them in the past. In this study under laboratory‐scale conditions, the feasibility of culturing L. vannamei in effluents derived from a commercial facility raising tilapia in recirculating aquaculture systems (RAS), supplemented with various salt combinations, was compared to the shrimp’s survival and growth in well water supplemented with 17.6 (control) and 0.6 (freshwater treatment) g/L synthetic sea salt. Three independent trials were conducted in RAS in which survival and growth in the control, the freshwater treatment, and two effluent treatments were compared. Water quality during this study was within safe levels and no differences (P < 0.05) between treatments were observed for dissolved oxygen, nitrite, pH, total ammonia nitrogen, and temperature. However, average nitrate and orthophosphate levels were consistently more than an order of magnitude greater in the effluent treatments compared to the control and the freshwater treatments. Survival and growth of shrimp over 6‐wk periods did not vary significantly between the control and the freshwater treatments; however, shrimp tested in the tilapia effluents often exhibited significant effects (P < 0.05) depending on the salts added. In the low‐salinity waters, correlations (P < 0.05) were observed between Ca2+, Mg2+, Ca2+ and Mg2+, K+, Na+ : K+ and Ca2+ : K+, and shrimp survival and growth. The results of this study revealed that L. vannamei can be raised in tilapia effluent when supplemented with synthetic sea salt (0.6 g/L), CaO (50 mg/L Ca2+), and MgSO4 (30 mg/L Mg2+).  相似文献   

10.
The motility and fertilizing ability of the Persian sturgeon, Acipenser persicus, spermatozoa were investigated. Optimum ionic content (Na+, K+, Ca2+ and Mg2+) and pH of activation solution as well as the optimum dilution rate were determined. The results show optimum motility characteristics of spermatozoa in buffered solutions containing 25, 0.2, 3 and 10 mM L?1 Na+, K+, Ca2+ and Mg2+, respectively, at dilution rate 1:50 and pH 8.0. To test the fertilizing ability of sperm, two buffered saline solutions were used as activation solution of sperm motility. The present study indicated (1) spermatozoa motility is one of key factors that influence on fertilizing ability of sperm, (2) a high fertilizing ability of sperm is obtained after dilution in saline solutions rather than in freshwater and (3) a maximum fertilization rate occurs in buffered saline solution containing 0.2 mM L?1 K+. There is also a good correlation between biochemical characteristics of seminal plasma and fertilizing ability of sperm.  相似文献   

11.
The culture of Litopenaeus vannamei in inland low salinity waters is currently being practiced in various countries around the world. These environments are often deficient in key ions essential for normal physiological function, including potassium (K+) and magnesium (Mg2+). Farmers have sometimes been able to counteract ionic deficiencies in the water profile by adding mineral salts containing sources of K+ and Mg2+. The purpose of this study was to explore the possibility of correcting deficiencies of K+ and Mg2+ in the water profile with dietary supplementation of these minerals. Two separate 7‐week experiments were conducted in 4.0 g−1 artificial low salinity water to evaluate the effects of mineral supplements (K+, Mg2+ and NaCl) to diets of L. vannamei reared in low salinity waters. In trial 1 seven diets were formulated (10 g NaCl kg−1, 20 g NaCl kg−1, 150 mg kg−1 Mg2+, 300 mg kg−1 Mg2+, 5 g K+ kg−1, 10 g K+ kg−1, and a basal diet to serve as a control). Minerals were added in the form of purified potassium chloride (KCl), magnesium chloride (MgCl2·6H2O) and NaCl. Trial 2 evaluated the use of a coating agent for the Mg2+ and NaCl treatments, while a K+ amino acid complex was utilized in the K+ treatments to reduce mineral leaching. Trial 2 was performed using similar treatment levels as trial 1. Shrimp survival and growth were assessed in both experiments. Results from trial 1 indicated no significant differences in survival, growth or percent weight gain. Results from trial 2 revealed no significant differences in survival and growth in the NaCl and Mg2+ treatments. However, significant differences in growth (P < 0.05) were observed when using the 10 g K+ kg−1 treatment, suggesting that dietary supplementation of a K+ amino acid complex may help improve growth of the species in low salinity waters.  相似文献   

