The effect of allostatic load on hypothalamic–pituitary–interrenal (HPI) axis before and after secondary vaccination in Atlantic salmon postsmolts (Salmo salar L.)

The experiment consisted of three experimental groups: (1) “vaccine and stress”, (2) “stress and vaccine” and (3) control. All groups have previously been vaccinated 6 months prior to the start of the experiment. At the start of the experiment, the “vaccine and stress” group was vaccinated with Pentium Forte Plus for the second time (25.02.2008) and then given a daily stressor (confinement stressor 267 kg m-3 in 15 min) for a period of 4 weeks. The “stress and vaccine” group was given a similar daily stressor for 4 weeks and then vaccinated for the second time. The control group was neither stressed nor vaccinated a second time. The results indicates that fish in the “stress and vaccine” group may have entered an allostatic overload type 2 due to oversensitivity to ACTH, a reduced efficient negative feedback system with elevated baseline levels of plasma cortisol and reduced immune response with pronounced effects on the well-being of the animal. The “vaccine and stress” group may likewise have entered an allostatic overload type 1 response, with oversensitivity to ACTH and transient reduced efficient negative feedback system. This study shows that if plasma cortisol becomes elevated prior to vaccination, it could perhaps instigate an allostatic overload type 2 with dire consequences on animal welfare. To reduce the risk of compromising the animal welfare during commercial vaccination of salmon, one propose to grade the fish minimum a week prior to vaccination or grade simultaneously with vaccination. This could reduce the overall allostatic load during handling and vaccination and secure a healthy fish with intact immune response and improved animal welfare.     

Changes in ide Leuciscus idus (L.) females’ reproductive parameters after stimulation with carp pituitary homogenate (CPH) and Ovopel: the effect of domestication?

Three groups (wild—WS, semi-pond—SPS, and pond-cultured—PS) of ide Leuciscus idus (L.) were examined. Each group consisted of 30 females and 10 males, aged 5–8 years. All groups were stimulated with two agents: carp pituitary homogenate (CPH) and a synthetic hormonal preparation Ovopel. The amount of ovulating females decreased in conjunction with females’ domestication level, mainly because of very low efficacy of CPH for pond-reared ide stimulation. The percentage of ovulating females stimulated with Ovopel (97.0 %) was significantly higher comparing to CPH (63.0 %). No significant differences were found in latency time between the groups but spawning synchronization increased in conjunction with ide domestication. The positive correlation between domestication level and latency time, i.e., the higher the domestication level, the higher the latency time, was stated. No significant differences were found in PGSI as well as in total volume of obtained eggs, but groups differed significantly in the number of dry eggs and in number of swollen egg. Significant negative correlation between domestication level and number of swollen eggs, i.e., the higher the domestication level, the lower the number of eggs, was detected. The survival rate at the eyed stage was the highest in WS group (60.4 %) and PS group (57.7 %), and was significantly higher than in SPS group (51.8 %). Eggs obtained after CPH stimulation had higher survival rate at the eyed-egg stage (60.3 %) than eggs obtained from the fish stimulated with Ovopel (53.0 %). The data suggest that some form of domestication appeared in ide cultivated for several generations in carp pond.     

Distinct alpha (α)-subunits of salmon glycoprotein hormones: production sites in the pituitary with sexual maturity

Salmon pituitary glands contain two structurally distinct -subunit proteins (1 and 2) of glycoprotein hormones: the 2-subunit is common to all salmon gonadotropins (GTH I and GTH II), whereas the 1-subunit is present in only some GTH I molecules. GTH I is predominant in the pituitary gland and plasma during gametogenesis of salmon, but the roles of the 2 GTHs in gametogenesis remain unclear. To understand the roles of GTH I, it is important to clarify patterns of 1- and 2-subunit production with sexual maturity. Thus, we produced antisera that recognized the 1- or 2-subunit, and then immunohistochemically examined the production sites of these subunits in the trout pituitary gland during ovarian development. In all pituitary glands examined, the immunoreactivity of both the 1- and 2-subunits was strong in the GTH II-producing cells, although salmon GTH II, both 1- and II-subunits, has not been detected. However, GTH I-producing cells showed a less dense immunoreactivity for 1- and 2-subunits, whereas the I-subunit was abundant. On the other hand, TSH cells, reacted with 2 but not with 1.     

