Acipenser Persicus Research Articles

Use of geometric morphometrics to identify ecophenotypic variation of juvenile Persian sturgeon <em>Acipenser persicus</em>

Study of phenotypic variation is essential for identifying discrete phenotypic stocks. We sampled immature Persian sturgeon from the eastern and western portion of the southern Caspian Sea to test for morphological differences that could predict the ecophenotypic variation of Persian sturgeon. Geometric morphometric methods were used to quantify body shape. Configuration of landmark coordinates of fish body were scaled, translated and rotated using generalized Procrustes analysis, followed by univariate analysis of variance of resulting shape coordinates to evaluate potential morphological differences between regions. A principal component analysis was carried out to reduce the number of dimensions without the loss of information. The discriminate function analysis was performed to determine the efficacy of body landmarks for discrimination by geographic variants. Within-group linkage was inferred for dendrogram clusters using Pearson correlation distance on the basis of the average linkage method as a complement for discriminate analysis. Principle component analysis revealed that the largest differences were in body size. Most notable were differences in distance between head landmarks and the dorsal fin between eastern and western regions. Fish from the western region exhibited a longer distance from head landmarks to the dorsal fin than fish from the eastern region. Furthermore, the ventral portion of fish from the western region was longer than that of the eastern individuals. These findings show that juvenile Persian sturgeon already possess morphological traits that can be used to discriminate fish from different regions. Furthermore, these differences are discernible in spite of the volume of artificially-inseminated sturgeon larva that have been released during the past 40 years.

Growth, development and behaviour of Persian sturgeon Acipenser persicus larvae in different light regimes

The effects of five different light regimes on growth performance and behaviour of Persian Sturgeon larvae were examined. Larvae were reared under five different photoperiods (24L, 12L:12D, 16L:8D, 8L:16L and 24D), from hatching (25.8 ± 8.1 mg; 12 ± 0.6 mm) to 28 days post-hatch (dph). Except the last week, there was no significant difference in growth parameters among the experimental groups. Growth performance significantly improved in larvae reared under a continuous light regime. The highest final length (34.5 ± 1.7 mm) was measured in 24L and the lowest one (29.5 ± 0.4 mm) in the constant darkness. Relative to other experimental groups, the continuous darkness had a retarding impact on the yolk sac absorption and swarming behaviour. Among the whole body compositions, the lowest body moisture content was measured in the continuous light group. Persian Sturgeon pre-larvae and larvae were not completely dependent on light regimes (in 1–21 days), whereas on the basis of measured parameters (total length, wet and dry weight and digestive fullness index) a continuous light regime played a decisive role on growth performance beyond 21 dph.

Effect of dietary taurine and methionine supplementation on growth performance, body composition, taurine retention and lipid status of Persian sturgeon,Acipenser persicus(Borodin, 1897), fed with plant-based diet

The aim of this study was to investigate the effects of dietary taurine and methionine on Persian sturgeon (Acipenser persicus) fed with plant-based diets. To this purpose, sturgeons were fed with either of methionine + taurine-supplemented (MT), without taurine supplementation (M) or without methionine supplementation (T) diets. Growth performance, body composition, tissue amino acids and serum glucose and lipids were studied at the end of the experiment. Results showed that the treatments T and MT had similar growth performance and feed efficiency, which were significantly higher than the treatment M. Dietary taurine and methionine significantly altered carcass and liver taurine and methionine contents. The highest serum glucose was observed in the treatment M and the lowest in treatment MT. Serum cholesterol and triglyceride levels in the treatments T and MT were similar and significantly higher than those of the treatment M. This study showed that Persian sturgeon needs taurine supplementation when fed with plant-based diets, but the supplemented level seems to be lower than those of the other species. Taurine has hypoglycaemic and lipidogenesis effects on Persian sturgeon. However, further studies are required to illustrate taurine and methionine metabolism in Persian sturgeon.

