Crowding Stress Research Articles

Humoral immunomodulation of the gilthead seabream (Sparus aurata L.) subjected to long-term crowding stress

The welfare of farmed fish is influenced by management factors (stocking density, grading procedures, transport, feeding, water quality and prophylactic treatment), and stress in fish has been traditionally evaluated by behavioural, anatomical and physiological measurements. However, skin mucus has received less attention about its response of the fish surface after different stress stimuli, despite being the production or release of mucus the first response to stress in teleost’s fish. Thus, the aim of this study was to compare some immune parameters on serum and skin mucus of gilthead seabream (Sparus aurata) specimens after long-term crowding stress. Fish were subjected to 10 kg m (low density, control group) and 50 kg m (high density as crowding group) during 2, 24 and 48 h. Then, IgM levels, peroxidase, protease and antiprotease activities were evaluated in serum and skin mucus samples. Ours results demonstrated that the IgM levels and peroxidase activity in the serum samples decreased and increased in a statistically significant way after 24 and 48 h of trial, respectively. However, protease and antiprotease activity did not show any significant variations among the different experimental groups. In the case of skin mucus, IgM levels and antiprotease activity did not show any significant variations between the experimental groups. However, peroxidase activity showed a significant increase after 48 h of trial respect to values found in control fish. In addition, protease activity evidenced a decreased and increase after 2 and 24 hours, respectively. Therefore, peroxidase and protease activities in skin mucus could be used as possible stress bioindicators in fish. This study represents an advance on our knowledge about the interaction between stress and skin mucosal immunity in fish. Further investigations are needed in the evaluation of stress bioindicators in skin mucus of fish subject to other stressor situations and their possible use as simple, fast, non-invasive and relatively inexpensive technique in intensive aquaculture systems.

Effects of astaxanthin and emodin on the growth, stress resistance and disease resistance of yellow catfish (Pelteobagrus fulvidraco).

Yellow catfish (Pelteobagrus fulvidraco) has become a commercially important fish species in China and eastern Asia. High-density aquaculture has led to congestion and excessive stress and contributed to bacterial infection outbreaks that have caused high mortality. We investigated the effects of dietary supplementation with astaxanthin and emodin alone and in combination on the growth and stress resistance of yellow catfish. After 60 days of feeding, each group of fish (control, astaxanthin, emodin, and astaxanthin plus emodin (combination) groups) was exposed to acute crowding stress for 24 h, and a subsample of fish from the four groups was challenged with the bacterial septicemia pathogen Proteus mirabilis after the end of the crowding stress experiment. Compared with the control, the astaxanthin and emodin groups showed increases in serum total protein (TP), hepatic superoxide dismutase (SOD) activity and hepatic heat shock proteins 70 (HSP70) mRNA levels at 12 and 24 h after the initiation of crowding stress. The combination group exhibited increases in alanine aminotransferase (ALT) activity, aspartate aminotransferase (AST) activity, serum TP, hepatic SOD activity and hepatic HSP70 mRNA levels within 24 h after the initiation of crowding stress. However, decreases relative to the control were observed in the serum cortisol and glucose contents in the three treatment groups at 12 and 24 h after the initiation of crowding stress, in ALT and AST activity in the astaxanthin and emodin group at 24 h after the initiation of crowding stress, and in the serum lysozyme activity, serum alkaline phosphatase (ALP) activity, and hepatic catalase (CAT) and malondialdehyde (MDA) activity in the combination group at 24 h after the initiation of crowding stress. Additionally, the cumulative mortality after P. mirabilis infection was lower in all three treatment groups (57.00%-70.33%) than in the control (77.67%). Dietary supplementation with astaxanthin and emodin decreased the specific growth rate (SGR) and weight gain (WG) of healthy yellow catfish, although significant differences in mortality were not observed. These results indicate that dietary supplementation with 80 mg/kg astaxanthin and 150 mg/kg emodin can improve the anti-oxidative capabilities, hepatic HSP70 levels, and resistance to acute crowding stress of yellow catfish. Finally, an appropriate strategy for enhance yellow catfish stress resistance and disease resistance is proposed.

Identification of Crowding Stress Tolerance Co-Expression Networks Involved in Sweet Corn Yield.