Shrimp lectin–conjugated copper sulfide nanoparticles enhance immune response and gene expression in Etroplus suratensis infected with Aeromonas hydrophila

Aquaculture International - Lectins are hemagglutinating glycoproteins which act as pathogen recognition receptors that can bind to the pathogen-associated molecular patterns. Shrimp lectin...     

Effect of brewer’s yeast on immune response of giant freshwater prawn, Macrobrachium rosenbergii, and its resistance to white muscle disease

The present study was conducted to find the effect of dietary brewer’s yeast on growth, survival, immune response, and resistance to white muscle disease in giant freshwater prawn, Macrobrachium rosenbergii. The brewer’s yeast was supplemented at graded levels 0, 5, 10, and 20?g per kg diet, and the experiment was conducted for 75?days. After the feeding trials, growth, survival, immune parameters like prophenoloxidase activity, respiratory burst, and total hemocyte count were assessed. The growth, specific growth rate, and survival were not found significantly different among the treatment and control groups “prophenoloxidase activity and respiratory burst” were found significantly different (p?<?0.05) among the treatment and control groups. The total hemocyte count was significantly different (p?<?0.05) among control and treatment groups. Cumulative percent survival was higher in M rosenbergii fed 1?% brewer’s yeast-supplemented diet when they were challenged with white muscle disease virus (MrNV (Macrobrachium rosenbergii nodavirus) and XSV (extra small virus)). The present work revealed that the incorporation of brewer’s yeast in the diet is effective in enhancing immune response and controlling the white muscle disease in M rosenbergii.     

Effect of diet and β-naphthoflavone on hepatic and renal glutathione S-transferase isoenzymes in carp (Cyprinus carpio)

Glutathione S-transferase (GST) isoenzymes were isolated from liver and kidney of carp (Cyprinus carpio) by glutathione affinity chromatography and chromatofocusing. Ten hepatic and eight renal catalytically active isoenzymes were identified. GST subunits from purified isoenzymes were further separated by high-performance liquid chromatography (HPLC) and were used as standards for the experimental sample analysis. Experimental samples came from carp that were fed fish meal (standard diet) or soybean bas ed diets for one year, injected or not with -naphthoflavone (BNF; i.p. injection of 50 mg kg-1). HPLC did not allow us to identify precisely the GST isoenzyme pattern in experimental carp. However, GSTs could be pooled in three categories: homodimeric, heterodimeric and unidentified GST subunits. On this basis, the effect of diet and BNF on the GST isoenzyme pattern was investigated. The homodimer/heterodimer ratio was decreased in liver of carp fed a standard diet and in kidney of both dietary groups. BNF increased the total specific GST activity in liver and kidney. However, the GST isoenzyme pattern was not modified in carp fed the standard diet while tissue specific modifications occured in carp fed the soybean diet. BNF decreased the homodimer/heterodimer ratio in liver and increased it in kidney. Abbreviations: BNF - -naphthoflavone; CDNB - 1-chloro-2,4-dinitrobenzene; GSH - reduced glutathione; GST - glutathione S-transferase; HPLC - high-performance liquid chromatography; SDS-PAGE - SDS-polyacrylamide gel electrophoresis.     

