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.     

Acute effects of ammonia exposure on the plasma and haematological parameters and histological structure of the juvenile blunt snout bream,Megalobrama amblycephala,and post‐exposure recovery

In this study, we investigated the toxic effects of ammonia‐N on the plasma and haematological parameters and histological structure of blunt snout bream (Megalobrama amblycephala) juveniles. The fish (initial weight, 14.79 ± 0.01 g) were randomly sorted into six tanks (200 L), and each tank was stocked with 40 fish for culture. The juveniles were exposed to two ammonia‐N levels—0 mg/L (control group) and 25 mg/L (experimental group)—and sampled at 0, 6, 12, 24, 48 and 72 hr, and then they underwent 96 hr of post‐exposure recovery. The results showed that ammonia‐N had significant effects on the plasma and haematological parameters. The treatment group showed increased cortisol, plasma ammonia and haematocrit levels and white blood cell count with increasing exposure time, up to 24 hr, and then the levels and count decreased. A significantly higher plasma glucose level was observed in the treatment group at 12 hr. After 96 hr of post‐exposure recovery, all parameter levels decreased to the control levels. The fish displayed histopathological alterations in the gills, liver and kidney. The results indicate that the severity of the lesions clearly differed among the organs, with the liver showing the most extensive damage, followed by the gills and kidney. Adverse effects to physiological indicators and histological structure increased with increasing exposure time before 24 hr. The fish showed self‐regulation; however, the histological structure could not recover fully, the gill tissue showed irreversible changes and the kidney tissue exhibited the worst recovery ability.     

A metabolic approach to understanding adaptation to sea water by endangered Persian sturgeon,Acipenser persicus fingerlings

In this study, metabolic responses of Persian sturgeon fingerlings to hyperosmotic condition were investigated by NMR‐based metabolomics. Persian sturgeon fingerlings (n = 2010, mean total weight: 3.2 ± 0.6 g; mean total length: 8.5 ± 1.5 cm) were held in freshwater (FW) for 96 hr and then acclimated in brackish water (BW) (12 g/L) for 24 hr. Blood samples were taken before and after salinity acclimation. The major metabolite changes corresponding to salinity acclimation were related to amino acids, osmolytes and energy metabolites. The plasma glucose levels increased significantly after 24 hr acclimation in BW (p < .05). Other energetic metabolites (acetate, acetoacetate, beta‐hydroxybutyrate, phosphocreatine, creatine, glycerol) showed no significant changes after 24 hr salinity challenge (p > .05). The osmolytes (taurine, trimethylamine‐N‐oxide, choline, N,N‐dimethylglycine) and amino acids (aspartate, glutamate, glutamine, leucine, phenylalanine, β‐alanine, histidine, threonine, cysteine) declined significantly after 24 hr acclimation in BW (p < .05). However, the levels of glycine elevated after 24 hr acclimation in BW (p < .05). Other amino acids including aspargine, isoluecine, Tyrosine, Tryptophan, Valine, and Lysine showed no significant changes after salinity challenge (p > .05). The considerable decreases in almost all plasma amino acids and all osmolytes showed specific importance of these metabolites in osmotic adaptation of fish in BW. Also, it seems that Persian sturgeon fingerlings rely more on oxidation of glucose to meet energetic requirements of osmoregulation than oxidation of lipids, as we observed no detectable changes in metabolites associated with lipid oxidation during osmotic acclimation in BW. Our results may help to understand osmoregulation in a chondrostei fish species from a metabolic approach.     

Alteration of the haemocyte parameters,expression of immune‐related and neurohormone bursicon genes of giant river prawn Macrobrachium rosenbergii (de Man) in the response to salinity stress and ammonia stress

