Karyotype variability in successive generations after hybridization between the great sturgeon, Huso huso (L.), and the sterlet, Acipenser ruthenus L.

Effects of particle size, fish size and temperature on the filtration rate of silver carp were determined. When feeding at 20°C on zooplankton and spherical particles (yeast, micronic beads and pollen), 32-g silver carp filter particles larger than 70 urn at a maximum rate of 18.251 h⁻¹. For particles smaller than 70 μm, filtration rates decrease with decreasing particle size until there is no measured filtration for particles smaller than 10 μm. Filtering rates ( FR ) for particles between 10 and 50 μm are described by the equation, FR =−20.8 + 21.7 × log particle diameter. Filtration rates rise as fish size, particle size and temperature increase. Filtration rates per unit biomass, however, fall as fish size increases: FR = 1.54 W^0.713, where FR is the maximum filtration rate in ¹ h ¹ fish ¹ and W is weight of fish in grammes. The results of these trials are consistent with the hypothesis that particle selection by silver carp is a mechanical, passive function of gill raker morphology.     

Determination of sex and maturity stage of great sturgeon (Huso huso) using steroid sex hormones profiles,histology and laparoscopic images of gonads

We studied sex and maturity stage of great sturgeon with different reproductive stages using sex steroid hormones concentrations in blood plasma, gonad histology and laparoscopic technique. One hundred sixty farmed great sturgeons at ages between 1 and +12 years and weight ranged from 0.45 to 49.65 kg (80 males and 80 females, 20 fish of each maturity stage) were selected. Mean sex steroid levels showed that testosterone (T) and 11ketotestosterone (11KT) in plasma varied significantly by sex and maturity stage. But the mean concentrations of 17B‐estradiol (E2) varied significantly only between the maturity stages I and III. All fish were sex determined by laparoscopy and histology examinations confirmed it. Our results showed, however laparoscopy was effective method for sex determination at four maturity stages, but young fish at maturity stage I required gonadal histology examinations to confirm sex. The present study results showed that some steroid sex hormones (T and 11KT) can be used to determine sex and reproductive stage in great sturgeon, especially in later maturity stages. Although the laparoscopy may be stressful and cause small scars on the body of the fish, but it is a fast, effective, and cheap method for sex and maturity stage assessment (30 to 40 s for each fish), especially at later maturity stages. Histology of gonads is a very accurate, but it is an invasive method and not a suitable technique for commercial purposes. Histology is more suited for scientific studies than commercial application. The ability to use minimally invasive methods for sex determination will assist broodstock management and conservation in sturgeons.     

A comparative study of feeding methods: Effect on the growth,behaviour and biochemical performance of juvenile Beluga sturgeon (Huso huso Linnaeus, 1758)

This study compared the influence of feeding methods on growth parameters of young‐of‐year Beluga sturgeon Huso huso in a 6‐week trial. Fish with an average weight 150.3 ± 0.8 g (±SE) were stocked into nine circular concrete tanks (30 fish per tank) in an open circular system with water temperature of 18.9°C. All fish were fed by three different feeding methods: (a) hand‐fed (HF), (b) continuously available (automated feeder; AF), (c) half of daily feed provided by hand, and another half by automated feeder (combined feeding). For the hand‐feeding method, fish were fed at 09:00, 14:00, 19:00, and 24:00. The entire automatic feeding groups were fed with the same amount of feed. The mean final body weight was the highest in fish fed by AF compared to fish fed by HF. Body weight increase, condition factor, specific growth rate, and feed conversion ratio did not differ among the feeding groups. Fish fed by AF revealed higher swimming activity than the HF group. No significant changes were found in hematocrit, glucose and total protein concentrations among treatments. The results showed less dependence of growth and physiology of Beluga sturgeon on feeding method, but automated‐feeding was shown to be suitable for sturgeon rearing because of further low labour costs in rearing systems.     

Immune responses of great sturgeon Huso huso to Aeromonas hydrophila bacterin

The immunocompetent cell population, lysozyme activity, chemiluminescence response and antibody titre were assessed in great sturgeon Huso huso after intraperitoneal immunization with formalin-inactivated whole cells of Aeromonas hydrophila . Generally an increase was seen in indices of immunocomptent cell counts of immunized fish compared to the control group. The neutrophil count was higher in immunized fish from day 29. Lysozyme activity in liver and spleen samples of immunized fish was initially significantly higher than unimmunized fish, but was not different in serum and kidney. Antibody titre and respiratory burst in immunized fish were mainly significantly higher than unimmunized fish.     