Tolerance to crowding stress has played a crucial role in improving agronomic productivity in field corn; however, commercial sweet corn hybrids vary greatly in crowding stress tolerance. The objectives were to 1) explore transcriptional changes among sweet corn hybrids with differential yield under crowding stress, 2) identify relationships between phenotypic responses and gene expression patterns, and 3) identify groups of genes associated with yield and crowding stress tolerance. Under conditions of crowding stress, three high-yielding and three low-yielding sweet corn hybrids were grouped for transcriptional and phenotypic analyses. Transcriptional analyses identified from 372 to 859 common differentially expressed genes (DEGs) for each hybrid. Large gene expression pattern variation among hybrids and only 26 common DEGs across all hybrid comparisons were identified, suggesting each hybrid has a unique response to crowding stress. Over-represented biological functions of DEGs also differed among hybrids. Strong correlation was observed between: 1) modules with up-regulation in high-yielding hybrids and yield traits, and 2) modules with up-regulation in low-yielding hybrids and plant/ear traits. Modules linked with yield traits may be important crowding stress response mechanisms influencing crop yield. Functional analysis of the modules and common DEGs identified candidate crowding stress tolerant processes in photosynthesis, glycolysis, cell wall, carbohydrate/nitrogen metabolic process, chromatin, and transcription regulation. Moreover, these biological functions were greatly inter-connected, indicating the importance of improving the mechanisms as a network.

Impact of water column reduction rate at harvesting of Nile tilapia (oreochromis niloticus) on skin injuries, hematological and biochemical parameters and bacterial load of fish and water: a field study

The aim of this study was to evaluate the impact of reduced water column in different periods on health and welfare of the Nile tilapia during harvesting. As a common practice for gathering and harvesting of tilapia in Egypt, the water column was reduced gradually until reach the lowest level (30 cm). The water column was reduced from 150 to 30 cm in different periods as follow; Group1 (G1, control group), at which the water column was reduced from 150 to 30 cm in 72 hour (h). Group 2 (G2), at which the water column was reduced from 150 to 30 cm in 48 h. Group 3(G3), at which the water column was reduced from 150 to 30 cm in 24 h. The results showed that, there was a significant (P˂0.05) decrease in muscle total bacterial count (TBC), fish injuries, heterophil /lymphocyte (L/H) ratio, serumglucose, Lactate dehydrogenase, alkaline phosphatase and an increase in water, skin TBC, dissolved oxygen (DO), unionized ammonia (UIA), and total leucocyte count (TLC) in G3 compared to G2 and G1.In conclusion, the process of reduced water column before gathering and harvesting needs to be carried out within 24 h to reduce injuries and bacterial load of fish. In addition, it improves the immune system and health of fish that reducing therisk of infection. Therefore, slow reduction of water column height during harvesting produces crowding stress altering health status and welfare of Nile tilapia (Oreochromis niloticus).

Relationships among phenotypic traits of sweet corn and tolerance to crowding stress

Crowding stress tolerance is defined as the extent to which the crop maintains yield per unit area as plant population density increases beyond standard levels. Sweet corn (Zea mays L.) hybrids grown for processing vary widely in tolerance to crowding stress; however, the mechanisms involved in crowding stress tolerance are unknown. The objective of the study was to determine the extent to which crop traits, individually and in combination, relate to crowding stress tolerance in processing sweet corn. Twenty-six modern shrunken-2 processing hybrids from eight sources were grown under conditions of crowding stress (i.e. 72,000 plantsha−1) over a three-year period. Seventeen crop traits measured from emergence to harvest were related to four measures of crowding stress tolerance, including ear mass, recovery, case production, and gross profit margin. Of individual crop traits, kernel mass plant−1 was among the best predictors of crowding stress tolerance in processing sweet corn, as long as sweet corn lines were grown at a uniformly high plant population. Two categories of traits related to crowding stress tolerance in sweet corn, including a ‘source-sink relationship’ factor and a ‘photosynthetic capacity’ factor. Factor regression showed the combination of traits loading into the source-sink relationship factor was positively related to ear mass, case production, and gross profit margin. This research points to the underlying mechanisms involved in crowding stress tolerance in processing sweet corn.