We examined the effects of salinity stress and ammonia stress on alteration of the haemocyte count, phenoloxidase activity, expressions of immune‐related genes including prophenoloxidase (proPO), crustin, heat shock protein 70 (HSP70), and expressions of stress‐responsive neurohormone (Bur‐α and Bur‐β) in the thoracic and abdominal ganglia of giant river prawn Macrobrachium. These parameters of prawn that subjected to salinity stress (transferred from 0‰ to 5‰ and 10‰), and subjected to ammonia‐nitrogen (ammonia‐N) stress (transferred from 0 to 0.262 mg/L and 0.786 mg/L) were examined after 0, 3, 6, 24, 72 and 168 hr respectively. During the initial period of 3, 6 and 24 hr, granulocyte haemocyte (granular and semi‐granular hemocyte) count and PO activity significantly decreased, while expressions of Bur‐α and Bur‐β significantly increased. After 24 hr, granulocyte haemocyte count and PO activity significantly increased, whereas expressions of Bur‐α and Bur‐β significantly decreased. The expressions of proPO, crustin and HSP70 were significantly downregulated in the prawn that subjected to salinity stress and ammonia‐N stress at all time periods of 3–168 hr. In conclusion, changes in the granulocyte haemocyte count of M. rosenbergii following salinity stress and ammonia‐N stress are closely associated with the changes of Bur‐α and Bur‐β expressions.     

Effects of filleting method,stress, storage and season on the quality of farmed Atlantic cod (Gadus morhua L.)

The effects of filleting method, pre‐slaughter stress, storage and season on drip loss, water content, water‐holding capacity, rigour contraction and colour in Atlantic cod, Gadus morhua L., were examined. A total of 182 fish were sampled under commercial conditions. To test the effects of filleting method and stress, stressed (S) and unstressed (C) fish were filleted either pre (Pr) or post rigour (Po) at 1 and 48 h post mortem, receptively. The muscle pH significantly decreased from 0 to 144 h of storage in all groups. The onset of the rigour contraction was more pronounced in the Pr‐S group as compared with the Pr‐C group, but after 144 h of storage, no difference in degree of contraction was observed. Filleting method, stress and storage time influenced the colour of the fillets. Post‐rigour filleting caused a significantly increased in measured Lightness (L*) during storage. Stress caused a significant increase in measured redness (a*). No significant difference was found for water‐holding capacity. The water content was influenced by filleting method, where the Pr‐S group had a significantly lower water content compared with the Pr‐C groups; water content changed also according to season. The findings of this study show that stress, filleting method, time of storage and season had a significant effect on the drip loss, where a combination of all factors will determine the total loss.     

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.     

Effects of dietary zinc level on performance,zinc status,tissue composition and enzyme activities of juvenile Siberian sturgeon,Acipenser baerii (Brandt 1869)

This study conducted to evaluate the effect of dietary zinc (Zn) levels on feed utilization, tissue Zn composition and serum enzyme activities of juvenile Siberian sturgeon, Acipenser baerii. Five isoenergetic and isonitrogenous semi‐purified diets were formulated with increasing Zn sulphate (ZnSO₄.5H₂O) level to provide the actual Zn values of 14.7 (control), 20.8, 27.3, 37.7 and 46.4 mg/kg diet. Each diet was assigned to three groups of 20 experimental Siberian sturgeons with uniform size (initial weight of 26.52 ± 0.94 g) for a period of 8‐week feeding trial. Results showed that growth performance and muscle protein content were significantly increased with increasing dietary Zn level up to 27.3 mg/kg (p < .05), beyond which they remained significantly unchanged (p > .05). Muscle lipid content significantly declined with increasing dietary Zn level. While muscle and serum Zn contents were not significantly changed among treatments (p > .05), liver Zn content tended to rise with increasing dietary Zn supplementation. Alkaline phosphatase, superoxide dismutase and glutathione peroxidase activities were also raised with increasing dietary Zn level. The adequate amount of dietary Zn requirements for the Siberian sturgeon was estimated to be 28.24 mg/kg based on the relative growth rate and 34.60 mg/kg based on the liver Zn content.     

Effect of stocking density on growth and serum concentrations of thyroid hormones and cortisol in Amur sturgeon, Acipenser schrenckii