Metabolic changes in droplet vitrified semen of wild endangered Persian sturgeon Acipenser persicus (Borodin, 1997)

Comparative quantitative metabolite profiling can be used for better understanding of cell functions and dysfunctions in particular circumstances such as sperm banking which is an important approach for cryopreservation of endangered species. Cryopreservation techniques have some deleterious effects on spermatozoa which put the obtained results in controversy. Therefore, in the present study, quantitative 1H NMR (Nuclear Magnetic Resonance) based metabolite profiling was conducted to evaluate metabolite changes related to energetics and some other detected metabolites in vitrified semen of critically endangered wild Acipenser persicus. The semen was diluted with extenders containing 0, 5, 10, and 15 μM of fish antifreeze protein (AFP) type III as a cryoprotectant. Semen-extenders were vitrified and stored for two days. Based on post-thaw motility duration and motility percentage assessments, two treatments with 10 μM and 0 μM of AFP had the highest and the lowest motility percentages respectively and they were objected to 1H NMR spectroscopy investigations in order to reveal the extremes of the metabolites dynamic range. Univariate (ANOVA) and multivariate (PCA) analysis of the resulting metabolic profiles indicated significant changes (P > 0.05) in metabolites. The level of some metabolites including acetate, adenine, creatine, creatine phosphate, lactate, betaine, sarcosine, β-alanine and trimethylamine N-oxide significantly decreased in vitrified semen while some others such as creatinine, guanidinoacetate, N, N-dimethylglycine, and glycine significantly increased. There were also significant differences between vitrified treatments in levels of creatine, creatine phosphate, creatinine, glucose, guanidinoacetate, lactate, N, N-dimethylglycine, and glycine, suggesting how fish AFP type III can be effective as a cryoprotectant.

Immunolocalization of Na+ /K+ -ATPase, Na+ /K+ /2Cl− co-transporter (NKCC) and mRNA expression of Na+ /K+ -ATPase α-subunit during short-term salinity transfer in the gills of Persian sturgeon (Acipenser persicus , Borodin, 1897) juveniles

The study tests the physiological responses of Persian sturgeon, Acipenser persicus, during the abrupt release of juveniles from freshwater (FW) into brackish waters (BW = 11‰) of the Caspian Sea. Fish weight at release was 2-3 g (2.55 ± 0.41 g; 8.8 ± 0.58 cm TL). Totals of 160 individuals were randomly distributed into four fiber-glass aerated tanks (volume 60-L). Two tanks served as controls (FW groups), and two as exposure tanks for BW (Caspian Sea water = CSW). Fish were sampled at 0, 3, 6, 12, 24, 48 and 96 hr after abrupt transfer to CSW. Plasma osmolality, immunolocalization of Na+, K+ -ATPase (NKA) and Na+/K+/2Cl– (NKCC) Co-transporter, NKA activity and the NKA α-subunit mRNA expression were analyzed. Blood osmolality of fish transferred from FW to CSW increased significantly within hours post-transfer (p < .05) and remained at a high level for up to 96 hr. Immunolocalization of NKCC indicated co-localization with NKA in the chloride cells in the gill epithelium. A partial sequence of the NKA α-subunit (632 bp) is described. Its expression levels were up-regulated at 12 and 48 hr following salinity transfer (p < .05). However, NKA activity sharply increased in CSW specimens by almost 2.8-fold (p < .05) between 48 and 96 hr after transfer. Gill NKCC co-transporter abundance increased, coinciding with increased gill NKA activity. The increased activity of NKCC during salt excretion in CSW may lead to an influx of Na+ into the chloride cells. Consequently, NKA activity increases to maintain intracellular Na+ homeostasis.

Determination of Cd, Cu, Mn and Zn Concentrations in Iranian Caspian Sea Caviar of Acipenser persicus Using Anodic Stripping Voltammetry

In this study, anodic stripping voltammetry was used to assess the contents of Cd, Cu, Mn and Zn in caviar of Acipenser persicus caught from Southern Caspian Sea sampling site. The range (μg g−1) of metals in caviar samples was: 0.025–0.069 for Cd, 1.08–1.76 for Cu, 0.009–0.01 for Mn and 12.9–21.1 for Zn, respectively. These levels are significantly lower than the adverse levels for human consumption based on FAO/WHO permissible limits. Therefore, caviar’s contribution to the total body burden of these heavy metals can be considered as negligibly small, especially given that caviar is a luxury product. The result of the one-way analysis of variance suggested significant variations (p < 0.05) in the mean concentration of the metals in the samples of caviar analyzed in this research.