English

This study was carried out to evaluate the growth performance and some haematological functions of Clarias gariepinus fed different levels of crude protein under varying stocking densities. Fish of even sizes were randomly selected and stocked in plastic circular tanks (0.05 x 0.03 x 0.03 m) at three stocking densities of 10 fish/m3 (control), 15 fish/m3 and 20 fish/m3. The fish of each stocking density were fed either a diet containing 40% Crude protein (CP) or 45% CP with a feeding rate of 3% body weight twice daily. The experiment was replicated thrice and it lasted for 12 weeks during which haematological parameters and plasma biochemistry were measured. From this study, haemoglobin (Hb) and Red Blood Cell (RBC) slightly increased in all treatments but the variation was not significant in relation to protein level in the diets. Plasma glucose increased significantly (P<0.05) in relation to the stocking densities. The plasma protein showed insignificant variation in relation to the stocking density but the variation was more pronounced (P<0.05) at the lowest stocking density as the protein level in the diets varied. It can be concluded that enhancing feed quality especially protein level in the fish diet may ensure faster growth, stress reduction and improve health status of the fish. Key words: Crowding stress, haematological functions, Clarias gariepinus, diet quality.

Effects of emodin and vitamin E on the growth and crowding stress of Wuchang bream (Megalobrama amblycephala)

This study aimed to investigate the effects of dietary emodin, high-dose vitamin E and their combination on the growth of Megalobrama amblycephala and its resistance to acute crowding stress. The fish were randomly divided into four groups: a control group fed with basal diet, and three treatment groups fed with basal diet supplemented with 60 mg/kg emodin (the emodin group), 500 mg/kg vitamin E (the vit E group), and 60 mg/kg emodin together with 500 mg/kg vitamin E (the combination group). After 60 days, the fish were exposed to acute crowding stress for 24 h. The results showed that the weight gain of the vit E group, specific growth rate of the vit E group, total serum protein concentration (TP) of the vit E group, serum lysozyme activity of the emodin group, serum superoxide dismutase (SOD) activity of the emodin group, hepatic heat shock protein 70 (HSP70) levels of the vit E group and the emodin group, and serum alanine aminotransferase (ALT) activity of the combination group significantly increased while the weight gain and specific growth rate of the combination group significantly decreased compared with the control group before stress.After crowding stress, the vit E group had improved serum TP 12 h post-stress, hepatic SOD activity 24 h post-stress, and hepatic HSP70 mRNA levels 12 and 24 h post-stress while the emodin group had enhanced serum SOD activity 12 and 24 h post-stress and hepatic HSP70 mRNA levels 12 and 24 h post-stress, as compared with the control. However, the serum cortisol content of the three treatment groups 12 and 24 h post-stress, ALT activity in the vit E group and emodin group 24 h post-stress, and serum alkaline phosphatase and liver catalase activity in the combination group 24 h post-stress were lower than those in the control group. The cumulative mortality was lower in the emodin, vit E, and combination group after Aeromonas hydrophila infection compared with the control group. Therefore, dietary supplementation with 60 mg/kg emodin or 500 mg/kg vitamin E can improve HSP70 mRNA levels and antioxidant capabilities, resistance to crowding stress, and growth in M. amblycephala. However, the combination of emodin and vit E does not have a synergistic effect in M. amblycephala.

Effect of Noise and Crowding Stresses on Hypothalamic–Pituitary–Gonadal Axis and Protective Effect of Sulpiride Drug in Adult Female Albino Rats

Background: Noise and crowdingare the most stressful factors which cause depressant effects on human beings, especially females.Therfore this study was aimed at clarifying their effects on hypothalamus pituitary gonadal axis hormones (luteinizing hormone (LH) and follicle-stimulating hormone (FSH), estrogen (E2)and progesterone as well as prolactin (PRL)and the possible protective effect of antidepressant drug;sulpiride. Material and Methods: Sixty adult female rats were divided into six groups (10/each): 1- Rats served ascontrol, 2- Rats treated with sulpiride drug only, 3- Rats exposed to noise (90db, 3hr. per day) for 45 days, 4- Rats exposed to noise and treated with sulpiride drug, 5- Rats exposed to crowding and 6- Rats exposed to crowding and treated with sulpiride drug. Results: Noise and crowding stresses caused a significant decrease of estrogen (E2), progesterone (P), LH and FSH levels and high significant increase in PRL level. Sulpiride drug ameliorated these parameters changes except PRL level which showed a high significant level compared to control group. Conclusion: it is useful to use antidepressant drug (e.g. sulpiride) with people who are exposing to noise and crowding stress.

