A comparison of constant acceleration swimming speeds when acceleration rates are different with critical swimming speeds in Chinese bream under two oxygen tensions

To investigate the effect of acceleration rates on the constant acceleration test speed (U _cat) and to compare U _cat with the critical swimming speed (U _crit) in Chinese bream (Parabramis pekinensis), the U _cat test at acceleration rates of 0.05, 0.1, 0.2, 0.4 and 0.8 cm s^?2 and the U _crit test in juvenile fish at 20 °C in either normoxia (>90 % saturation oxygen tension) or hypoxia (30 % saturation) were compared. The lactate concentration ([lactate]) of white muscle, liver and plasma and the glycogen concentration ([glycogen]) of white muscle and liver were also measured to identify whether tissue substrate depletion or tissue lactate accumulation correlated with exhaustion. The U _cat decreased with the acceleration rate, and there was no significant difference between U _crit and U _cat at lower acceleration rates. Hypoxia resulted in lower U _cat and U _crit, and the difference increased with decreased acceleration rates of the U _cat test, possibly due to the increased contribution of aerobic components in U _crit or U _cat at low acceleration rates. Hypoxia elicited a significant decrease in muscle [glycogen] and an increase in muscle and liver [lactate] in resting fish. All post-exercise fish had similar muscle [lactate], suggesting that tissue lactate accumulation may correlate with exercise exhaustion. Unlike hypoxia, exercise induced an increase in muscle [lactate] and a significant increase in plasma [lactate], which were worthy of further investigation. The similar swimming speed and biochemical indicators after exercise in the U _crit and U _cat groups at low acceleration rates suggested that U _cat can be an alternative for the more frequently adopted protocols in U _crit in Chinese bream and possibly in other cyprinid fish species.     

Metabolic,behavioral, and locomotive effects of feeding in five cyprinids with different habitat preferences

Fish generally perform routine swimming behaviors during food digestion; thus, changes in swimming performance and adjustments to spontaneous behavior resulting from digestion can have important ecological significance for wild fishes. The effects of feeding on metabolism, spontaneous activity, fast-start escape movement, and critical swimming speed (U _crit) were investigated in five cyprinids with different habitat preferences, specifically the Chinese crucian carp (Carassius auratus), common carp (Cyprinus carpio), black carp (Mylopharyngodon piceus), Chinese bream (Parabramis pekinensis), and qingbo (Spinibarbus sinensis). Generally, species in still water exhibited increased feeding metabolism, whereas species in flowing water showed higher spontaneous activity and locomotion performance. Digestion had no significant effects on either spontaneous activity or fast-start escape movement in the five cyprinids. These results could be due to the small meal sizes (approximately 2% body mass) and active foraging modes of cyprinids. The changes in aerobic swimming performance due to feeding were more complex. No effect of digestion on U _crit was observed in crucian carp (still water, high feeding metabolism, and low U _crit), common carp (widely distributed, high feeding metabolism, and high U _crit), and qingbo (flowing water, low feeding metabolism, and high U _crit), but digestion resulted in a significant decrease in the U _crit of Chinese bream (moderate feeding metabolism but high U _crit) and black carp (moderate feeding metabolism and low U _crit), suggesting no connection between postprandial U _crit changes and feeding metabolism (or between U _crit and preferred habitat). The maximum metabolic rate (MMR) of common carp and crucian carp increased after feeding, whereas the corresponding values for the other three cyprinids remained the same. The oxygen uptake capacity appears to meet the oxygen demand of both aerobic swimming and digestion in common carp and crucian carp, whereas qingbo sacrifices digestion for locomotion, and black carp and Chinese bream sacrifice locomotion for digestion under postprandial swimming conditions. The locomotion-priority mode of qingbo is adaptive to its active foraging mode in the demanding swimming habitat of rapidly flowing water, whereas the high respiratory capacities of postprandial crucian carp and common carp and hence the maintenance of their aerobic swimming performances might be a by-product of natural selection for hypoxia tolerance rather than for swimming speed.     

