Membrane-Bound Ferric Hemoglobin in Nucleated Erythrocytes of the Black Scorpionfish Scorpaena porcus, Linnaeus 1758.

The content of membrane-bound methemoglobin (MtHb) in nucleated erythrocytes was studied in the black scorpionfish Scorpaena porcus (Linnaeus, 1758) in vitro. Spectral characteristics were determined for a whole hemolysate, a hemolysate obtained by stroma precipitation (a clarified hemolysate), and a resuspended stroma. The MtHb proportion in the erythrocyte stroma was found to exceed 80% (6.20 ± 0.59 µM). Clarified hemolysates were nearly free of MtHb (0.5 ± 0.2 µM). Membrane-bound ferric hemoglobin did not affect the erythrocyte resistance to osmotic shock. The osmotic fragility range was determined using a LaSca-TM laser microparticle analyzer (BioMedSystems, Russia) to be 102-136 mOsm/kg, much the same as in other bony fish species. A nitrite load (10 mg/L) significantly increased the MtHb content in the blood. However, the membrane-bound ferric hemoglobin content did not change significantly, amounting to 6.34 ± 1.09 µM (approximately 95%). The finding suggested a functional importance for MtHb present in the plasma membrane of nucleated erythrocytes. Membrane-bound MtHb was assumed to neutralize the external oxidative load and the toxic effect of hydrogen sulfide in bottom water layers, where the species lives.

Enhanced oxygen unloading in two marine percomorph teleosts.

Teleost fishes are diverse and successful, comprising almost half of all extant vertebrate species. It has been suggested that their success as a group is related, in part, to their unique O2 transport system, which includes pH-sensitive hemoglobin, a red blood cell ß-adrenergic Na+/H+ exchanger (RBC ß-NHE) that protects red blood cell pH, and plasma accessible carbonic anhydrase which is absent at the gills but present in some tissues, that short-circuits the ß-NHE to enhance O2 unloading during periods of stress. However, direct support for this has only been examined in a few species of salmonids. Here, we expand the knowledge of this system to two warm-water, highly active marine percomorph fish, cobia (Rachycentron canadum) and mahi-mahi (Coryphaena hippurus). We show evidence for RBC ß-NHE activity in both species, and characterize the Hb-O2 transport system in one of those species, cobia. We found significant RBC swelling following ß-adrenergic stimulation in both species, providing evidence for the presence of a rapid, active RBC ß-NHE in both cobia and mahi-mahi, with a time-course similar to that of salmonids. We generated oxygen equilibrium curves (OECs) for cobia blood and determined the P50, Hill, and Bohr coefficients, and used these data to model the potential for enhanced O2 unloading. We determined that there was potential for up to a 61% increase in O2 unloading associated with RBC ß-NHE short-circuiting, assuming a - 0.2 ∆pHa-v in the blood. Thus, despite phylogenetic and life history differences between cobia and the salmonids, we found few differences between their Hb-O2 transport systems, suggesting conservation of this physiological trait across diverse teleost taxa.

Molecular identification of an androgen receptor and the influence of long-term aggressive interaction on hypothalamic genes expression in black rockfish (Sebastes schlegelii).

This study aims to explore the mechanism on how aggressive interaction alters reproductive physiology by testing whether aggressive interaction can activate the reproductive neuroendocrine function via the hypothalamus-pituitary-gonadal (HPG) axis in black rockfish (Sebastes schlegelii). The expressions of the androgen receptor gene (ar) and gonadotropin-releasing hormone genes (gnrhs), the concentration of plasma androgens, and GSI (the ratio of testes mass to body mass) were compared between the interaction group (dominant males or subordinate males) and the isolation group in male black rockfish after 3 weeks. A full-length cDNA encoding an androgen receptor (AR) of 766 amino acids was isolated. Transcripts encoding this AR were detected at a high relative abundance in the liver, kidney, testis, ovary, muscle, and intestine tissue. Further evaluation of brain genes transcripts abundance revealed that the mRNA levels of gnrh I and ar genes were significantly different between the interaction group and the isolation group in the hypothalamus. However, no significant difference was detected in testosterone, 11-keto-testosterone, and GSI between these two groups. This study indicates that a long-term aggressive interaction affect the expression of hypothalamic gnrh I and ar but may not change the physiological function of the HPG axis in an all-male condition.

Dietary supplementation of fermented lemon peel enhances lysozyme activity and susceptibility to Photobacterium damselae for orange-spotted grouper, Epinephelus coioides.