This study investigated the effects of different stocking densities on growth and serum concentrations of thyroid hormones and cortisol in Amur sturgeon, Acipenser schrenckii. Fish were reared at low, medium, and high stocking densities (initial experimental densities were 0.30, 0.75, and 1.78 kg m⁻², respectively) for 70 days. The results showed that high stocking density had negative effects on growth and feeding efficiency, and altered serum levels of thyroid hormones and cortisol in Amur sturgeon. A significant decrease in specific growth rate was observed as stocking density was increased. The feeding rate decreased significantly in the medium and high density groups, indicating that high stocking density reduced the food consumption of sturgeon. Food conversion ratio increased with increasing stocking density, suggesting that high stocking density might inhibit fish growth through decreasing food conversion efficiency. Serum concentrations of total triiodothyronine, free thyroxine, and free triiodothyronine were inversely related to stocking densities, whereas serum total thyroxine level of sturgeon stocked at different densities remained stable. Also, higher stocking density resulted in an elevation of serum cortisol level, indicating that the sturgeon stocked at the higher density experienced density-dependent physiological stress. These results suggest growth suppression caused by high stocking density might be related to both crowding stress and the declines in peripheral circulating levels of thyroid hormones, as well as associated with the reductions in both food consumption and food conversion efficiency.     

Growth response,body composition,plasma metabolites,digestive and antioxidant enzymes activities of Siberian sturgeon (Acipenser baerii,Brandt, 1869) fed different dietary protein and carbohydrate: lipid ratio

Knowing the effect of dietary nutrients on physiological parameters, especially oxidative stress, during fish rearing can be useful to improve fish health and optimize production in aquaculture. In this study, four iso‐energetic (2 × 2 factorial design) diets differing in nutrient composition were submitted to the Siberian sturgeon juveniles, to analyse biochemical and physiological responses. The juveniles were fed for as long as 10 weeks with the following diets: low protein–high carbohydrate (CHO): lipid ratio (LP‐St), high protein–high CHO: Lipid ratio (HP‐St), low protein‐low CHO: Lipid ratio (LP‐L) and high protein‐low CHO: Lipid ratio (HP‐L). It was shown that HP‐L diet significantly induced higher growth performance in the juveniles than LP‐L; however, there was not a significant difference between them with other treatments. HSI was increased by higher dietary CHO: L ratio. The result obviously showed the higher dietary fat led to an increase in sturgeon body fat content. In addition, dietary protein and CHO: lipid ratio significantly affected plasma metabolites (glucose, cortisol, cholesterol and triglyceride) but did not affect IGF‐1 and insulin levels. Based on enzyme activities results, incorporation of high protein (44%) in the diet induced lower amylase activity and carbohydrate digestion in the sturgeon juveniles. Moreover, antioxidant enzyme activities in this species were more influenced by lipid than other nutrients. In conclusion, using appropriate carbohydrates (~30%) in the sturgeon diet helps to spare protein. Furthermore, it is suggested to decrease the amount of lipid in high protein diet, to improve higher sturgeon fillet quality and less oxidative damage in liver.     

Growth performance,lipid requirement and antioxidant capacity of juvenile Russian sturgeon Acipenser gueldenstaedti fed various levels of linoleic and linolenic acids

To evaluate the effects of dietary linoleic (LA) and linolenic acids (LN) on growth, enzyme activities to lipid addition and antioxidant capacity of the Russian sturgeon, Acipenser gueldenstaedti, 10 diets with different sources of lipid were formulated. Coconut oil in the basal diet was replaced by sunflower oil to make three diets (LA0.5 + LN0, LA1.0 + LN0 and LA2.0 + LN0) with dietary LA at 0.5%, 1.0% and 2%, by perilla oil to obtain three diets (LA0 + LN0.5, LA0 + LN1.0 and LA0 + LN2.0) with dietary LN at 0.5%, 1.0% and 2%, and by the combination of sunflower oil and perilla oil to provide three diets (LA0.25 +LN0.25, LA0.5 + LN0.5 and LA1.0 + LN1.0) containing LA and LN at 0.25, 0.50 and 1.00%. Coconut oil was used as the control diet at 10%, but without LA and LN (LA0 + LN0). After feeding for 56 days, the fish whole body, the serum and the liver of sturgeon were sampled. Fish fed LA0 +  LN0 and LA0 + LN2.0 gained lowest weight but was not significantly different from the fish fed LA0 +  LN1.0. Fish fed LA1.0 + LN1.0 gained highest weight among all groups. Feed conversion ratio was the best in fish fed LA1.0 +  LN1.0. Survival, condition factor and viscerosomatic index did not differ among treatments. Total body n‐6 fatty acids increased with the levels of n‐6. Total body n‐3 fatty acids also increased with dietary n‐3, and fish fed 2.0% LN had the highest content of total body n‐3 fatty acids among all groups. Triglyceride and cholesterol in the serum of fish fed LA1.0 +  LN1.0 were lowest. Fish fed LA1.0 +  LN1.0 showed the highest lipoprotein lipase and lipase activities, but the lowest malate dehydrogenase activity. Fish fed LA1.0 +  LN1.0 showed higher catalase, superoxide dismutase activity and total antioxidant capacity than fish fed other diets. This study indicates that diets containing both LA and LN are best for the growth of Russian sturgeon. The level of LA1.0 + LN1.0 in the diet is most beneficial for growth performance and antioxidant capacity in juvenile Russian sturgeon.     