The effects of starvation and re-feeding on growth and swimming performance of juvenile black carp (<Emphasis Type="Italic">Mylopharyngodon piceus</Emphasis>)

We investigated the effects of starvation and re-feeding on growth and swimming performance and their relationship in juvenile black carp (Mylopharyngodon piceus). We measured the specific growth rate (SGR), resting metabolic rate (RMR) and constant acceleration test speed (U _CAT, the maximum swimming speed at exhaustion by constant acceleration test with 0.1667 cm s^?2 rate) in a treatment group (21 days of starvation then 21 days of re-feeding) and control group (routine feeding) (n = 20). Starvation resulted in a 17 % decrease in body mass of black carp (P < 0.05). After 21 days of re-feeding, body mass was greater than that of pre-starvation but still less than that of the control group at 42 days. During the re-feeding phase, the SGR of the treatment group was higher than that of the control group (P < 0.05). Starvation resulted in a significant decrease in the RMR and U _CAT. After 21 days of re-feeding, both the RMR and U _CAT recovered to the pre-starvation levels. In the control group, individual juvenile black carp displayed strong repeatability of the RMR and U _CAT across the measurement periods (P ≤ 0.002). In the treatment group, RMR showed significant repeatability between pre-starvation and re-feeding (P = 0.007), but not between pre-starvation and starvation or between starvation and re-feeding. U _CAT showed significant repeatability between pre-starvation and starvation (P = 0.006) and between pre-starvation and re-feeding (P = 0.001), but not between starvation and re-feeding. No correlation or only a weak correlation was found between any two variables of RMR, U _CAT and SGR, whereas the increment of the U _CAT (ΔU _CAT) was negatively correlated with that of SGR during the starvation phase (r = ?0.581, n = 20, P = 0.007) and re-feeding phase (r = ?0.568, n = 20, P = 0.009). This suggested that within individual black carp, there is a trade-off between growth and maintenance (or development) of swimming performance under food-limited conditions.     

The effect of temperature on the resting and post-exercise metabolic rates and aerobic metabolic scope in shortnose sturgeon <Emphasis Type="Italic">Acipenser brevirostrum</Emphasis>

The effects of acclimation temperature (15, 20, 25 °C) on routine oxygen consumption and post-exercise maximal oxygen consumption rates (MO₂) were measured in juvenile shortnose sturgeon (Acipenser brevirostrum LeSueur, 1818). The routine MO₂ of shortnose sturgeon increased significantly from 126.75 mg O₂ h^?1 kg^?1 at 15 °C to 253.13 mg O₂ h^?1 kg^?1 at 25 °C. The temperature coefficient (Q ₁₀) values of the routine metabolic rates ranged between 1.61 and 2.46, with the largest Q ₁₀ values occurring between 15 and 20 °C. The average post-exercise MO₂ of all temperature groups increased to a peak value immediately following the exercise, with levels increasing about 2-fold among all temperature groups. The Q ₁₀ values for post-exercise MO₂ ranged from 1.21 to 2.12, with the highest difference occurring between 15 and 20 °C. Post-exercise MO₂ values of shortnose sturgeon in different temperature groups all decreased exponentially and statistically returned to pre-exercise (resting) levels by 30 min at 15 and 20 °C and by 60 min at 25 °C. The aerobic metabolic scope (post-exercise maximal MO₂-routine MO₂) increased to a maximum value ～156 mg O₂ h^?1 kg^?1 at intermediate experimental temperatures (i.e., 20 °C) and then decreased as the temperature increased to 25 °C. However, this trend was not significant. The results suggest that juvenile shortnose sturgeon show flexibility in their ability to adapt to various temperature environments and in their responses to exhaustive exercise.     