Distinct expression of three estrogen receptors in response to bisphenol A and nonylphenol in male Nile tilapias (Oreochromis niloticus)

Environmental estrogens, such as bisphenol A (BisA) and nonylphenol (NP), have been shown to affect the estrogen receptor (ER) expression and induce male reproductive abnormalities. To elucidate molecular mechanisms of action of xenoestrogenic chemicals on the expression of estrogen receptors in the testes of Nile tilapia (Oreochromis niloticus), three full-length cDNAs respectively encoding ntERα, ntERβ1 and ntERβ2 were cloned from testes. The amino acid sequences of ntERα, ntERβ1 and ntERβ2 showed a high degree of similarity to the relevant fish species. Tissue-specific expression study showed that three receptors were highly expressed in pituitary, liver, testis, kidney and intestine tissues. The ntERα, ntERβ1 and ntERβ2 mRNA expressions were significantly higher at the sexual early recrudescing stage than at other recrudesced stages. After being exposed to xenoestrogens from weeks 2 to 4, the ntERα mRNA levels were increased significantly in testes after NP treatment at all sampling times or after 4 weeks of exposure to BPA. The ntERβ1 mRNA levels remained unchanged, while a significant decrease of the ntERβ2 mRNA level was observed in testes after exposure to NP and BPA. The present study demonstrates that the regulation of all three ntER subtypes in testes may act via different molecular mechanisms of exposure to NP and BPA.     

Effect of enrofloxacin and emodin on heat-shock proteins’ expression in hepatic cells of grass carp (Ctenopharyngodon idellus)

The aim of the present study was to compare the expression pattern of heat-shock protein 60 (HSP60), 70 (HSP70), and 90 (HSP90) mRNA in hepatic cells of grass carp exposed to enrofloxacin and emodin concentrations. The expression pattern of different genes encoding heat-shock proteins in hepatic cells of grass carp was exposed to graded levels of enrofloxacin (12.5, 25, 50, 100, and 200 μg/ml) or emodin (0.04, 0.2, 1, 5, and 25 μg/ml) for 24 h and were investigated by real-time quantitative PCR. When cells were exposed to up 50 μg/ml enrofloxacin, both HSP60 and HSP70 mRNA levels firstly were increased and thereafter significantly dropped at high concentrations (P < 0.05), while HSP90 decreased with increasing enrofloxacin concentration. Besides, HSP60 and HSP70 expressions were significantly inhibited in the high-concentration groups. In addition, the HSP90 mRNA levels in the treatment exposed to 100 and 200 μg/ml enrofloxacin were significantly lower than those of the control group (P < 0.05). Furthermore, when cells were exposed to graded levels of emodin, HSPs (HSP60, 70, and 90) mRNA levels significantly increased in the groups exposed to 5 and 25 μg/ml of emodin. The different expression pattern of HSPs implied that enrofloxacin could inhibit the expression levels of HSPs, while optimal level of emodin could trigger higher expression levels of HSPs in hepatic cell of grass carp to protect against further damage.     

Effects of supplementary feeds with different protein levels on growth and economic performances of Nile tilapia (Oreochromis niloticus) cultured in a rain-fed rice–fish ecosystem

This study investigated the effects of supplementary feeds with different crude protein (CP) levels on the growth and economic performances of sex-reversed Nile tilapia (Oreochromis niloticus) reared in a rain-fed rice–fish ecosystem for a period of 120 days. There were four treatments—namely, traditional feed (21% CP), formulated feed (26% CP), commercial feed (30% CP), and control (no feed was used)—with three replicates per treatment. Fish (30.04 g) were stocked in ditches at a rate of 0.5 fish m^?2 considering the total area and fed one of the tested feeds twice daily at the rate of 2%–5% of body weight. Water-quality parameters of the ditches were monitored fortnightly, and these parameters were found suitable for fish farming. Organic matter, total nitrogen, and available phosphorous in soil were increased significantly (P < 0.05) in the feed treatments after fish cultivation. Highly significant weight gain and SGR were observed with fish fed the commercial feed as compared with other treatments. The highest benefit-cost ratio (2.15) was found in the control, followed by formulated feed (1.90), but in the case of numerical net return, it was the opposite. However, commercial feed showed the lowest benefit-cost ratio (1.67) due to higher feed cost than other supplementary feeds. Therefore, this study suggests that fish fed with a formulated feed (26% CP) produced significantly higher net economic return in the rice–fish farming system.     