Dietary microbial levan ameliorates stress and augments immunity in Cyprinus carpio fry (Linnaeus, 1758) exposed to sublethal toxicity of fipronil

A 45‐day feeding trial was conducted to study the stress ameliorating and immunomodulatory role of microbial levan in Cyprinus carpio fry exposed to sublethal dose (1/10th LC₅₀) of fipronil [(±)‐5‐amino‐1‐(2,6‐dichloro‐α,α,α‐trifluoro‐p‐tolyl)‐4‐trifluoromethylsulfinylpyrazole‐3‐carbonitrile]. Two hundred and twenty‐five fry were randomly distributed in five treatments in triplicates. Four purified diets were prepared with graded levels of microbial levan. Five different treatment groups were levan control L₀P₀ (basalfeed + 0% levan without exposure to pesticide); pesticide control L₀P₁ (basalfeed + 0% levan with exposure to pesticide); L_0.25P₁ (basalfeed + 0.25% levan with exposure to pesticide); L_0.50P₁ (basalfeed + 0.50% levan with exposure to pesticide) and L_0.75P₁ (basalfeed + 0.75% levan with exposure to pesticide). Lactate dehydrogenase (LDH), malate dehydrogenase (MDH) and fructose‐1,6‐diphosphatase (FDPase) activites were significantly (P < 0.05) increased, whereas alkaline phosphatase (ALP), adenosine triphosphatase (ATPase) and acetyl choline esterase (AchE) activities were significantly (P < 0.05) reduced in higher levan‐fed groups. RBC, haemoglobin and WBC counts were significantly (P < 0.05) increased in the levan‐fed groups. Similar trends were also observed for the total serum protein, globulin, NBT and lysozyme activities. Blood glucose and serum cortisol exhibited a third order polynomial relationship with increasing level of dietary levan. Overall result showed stress ameliorating, immunostimulating and protective role of microbial levan against fipronil‐induced stress in C. carpio fry at 0.75% level of dietary levan supplementation.     

Effects of low salinity stress on immune response and evaluating indicators of the swimming crab Portunus trituberculatus

The purpose of the present study was to investigate the effects of salinity stress on immune responses and evaluating indicators in swimming crab Portunus trituberculatus. The crabs (150 ± 8.5 g in body weight) were exposed to different salinities as 21, 26 and 31‰ (control) for 6 days. The results showed the total haemocyte counts (THC) and prophenoloxidase (proPO) activity in the haemocytes decreased significantly in the treatment groups after 6 hr, and reached the lowest levels at 12 hr. The phenoloxidase (PO) activity in the plasma increased significantly and peaked at 12 hr, then recovered to control level after 24 hr. The phagocytic per cent of haemocyte, antibacterial and bacteriolytic activities in the plasma decreased significantly in the treatment groups, and reached the lowest level at 12 hr, then recovered to control level after 72 hr. The dopamine (DA) and 5‐hydroxytryptamine (5‐HT) contents in the plasma increased significantly and peaked at 12 hr, then recovered to control level, while the noradrenaline (NE) content in the plasma had no significant change throughout the duration of the experiment. The DA and 5‐HT receptors were significantly up‐regulated in the treatment groups. The highest value of mRNA expression of DA and 5‐HT receptors occurred at 12 hr and recovered to control level after 24 hr. In addition, the cAMP and protein kinase A (PKA) contents in the haemocytes increased significantly and peaked at 12 hr, then recovered to control level after 72 hr. The phospholipase C (PLC) and protein kinase C (PKC) contents in the haemocytes increased significantly and peaked at 12 hr, then resumed to control level after 24 hr. These results speculated that biogenic amine (DA and 5‐HT) is likely to play an important role in immune modulation via cAMP/PKA signalling pathway or PLC/PKC signalling pathway when P. trituberculatus is exposed to low salinity and these results will provide scientific data for immune evaluation.     