The effects of starvation on fast-start escape and constant acceleration swimming performance in rose bitterling (<Emphasis Type="Italic">Rhodeus ocellatus</Emphasis>) at two acclimation temperatures

To investigate the effects of starvation and acclimation temperature on the escape ability of juvenile rose bitterling (Rhodeus ocellatus), we measured the fast-start escape and constant acceleration swimming performance of fish fasted for 0 (control), 1 and 2 weeks and half-lethal periods (6 or 4 weeks) at two temperatures (15 and 25 °C). Fish acclimated at a high temperature exhibited shorter response latency (R), higher maximum linear velocity (V _max) and longer escape distance during escape movement (D _120ms) than those at the low temperature. Starvation resulted in a significant decrease in V _max and D _120ms at either low or high temperature and a significant increase in R at only the high temperature in the half-lethal period groups (P < 0.05). The relationship between V _max (Y, m s^?1) and starvation time (X, week) was Y ₁₅ = ?0.062X + 1.568 (r = ?0.665, n = 36, P < 0.001) at low temperature and Y ₂₅ = ?0.091X + 1.755 (r = ?0.391, n = 40, P = 0.013) at high temperature. The relationship between U _cat (Y, cm s^?1) and starvation time (X, week) was Y ₁₅ = ?1.649X + 55.418 (r = ?0.398, n = 34, P = 0.020) at low temperature and Y ₂₅ = ?4.917X + 62.916 (r = ?0.793, n = 33, P < 0.001) at high temperature. The slopes of equations showed a significant difference between low and high temperature (F _1,63 = 9.688, P = 0.003), which may be due to the different energy substrate utilization when faced with food deprivation at different temperatures.     

Effect of the early temperature on the growth of larvae and postlarvae turbot, <Emphasis Type="Italic">Scophthalmus maximus</Emphasis> L.: muscle structural and ultrastructural study

Turbot specimens were kept at three temperatures (T _s ): warm (W) (21–22 °C), ambient (A) (17–18 °C) and cold (C) (13–14 °C) during the larval and early postlarval stages. At 90 days posthatching (dph), all of them were transferred to ambient T until 190 dph. At 2–3 dph, the specimens showed a monolayer of red muscle and immature white fibres; external or dermomyotome cells (presumptive myogenic cells) were observed on the surface of the red muscle. In the following stages, many myogenic cells and presumptive myogenic precursors were observed within the myotome, presumably derived of the dermomyotome. When comparing the growth at the same age (2, 10, 25, 37 dph), the body length and the muscle growth were positively influenced by the warm T, being the hyperplasia the muscle parameter more significantly influenced. The development rate was also positively correlated with the high T: the beginning of the metamorphosis took place at 15, 23 and 25 dph at W, A and C temperatures, respectively, with the highest body length values at ambient temperature. The metamorphosis finished at 25, 30 and 37 dph at W, A and C temperatures, respectively, with the highest body length values at warm temperature. However, the muscle cellularity was similar in all the groups at the end of the metamorphosis. At 90 and 190 dph, the largest body length was observed at W temperature. However, the muscle cellularity was similar between A and W; the number of fibres was similar in all the groups at 190 dph, which shows the beginning of a compensatory muscle growth in A and C, mainly in A.     

Comparison of low temperature adaptation ability in three native and two hybrid strains of the rotifer <Emphasis Type="Italic">Brachionus plicatilis</Emphasis> species complex

The low temperature adaptation ability of five selected strains of the Brachionus plicatilis species complex, i.e., three native strains [ Japanese (NH1L), Australian, German] and two hybrid strains [♀NH1L and ♂Australian (N × A) and ♀NH1L and ♂German (N × G),was investigated in terms of life history traits, reproductive characteristics, and mobility under different thermal conditions (12 and 25 °C). The life history traits of these five strains included a longer lifespan, reproduction period and generation times at 12 °C than at 25 °C, combined with reduced lifetime egg and offspring production. At 12 °C, the intrinsic rate of natural increase was higher in NH1L and N × A strains. Reproductive characteristics determined at 12 °C by batch culture showed active population growth for NH1L and N × G strains, while no resting egg production was observed in all of the strains tested. The ratio of swimming rotifers at 12 °C was monitored every hour for 6 h (short term) and every day for 10 days (long term). In the short-term study there was a 81% ratio of swimming rotifers of the NH1L strain, while other strains exhibited low swimming ratios (<60%). In the long-term study NH1L and two hybrid strains showed a >75% swimming ratio from the initial day of the study. These results suggest that outcrossing of rotifer strains is useful to obtain live food resources for the larviculture of cold water fish.     