The waste recycling of lemon peel, as a functional feed additive in aquafeed was evaluated by estimating the effects of fermented lemon peel (FLP) supplementation in diet on growth performance, innate immune responses, and susceptibility to Photobacterium damselae of grouper, Epinephelus coioides. A basal diet was added FLP at 0%, 1%, 3%, and 5%. Four tested diets were each fed to juvenile grouper (initial weight: 15.89 ± 0.10 g, triplicate groups) in a recirculation rearing system for eight weeks. Fish fed diets with 0%-3% FLP exhibited higher (p < 0.05) final weight, weight gain, and feed efficiency than fish fed the 5% FLP-diet. After challenge test, fish fed the 3% FLP-diet appeared the lowest mortality, followed by fish fed the 1% FLP-diet, and lowest in fish fed 0% and 5% FLP-diets. Plasma lysozyme activities were higher in fish fed diets with FLP than in fish fed the FLP-free control diet before challenge test. After challenge, fish fed diets with 1% and 3% FLP showed highest lysozyme activities, followed by fish fed the diet with 5% FLP, and lowest in fish fed the control diet. Hepatic malondialdehyde content was higher in fish fed the control diet than in fish fed diets with 1%-3% FLP. Results found that diets supplemented with 1%-3% fermented lemon peel can enhance lysozyme activity and resistance to pathogen P. damselae of grouper.

Effects of acute low temperature stress on the hormones and gene expression of glucocorticoid receptor of large yellow croaker Larimichthys crocea.

The neuroendocrine system of fish responds to low temperature via regulating hormones. To explore the adaptability of Larimichthys crocea to low temperature, the levels of the plasma cortisol, thyroid stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), total cholesterol (TC), and glucose were determined after exposure to low temperature and during subsequent rewarming. Furthermore, the mRNA expression of the glucocorticoid receptor (GR) gene was analyzed under the stress. We found that the levels of the plasma cortisol, TSH, T3, glucose, and TC increased under the low temperature stress, suggesting that elevated hormones may be conducive to promoting the mobilization of the glucose and lipid in L. crocea exposed to low temperature. During the rewarming period, the plasma cortisol level decreased, whereas the T3 level was still significantly higher than that in the control group. Notably, the plasma T4 level was unaffected by the temperature changes. Furthermore, the sequence alignment and phylogenetic tree analysis revealed that the GR protein of L. crocea had high homology and a similar protein structure with those from other teleosts. Under the low temperature stress, the GR mRNA expression increased in the brain and head kidney, whereas it basically returned to the control level following rewarming. These findings revealed the changes of the hormones and the potential function of the GR gene in L. crocea following exposure to low temperature, providing some insights into breeding low temperature-resistant varieties of L. crocea.

Regulation of splenic contraction persists as a vestigial trait in white-blooded Antarctic fishes.

In fishes, the spleen can function as an important reservoir for red blood cells (RBCs), which, following splenic contraction, may be released into the circulation to increase haematocrit during energy-demanding activities. This trait is particularly pronounced in red-blooded Antarctic fishes in which the spleen can sequester a large proportion of RBCs during rest, thereby reducing blood viscosity, which may serve as an adaptation to life in cold environments. In one species, Pagothenia borchgrevinki, it has previously been shown that splenic contraction primarily depends on cholinergic stimulation. The aim of the present study was to investigate the regulation of splenic contraction in five other Antarctic fish species, three red-blooded notothenioids (Dissostichus mawsoni Norman, 1937, Gobionotothen gibberifrons Lönnberg, 1905, Notothenia coriiceps Richardson 1844) and two white-blooded "icefish" (Chaenocephalus aceratus Lönnberg, 1906 and Champsocephalus gunnari Lönnberg, 1905), which lack haemoglobin and RBCs, but nevertheless possess a large spleen. In all species, splenic strips constricted in response to both cholinergic (carbachol) and adrenergic (adrenaline) agonists. Surprisingly, in the two species of icefish, the spleen responded with similar sensitivity to red-blooded species, despite contraction being of little obvious benefit for releasing RBCs into the circulation. Although the icefish lineage lost functional haemoglobin before diversifying over the past 7.8-4.8 millions of years, they retain the capacity to contract the spleen, likely as a vestige inherited from their red-blooded ancestors.

Altered physiological response and gill histology in black rockfish, Sebastes schlegelii, during progressive hypoxia and reoxygenation.