Effect of Noise and Crowding Stresses on Hypothalamic–Pituitary–Gonadal Axis and Protective Effect of Sulpiride Drug in Adult Female Albino Rats

Background: Noise and crowdingare the most stressful factors which cause depressant effects on human beings, especially females.Therfore this study was aimed at clarifying their effects on hypothalamus pituitary gonadal axis hormones (luteinizing hormone (LH) and follicle-stimulating hormone (FSH), estrogen (E2)and progesterone as well as prolactin (PRL)and the possible protective effect of antidepressant drug;sulpiride. Material and Methods: Sixty adult female rats were divided into six groups (10/each): 1- Rats served ascontrol, 2- Rats treated with sulpiride drug only, 3- Rats exposed to noise (90db, 3hr. per day) for 45 days, 4- Rats exposed to noise and treated with sulpiride drug, 5- Rats exposed to crowding and 6- Rats exposed to crowding and treated with sulpiride drug. Results: Noise and crowding stresses caused a significant decrease of estrogen (E2), progesterone (P), LH and FSH levels and high significant increase in PRL level. Sulpiride drug ameliorated these parameters changes except PRL level which showed a high significant level compared to control group. Conclusion: it is useful to use antidepressant drug (e.g. sulpiride) with people who are exposing to noise and crowding stress.

Effect of Noise and Crowding Stresses on Hypothalamic-Pituitary-Gonadal Axis and Protective Effect of Sulpiride Drug in Adult Female Albino Rats

Effect of Noise and Crowding Stresses on Hypothalamic-Pituitary-Gonadal Axis and Protective Effect of Sulpiride Drug in Adult Female Albino Rats

Social crowding in the night-time reduces an anxiety-like behavior and increases social interaction in adolescent mice

Rearing in crowded conditions is a psychosocial stressor that affects biological functions. The effects of continuous crowding for many days have been studied, but those of crowding over a limited time have not. In this study, we examined the effects of night-time or daytime crowding over 2 weeks on behavior in adolescent and adult mice. Crowding (20 mice/cage) in either the night-time or daytime did not affect locomotor activity in the open field test or cognitive function in the fear conditioning test. In contrast, night-time crowding, but not daytime crowding, had an anxiolytic effect in the elevated plus-maze test and increased social interaction in adolescent mice, but not in adult mice. The first night-time, but not daytime, crowding increased plasma corticosterone levels in adolescent mice, although night-time crowding over 2 weeks did not affect the corticosterone levels. Furthermore, no significant effects of the first crowding were observed in adult mice. In a second crowding condition (six mice/small cage), the anxiolytic-like effects of night-time crowding and the change in plasma corticosterone levels were not observed, suggesting that the density of mice is not important for the behavioral consequences of crowding. Night-time crowding did not affect neurotrophic/growth factor levels and hippocampal neurogenesis in adolescent mice. These findings suggest that night-time crowding leads to anxiolytic-like behaviors in adolescent mice, and imply that night-time crowding stress in adolescence may be beneficial to brain functions.

Effects of chronic crowding stress on growth, feeding, and behavior in Chinese sturgeon &lt;I&gt;Acipenser sinensis&lt;/I&gt; F&lt;SUB&gt;2&lt;/SUB&gt; juveniles

Effects of chronic crowding stress on growth, feeding, and behavior in Chinese sturgeon &lt;I&gt;Acipenser sinensis&lt;/I&gt; F&lt;SUB&gt;2&lt;/SUB&gt; juveniles

Senescence and yield responses to plant density in stay green and earlier-senescing maize hybrids from Argentina