Effects of anesthesia and surgery on U crit performance and MO2 in chum salmon, Oncorhynchus keta

Telemetry is a useful technique for elucidating salmon behavior, but the recovery periods before fish can be safely released after the attachment of telemetry devices have not yet been established. Reported recovery times vary widely, from 2 h to 13 days. We examined how anesthesia and surgery to attach external electromyogram (EMG) transmitters affected chum salmon (Oncorhynchus keta) recovery based on three physiological parameters. Fish subjected to anesthesia plus EMG transmitter attachment (EMG group), anesthesia only (AO group), and no handling (control) were placed in a swim tunnel. Critical swimming speed (U _crit), oxygen consumption (MO₂), and muscle activity (EMG values) were assessed 0, 1, 6, 12, 24, and 30 h after treatment. The MO₂ in the EMG and AO groups was higher than in the control group 1 h after treatment, but did not differ significantly from the control in all subsequent trials (from 6 to 30 h after treatment). Values for U _crit and EMG were not significantly different from the control group in any of the trials conducted 1–30 h after treatment. We concluded that chum salmon had regained their normal swimming ability by 6 h after treatment and could be safely released into the natural environment.     

Changes in the physicochemical and microbiological properties of dried anchovy <Emphasis Type="Italic">Engraulis japonicus</Emphasis> during storage

This study investigated the changes in the pH, thiobarbituric acid (TBA) value, volatile basic nitrogen (VBN), color L*, a*, b*, shear force, and microbial content (total plate count; TPC) of dried anchovy Engraulis japonicus in a home refrigerator and freezer at 2, ??1, ??5, and ??20 °C. The TBA value and shear force significantly decreased with increasing storage duration at all of the tested temperatures (p?<?0.05), whereas the VBN and TPC values increased (VBN significantly so) with increasing storage duration (p?<?0.05). The anchovy L* values decreased, whereas the a* (redness) and b* (yellowness) values increased as the storage period was lengthened. The pH decreased after 9 months. The results suggest that the optimum storage period of the dried anchovy is within 6 months. It can be stored below 2 °C for 3 months, but for storage exceeding 3 months, it should be frozen at ??5 °C.     

Dietary supplementation of curcumin augments heat stress tolerance through upregulation of <Emphasis Type="Italic">nrf-2</Emphasis>-mediated antioxidative enzymes and <Emphasis Type="Italic">hsps</Emphasis> in <Emphasis Type="Italic">Puntius sophore</Emphasis>

Heat stress is one of the major environmental concerns in global warming regime and rising temperature has resulted in mass mortalities of animals including fishes. Therefore, strategies for high temperature stress tolerance and ameliorating the effects of heat stress are being looked for. In an earlier study, we reported that Nrf-2 (nuclear factor E2-related factor 2) mediated upregulation of antioxidative enzymes and heat shock proteins (Hsps) provide survivability to fish under heat stress. In this study, we have evaluated the ameliorative potential of dietary curcumin, a potential Nrf-2 inducer in heat stressed cyprinid Puntius sophore. Fishes were fed with diet supplemented with 0.5, 1.0, and 1.5% curcumin at the rate 2% of body weight daily in three separate groups (n = 40 in each group) for 60 days. Fishes fed with basal diet (without curcumin) served as the control (n = 40). Critical thermal maxima (CTmax) was determined for all the groups (n = 10, in duplicates) after the feeding trial. Significant increase in the CTmax was observed in the group fed with 1.5% curcumin- supplemented fishes whereas it remained similar in groups fed with 0.5%, and 1% curcumin-supplemented diet, as compared to control. To understand the molecular mechanism of elevated thermotolerance in the 1.5% curcumin supplemented group, fishes were given a sub-lethal heat shock treatment (36 °C) for 6 h and expression analysis of nrf-2, keap-1, sod, catalase, gpx, and hsp27, hsp60, hsp70, hsp90, and hsp110 was carried out using RT-PCR. In the gill, expression of nrf-2, sod, catalase, gpx, and hsp60, hsp70, hsp90, and hsp110 was found to be elevated in the 1.5% curcumin-fed heat-shocked group compared to control and the basal diet-fed, heat-shocked fishes. Similarly, in the liver, upregulation in expression of nrf-2, sod, catalase, and hsp70 and hsp110 was observed in 1.5% curcumin supplemented and heat shocked group. Thus, this study showed that supplementation of curcumin augments tolerance to high temperature stress in P. sophore that could be attributed to nrf-2-induced upregulation of antioxidative enzymes sod, catalase, gpx, and the hsps.     