Metal accumulation in Caspian sturgeons with different feeding niches, condition factor, body size and age

The present study investigated metal accumulation in the muscle of the Caspian sturgeons, Acipenser nudiventris, Acipenser persicus, Acipenser stellatus and Huso huso with different feeding niches, condition factor, body size and age, sampled in the spring of 2014, using an ICP-OES (Shimadzu). We used redundancy analysis to examine relationship between metals concentrations and the measured variables in the species. Huso huso specimens tended to have a higher concentration of Ba, Cr, K and Mn relative to the other species. Most metals had positive correlations with the body length, weight and age. Condition factor was not correlated with other parameter measured. The mean concentrations of the measured metals in muscles were higher than those of previous studies of sturgeons from the Caspian Sea suggesting increased pollution. The present study suggests that non-dietary sources of metals may play an important role in the accumulation of metals in the muscles of sturgeons.

Evolutionary relations and population differentiation of Acipenser gueldenstaedtii Brandt, Acipenser persicus Borodin, and Acipenser baerii Brandt

Russian ( Acipenser gueldenstaedtii), Persian ( A. persicus) and Siberian ( A. baerii) sturgeons are closely related ‘Ponto-Caspian’ species. Investigation of their population structure is an important problem, the solution of which determines measures for conservation of these species. According to previous studies, ‘baerii-like’ mitochondrial genotypes were found in the Caspian Sea among 35% of Russian sturgeon specimens, but were not found in Persian sturgeons. This confirms genetic isolation of the Persian sturgeon from the Russian sturgeon in the Caspian Sea. However, in order to clarify the relationships of these species it is necessary to analyze nuclear DNA markers. The amplified fragment length polymorphism (method) allows estimating interpopulation and interspecific genetic distances using nuclear DNA markers. In the present study, four samples were compared: Persian sturgeons from the South Caspian Sea, Russian sturgeons from the Caspian Sea and the Sea of Azov, and Siberian sturgeons from the Ob’ River, which are close to the latter two species, but are also clearly morphologically and genetically distinct from them. For the amplified fragment length polymorphism (AFLP) method, eight pairs of selective primers were used. The analysis revealed that the Siberian sturgeon has formed a separate branch from the overall Persian-Russian sturgeons cluster, which was an expected result. In addition, the results showed that the Caspian Russian sturgeon is closer to the Persian sturgeon from the Caspian Sea than to the Russian Sturgeon from the Sea of Azov. The present DNA marker data confirm that despite the genetic isolation of the Persian sturgeon from the Russian sturgeon in the Caspian Sea, the Persian sturgeon is a young species.

Evolutionary relations and population differentiation of Acipenser gueldenstaedtii Brandt, Acipenser persicus Borodin, and Acipenser baerii Brandt

Russian ( Acipenser gueldenstaedtii), Persian ( A. persicus) and Siberian ( A. baerii) sturgeons are closely related ‘Ponto-Caspian’ species. Investigation of their population structure is an important problem, the solution of which determines measures for conservation of these species. According to previous studies, ‘baerii-like’ mitochondrial genotypes were found in the Caspian Sea among 35% of Russian sturgeon specimens, but were not found in Persian sturgeons. This confirms genetic isolation of the Persian sturgeon from the Russian sturgeon in the Caspian Sea. However, in order to clarify the relationships of these species it is necessary to analyze nuclear DNA markers. The amplified fragment length polymorphism (method) allows estimating interpopulation and interspecific genetic distances using nuclear DNA markers. In the present study, four samples were compared: Persian sturgeons from the South Caspian Sea, Russian sturgeons from the Caspian Sea and the Sea of Azov, and Siberian sturgeons from the Ob’ River, which are close to the latter two species, but are also clearly morphologically and genetically distinct from them. For the amplified fragment length polymorphism (AFLP) method, eight pairs of selective primers were used. The analysis revealed that the Siberian sturgeon has formed a separate branch from the overall Persian-Russian sturgeons cluster, which was an expected result. In addition, the results showed that the Caspian Russian sturgeon is closer to the Persian sturgeon from the Caspian Sea than to the Russian Sturgeon from the Sea of Azov. The present DNA marker data confirm that despite the genetic isolation of the Persian sturgeon from the Russian sturgeon in the Caspian Sea, the Persian sturgeon is a young species.