Growth performance,haematological parameters,antioxidant status and salinity stress tolerance of juvenile Pacific white shrimp (Litopenaeus vannamei) fed different levels of dietary myo‐inositol

A 10‐week growth trial was run to evaluate effects of myo‐inositol (MI) on growth performance, haematological parameters, antioxidative capacity and salinity stress tolerance of Litopenaeus vannamei. Six practical diets supplemented with graded levels of MI (designated as MI0, MI600, MI1200, MI2400, MI 3600 and MI4800 for 448.8, 974.2, 1568.0, 2810.6, 3835.5 and 4893.6 mg/kg diet, respectively) were fed to six replicate groups of L. vannamei (mean initial body weight 0.63 ± 0.00 g). The results showed that significant increment of growth performance was observed in shrimp fed MI600 diet than those fed MI1200 diet. Lipid concentration in whole body of the shrimp fed MI600 diet was significantly increased. Shrimp fed MI0 diet had lower total protein (TP) as compared to shrimp fed the MI‐supplemented diets (except MI4800 diet). In general, lower activities of antioxidant enzymes and higher malondialdehyde (MDA) content in haemolymph and hepatopancreas were recorded in shrimp fed MI0 diet, compared to those fed the MI‐supplemented diets. Reduced survival after 7‐h salinity stress was present in shrimp fed MI0 diet as compared to those fed MI4800 diet. Dietary MI requirement for glutathione peroxidase activity of L. vannamei was 2705 mg/kg diet.     

Tuna viscera protein hydrolysate: nutritive and disease resistance properties for Persian sturgeon (Acipenser persicus L.) larvae

The effect of fish protein hydrolysate (FPH) on the growth, feed utilization, digestive enzymes, gut microflora and resistance to bacterial challenge in Persian sturgeon (Acipenser persicus) larvae during a 45‐day feeding trial has been investigated. Artificial diets containing different levels of tuna visceral protein hydrolysate (PH0, PH10, PH25 and PH50) and live foods (Artemia: 5 days, Daphnia: 40 days) were fed to Persian sturgeon larvae. Larvae fed on the PH10 and PH25 had growth, feed utilization, protein content and trypsin activity significantly better than PH0 and PH50 groups (P < 0.05). Condition factors, survival rate and pepsin activity were not significantly different (P > 0.05). Brush border membrane enzymes to cytosolic enzyme ratio revealed that maturation had been occurred in 41 days post hatch (dph) at moderate FPH levels. In 54 dph larvae, this ratio was not affected by the level of FPH in the diet. No significant differences were observed in the total number of gut microflora or in the resistance to Aeromonas hydrophila (P > 0.05), whereas lactic acid bacteria was significantly higher in PH50 (P < 0.05). The results of this study show that application of moderate levels of FPH in Persian sturgeon diets could enhance larvae performance due to the early maturation in intestinal.     

The effects of temperature on respiration of Amur sturgeon,Acipenser schrenckii,at two acclimation temperatures

In order to clarify the respiratory responses strategy of Amur sturgeon Acipenser schrenckii exposed to water temperature changes, respiratory parameters of the fish were studied under two temperature regimes: fish acclimated at 13°C for Group I, temperature was increased to 16°C, 19°C, 22°C and 25°C and then returned stepwise to 22°C, 19°C, 16°C and 13°C; and fish acclimated at 25°C for Group II, the water temperature was reduced in steps to 22°C, 19°C, 16°C and 13°C, subsequently, returned to 16°C, 19°C, 22°C and 25°C. The results showed that the respiratory frequency (f_R), oxygen consumption rate (VO₂) and gill ventilation (V_G) of the fish were directly dependent on the acute temperature in both acclimation groups (p < .05). The initial 25°C VO₂ in Group II was significantly higher than the initial 13°C VO₂ in Group I (p < .05), but was significantly lower than that at 25°C in Group I (p < .05). In Group I, respiratory stroke volume (V_S.R) of fish significantly increased or decreased with the acute temperature increases or decreases, respectively (p < .05); oxygen consumption efficiencies (EO₂) of fish did not significantly show differences when temperature increased to 25°C from 13°C (p > .05), but the EO₂ significantly declined while returning to acclimation temperature (p < .05). In Group II, the V_S.R of the fish did not significantly change with acute temperature fluctuations between 25 and 13°C (p > .05), while the EO₂ increased with acute temperature increases (p < .05). The Q₁₀ values for f_R, VO₂, V_S.R, V_G and EO₂ were 1.53–1.72, 1.92–2.06, 1.07–1.60, 1.78–2.44 and 1.11–1.65 at 13–25°C of temperature interval respectively. Amur sturgeon showed partial metabolic compensation to temperature changes. The study results suggest that the ability of Amur sturgeon to regulate metabolism in response to acute temperature changes makes this species good adaptability in the aquaculture rearing.     