Molecular cloning and expression of the heat shock protein 70 gene in the Kumamoto oyster <Emphasis Type="Italic">Crassostrea sikamea</Emphasis>

Episodes of summer mortality of the Kumamoto oyster Crassostrea sikamea are a major problem for its cultivation. Expression of the heat shock protein 70 (HSP70) is induced by various environmental stresses, including heat. We cloned and sequenced hsp70 complementary DNA from C. sikamea to investigate the relationship between hsp70 expression and heat tolerance in this oyster. Quantitative real-time polymerase chain reaction was performed using gill tissue dissected from oysters before and after heat shock for 1 h. The results showed hsp70 expression was faster and greater in oysters cultured at 20–22 °C than at 10–12 °C, and survival was lower among oysters cultured at 20–22 °C than at 10–12 °C. Moreover, heat tolerance was investigated by a 1-h pre-heat treatment, followed by exposure to heat shock conditions 5 days later. Survival was higher and hsp70 expression was notably lower in oysters that received the pre-heat treatment compared with those that did not. We conclude that a pre-heat treatment of only 1 h may be useful for inducing heat tolerance in C. sikamea, and that a low level of hsp70 expression after heat shock is an important index in selecting for high heat tolerance in these oysters.     

Molecular mobility of fish flesh measured by low-field nuclear magnetic resonance (LF-NMR) relaxation: effects of freeze–thaw cycles

In this study, the molecular mobility of fish flesh was measured by low field nuclear magnetic resonance (LF-NMR) relaxation. Sardine, tuna and mackerel were frozen at ?40 °C and stored for 1 day (24 h); and then these samples were thawed at room temperature (20 °C). The relaxation of water protons in fish flesh was measured for fresh (i.e., before freezing) and multi-cycle freeze–thaw samples (i.e., up to 12 times). Three domains from different pools of protons (i.e., low-mobile, medium-mobile and high-mobile) were identified from the relaxation curve. The T _2b (low-mobile), T ₂₁ (medium-mobile) and T ₂₂ (high-mobile) indicated the proton populations in the protein molecules, strongly bound water molecules, and weakly bound water molecules, respectively. In all cases, the relaxation time (T _2b: sardine r = 0.736 and p < 0.01, tuna r = 0.857 and p < 0.001, mackerel r = 0.904 and p < 0.001; and T ₂₂: sardine r = 0.956 and p < 0.0001, tuna r = 0.927 and p < 0.0001, mackerel r = 0.890 and p < 0.0001) increased with the freeze–thaw cycles and it reached a nearly constant value after 6 freeze–thaw cycles. The increased relaxation time (i.e., higher mobility) up to 6 freeze–thaw cycles could be due to the increase in proton mobility. However, relaxation time (T ₂₁: sardine r = ?0.510 and p > 0.05, tuna r = 0.162 and p > 0.5, mackerel r = 0.513 and p > 0.01) showed insignificant change with the increase of freeze–thaw cycles, which indicated minimal change in the medium-mobile protons. The results in this study revealed that the changes in proton mobility in the fish flesh during freeze–thaw cycles could be identified using T _2b and T ₂₂ relaxation of LF-NMR.     