Hypoxia has gradually become common in aquatic ecosystems and imposes a significant challenge for fish farming. The loss of equilibrium (LOE), 50% lethal time (LT50), plasma cortisol, glucose, red blood cells (RBC), hemoglobin (Hb), gill histological alteration, and related parameters (lamellar length [SLL] and width [SLW], interlamellar distance [ID], basal epithelial thickness [BET], lamellar surface area [LA], and gill surface area [GSA]); respiratory rate; the proportion of the secondary lamellae available for gas exchange (PAGE); and hypoxia-inducible factor (hif-1α, hif-2α) mRNA expression were determined during progressive hypoxia and reoxygenation (R-0, R-12, R-24 h) to illustrate the underlying physiological response mechanisms in black rockfish Sebastes schlegelii. Results showed that the DO concentration significantly decreased during progressive hypoxia, while DO at LOE and LT50 were 2.42 ± 0.10 mg L-1 and 1.67 ± 0.38 mg L-1, respectively. Cortisol and glucose were significantly increased at LOE and LT50, with the highest levels observed at LT50, and then gradually recovered to normal within reoxygenation 24 h. RBC number and Hb results were like those of glucose. Hypoxia stress resulted in lamellar clubbing, hypertrophy, and hyperplasia. Respiratory frequency significantly increased at LOE and decreased at LT50. Lamellar perimeters, SLL, ID, LA, GSA, and PAGE, significantly increased at LOE and LT50, with the highest values observed at LT50. However, SLW and BET significantly decreased at LOE, LT50, and R-0. These parameters recovered to nearly normal levels at R-24 h. hif-1α mRNAs in gill and liver were significantly upregulated at LOE and LT50, and recovery to normal after reoxygenation 24 h. hif-2α mRNAs in gill was similar to that of hif-1α, whereas hepatic hif-2α mRNAs remained unchanged during hypoxia-reoxygenation. These results indicated that progressive hypoxia stress elevated RBC number, Hb, cortisol, and glucose levels, induced the alteration of gill morphology, increased LA and GSA, stimulated respiratory frequency and PAGE, and upregulated the transcription of hif-1α and hif-2α in gill and liver. Reoxygenation treatment for 24 h alleviated the stress mentioned above effects. These findings expand current knowledge on hypoxia tolerance in black rockfish Sebastes schlegelii.

Kiss2 but not kiss1 is involved in the regulation of social stress on the gonad development in yellowtail clownfish, Amphiprion clarkii.

The yellowtail clownfish (Amphiprion clarkii) is a hermaphrodite fish, whose sex differentiation and gonad development are closely related to its social status. The kisspeptin/KissR system is regarded as a key factor mediating social stress on reproductive regulation. In order to understand the effects of social rank stress on the yellowtail clownfish gonadal differentiation, full-length cDNAs of two paralogous genes encoding kisspeptin (kiss1 and kiss2) and KissR (kissr2 and kissr3) were cloned and characterized. The results of real-time PCR showed that kiss1 was primarily expressed in the hypothalamus, and kiss2/kissr2 were abundantly expressed in the liver, while kissr3 was almost exclusively concentrated in the cerebellum and pituitary. Moreover, both Kiss1-10 and Kiss2-10 peptides could initiate downstream signaling pathways by interacting with cognate receptors expressed in eukaryotic cells. Among the three social status groups, the mRNA levels of kiss2 in the hypothalamus and pituitary as well as kissr2 in the pituitary were significantly higher in subordinate individuals (nonbreeders) than dominate individuals (females and males); while the mRNA levels of kissr3 in the hypothalamus and gonad were low in subordinate individuals. Furthermore, the plasma estradiol (E2) and testosterone (T) levels were higher in subordinate than dominate individuals. This study shows that kiss2 is involved in the regulation of social stress on the gonad development in the yellowtail clownfish, but not kiss1.

Endocrine regulation of long-term enhancement of spermiation in meagre (Argyrosomus regius) with GnRHa controlled-delivery systems.

Meagre (Argyrosomus regius) undergo spermatogenesis and spermiation when reared in captivity, but often produce low milt volumes, sometimes with reduced quality and for a limited time period. In the present study we a) compared the efficiency of gonadotropin releasing hormone agonist (GnRHa) implants versus injections on testicular stimulation and spermiation enhancement, b) investigated the effect of GnRHa on the endocrine spermiation regulation (sex steroid hormones), and c) evaluated a commercial induced spawning simulation scenario. Firstly, males (n = 5) were injected with 15.0 ± 0.2 µg GnRHa kg-1 (Injections) or implanted with 51.0 ± 5.1 µg GnRHa kg-1 (Implant) and compared their sperm production response. Secondly, the best hormonal treatment (Implant) was tested treating males (n = 8) with 57.5 ± 7.5 µg GnRHa kg-1 every 3 weeks for a period of 70 days. Milt production was improved by the GnRHa implants with only minor sperm quality alterations (improved sperm motility percentage). Elevated plasma testosterone (T) and 11-ketotestosterone (11-KT) levels were recorded in response to GnRHa implants, while no significant difference for 17,20ß-dihydroxy-4-pregnen-3-one (17,20ß-P) was observed. In the commercial induced spawning simulation, it was shown that meagre females are capable of on-demand induction of spawning at random intervals (5-21 days) using GnRHa injections, over a period of at least 2.5 months. During this period, spermiation enhancement was achieved with GnRHa implants every 3 weeks, producing sperm with stable, in general, quality and motility parameters. Percentage of motile cells, motility duration and density fluctuated significantly, but remained within levels that are considered appropriate for high fertilization success in this species.