Short-term crowding stress in Atlantic cod, Gadus morhua L. modulates the humoral immune response

Considering overcrowding as a stressor, the effects of a short-term exposure on the immune responses of Atlantic cod, Gadus morhua L. were determined at 2, 24 and 72 h post-crowding. While plasma glucose and total antioxidant capacity were quantified as stress responses, immune responses were based on humoral indices. Bactericidal capacity of plasma was also assessed. There was a significant increase in plasma glucose and total antioxidant capacity at 2 h post-crowding, however the former returned to pre-stress levels 24 h later and the latter remained elevated until 72 h. The plasma protein did not reveal any significant change, but there was a transient upregulation of globulin at 24 h post-crowding. The myeloperoxidase activity increased at 2 h after the stress, but returned to its pre-stress levels at 24 h. The lysozyme activity was upregulated even from the first time point after stress, although the differences were significant only at 24 and 72 h compared to the activity prior to stress. At 72 h post-crowding there was a significant increase in alkaline phosphatase activity while haemolytic activity showed a significant decrease. An increase in the proliferation of the bacterial pathogens, Vibrio anguillarum and Aeromonas salmonicida was seen from 24 h in the plasma of the stressed fish. Thus, our finding suggests that short-term crowding stress modulates the immune responses in Atlantic cod and therefore husbandry procedures should consider these effects while addressing better management strategies.     

Changes in selected stress and immune‐related genes in Atlantic cod,Gadus morhua,following overcrowding

Using Atlantic cod, Gadus morhua, as a model for the stress response in gadoid fish, the changes in the expression of some stress and immune genes as well as the profiles of plasma cortisol were examined. Adult fish were kept at a density of ca. 100 kg m^?3 by lowering the water level in the rearing tank for 1 h and this short‐term crowding stress was repeated thrice over a 12‐h interval period. Blood samples were collected before exposure and at 2, 24 and 72 h post crowding. Plasma cortisol level significantly increased at 2 h post crowding but returned to pre‐crowding levels 24 h after exposure. The relative expression of the stress response genes, glucose transporter‐3 and a putative heat shock protein 70 significantly increased at 2 and 24 h post crowding respectively. Significant up‐regulation of the pro‐inflammatory cytokines, interleukin (IL)‐1β and IL‐8, as well as anti‐bacterial genes, g‐type lysozyme and bactericidal permeability‐increasing protein/lipopolysaccharide‐binding protein (BPI/LBP) was also observed at 2 h and the levels were maintained until 72 h post exposure, except for BPI/LBP which had maximum up‐regulation at 24 h. The present observations have implications with respect to fish welfare and assessment of the health status of the farmed fish.     

Novel droplet vitrification combined with fish antifreeze protein type III enhances cryoprotection of semen in wild endangered Persian sturgeon Acipenser persicus (Borodin, 1897)