Increases in maize (Zea mays L.) yield over the past few decades have been associated with breeding for tolerance to progressively higher plant densities. Since high plant density exacerbates interplant competition, it has been suggested that improved resource capture through delayed senescence might be advantageous in such situations. The main objectives of this work were to determine (1) the time-course of canopy senescence, (2) post-silking C and N accumulation and (3) yield responses of contemporary maize hybrids with different expression of the stay green (SG) character grown in a range of plant densities from moderate to intense crowding stress. Three experiments consisting of a combination of different plant densities (from 6 to 10plm−2) and commercial hybrids with different timing of senescence were carried out. High density accelerated leaf senescence at the lower canopy layer. The SG hybrids delayed senescence and retained green leaves at physiological maturity at all tested densities. One of these hybrids (NK880), with a strong SG character, retained green leaves at all canopy layers, even at the lower layer exposed to limiting irradiance. Lower canopy leaves maintained high respiratory rates in NK880, while leaves of the NSG hybrid (DK682) senesced and their respiration became not detectable. At the highest tested density, the NSG DK682 achieved greater grain yields than the SG NK880. Increased density reduced kernel weight (KW), and this decrease was more pronounced for the SG NK880 (6–18% comparing 10 vs. 8plm−2). In spite of delayed senescence in NK880, no hybrid differences were found for post-silking dry matter accumulation and plant dry matter at physiological maturity. Unexpectedly, plant nitrogen content (Nc) at harvest was similar (Exp. I) or even lower (P<0.05, Exp. II) in the SG NK880. This was the result of lower net N accumulation during the post-silking period (Exp. I) or lower Nc achieved at silking (Exp. II) in the SG NK880. A strong positive relation was found between KW and N concentration in kernels, with %N in kernels being below the critical N concentration to achieve potential KW (around 1.4%) in the SG hybrid. This suggests that yield in NK880 was limited by N. In the SG genotype, N remobilization from vegetative organs did not seem to compensate for the N deficit for optimum grain growth. In summary, at high densities the NK880 hybrid displayed a strong, constitutive SG character, even if it accumulated less N, and senescence delay was not reflected in higher grain yield.

Quantitative Trait Loci Affecting Response to Crowding Stress in an F2 Generation of Rainbow Trout Produced Through Phenotypic Selection

Selective breeding programs for salmonids typically aim to improve traits associated with growth and disease resistance. It has been established that stressors common to production environments can adversely affect these and other traits which are important to producers and consumers. Previously, we employed phenotypic selection to create families that exhibit high or low plasma cortisol concentrations in response to crowding stress. Subsequent crosses of high × low phenotypes founded a multigenerational breeding scheme with the aim of dissecting the genetic basis for variation underlying stress response through the identification of quantitative trait loci (QTL). Multiple methods of QTL analyses differing in their assumptions of homozygosity of the causal alleles in the grandparental generation yielded similar results in the F1 generation, and the analysis of two stress response phenotype measurement indexes were highly correlated. In the current study, we conducted a genome scan with microsatellites to detect QTL in the F2 generation of two families created through phenotypic selection and having larger numbers of offspring than families screened in the previous generation. Seven suggestive and three significant QTL were detected, seven of which were not previously detected in the National Center for Cool and Cold Water Aquaculture germplasm, bringing the total number of chromosomes containing significant and suggestive stress response QTL to 4 and 15, respectively. One significant QTL which peaks at 7 cM on chromosome Omy12 spans 12 cM and explains 25 % of the phenotypic variance in family 2008052 particularly warrants further investigation. Five QTL with significant parent-of-origin effects were detected in family 2008052, including two QTL on Omy12. The 95 % confidence intervals for the remaining QTL we detected were broad, requiring validation and fine mapping with other genotyping approaches and mapping strategies. These results will facilitate identification of potential casual alleles that can be employed in strategies aimed at better understanding the genetic and physiological basis of stress responses to crowding in rainbow trout aquaculture production.

Stress response ofCaenorhabditis elegansinduced by space crowding in a micro-column array chip

Crowding stress has been reported to play an important role in affecting physiological behaviour. To study this process, a reliable analytical method under confined space is essential. In this work, we demonstrated a microfluidic approach for investigating physiological responses of C. elegans to confined spaces. The PDMS microfluidic chip consisting of arrays of micro-columns enabled us to mimic different crowding conditions by changing the intervals among micro-columns. C. elegans were transferred into this micro-column array and the subcellular distribution of DAF-16, which is a well-known transcription factor regulating different stress responses, was monitored for analysing the physiological responses to the confined spaces. We found that the worms exhibited a gradual increase in DAF-16 nuclear localization in the micro-column array with intervals from 200 μm to 40 μm. Moreover, the results showed that the absence of food and crowding stress could cooperate to promote increased DAF-16 nuclear localization. Finally, loss-of-function mutations in mec-4 and mec-10, which are amiloride-sensitive Na(+) channel genes expressed in all six gentle touch neurons, accelerated the velocity of DAF-16 nuclear localization, induced by confined space, revealing that mec-4/mec-10 were not required for this stress response. Thus, this device will provide a versatile, reliable and controllable platform for crowding stress studies.

Evaluation of a fast and simple method for measuring plasma lactate levels in Atlantic cod, Gadus morhua (L.)