Application of enriched 137Ba tracer to mark juvenile Persian sturgeon (Acipenser persicus)

The present study evaluates the variations of 137Ba abundance in pectoral fin spine of 1-month-old juvenile Persian sturgeon (Acipenser persicus) upon marking using the stable isotope approach. The marking of the fish was achieved by incorporation of 137Ba2+ in the calcified lattice of the pectoral fin spine through substitution with structural Ca2+. This process was carried out by rearing juveniles in treatment tanks containing elevated concentrations of 137Ba for 1, 3 and 5 days. The marked fish were then retained in natural abundance fresh and brackish waters, to evaluate the trend of exchange of 137Ba from the fin spines. The abundance of 137Ba in fin spines during marking and post-marking experiments were detected by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that a significant isotope mark can be obtained with no mortality and 100% marking rate on the first day of exposure to the isotope. The marked juveniles maintained their isotopic signature for at least 25 days. Statistical analysis of the obtained 138Ba/137Ba ratios demonstrated that the successful incorporation of 137Ba2+ in pectoral fin spines provides an effective marking method for Persian sturgeon restocking programs.

The effect of dietary taurine on growth performance and liver histopathology in Persian sturgeon,Acipenser persicus(Borodin, 1897) fed plant-based diet

This experiment was conducted to illustrate the effect of dietary taurine levels on Persian sturgeon, Acipenser persicus (mean weight of ~35 g) fed plant-based diet. A basal diet containing low level of fishmeal (19%) was formulated containing 0.05% endogenous taurine (control diet). To this diet were added five levels of exogenous taurine: 0.25 (0.25T), 0.5 (0.5T), 0.8 (0.8T), 1.2 (1.2T) and 1.6% (1.6T). These diets were fed to the experimental fish for 42 days. Results showed that growth performance decreased and food conversion ratio increased as dietary taurine increased, although no significant difference was observed between the control and 0.25T treatments. Increased dietary taurine led to increased carcass moisture and decreased carcass lipid percentages. Feed intake was significantly and negatively correlated with dietary taurine. Carcass taurine content significantly increased with dietary taurine elevation up to 1.2% and then decreased. Hepatic taurine content showed a significant increase in 0.25T treatment and then decreased along with dietary taurine elevation and reached the control values at 1.6% taurine level. Dietary taurine elevation led to more hepatic damages compared to the control. In conclusion, although within the range reported for other studied fish, the tested taurine levels in this study might be supra-optimal causing adverse effects in Persian sturgeon and further study with lower taurine levels is encouraged.

Evolutionary relations and population differentiation of Acipenser gueldenstaedtii Brandt, Acipenser persicus Borodin, and Acipenser baerii Brandt.