In this study, the efficiency of a novel droplet vitrification technique along with different doses of fish antifreeze protein (AFP) type III on Persian sturgeon thawed spermatozoa quality (motility duration and motility percentage) was investigated. Semen of seven male individuals was pooled in equal volumes and diluted with 4°C Tris‐Hcl (100 mM), pH = 8 extenders containing 0, 5, 10, 15 μM of AFP type III in a ratio of 1:1 (semen/extenders). Treated semen was dropped into liquid nitrogen. Solidified droplets were stored for 2, 60 and 120 days and thawed by plunging them into a tube containing 5 mL Tris‐Hcl (100 mM), pH=8 with 1% BSA at 37°C. Motility duration in all treatments had no significant difference comparing to fresh sperm (P > 0.05), but their motility percentage was significantly lower. Treatment with 10 μM of AFP had significantly higher motility percentage (16.11 ± 0.5%) comparing to other treatments (P < 0.05). There was no significant difference between 0, 5, 15 μM of antifreeze protein treatments (P > 0.05), suggesting that antifreeze protein effectiveness are highly dose dependent, and dose of 10 μM is appropriate in Persian sturgeon spermatozoa droplet vitrification. Besides, the present technique obtained higher quality of spermatozoa comparing to its analogue techniques.     

Hepatoprotective and antioxidant effects of dietary Angelica sinensis extract against carbon tetrachloride‐induced hepatic injury in Jian Carp (Cyprinus carpio var. Jian)

The present study aimed to evaluate the hepatoprotective effects of Angelica sinensis extract (ASE) against carbon tetrachloride (CCl₄)‐induced hepatotoxicity in Jian carp (Cyprinus carpio var.Jian). Fish were fed diets containing four doses of ASE (0%, 0.1%, 0.5% and 1.0%) for 60 days, and then given an intraperitoneal injection of 30% CCl₄ in olive oil at a volume of 0.05 mL/10 g body weight. At 72 h post injection, blood and liver samples were collected for biochemical analysis, comet assay, histopathological examination and CYP3A mRNA expression. Results showed that the increases of glutamate pyruvate transaminase (GPT) and glutamate oxalate transaminase (GOT) induced by CCl₄ were significantly inhibited by pre‐treating the fish with 0.1%, 0.5% and 1.0% ASE in the diets. The elevation of lactate dehydrogenase (LDH) and the reductions of the total protein (TP) and albumin (Alb) in the serum induced by CCl₄ were also inhibited by pre‐treatments with 0.5 and 1.0% ASE. In the liver tissue, pre‐treatment with 1.0% ASE significantly inhibited the malondialdehyde (MDA) formation and the reductions of the total antioxidant capacity (T‐AOC), superoxide dismutase (SOD), glutathione (GSH) and CYP3A mRNA expression induced by CCl₄. Comet assay showed that tail moment, olive tail moment, tail length and tail DNA% were positively changed in fish pretreated with 0.5 and 1.0% ASE. CCl₄‐induced histological changes were obviously reduced by 0.5% and 1.0% ASE. Overall results prove the hepatoprotective effect of ASE in a dose‐dependent manner and support the use of ASE (1.0%) as a hepatoprotective and antioxidant agent in fish.     

In vitro oocyte maturation and blood‐circulating steroid hormones in Sterlet (Acipenser ruthenus) and Siberian sturgeon (Acipenser baeri)

The oocyte of Sterlet (Acipenser ruthenus) and Siberian sturgeon (Acipenser baeri) was evaluated after incubation with 17α, 20β‐Dihydroxyprogesterone (DHP) in artificial media. Concentration of testosterone (T), progesterone (P4) and 17‐β estradiol (E2) in blood and their relation to fertilization rate were measured during experimental period. The oocytes at the same developmental stages were incubated in SIS (based on sturgeon blood ionic composition), RM2 (Ringer solution modified for sturgeons) and L‐15 (Leibovitz medium) artificial mediums in the presence of 1 μg/ml of 17α, 20β‐Dihydroxyprogesterone for 12, 18 and 24 hr. The result of this study demonstrated that fertilization rate decreased with the increasing duration of incubation in all mediums. In the Siberian and Sterlet sturgeon, the highest fertilization rate was observed in the oocytes incubated in RM2 (0.81 ± 0.4) and SIS (0.44 ± 0.8) mediums for 12 hr respectively. In the Siberian sturgeon, fertilization rate decreased significantly (p < .05) with incubation time in all three mediums. In Starlet, fertilization rate decreased significantly (p < .05) with time and reached a minimum after 24 hr (0.16 ± 0.1) in L‐15 medium. No significant (p > .05) differences were observed between blood plasma hormones and fertilization rate. The results of this study indicated that 17α, 20β‐Dihydroxyprogesterone is essential for induction of in vitro oocyte maturation in these species.