12.
Two approaches (i.e. water and dry or semi‐dry transport) have been developed for the transport of swimming crabs Portunus trituberculatus in recent years. To evaluate their differential effects on physiological responses of crabs, we measured haemolymph components (metabolic substrates, metabolites and ions) and hepatopancreas glycogen level at different time intervals after exposure of crabs to thermal stresses in water and air. The immersed crabs exhibited no significant change in all metabolic substrates except the glucose level in the hypothermal stressed treatment (P > 0.05), whereas there was a great variation in haemolymph glucose and lipid level of air exposed crabs under both thermal stresses (P < 0.05). With respect to metabolites in immersed crabs, only urea concentration in hypothermal stressed crabs and lactate concentration in hyperthermal stressed crabs changed significantly during the experiment; by contrast, the air exposed crabs responded significantly in all metabolites to thermal stresses (P < 0.05). The immersed crabs decreased the concentration of Na+ and Mg2+, but increased the concentration of K+ and Ca2+. The change in Na+ and Ca2+ were not significant in the hyperthermal stressed crabs (P > 0.05). Nevertheless, all ions except K+ accumulated significantly in the air exposed crabs after thermal stresses (P < 0.05). Crabs in the two different media responded similar to thermal stresses in metabolism but differed greatly in ions regulation. The effects of thermal stresses on crabs could be magnified by exposure to air, leading to animals relying more on anaerobic metabolism and therefore limiting the usage of dry or semi‐dry transport approach especially at high temperature.  相似文献   

13.
An alternative larval shrimp feeding regime, in which umbrella‐stage Artemia were constituting the first zooplankton source was evaluated in the culture of Litopenaeus vannamei. In a preliminary experiment, umbrella‐stage Artemia were fed to larvae from zoea 2 (Z2) to mysis 2 (M2) stages to identify the larval stage at which raptorial feeding starts and to determine daily feeding rates. The following experiment evaluated the performance of two feeding regimen that differed during the late zoea/early mysis stages: a control treatment with frozen Artemia nauplii (FAN), and a treatment with frozen umbrella‐stage Artemia (FUA). The ingestion rate of umbrella‐stage Artemia increased from nine umbrella per larvae day?1 at Z2 stage to 21 umbrella per larvae day?1 at M2. A steep increase in ingestion and dry weight from Z3 to M2 suggests a shift to a raptorial feeding mode at the M1 stage. Treatment FUA exhibited a significantly higher larval stage index (P < 0.05) during the period that zoea larvae metamorphosed to the mysis stage, and a higher final biomass, compared with treatment FAN. Based on these results and on practical considerations, a feeding regime starting with umbrella‐stage Artemia from Z2 sub‐stage can be recommended for L. vannamei larvae rearing.  相似文献   

14.
The toxic effects of Cd2+ on Ca2+ influx kinetics in developing tilapia (Oreochromis mossambicus) larvae were evaluated. Addition of 20 µg l-1 of Cd2+ to the environment of 0 and 3 day-old larvae competitively inhibited the Ca2+ uptake within 4h resulting in a great increase in Km values for Ca2+ influx (19.3 and 17.4 fold, respectively) as compared with their respective controls. Consequently, the actual Ca2+ influx of larvae in solutions of 0.2 mM Ca2+ are suppressed by 32–45%. Also, 3 day-old larvae were more sensitive to internally accumulated Cd2+ than 0 day-old larvae. Although the Ca2+ influx in 0 and 3 day-old larvae may be restored to the levels of their respective controls with 24h of being transferred to a 20 µg l-1 Cd2+ solution, total body Ca2+ content was significantly reduced in 3 day-old larvae. Increased Ca2+ uptake efficiency ensures sufficient Ca2+ for normal growth. However, rapid increase in Ca2+ influx after hatching also leads to higher Cd2+ uptake. Exposure to Cd2+ will lead to a drop in body Ca2+ content resulting in retardation of larval growth. Therefore, we conclude that if Ca2+ uptake is interfered with at this critical stage of development, larvae will not be able to maintain normal levels of body Ca2+ and will show signs of Cd2+ poisoning.  相似文献   