Russian ( Acipenser gueldenstaedtii), Persian ( A. persicus) and Siberian ( A. baerii) sturgeons are closely related 'Ponto-Caspian' species. Investigation of their population structure is an important problem, the solution of which determines measures for conservation of these species. According to previous studies, 'baerii-like' mitotypes were found in the Caspian Sea among 35% of Russian sturgeon specimens, but were not found in Persian sturgeons. This confirms genetic isolation of the Persian sturgeon from the Russian sturgeon in the Caspian Sea. However, in order to clarify the relationships of these species it is necessary to analyze nuclear DNA markers. The amplified fragment length polymorphism (method) allows estimating interpopulation and interspecific genetic distances using nuclear DNA markers. In the present study, four samples were compared: Persian sturgeons from the South Caspian Sea, Russian sturgeons from the Caspian Sea and the Sea of Azov, and Siberian sturgeons from the Ob' River, which are close to these two species, but are also clearly morphologically and genetically distinct from them. For the AFLP method, eight pairs of selective primers were used. The analysis revealed that the Siberian sturgeon has formed a separate branch from the overall Persian-Russian sturgeons cluster, which was an expected result. In addition, the results showed that the Caspian Russian sturgeon is closer to the Persian sturgeon from the Caspian Sea than to the Russian Sturgeon from the Sea of Azov. The present DNA marker data confirm that despite the genetic isolation of the Persian sturgeon from the Russian sturgeon in the Caspian Sea, the Persian sturgeon is a young species.

Study on Bacillus Isolated from Intestine of Persian Sturgeon (&lt;i&gt;Acipenser persicus&lt;/i&gt;) Comparing with Commercial Probiotics

At present, probiotic bacteria are proposed as an important alternative for antibiotic elimination and for providing renewable products through biological control in cultivation systems of marine fish larvae. The aim of this study is to compare the effects of native and commercial probiotics on growth parameters of Persian sturgeon (Acipenser persicus) larvae fed with controlled biomar diet. Experimental diets with three probiotic bacterial mixture including commercial lactobacillus (L. plantarum and L. rhamnosus), commercial Bacillus (B. subtillis and B. licheniformis) and Bacillus isolated from intestine of Persian sturgeon (B. mycoides) were completed in two levels (6.1 and 7.2 log CFU in each g of feed) and were fed to larvae of Persian sturgeon in six experimental treatments. The control treatment was fed with diet without supplementation. The experiment was done in randomized design. In all the treatments, feed conversion index was increased considerably and had significant difference with control treatment and in all the experimental treatments influenced by probiotics were higher than that of control treatment (P&lt;0.05). The highest rate means of special growth (1.84±0.21%) and thermal growth index (3.44±0.37%) was obtained respectively in treatment C1 and C2 (isolated from intestine). Maximum special growth rate (SGR %) were obtained from C1 (4.69±0.71%) and B2 (4.62±0.87%, commercial Bacillus). In addition, native probiotic bacteria had better performance than the non native commercial species as well as selection of suitable probiotic (natural) with respect to fish species, region and condition of culture plays a special importance role in enhancing the yield of Persian sturgeon larvae.

Study on Bacillus Isolated from Intestine of Persian Sturgeon (&lt;i&gt;Acipenser persicus&lt;/i&gt;) Comparing with Commercial Probiotics

At present, probiotic bacteria are proposed as an important alternative for antibiotic elimination and for providing renewable products through biological control in cultivation systems of marine fish larvae. The aim of this study is to compare the effects of native and commercial probiotics on growth parameters of Persian sturgeon (Acipenser persicus) larvae fed with controlled biomar diet. Experimental diets with three probiotic bacterial mixture including commercial lactobacillus (L. plantarum and L. rhamnosus), commercial Bacillus (B. subtillis and B. licheniformis) and Bacillus isolated from intestine of Persian sturgeon (B. mycoides) were completed in two levels (6.1 and 7.2 log CFU in each g of feed) and were fed to larvae of Persian sturgeon in six experimental treatments. The control treatment was fed with diet without supplementation. The experiment was done in randomized design. In all the treatments, feed conversion index was increased considerably and had significant difference with control treatment and in all the experimental treatments influenced by probiotics were higher than that of control treatment (P&lt;0.05). The highest rate means of special growth (1.84±0.21%) and thermal growth index (3.44±0.37%) was obtained respectively in treatment C1 and C2 (isolated from intestine). Maximum special growth rate (SGR %) were obtained from C1 (4.69±0.71%) and B2 (4.62±0.87%, commercial Bacillus). In addition, native probiotic bacteria had better performance than the non native commercial species as well as selection of suitable probiotic (natural) with respect to fish species, region and condition of culture plays a special importance role in enhancing the yield of Persian sturgeon larvae.