Changes in sodium,calcium and magnesium ion concentrations in sturgeon (Huso huso) urine and in kidney morphology

During adaptation to brackish water the young great sturgeon Huso huso is able to regulate its serum osmolarity and ion concentrations. After transfer from fresh water to brackish water the ion concentrations in the urine increase and the urine becomes isoosmotic to the blood serum after 24h. The Na⁺ and K⁺ concentrations in the urine increase during the first 12 h by 4.4 and 7.7 times, respectively, later decreasing again. The Mg²⁺ and Ca²⁺ concentrations in the urine increase by 3.4 and 14 times during the first 72h in brackish water and remain high thereafter. These results suggest that the kidneys play an important part in the regulation of serum osmolarity and in the removal of Ca²⁺; however, in contrast to teleosts, Mg²⁺ must be removed extrarenally. During adaptation to a hyperosmotic medium the diameters of the Malpighian bodies, the glomeruli and the diameter of the tubules initially all decrease, but the distal tubules become morphologically differentiated into two regions and the diameter of the distal section later increases again. It is suggested that this is the site of Ca²⁺ secretion into the urine.     

The effect of feeding rate on growth of pectoral fin spine of juvenile great sturgeon Huso huso (Linnaeus, 1758)

The effect of two feeding rates (0.5 and 1.5% of total body weight) was assessed on the growth of pectoral fin spines of captive juvenile great sturgeon, Huso huso, after second year of life. The fish received Oxytetracycline (OTC) twice in the first and second years of their lives under basic diet. During the 5‐month experimental period, juveniles (mean 1,187.4 g, 0.1 standard deviation [SD]), n = 50) were reared with two feeding rates under similar conditions in 10 fiberglass tanks (1.5 m³). The fish were fed manually with a commercial diet twice a day (35% Biomar, Nersac, France) throughout the experiment. The OTC marks were distinguished in all pectoral fin spine sections under ultraviolet light. The means of the first and second annular radii were 806.6 µm (27.2 SD) and 2,246.5 µm (50.2 SD), respectively. The marginal increment analysis beyond the second OTC mark revealed a significantly smaller marginal increment for low feeding rate treatment (143.9, 11.2 SD) as compared to the high feeding rate one (269.0, 14.6 SD). The results indicate the slower growth rate in the fish fed the low feeding treatments seen in the pectoral fin spine formation, which can be used as an indicator of recent feeding history in sturgeon juveniles. The best daily feeding rate for great sturgeon of 2,460 g was determined to be 1.5% body weight/day in this study.     

Effect of prebiotic mannan oligosaccharide on hematological and blood serum biochemical parameters of cultured juvenile great sturgeon (Huso huso Linnaeus, 1754)

The nutritional effects of prebiotic mannan oligosaccharide were evaluated using hematological and blood serum biochemical parameters in cultured juvenile great sturgeon (Huso huso). Fish were offered formulated diets containing two levels of prebiotic mannan oligosaccharide (2 and 4 g kg^?1); a basal diet with no prebiotics was used as control. The experiment lasted for 46 days. Blood samples were collected from the caudal veins of 18 apparently healthy fish (average weight 217.77 ± 29.8 g) at the end of the trial. No significant differences were found in the serum enzyme activity levels between treatments (P > 0.05). However, adding mannan oligosaccharide as a supplement to the basal diet resulted in significant differences in lymphocytes and eosinophils between the control and the 2 g kg^?1 treatment (P < 0.05) as well as a significant difference in the creatinine factor in the 2 g kg^?1 mannan oligosaccharide treatment (P < 0.05). The results show that it would be advantageous to add 2 g kg^?1 mannan oligosaccharide to the diets of juvenile great beluga sturgeon (Huso huso).     

Differential expression of foxl2 and cyp19a1a mRNA during gonad developmental stages in great sturgeon Huso huso

This study aimed to determine the sex specificity and expression pattern of foxl2 and cyp19a1a genes in great sturgeon Huso huso gonads during gonadal sex differentiation and development. The results revealed that foxl2 and cyp19a1a mainly expressed in female gonads and during gonad development the foxl2 and cyp19a1a mRNA expression is required for ovarian development.     