Oxygen consumption and ammonia excretion of black carp (Mylopharyngdon piceus Richardson) and allogynogenetic crucian carp (Carassius auratus gibelio ♀?×?Cyprinus carpio ♂) fed different carbohydrate diets

Oxygen consumption and ammonia excretion of black carp (Mylopharyngdon piceus Richardson) (4.6 ± 0.3 g) and allogynogenetic crucian carp (Carassius auratus gibelio ♀ × Cyprinus carpio ♂) (5.7 ± 0.5 g) were examined when fish fed two types of carbohydrate (dextrin and glucose) at two levels (20 and 40%) each. The diets were isonitrogenous (40% dry matter) and isocaloric at 18.5 kJ g⁻¹ (dry matter) by adjusting the oil content to 10.1 and 1.5%, respectively. In black carp, the interactions between the carbohydrate type and level were found in oxygen consumption at 3 and 6 h and in ammonia excretion at 6 h after feeding. At 20% carbohydrate, no significant difference was observed between dextrin and glucose in oxygen consumption. However, at 40% carbohydrate, oxygen consumption in fish fed glucose was significantly higher than that in fish fed dextrin at 3 and 6 h after feeding. Within the dextrin diets, no significant differences in both oxygen consumption and ammonia excretion were detected between the two carbohydrate levels. Within the glucose diets, however, fish fed 40% glucose showed significantly higher oxygen consumption than those fed 20% glucose at 3 and 6 h after feeding. Ammonia excretion in black carp fed 40% glucose was higher than that in black carp fed 40% dextrin at 6 h and also found higher than those in the other three treatments at 24 h after feeding. The postprandial oxygen consumption and the ammonia excretion in crucian carp fed 40% glucose were the highest, but no significant differences were observed. Our data indicate that the escalation of glucose to 40% in a fish diet results in high oxygen consumption and ammonia excretion in black carp, suggesting that the efficiency of glucose as an energy source for this fish is compromised by the high metabolic expenditure after feeding. Crucian carp, on the other hand, have a better ability to cope with dietary carbohydrates.     

Recruitment of common sardine (Strangomera bentincki) and anchovy (Engraulis ringens) off central-south Chile in the 1990s and the impact of the 1997–1998 El Niño

The recruitment of Strangomera bentincki (common sardine) and Engraulis ringens (anchovy) and the relationships with oceanographic conditions in the upwelling ecosystem of central-south Chile were investigated from 1990 to 1998, with emphasis on the 1997–1998 El Niño. Time series of recruitment, biomass, local sea surface temperature, and a coastal upwelling index were used to explore relationships during the spawning (July–August) and pre-recruitment (August–December) periods. The 1997–1998 El Niño caused physical changes in the small pelagic fish habitat off central-south Chile. Anomalous sea surface temperatures (SST) and upwelling indexes began to be detected from May 1997 and persisted into 1998. Recruitment of common sardine showed significantly negative relationship with SST anomalies during the pre-recruitment period, as well as with the upwelling index during the peak of spawning. However, the recruitment of anchovy did not seem to be affected by the environmental changes observed in the 1990s. Instead, the recruitment rate of anchovy showed negative relationship with the recruitment rate of common sardine. We conclude that the conditions of the 1997–1998 El Niño off central-south Chile affected the survival of common sardine offspring, and that the recruitment success of anchovy could be determined by less-abundant cohorts of common sardine through a biological mechanism of interaction.     