Effects of dietary administration of Rose hip and Safflower on growth performance, haematological, biochemical parameters and innate immune response of Beluga, Huso huso (Linnaeus, 1758)

The aim of this study was to investigate effects of two dietary medicinal herbs, Rose hip (Rosa canina) and Safflower (Carthamus tinctorius) supplementation on growth performance, haematological, biochemical parameters and innate immune response of in juvenile beluga, Huso huso. Fish (26.3 ± 0.4 g) were allocated into 15 tanks (20 fish per tank) and triplicate groups were fed a control diet or diets containing 1% and 2% of medicinal herbs, respectively. Feed conversion ratio (FCR), specific growth rate (SGR) and condition factor (CF) did not show significant differences (P > 0.05) in fish given herbal diets. Significant differences were observed in number of white blood cells (WBC) and haemoglobin (Hb) values among the dietary treatments. The serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were significantly lower in supplemented diet groups compared with the control. Innate immune responses (lysozyme activity and ACH50) were significantly higher in 2% Safflower-fed fish compared with other groups (P < 0.05). These results indicate that medicinal herbs in diets can be considered as a beneficial dietary supplement for improving the physiological parameters and enhance the immune response of Persian sturgeon.

Hydrology and water resources in Caspian Sea

Abstract. Precipitation is the main driver of the water balance variability of the water over space and time, and changes in precipitation have very important implications for hydrology and water resources. Variations in precipitation over daily, seasonal, annual, and decadal time scales influence hydrological variability over time in a catchment. Flood frequency is affected by changes in the year-to-year variability in precipitation and by changes in short-term rainfall properties. Desiccation of the Caspian Sea is one of the world's most serious ecosystem catastrophes. The Persian Sturgeon (Acipenser persicus) caught under 10 m depth using bottom trawl net by research vessel during winter 2012, summer and winter 2013 and spring 2014 in east, central and west of southern parts of Caspian Sea, then, their diets were investigated. During 136 trawling in the aimed seasons, Persian sturgeon with 1 to 2 years old and 179.67 × 0.2 g (body weight) and 29.97 ± 0.4 cm (Total length) captured. Examination of stomach contents in the sturgeon specimens revealed that the food spectrum was composed of bony fishes (Neogobius sp., Atherina sp. and Clupeonella delicatula), invertebrates belonging to the family Ampharetidae polychaeta worms including (Hypanai sp. and Nereis diversicolor), various crustaceans (Gammarus sp. and Paramysis sp.). Investigation on stomach contents of sturgeon Acipenser persicus caught under 10 m depth in 2012 to 2013 surveys showed that there is significant difference in the consumed food. The most food diversity have been observed in winter 2013, also Polychaeta is the primary consumed food and crustacean is the secondary one (P &gt; 0.05), no new types of food (such as bony fishes or benthics) have been observed on food chain of Acipenser persicus and shows no significant difference (P &gt; 0.05).

Retracted: Antioxidant characteristics of Persian sturgeon (Acipenser persicus) seminal plasma did not show significant changes duringin vitrostorage (48 h at 4°C)

The below article, published online on Wiley Online Library (wileyonlinelibrary.com) has been retracted by agreement between the submitting author, Mohammad Sadegh Aramli, the Editors, Ronald Hardy, Lindsay Ross, Shi-Yen Shiau, Marc Verdegem, and John Wiley & Sons Ltd. After a thorough investigation, there is strong evidence to indicate that the peer review of this paper was compromised. The identities of the reviewers were unable to be verified and it is believed that the paper was accepted based on recommendations from reviewers not suitably qualified. REFERENCE Aramli, M. S., & Kalbassi, M. R. (2016). Antioxidant characteristics of Persian sturgeon (Acipenser persicus) seminal plasma did not show significant changes during in vitro storage (48 hr at 4°C). Aquaculture Research doi: https://doi.org/10.1111/are.13204 http://onlinelibrary.wiley.com/wol1/doi/10.1111/are.13204/abstract

Study on the effect of climate change on feeding of Persian sturgeon (Acipenser persicus Bordin,1987) in coastal zone of Caspian Sea (Iranian water)

Abstract Ecosystems in the Caspian Sea region have been heavily modified by anthropogenic activities, mainly as a result of changes in the water flow and degradation of the water quality in the eco...