Effect of temperature on swimming performance of juvenile Schizothorax prenanti

The migration of Schizothorax prenanti, an ecologically important and commercially valuable species, is impeded by dams. Effective fishways would contribute to conservation of wild populations, and swimming performance data are necessary for fishway design. The swimming performance of S. prenanti was investigated at four temperatures (15, 19, 23, 27 °C), and numerical models were used to characterize the effect of temperature on swimming performance. As temperature increases, critical swimming speed (U _crit) increases from 15 to 23 °C and then decreases significantly. The highest U _crit (7.71 BL/s) occurs at 24 °C, as estimated by interpolation. Swimming efficiency was similar from 19 to 23 °C, but decreases significantly at 27 °C. The temperature range 15–23 °C is suitable for S. prenanti. However, the excess post-exercise oxygen consumption values of Q ₁₀ for the four temperature increments indicate that 19–23 °C is the optimal range for swimming performance. Maximum tail beat amplitude increased >25 % (0.35–0.45 BL) over the temperature range considered, but variation of tail beat frequency was erratic. White muscle fiber begins to contribute to swimming at swimming speeds ~40 % U _crit at the lower three temperatures, but increases to almost 60 % at 27 °C, and the contribution is relatively small. The results of this investigation advance the knowledge of fish metabolism while swimming provides data critical for fishway design.     

Effects of pectoral fin ray removal on Siberian sturgeon <Emphasis Type="Italic">Acipenser baerii</Emphasis> swimming performance

Fin ray biopsies are commonly used to age sturgeon, but the effects of fin ray biopsy on Siberian sturgeon Acipenser baerii swimming performance are unknown. Therefore, the effects of two fin ray biopsy methods on swimming performance of hatchery-reared, juvenile Siberian sturgeon were evaluated in this study. Treatment fish were subjected to one of two biopsy methods: removal of a 2- to 4-cm section from a marginal pectoral fin ray, or full removal of a marginal pectoral fin ray. Control fish were only subjected to a sham operation. A modified 2,936-l Brett-type swim tunnel was used to evaluate 10-min critical station-holding speeds (C _SHS) and behavioral swimming characteristics of sturgeon immediately after fin ray biopsies were carried out. Fish sizes (range 65- to 84-cm fork length) were comparable among treatments. Mean 10-min C _SHS (mean ± SE) were 113 ± 3.4, 109 ± 2.5, and 111 ± 2.8 cm s^?1 for the segment removal treatment, full removal treatment, and control treatment, respectively. ANOVA indicated that the two methods had no significant effect on the 10-min C _SHS of Siberian sturgeon compared to the control treatment. Results indicate that fin ray removal has no effect on Siberian sturgeon swimming performance.     

Effects of starvation and feeding on blood chemistry,fatty acid composition and expression of vitellogenin and fatty acid-binding protein genes in female swimming crab <Emphasis Type="Italic">Portunus trituberculatus</Emphasis> broodstock

Portunus trituberculatus broodstock were stocked in plastic tanks to evaluate the effects of starvation and feeding on gonadal development, blood chemistry, fatty acid composition, and expression of vitellogenin (Vtg) and fatty acid-binding protein genes (FABP) in females. Two treatments (starved and fed) were randomly assigned to triplicate groups of 90 swimming crab broodstock (approximately 230 ± 45 g). In the starved treatment, crabs were starved for 30 days, whereas in the fed treatment crabs were fed once a day with clams. The gonadosomatic index decreased significantly in starved crabs (P < 0.05), as did the serum glucose and cholesterol concentrations; conversely, the total protein concentration in serum significantly increased (P < 0.05). In the ovary, there was a significant relative decline of 18:0, 16:1n-7 and 20:1n-9 fatty acids and relative increases of 20:4n-6, 22:6n-3, 18:1n-9 and 20:5n-3 in starved crabs compared to fed crabs (P < 0.05). Relative expression of Vtg in the ovary decreased significantly in starved crabs (P < 0.05), while there was no significant difference in hepatopancreas Vtg expression between starved and fed crabs (P > 0.05). Starvation suppressed gonadal development in female swimming crab broodstock.     