15.
Inland shrimp culture is being practiced in several regions of the United States. In Alabama, the culture of shrimp (Litopenaeus vannamei) in inland low salinity well water (approximately 4.0 ppt) faces several challenges. The ionic composition of these waters is deficient in several key minerals, including potassium (K+) and magnesium (Mg2+). The objective of the present study was to evaluate the effects of several aqueous K+ and Mg2+ concentrations on survival, growth, and respiration in juvenile L. vannamei. Two experiments, a 14-day trial with postlarvae and a 7-week trial with juvenile (∼ 0.2 g) shrimp were conducted to evaluate effects of K+ supplementation to culture water. Four different levels of K+ (5, 10, 20, and 40 mg l− 1) were utilized and a treatment of 4 ppt reconstituted seawater was used as a reference for comparison to ideal ionic ratios. Additionally, a 6-week growth trial (∼ 1 g juvenile shrimp) was performed to evaluate the effects of five concentrations of Mg2+ (10, 20, 40, 80, 160 mg l− 1). Following completion of growth trials, measurements of basal respirometry rates were conducted to assess stress. Results from the 7-week K+ growth trial indicated significant differences (P < 0.05) in survival and growth among treatments. Individual weight, specific growth rate, and percent weight gain appeared to increase with increasing K+ concentration (decreasing Na:K ratios). Results from the Mg2+ experiment reveal a significant difference in survival between the lowest Mg2+ treatment (60%) and all other experimental treatments (90–97%). However, no differences in growth were observed. Shrimp respiration in the lowest Mg2+ treatment (10 mg l− 1) was significantly higher than in the 80 mg l− 1 treatment. These results suggest a potentially higher energetic cost associated with depressed aqueous Mg2+ concentrations that are common in low salinity environments.  相似文献   

16.
An increase in salinity of freshwater can affect the physiology and metal uptake in fish. In the present study, Nile tilapia Oreochromis niloticus were exposed to copper (1.0 mg/l) in increased salinities (2, 4, and 8 ppt) for 0, 1, 3, 7, and 14 days. Following the exposures, the activities of Na+/K+-ATPase, Mg2+-ATPase, and Ca2+-ATPase were measured in the gill, kidney, and intestine to evaluate the changes in osmoregulation of fish. Results showed that increases in salinity and Cu exposure of fish significantly altered the ATPase activities depending on the tissue type, salinity increase, and exposure durations. Salinity-alone exposures increased Na+/K+-ATPase activity and decreased Ca2+-ATPase activity. Na+/K+-ATPase activity decreased following Cu exposure in 2 and 4 ppt salinities, though the activity increased in 8 ppt salinity. Ca2+-ATPase activity decreased in the gill and intestine in all salinities, while the activity mostly increased in the kidney. However, there were great variations in Mg2+-ATPase activity following exposure to salinity alone and salinity+Cu combination. Cu accumulated in the gill and intestine following 14 days exposure and accumulation was negatively correlated with salinity increase. Data indicated that ATPases were highly sensitive to increases in salinity and Cu and might be a useful biomarker in ecotoxicological studies. However, data from salinity increased freshwaters should carefully be handled to see a clear picture on the effects of metals, as salinity affects both metal speciation and fish osmoregulation.  相似文献   

17.
The performance of the Pacific white shrimp Litopenaeus vannamei (Boone) under various stocking strategies was evaluated in earthen ponds filled with freshwater amended with major ions. Six 0.1‐ha earthen ponds located in Pine Bluff, AR, USA, were filled with freshwater in 2003 and 2004, and potassium magnesium sulphate added to provide 50 mg K+ L?1 and stock salt added to provide 0.5 g L?1 salinity. In 2003, three ponds either were stocked with PL15 shrimp (39 PL m?2) for 125 days of grow out or with PL25 shrimp for 55 days (23 PL m?2) followed by a 65‐day (28 PL m?2) grow‐out period. In 2004, ponds were stocked with 7, 13 or 30 PL15 m?2 for 134 days of grow out. Salinity averaged 0.7 g L?1 during both years, and concentration of SO4?2, K+, Ca2+ and Mg2+ was higher, and Na+ and Cl? was lower in amended pond water than in seawater at 0.7 g L?1 salinity. Potassium concentration in amended water was 52–61% of the target concentration. Shrimp yields ranged from 3449 kg ha?1 in 2003 to 4966 kg ha?1 in 2004 in ponds stocked with 30–39 PL15 m?2 for a 125–134‐day culture period. At harvest, mean individual weight ranged from 17.1 to 19.3 g shrimp?1. In ponds stocked with PL25 shrimp, yields averaged 988 and 2462 kg ha?1 for the 1st and 2nd grow‐out periods respectively. Gross shrimp yield in 2004 increased linearly from 1379–4966 kg ha?1 with increased stocking rate. These experiments demonstrated that L. vannamei can be grown successfully in freshwater supplemented with major ions to a final salinity of 0.7 g L?1.  相似文献   