The aim of the present study was to investigate the validity of measuring circulatory lactate levels in plasma from Atlantic cod using Lactate ProTM, a portable meter described for measuring whole blood lactate in this species. Atlantic cod were either unstressed or subjected to short- or long-term crowding stress. Whole blood was analyzed on site, and a strong positive relationship was evident between lactate concentrations measured in whole blood and 5 months later in frozen and thawed plasma. Our results indicate that the portable meter can be effectively used also to detect differences in plasma lactate in this species. Key words: Blood, exercise, portable meter, stress.

Effects of stocking density and sustained aerobic exercise on growth, energetics and welfare of rainbow trout

Two stocking densities, “low” (L, between ~19 and ~25kgm−3) and “high” (H, between ~75 and ~100kgm−3) were compared for effects on specific growth rate (SGR), feed conversion, energetics and welfare of rainbow trout reared at 14°C either in static water (S) or swimming in a gentle current of ~0.9 bodylengths s−1 (C). Trout (initial mass ~110g) were reared for 9weeks in circular tanks (volume 0.6m3), in triplicate of four conditions (LS, LC, HS, HC). Fish were fed ad-libitum daily; waste pellets were swirl-collected at the outflow to calculate feed intake. SGR was measured each three weeks for the last six weeks of the trial. The tanks functioned as intermittent-stopped flow respirometers, to permit metabolic rate to be measured as instantaneous oxygen uptake once per hour. Mean (±SD) SGR was significantly lower at H than L (1.51±0.03 vs 1.44±0.04% day−1, respectively, n=6) and lowest in HC. When compared over a similar interval of mass gain, H groups had approximately 25% higher metabolic rates than L, with the highest rates in the HC condition. As a result, fish in the H groups dissipated a greater amount of feed energy as metabolism and, across all groups, there was a direct negative relationship between the quantity of energy dissipated and their SGR. There was no evidence of a neuroendocrine stress response, plasma cortisol was around 1ngml−1 in all conditions. An acute crowding stress increased plasma cortisol to above 120ngml−1 in all groups, but C groups recovered to control levels within 8h whereas S groups required 20h. Respirometry on individuals revealed that H fish had approximately 14% higher metabolic rates than L fish, indicating that increased metabolic rate in rearing tanks was in part physiological. The H groups had approximately 15% lower critical swimming speeds than the L groups which, together with their raised metabolic rate, indicated a physiological impairment. Thus, high density reduced SGR by raising energy dissipation, at least partially as a physiological response by the fish, although there was no evidence of an endocrine stress response. The only beneficial effect of C was in recovery from acute stress.

The Effect of Crowding Stress on Bacterial Growth and Sensory Properties of Chilled Atlantic Salmon Fillets

Atlantic salmon were subjected to minimal preslaughter crowding stress (Control), short-term crowding for 20 min (SS-group), or long-term crowding for 24 h (LS-group). The fish were filleted prerigor, cut into 270 g pieces, and packaged in modified atmosphere (60% CO₂ and 40% N₂). Fillet quality analyses were determined during 22 d of storage at 0.3 °C. Bacterial growth and unpleasant sensory properties increased earlier in the LS-group. The negative effects of long-term preslaughter stress were more pronounced for raw than cooked samples, and more pronounced for odor than flavor. Sequence analyses of bacterial DNA at the end of storage revealed that 100% of the bacteria were comprised by Photobacterium phosphoreum of the SS- and LS-group, whereas the Control group also contained 21% of Carnobacterium maltaromaticum (lactic acid bacteria, LAB). Counting of LAB, using Man-Rogosa-Sharke agar, similarly showed higher numbers of the Control group after 15 d of storage. A total bacterial count of log 6 CFU/g was observed after 15 d of storage of the LS-group, which was 3 and 7 d earlier compared with the Control and SS-group, respectively. Fillet color, texture, and liquid losses were not negatively affected by preslaughter crowding stress. From the sensory and bacterial analyses, it is concluded that long-term crowding stress accelerates bacterial growth and development of unpleasant sensory properties, hence reduces the shelf life of prerigor modified atmosphere packaged (MAP) salmon. Stressful handling of Atlantic salmon before slaughter resulted in faster reduction of fresh taste and smell, faster bacterial growth, and hence shorter shelf life. The deteriorative effects were more pronounced of raw compared to cooked salmon. Therefore, salmon should be handled carefully in connection with slaughter to avoid impaired welfare and fillet quality, in particularly for fish that is consumed raw, such as sushi.