Increased water temperature altered hemato-biochemical parameters and structure of peripheral erythrocytes in striped catfish <Emphasis Type="Italic">Pangasianodon hypophthalmus</Emphasis>

The increase of water temperature due to global warming is a great concern of aquaculturists and fishery biologists. In the present study, we examined the effects of high temperature on hematological parameters and blood glucose levels in striped catfish, Pangasianodon hypophthalmus exposed to three temperature conditions (28, 32, and 36 °C) for 7 days. Fish were sacrificed at days 1, 3, and 7. Erythroblasts (Ebs), erythrocytic cellular abnormalities (ECA), and erythrocytic nuclear abnormalities (ENA) were assayed using peripheral erythrocytes of the sampled fishes. Hemoglobin (Hb) and red blood cell (RBC) significantly (P?<?0.05) decreased at 36 °C after 3 and 7 days of exposure, whereas white blood cell (WBC) showed opposite scenario. Blood glucose levels significantly (P?<?0.05) increased at 36 °C on day 3. Frequencies of Ebs, ECA, and ENA were found to be elevated at increased temperature. Differential leucocytes count showed significant increases in neutrophil and decreases in lymphocytes in the highest temperature (36 °C). Dissolved oxygen decreased and free CO₂ increased significantly (P?<?0.05) with increasing temperature, while the pH and total alkalinity of the water were almost unchanged throughout the study period. Therefore, the present study demonstrated that striped catfish feel better adaptation at 28 and 32 °C, while high temperature 36 °C is likely stressful to this fish species.     

Immunogene expression in head kidney and spleen of common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.) following thermal stress and challenge with Gram-negative bacterium, <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

To evaluate the effect of thermal and microbial stress on the immune response of common carp (Cyprinus carpio L.), relative mRNA expression level of pro-inflammatory cytokines [tumor necrosis factor alpha (TNF-α) and interleukin (IL)-1β] and other genes related to immune or stress response [inducible nitric oxide synthase (iNOS), heat shock protein 70 (Hsp70), superoxide dismutase one (SOD1), and glucocorticoid receptor (GR)] was measured by quantitative PCR (qPCR). In addition, total protein and total immunoglobulin level in blood plasma of experimental common carp was also assayed. All the above parameters were estimated 24 h post-challenge with Gram-negative bacterium, Aeromonas hydrophila. Common carp (54.89?±?6.90 g) were initially exposed to 20 °C (control group) and 30 °C (thermal stress group) water temperature for 30 days, followed by experimental challenge with 2.29?×?10⁸ colony forming unit/mL (CFU/mL; LD₅₀ dose) of A. hydrophila. Exposure of fish to thermal stress and subsequently challenge with A. hydrophila significantly (P?<?0.05) increases the IL-1β mRNA expression in head kidney and spleen of common carp by ~?39.94 and ~?4.11-fold, respectively. However, TNF-α mRNA expression in spleen decreased ~?5.63-fold in control fish challenged with A. hydrophila. Thermal stress and challenge with bacterium suppresses the iNOS and GR mRNA expression in spleen of common carp. Moreover, significant (P?<?0.05) increase in total protein content of blood plasma (~?43 mg/g) was evident in fish exposed to thermal stress and challenged with A. hydrophila. In conclusion, our study highlights the importance of elevated temperature stress and microbial infection in differential regulation of expression of several immunogenes in common carp.     

Molecular cloning and expression analysis of <Emphasis Type="Italic">Megalobrama amblycephala</Emphasis> transferrin gene and effects of exposure to iron and infection with <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