Distribution and movement between habitats with growth of the hard clam Meretrix lusoria in the Shirakawa–Midorikawa estuary of the Ariake Sea

The distribution and movement between habitats with growth of the hard clam Meretrix lusoria were examined by comparing the size–frequency distributions among 17 sites in the Shirakawa–Midorikawa Estuary of the Ariake Sea. This clam is a commercially important bivalve in Japan, and its annual catch is largest in the Ariake Sea. At the study sites, new recruits were abundant at river mouths, and density was strongly affected by the distance from coastal tidal rivers and streams. In contrast, adults were widely distributed on tidal flats, although density was low at many sites. At marine site Oda, the density of adults was higher than that of new recruits at all sites and higher than that of juveniles at most sites. These results indicate that this species moves from riverine sites to marine sites with growth. Moreover, the observed low density of adult clams may indicate overfishing. The active movement of M. lusoria across the fishing grounds complicates the sustainable resource management of this species. Therefore, further studies are needed for effective resource management of M. lusoria.     

Daily rhythms of cortisol and glucose and the influence of the light/dark cycle on anaesthesia in Nile tilapia (Oreochromis niloticus): Does the timing of anaesthetic administration affect the stress response?

Although daily variations in drug pharmacokinetics have been reported for a variety of teleost species, the influence of this daily variation on the cortisol response following anaesthesia remains poorly understood. To address this, two experiments were performed. The first experiment described the daily patterns of cortisol and glucose secretion in tilapia (Oreochromis niloticus). The second experiment investigated how the timing of anaesthetic administration (specifically at mid‐light [ML] or at mid‐dark [MD]) affects the induction and recovery times and plasma cortisol and glucose levels of juvenile Nile tilapia exposed to benzocaine, clove oil or tricaine methanesulphonate (MS‐222). The results revealed that the effect on the stress response associated with the moment when anaesthesia took place (ML or MD) varied according to the treatment (p < 0.05). Cortisol levels were significantly higher at ML for MS‐222 (ML = 116.23 ± 25.55; MD = 48.25 ± 22.33 ng/dl) (p < 0.05) and clove oil (ML 59.73 ± 14.27; MD 38.26 ± 12.07 ng/dl) (p < 0.05), whereas no significant differences were found between ML and MD cortisol levels for the control treatment (ML = 72.91 ± 18.42; MD = 64.80 ± 10.68 ng/dl) (p > 0.05) or in the benzocaine‐treated group (ML = 38.7 ± 4.90; MD = 38.60 ± 3.69 ng/dl) (p > 0.05). The highest plasma cortisol level in ML was found in the MS‐222‐treated group. All the tested anaesthetics had similar cortisol levels at MD (p > 0.05).     

Study of food web structure and trophic level in the sea ponds of an optimized culture model (jellyfish–shellfish–fish–prawn)

The food sources of the main economic animals and trophic levels of biotic communities from an optimized culture model (Rhopilema–Sinonovacula constricta–Paralichthys olivaceus–Penaeus chinensis) in a sea water pond in Donggang, Liaoning province were studied using the stable carbon and nitrogen isotopes technique. The results indicated that the values of δ¹³C range from (?27.28 ± 0.35) ‰ to (?16.65 ± 0.20) ‰ and the values of δ¹⁵N range from (3.68 ± 0.23) ‰ to (13.91 ± 0.26) ‰, both of which exhibited significant fluctuations. The δ¹³C values of P. chinensis, Macrobrachium mipponensis and P. olivaceus were comparatively higher than those of other aquaculture animals, and the δ¹⁵N values of P. olivaceus was also comparatively higher. The contribution to the food sources of aquaculture animals (Rhopilema, S. constricta, P. olivaceus and P. chinensis) was analyzed by using the IsoSource software. The results indicated that fish meat had the greatest contribution to Rhopilema, S. constricta and P. chinensis; P. chinensis had the greatest contribution to P. olivaceus, followed by the M. mipponensis. The trophic level of the biotic communities under that optimized culture model in a sea water pond was 3.54, in which P. olivaceus was in the fourth level (3.54); P. chinensis, Synechogobius hasta, Ablennes anastomella, M. mipponensis, Ditrema temmincki Bleeker, Chelon haematocheilus were in the third trophic levels; Rhopilema, Engraulis japonius, S. constricta and zooplankton (1.00) in the second trophic levels, suspended matters (0.15) including phytoplankton, bacteria, humus, etc., were in the primary trophic levels.