Effects of long-term cortisol treatments on gonadal development, sex steroids levels and ovarian cortisol content in cultured great sturgeon Huso huso

The objective of this study was to examine the effect of cortisol implantations on gonadal development, sex steroid levels, and ovarian cortisol content in cultured great sturgeon Huso huso. Three groups of 5 fish for each treatment were considered. The experimental groups included: control (capsules containing cocoa butter alone), low cortisol (C(5); 5mg cortisol/kg body mass+cocoa butter) and, high cortisol (C(50); 50mg cortisol/kg body mass+cocoa butter). The capsules containing hormones and cocoa butter were intraperitoneally implanted into 3-year-old female fish at pre-vitellogenic stage (mean initial body mass 6809.7 ± 73 g) every 6 weeks over a 6-month period from January to June. The serum levels of cortisol, glucose, cholesterol and sex steroids (testosterone and 17β-estradiol) were determined at the initial time and three weeks after each implantation. Oocyte histological characteristics (the diameter and area of the oocyte, the diameter and area of the nucleus and the ratio of the nucleus area to the oocyte area) were measured at the end of the experiment and compared to those at the initial time. Ovarian cortisol content was measured at the end of the experiment. The results showed that serum cortisol levels varied in a dose-independent manner, so that the highest cortisol concentrations were observed in C(5)-treated fish throughout the experiment. Serum glucose levels were significantly higher in cortisol-treated groups than those in the control group. The high dose of cortisol elicited a significant constant increase in serum cholesterol concentrations. Fish implanted with the high cortisol dose showed significant declines in serum testosterone and 17β-estradiol concentrations throughout the experiment. No significant differences were found in oocyte histological characteristics among experimental groups. The cortisol implants elicited a dose-dependent increase in ovarian cortisol content. At the end of trial, body-growth indices were the lowest in C(50)-implanted fish, while the low cortisol dose had no effect on growth relative to the controls. These results indicated that chronic stress induced by cortisol implantation in great sturgeon suppressed gonadal steroidogenesis and somatic growth but had no effect on ovarian growth and development.     

Modifying the physiological responses to handling stress in beluga sturgeon Huso huso (Linnaeus, 1758); Interactive effects of feeding time and dietary fat

The present study investigated the interaction of feeding times with two dietary fat levels on physiological responses to handling stress in juvenile Beluga sturgeon. Fish were fed with two different diets (high energy; HE: 24% fat and low energy; LE: 12% fat) for 8 weeks at two feeding times; 09:00 and 16:00 (during the day) or 21:00 and 04:00 (during the night). At the end of the trial, blood samples were taken and the resting fish were held in a net out of water for 90 s as the handling stressor. Three hours after application of stress, post‐stress blood was taken. Cortisol, glucose, and lactate concentrations were considered as stress indicators. The mean values of cortisol and lactate levels did not reveal a significant difference between pre‐ and 3‐hr post‐stress samples, but the average concentration of glucose showed a significant difference. Cortisol, lactate and glucose concentrations were not influenced by the difference in the diets. Moreover, the cortisol and lactate concentrations were not affected by the different feeding times, while glucose levels were significantly affected by the feeding times with the lowest level in fish fed during the day. With respect to stress indicators, the results revealed that feeding times affected pre‐ and post‐stress secondary response to handling stress, but the rate and magnitude of metabolites (cortisol, glucose and lactate) were not affected by dietary fat levels. Therefore, it is necessary to examine the best feeding times with the interaction of feed ingredients in sturgeon farming.     

Multiple molecular forms of glucagon and insulin in the kaluga sturgeon, Huso dauricus

Five molecular forms of glucagon and two molecular forms of insulin were characterized from the kaluga sturgeon. Substitutions occurred at two to thirteen internal amino acid residues among the five molecular forms of glucagons, indicating that these glucagons were encoded by five distinct genes. The amino acid sequences of two insulins from the kaluga sturgeon were identical to those of paddlefish insulin-II and Russian sturgeon insulin except that kaluga sturgeon insulin-I had an extension of five residues at the B-chain N-terminus. This is the first demonstration that more than two molecular forms of glucagon have been characterized from a single animal species.     

Cortisol and glucose responses after acute stress by net handling in the sparid red porgy previously subjected to crowding stress

In red porgy Pagrus pagrus subjected to 3 weeks of chronic stress by crowding, plasma cortisol remained significantly higher in crowded fish compared to controls. There was no significant effect of crowding on plasma glucose levels. When the crowded fish were subjected to an acute handling the plasma cortisol response was similar to that of the uncrowded fish. No significant differences were found between the groups. The changes in plasma glucose following acute handling were also similar in both crowded and uncrowded fish.     