Transferrin (Tf) plays an important function in iron homeostasis and metabolism of organisms. In this study, we identified and characterized the Tf gene in Megalobrama amblycephala and evaluated its expression in basal conditions as well as after iron overload and experimental infection with Aeromonas hydrophila. Furthermore, we studied the iron binding properties of recombinant Tf. The full-length M. amblycephala Tf complementary DNA (cDNA) (GenBank accession no.: KX698308) of 2245 bp was cloned and contained a 1953 bp open reading frame (ORF) encoding 650 amino acid residues and flanked by a 68 bp 5′ and a 204 bp 3′ untranslated regions (UTR). Predicted conservative structure illustrated that M. amblycephala Tf consisted of two conservative Tf domains. Amino acid sequence alignment revealed that M. amblycephala Tf had high similarity with that of cyprinids deposited in Genbank, and phylogenetic analysis showed that M. amblycephala Tf clustered with Ctenopharyngodon idella and Hypophthalmichthys molitrix. Tissue expression pattern analyses demonstrated that the liver was the main Tf mRNA expressing organ, being significantly higher than other tissues (p < 0.05). In the liver, Tf mRNA expression in fish artificially injected with the pathogenic bacteria A. hydrophila was significantly upregulated, reaching a peak at 12 h post injection (hpi) and then decreasing afterward. The expression in FeCl₃-injected fish showed a similar tendency, but reached a peak at 8 hpi. Meanwhile, fish serum iron significantly decreased following A. hydrophila injection, but increased to peak at 4 hpi and then decreased in FeCl₃-injected fish. The recombinant M. amblycephala Tf showed iron binding capacity using CAS analysis. These results are helpful to understand the structure and regulation of expression of Tf, as well as the specific function of Tf for both immune responses and iron homeostasis.     

Effects of fasting,temperature, and photoperiod on <Emphasis Type="Italic">preproghrelin</Emphasis> mRNA expression in Chinese perch

Preproghrelin, a gut/brain peptide, plays an important role in the regulation of food intake and energy homeostasis in teleost and mammals. In the present study, we obtained the full-length preproghrelin cDNA in Chinese perch. The preproghrelin messenger RNA (mRNA) tissue expression showed that level was much higher in stomach and pituitary than in other tissues. The fasting study showed, after gastric emptying (3–6 h), short-term fasting (6–12 h) increased preproghrelin expression in the stomach. While in the pituitary, fasting reduced preproghrelin expression at 1, 3, 12, and 48 h, presenting state fluctuation of self-adjustment. The temperature study showed that the mRNA expression of preproghrelin was the highest in the brain at 26 °C and highest in the stomach at 32 °C, respectively, with different optimum temperature in these two tissues, reflecting spatiotemporal differences of regulation by central nervous system and peripheral organs. The photoperiod study showed that normal light (11 h of lightness and 13 h of darkness) led to highest preproghrelin expression, both in the brain and in the stomach, than continuous light or continuous dark, proving food intake is adapted to natural photoperiod or normal light in this study. These results all indicated that tissue-specific preproghrelin expression of Chinese perch could be significantly affected by environmental factors. Short-term fasting of 6 h after gastric emptying, 26 °C, and normal light led to higher preproghrelin expression, which indicated potential appetite increase in Chinese perch.     

Effect of irradiance on bioremediation capacity of the red algae Chondrus crispus and Palmaria palmata

To investigate the illuminance requirements for the culture of red algae in finfish effluent, both Chondrus crispus and Palmaria palmata were assessed simultaneously at three irradiances. Apical tips, 3.5 cm length, were stocked at 2 g L^?1 in 1-L glass flasks with enriched seawater in two 24-day experiments, at 10 and 14 °C, respectively. Palmaria grew up to 70 % better and up took more nutrients than Chondrus under five of the six experimental conditions, except at 14 °C and low irradiance (daily photon dose of 3.4 mol photon m^?2 day^?1). Specific growth rate of both species at high irradiance, 13.1 and 17.2 mol photon m^?2 day^?1, at each trial, 10 and 14 °C, respectively, was 40 and 20 % better than at medium irradiance, but nutrient uptake was similar at both medium and high irradiance. Chondrus growth rate was higher during Experiment 2 (14 °C and 17.2 mol photon m^?2 day^?1) than during Experiment 1 (10 °C and 13.1 mol photon m^?2 day^?1), while Palmaria growth rate was similar in both trials, but always significantly higher than Chondrus. In the range 10–14 °C, Palmaria is the best candidate for integration with Atlantic halibut juveniles (Hippoglossus hippoglossus).