Effects of diazinon on adaptation to sea-water by the endangered Persian sturgeon, Acipenser persicus, fingerlings

To replenish the depleting populations of sturgeon fishes especially Persian sturgeon, Acipenser persicus in the Caspian Sea, millions of Persian sturgeon fingerlings are farmed through artificial propagation and released into the Iranian river estuaries annually. Fish osmoregulation is a vital physiological process that can be affected during the release. Many Iranian river estuaries are under the influence of pesticides originating from farming activities that may affect osmoregulation. In this study, Persian sturgeon fingerlings were exposed to sublethal concentrations (0, 0.18, 0.54, 0.9mgL−1) of diazinon for 96h (short-term trial) and 12 days (long-term trial) in fresh water (FW) and then fish were exposed in brackish water (BW) for 24h. After 96h and 12 days of exposure in FW, the lower levels of plasma triidothyronine (T3), thyroxine (T4), Na+, Cl−, K+, gill Na+/K+- ATPase activity and number of chloride cells were observed in exposed fish (0.54 and 0.9mgL−1 diazinon) compared to control group and 0.18mgL−1 diazinon treatment. Also, higher levels of plasma cortisol (except 0.18mgL−1 diazinon treatment in long-term trial) were observed in diazinon exposed fish compared to control group. However, gill Na+/K+-ATPase activity and the number of chloride cells were higher in fingerlings exposed to diazinon compared than control. When fish were exposed in BW for 24h, the following changes occurred: (a) in short-term trial: increases in cortisol and Cl− levels (0.54mgL−1 diazinon ), Na+ (0.9mgL−1 diazinon ) and gill Na+/K+-ATPase activity (0.18mgL−1 diazinon ). In control group, cortisol, T4, Na+, gill Na+/K+-ATPase activity and the number of chloride cells increased significantly. (b) In long-term trial: increases in K+ levels in fish exposed to 0.9mgL−1 diazinon, Na+ in all diazinon concentrations and decreases in chloride cells number in fish exposed to 0.18mgL−1 diazinon. In control group, significant increases were observed in cortisol, T3, Na+ and chloride cells number. Finally, gill showed many histopathological damages during exposure in FW and BW. Our results suggest that the contamination of river estuaries with diazinon may alter the osmoregulation ability of released Persian sturgeon fingerlings, which could lead to a failure in their restocking program in the Caspian Sea.

Salinity effects on osmoregulation and gill morphology in juvenile Persian sturgeon (Acipenser persicus).

The effect of abrupt and 5-day gradual salinity transfers from freshwater (FW) to 11‰ Caspian Sea brackish water (BW) was investigated in juvenile Persian sturgeon Acipenser persicus with three different weight groups: 1-2g (1.62±0.27g), 2-3g (2.55±0.41g) and 3-5g (4.28±0.76g). Mortality rates, blood osmotic pressure, gill morphology and branchial Na+, K+-ATPase (NKA) activity were measured 4 and 10days after abrupt transfer and 9 and 15days after the initial gradual transfer (i.e. 4 and 10days after reaching Caspian Sea salinity). Fish under 3g could not survive increased salinity, and the blood osmotic pressure of the remaining surviving fish increased and remained elevated. However, heavier fish were able to survive and successfully acclimate, even to rapid salinity change with osmotic pressure reduced to Caspian Sea osmolality levels. At the gill level, the developmental increase in chloride cell volume and a higher NKA content most probably allow juveniles weighing more than 2g to sharply increase NKA activity if the fish are transferred to BW. The rapid chloride cell proliferation occurring with increased salinity should strengthen this acclimation response. Therefore, a drastic physiological change occurs when fish weigh more than 2g that allows migration to higher salinities. The triggering signal on chloride cells must be further investigated in order to optimize this functional step.