Biochemical and hemato-immunological parameters in juvenile beluga (Huso huso) following the diet supplemented with nettle (Urtica dioica)

The present study investigated the effects of different dietary nettle (Urtica dioica) levels on biochemical, hematological and immunological parameters in beluga (Huso huso). Fish were divided into 4 groups before being fed for 8 weeks with 0%, 3%, 6% and 12% of nettle. The blood samples were collected on week 4 and 8. The use of nettle did not significantly change the mean cell volume, mean cell haemoglobin, lymphocytes, eosinophils, albumin, glucose, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and lysozyme activity on week 4 and 8. After 4 weeks, the total red blood cell (RBC) and hematocrit (Ht) showed a significant increase in 12% nettle group compared to the 3% nettle and control groups but haemoglobin (Hb) had a significant change in 12% nettle compared to the control. At the same time was not found a significant change in the mean cell haemoglobin concentration (MCHC), total white blood cell (WBC), neutrophils, respiratory burst activity (RB), total immunoglobulin (Ig) and total protein (TP), triglyceride (Tri) and cholesterol (Chol). After 8 weeks, the fish treated with nettle exhibited significantly increase in neutrophil and Hb levels compared to the control and between treatment groups, 12% nettle group shown the highest Hb while RBC and Hct values significantly rose in fish fed by 12% compared to the control. Supplementing 6% and 12% nettle increased the WBC and MCHC compared to the other groups. The group fed 12% showed a highly significant difference in RB, TP and Ig after 8 weeks. However, Tri and Chol were significantly decreased in the juvenile beluga fed by the 6% and 12% nettle diet compared to the other groups. The results suggest that by using this herb there will be an improvement in hemato-biochemical parameters and immune function of juvenile beluga.     

Developmental structure of the vertebral column,fins, scutes and scales in bester sturgeon,a hybrid of beluga Huso huso and sterlet Acipenser ruthenus

In the larval bester, a hybrid sturgeon of beluga Huso huso and sterlet Acipenser ruthenus, development of cartilage around the notochord began 7 days post hatch (dph) (14·0 mm, total length, L_T). The vertebral cartilage develops in the following sequence: basidorsals and basiventrals, neural canals, neural spines and ribs. The development of ribs remained incomplete in the largest specimen (181 dph, 179 mm L_T) that was examined. Endoskeletal development of the fins began 4 dph for the dorsal and anal fins, 6 dph for the pectoral fin and 10 dph for the caudal and pelvic fins. Complete elements of all fins were observed by 91 dph and complete ossification of fin rays was observed by 122 dph in the double‐stained specimens. Observation of the histological sections, however, suggested that ossification occurred soon after the formation of the organic matrix in the fin rays. Dorsal scutes were first visible by 25 dph, followed by the lateral and ventral scutes, which were visible by 37 and 44 dph, respectively. The number of scutes was fixed at 44, 59 and 91 dph and ossification was complete by 59 (dorsal) and 91 dph (lateral and ventral scutes) in the double‐stained specimens. Ossification occurred soon after the formation of the scute organic matrix in the histological sections. Four types of scales were observed in the H. huso×A. ruthenus hybrid. Median predorsal, preanal and small scales on the anterior section of the head were visible by 59 dph. Scales on the caudal fin were visible by 91 dph and a variable assemblage of scales anterior to the anal fin was visible by 122 dph. Both the scutes and scales developed in a process that is similar to that of intramembranous ossification.     

3种野生地被植物对践踏胁迫的生理生态响应特征

不同强度践踏胁迫下,对3种野生地被植物主要生理生态响应特征进行了研究,结果表明：重度践踏胁迫下匍枝委陵菜的盖度、生物量下降幅度最大,和对照相比分别下降46.58%和43.53%。重度践踏胁迫下车前的纤维素含量最高,比对照增加43.31%。中度践踏胁迫下紫花地丁丙二醛含量积累最少,比对照升高28.57%。紫花地丁叶绿素含量对践踏胁迫响应敏感,轻度践踏可使叶绿素含量提高45.21%（p< 0.05）,重度践踏使匍枝委陵菜和紫花地丁的叶绿素含量分别下降了21.59%和29.37%。践踏胁迫使3种野生地被植物的群体净光合速率下降。综合分析结果为车前最耐践踏,紫花地丁次之,匍枝委陵菜最不耐践踏。     

Responses of Nitraria tangutorum to water and photosynthetic physiology in rain enrichment scenario