Effect of feeding modes of Ala-Gln on growth and resistance to crowding stress of Cyprinus carpio var. jian

The trial was carried out on healthy Cyprinus carpio var.jian with the initial weight(33.52±0.17) g in a single recirculating system for 8 weeks.Diet was administered at concentrations 0.0%(control diet)and 0.5%(trial diet)Ala-Gln of dietary dry matter,which were fed to the C.carpio var.jian in five different feeding modes.continuously fed by control diet during eight weeks(Ⅰ,control group),trail diet at an interval of two weeks(Ⅱ),trail diet before four weeks at an interval of four weeks(Ⅲ),trail diet after four weeks at an interval of four weeks(Ⅳ),and continuously fed by trail diet during eight weeks(Ⅴ).Acute crowding stress was implemented at the last of experiment.The trail was conducted to investigate the effects of feeding modes of Ala-Gln on growth and the resisence to acute crowding stress for C.carpio var.jian.Results indicated that growth of different feeding modes of Ala-Gln was significantly higher than that of control group(P0.05).Specific growth rate of Ⅱ was higher than that of Ⅲ,Ⅳ,Ⅴ groups(P0.05)and that of Ⅲ was higher than that of Ⅴ group(P0.05).After acute crowding stress,Serum cortisol reached peak at 0 h and glucose at 1h,serum HSP70 remained high level before 1-12 h then declined,at last,restored the normal level until 48 h.Serum cortisol and glucose were lower in every feeding mode than in control group(P0.05).The smallest increase of serum glucose was Ⅱ group,The first recovery occurred in Ⅱ and Ⅲ group after stress.Serum HSP70 in every feeding mode was significantly higher than that in the control group(P0.05),and returned to normal state in 48 h and 72 h.Serum HSP70 in Ⅳ and Ⅴ groups was still significantly higher than the control(P0.05).In the current experiment,it concluded that adding Ala-Gln could improve the growth and resistance to crowding stress of C.carpio var.jian.There were significant differences of every feeding mode.Given economic efficiency and practicability,interval feeding modes will be suggested in the practical culture of C.carpio var.jian.

Impact of acute stress on antimicrobial polypeptides mRNA copy number in several tissues of marine sea bass (Dicentrarchus labrax)

BackgroundIn comparison to higher vertebrates, fish are thought to rely heavily on innate immune system for initial protection against pathogen invasion because their acquired immune system displays a considerably poor immunological memory, and short-lived secondary response. The endogenous antimicrobial polypeptides (AMPPs) directly and rapidly killing pathogens such as bacteria, fungi, parasites, and viruses are included within the realm of innate defenses. In addition to piscidins, AMPPs that in recent years have been shown to be commonly linked to innate defense, are histones and their polypeptide fragments, and peptides derived from the respiratory protein hemoglobin. There is evidence that a number of stresses lead to significant regulation of AMPPs and thus their monitoring could be a highly sensitive measure of health status and risk of an infectious disease outbreak, which is a major impediment to the continued success of virtually all aquaculture enterprises and is often the most significant cause of economic losses.ResultsWe firstly isolated and deposited in Genbank database the cDNA sequences encoding for hemoglobin-β-like protein (Hb-LP) [GeneBank: JN410659], H2B histone-like protein 1 (HLP1) GenBank: JN410660], and HLP2 [GenBank: JN410661]. The "de novo" prediction of the three-dimensional structures for each protein is presented. Phylogenetic trees were constructed on Hb-LP, HLP1, and HLP2 sequences of sea bass and those of other teleost, avian, reptiles, amphibian and mammalian species. We then used real time RT-PCR technology to monitor for the first time in sea bass, dynamic changes in mRNA copy number of Hb-LP, HLP1, HLP2, and dicentracin in gills, skin, eyes, stomach and proximal intestine in response to acute crowding/confinement stress. We showed that acute crowding stress induces an increase in the expression levels of the aforementioned genes, in gills and skin of sea bass, but not in other tissues, and that this expression patterns are not always rapidly reversed upon re-exposure to normal conditions.ConclusionThe higher expression of the four target genes in gills and skin of sea bass suggests that this AMPP represents a first and immediate line of defense in combating pathogens and stressors since these tissues constitute the first physiological barriers of the animal.