18.
Gibel carp (Carassius auratus gibelio) of mean initial weight 3.1 g were fed one of seven casein‐dextrin‐based diets containing graded levels of magnesium (Mg) (39, 120, 220, 380, 700, 1600 and 2900 mg kg?1) for 3 months with the waterborne Mg concentration of 10.6–12.7 mg L?1. Magnesium sulphate was used as the supplementation Mg source in the diets. The experiment was carried out in a flow‐through system. Growth, survival rate, Na+/K+‐ATPase, Mg2+‐ATPase and tissue mineral contents were measured to investigate the effect of dietary magnesium in gibel carp. At the end of the experiment, the hepatopancreas of fish were collected for enzyme determination. The hepatopancreas, vertebrae and whole body were collected for tissue magnesium content analysis. After 3 months, dietary magnesium supplementation did not improve the growth performance, including feed intake, weight gain and feed conversion efficiency of juvenile gibel carp. On the contrary, negative impacts on survival, reduced growth performance and dramatically decreased Na+/K+‐ATPase, Mg2+‐ATPase and superoxide dismutase activities were observed in gibel carp fed a high Mg diet of 2900 mg kg?1. Although serum and hepatopancreas Mg and Ca contents were not affected by dietary Mg supplementation, vertebrae and whole‐body Mg contents increased significantly with the increasing dietary Mg concentrations. Based on the relationship between whole‐body Mg retention and dietary Mg concentration, a suitable dietary Mg level of 745 mg kg?1 could be estimated for gibel carp. It could be concluded that dietary Mg supplementation did not improve the growth performance, but could increase vertebrae Mg contents of gibel carp. Considering the adverse effects, a dietary Mg concentration of above 2900 mg kg?1 is not recommended and it should be careful to supplement magnesium in practical diets for gibel carp as most feed ingredients contain high magnesium concentrations.  相似文献   

19.
The present study evaluated various sodium and potassium concentrations in hatchery water to determine which proportions would be optimal for Macrobrachium rosenbergii larviculture. Using a closed RAS system (60‐L), experiments were conducted in two stages. In the first stage, larval quality parameters were compared among triplicate treatments of sodium (2000, 3000, 4000 and 5000 mg L?1) and potassium (100, 150, 200 and 250 mg L?1). During the second stage, these same parameters were compared from interactions of the two best concentrations determined in the first stage. Initial larval density was fixed at 100 larvae L?1 and larval quality parameters such as larval stage index (LSI), larval condition index (LCI), larvae dry weight, survival (%), LC50‐24 h for formalin stress and time of the first postlarvae (PL) appearance were measured. Results showed that during the early larval period time LSI, LCI and survival parameters were affected only by potassium and the interaction with sodium was not significant. At a later period of the larval development, interactions between both sodium and potassium were measurable for LSI (P < 0.05) while the interactions on LCI and survival were not significant. Measurable differences among the combined treatments 4000 mg L?1 sodium and 150 mg L?1 potassium resulted in the best performance for M. rosenbergii larviculture. This concentration also provided the highest final survival to PL metamorphosis (40.6 ± 2.5%) which was at least 10% higher than the other treatments.  相似文献   

20.
Growth hormone (GH) effectively promotes seawater (SW) adaptation in salmonids, but little is known of its effect in tilapias. Experiments were performed to investigate the effects of recombinant eel GH (reGH) on osmoregulatory actions and ultrastructural features of gill chloride cells in juvenile tilapia, Oreochromis niloticus. Tilapia showed a markedly improved SW survival, when directly transferred from freshwater (FW) to 62.5% SW 24h after a single reGH injection (0.25 or 2.5 µg g-1) or 3 reGH injections (0.25 µg g-1 every other day). Plasma Na+ and Mg2+ levels were significantly reduced by reGH (0.25 and 2.5 µg g-1) compared with saline injections; Ca2+ concentrations were reduced significantly by high dose of reGH (2.5 µg g-1) after SW transfer. However, fish failed to survive more than 24h when directly transferred to 70% SW, although the fish treated with reGH could survive longer than the controls. When examined by electron microscopy, the chloride cells were identified as mitochondrion-rich and an extensive tubular system was induced by GH treatment. The results of the present study suggest that, similar to its effect on salmonids, GH also exerts acute osmoregulatory actions and enhances SW adaptation in juvenile tilapia. GH also stimulates the differentiation of chloride cells toward SW adaptation.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号