Under the global warming conditions, great attention has been paid to the effects of precipitation on ecophysiological characteristics in desert plants. Nitraria tangutorum is one of the dominant shrubs distributes in desert outside Minqin oasis, Gansu Province. The artificial simulated rainfall experiments were carried out in four consecutive years from 2008 to 2011, in an attempt to understand the mechanisms of the photosynthetic response in desert plant to the variation of future precipitation pattern. The water and photosynthetic physiological characteristics of leaves in N. tangutorum were examined from July 24 to 26 in 2011 under different simulated rainfall increase gradients (increased 0%, 25%, 50%, 75% and 100% of mean annual precipitation, respectively). We measured leaf traits that could reflect both leaf water status (e.g., leaf water content and leaf water potential) and photosynthetic physiology (e.g., maximum net photosynthetic rate). The results showed that leaf water content and leaf water potential of N. tangutorum increased with increasing rainfall. Leaf water content and leaf water potential of N. tangutorum in the 100% increased rainfall treatment were significantly greater by 8.51% and 12.07% than the control (0% increased rainfall treatment). But leaf dry matter content and specific leaf weight gradually decreased with increasing rainfall. Leaf dry matter content and specific leaf weight in the 100% increased rainfall treatment were significantly lower by 6.92% and 25.93% than the control. Leaf maximum net photosynthetic rate (A_max), apparent quantum yield (AQY) and light saturation point (LSP) increased with increasing rainfall, while light compensation point (LCP) gradually decreased with increasing rainfall. AQY in the 100% increased rainfall treatment was significantly greater by 70.00% than the control. However, there were no significant differences in LSP and LCP between different treatments. A_max, transpiration rate (T_r), stomatal conductance (G_s) in the 100% increased rainfall treatment were significantly greater by 81.91%, 166.07% and 110.47% than the control, respectively. On the contrary, water use efficiency (WUE) in the 100% increased rainfall treatment was significantly less 48.28% than the control. There were no significant differences in intercellular CO₂ concentration (C_i) and stomatal limitation value (L_s) between different treatments. The correlation analysis showed that there were significantly positive correlations between leaf water content, leaf water potential, T_r and G_s. However, there were significantly negative correlations between leaf dry matter content, leaf specific mass and T_r, G_s, leaf water content and leaf water potential, suggesting that leaf gas exchanges were regulated by leaf water status. Therefore, N. tangutorum could adapt to the tendency of future increasing precipitation by the coordination of water physiology and photosynthesis.     

The physiological performance and immune responses of juvenile Amur sturgeon (Acipenser schrenckii) to stocking density and hypoxia stress

Stocking density and hypoxia are considered priority issues in aquaculture research. In this study, two experiments were carried out in order to investigate the effects of chronic stress (stocking density) and acute stress (hypoxia) on the immune physiology responses (hematology, serum cortisol, glucose, total protein and the mRNA expression of CYP 1A) of juvenile Amur sturgeon (Acipenser schrenckii). In the chronic stress study, three triplicate groups of Amur sturgeon (42.0 ± 2.3 g) were reared in nine square concrete ponds (4.4 × 4.4 × 0.45 m³) at three stocking densities (3.7, 6.9 and 9.0 kg/m³) for 50 days. In the acute stress study, three triplicate groups: normal group (7 mg/l), hypoxia group 1 (5 mg/l) and hypoxia group 2 (3 mg/l) were used in nine 100 L indoor tanks. Sampling was performed at the end of the stocking density experiment (50 days) and at 0, 0.5, 1.5, 3 and 6 h after hypoxia stress. The results showed that increased stocking density reduced the morphological indexes (hepatosomatic index, spleen-somatic index and kidney-somatic index), while total protein and hemoglobin increased significantly in the stressed group. In response to hypoxia, the levels of cortisol, glucose and hematological parameters elevated significantly after this stress. As for spleen-somatic index, there was a decline after hypoxia though H1 group returned to the normal level at 3 h and 6 h after hypoxia stress. Additionally, In order to better understand the immune response of Amur sturgeon to chronic and acute stressors, we cloned the complete coding sequence of Amur sturgeon CYP 1A for the first time and investigated its tissue-specific expression and stress-induced expression. CYP 1A mRNA in liver showed over expressions both in crowding condition and in hypoxia stress. The same trend was also found in spleen and kidney which may provide evidence that CYP 1A could serve as a good indicator of immune response in Amur sturgeon. In addition, the result suggested a typical immune response both in high stocking density and hypoxia stress. But the chronically stressed fish might have an adaptation capability to survive under a stable crowding condition without a change in some immune parameters (cortisol, glucose, WBCs and RBCs).