Comprehensive physiological and transcriptomic analysis revealing the responses of hybrid grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂) to the replacement of fish meal with soy protein concentrate.

Plant proteins are suitable and alternative to fish meals (FMs), with less cost compared with that of all other types of fish feeds. In recent years, soy protein concentrate (SPC) has emerged as a cost-effective alternative to FM; however, little is known regarding the effects of dietary SPC on general fish physiology and well-being. This study aimed to perform comprehensive physiological and transcriptomic analysis for testing the applicability of SPC as fish feeds in hybrid grouper (Epinephelus fuscoguttatus♀ נE. lanceolatus♂) [SPC replaced 0% (CK), 30% (SPC30), and 75% (SPC75) of FM protein]. Generally, SPC30 promoted fish survival and had less effects on the phenotype, while SPC75 reduced fish survival, promoted inflammation, and regulated multiple physiological responses. Thousands of differentially expressed genes (DEGs) by SPC were identified in the intestine, liver, and muscle, which were enriched in biological regulation, cellular process, metabolic process, single-organism process, cell, cell part, membrane, binding, and catalytic activity based on RNA-seq. Notably, some DEGs involved in amino acid and lipid metabolism in the digestive system highlighted the modulatory effect of SPC on these metabolic processes, consistent with the physiological responses including enzyme activities. The enriched aspects of these predominant DEGs might be directly related to the different effects of SPC30 and SPC75 on fish growth, digestibility, and underlying enzyme activities and histology. In conclusion, the comprehensive physiological and transcriptomic comparative analysis of CK, SPC30, and SPC75 was also effective in testing the applicability of SPC as fish feeds and in designing a proper diet with the best impact on the growth performance and health of fish in hybrid grouper.

Effects of dietary exogenous xylanase supplementation on growth performance, intestinal health, and carbohydrate metabolism of juvenile large yellow croaker, Larimichthys crocea.

An 8-week feeding trial was conducted to evaluate the effects of dietary xylanase supplementation on growth performance, digestive enzyme activity, intestinal morphology parameter, intestinal microbiome diversity, and carbohydrate metabolism for juvenile large yellow croaker (Larimichthys crocea). Four levels of xylanase were added to basal diets (0, 600, 1200, and 1800 U kg-1). The results indicated that fish fed the 1200 U kg-1 xylanase diet had higher weight gain than those fed the 0 and 600 U kg-1 xylanase diet. The highest intestinal folds and microvillous height were observed at fish fed the 1200 U kg-1 xylanase diet. High-throughput sequencing revealed that the majority of reads derived from the large yellow croaker digesta belonged to members of Proteobacteria followed by Chloroflex, Bacteroidetes, Spirochaetae, and Firmicute. Supplementation of xylanase in diets increased the relative abundance of Bacteroides and Gemmatimonadete. The higher hepatic glucokinase (GK) and glucose-6-phosphate dehydrogenase (G6PD) activities were observed in fish fed the xylanase supplementation diet. Accordingly, dietary xylanase supplementation upgraded the relative expressions of gk and g6pd genes in liver. In conclusion, optimum dietary xylanase supplementation (600-1200 U kg-1) could improve the growth performance, optimize the intestinal morphology structure and microbiota constitution, and enhance the ability of carbohydrate utilization of juvenile large yellow croaker.

Interactions of long-term food ration variation and short-term fasting on insulin-like growth factor-1 (IGF-1) pathways in copper rockfish (Sebastes caurinus).

Variation in food intake affects somatic growth by altering the expression of hormones in the somatotropic endocrine axis including insulin-like growth factor-1 (IGF-1). Here, we examined IGF-1 pathway responses to long- and short-term variation in food availability in copper rockfish (Sebastes caurinus), a nearshore Pacific rockfish important for commercial and recreational fisheries. Juvenile copper rockfish were raised under differing ration amounts (3% or 9% mass feed·g-1 fish wet mass·day-1) for 140 d to simulate 'long-term' feeding variation, after which some fish from both rations were fasted for 12 d to generate 'short-term' conditions of food deprivation. Rockfish on the 9% ration treatment grew more quickly than those on the 3% ration and were larger in mass, length, and body condition (k) after 152 d. Fish on the 9% ration had higher blood glucose than those on the 3% ration, with fasting decreasing blood glucose in both ration treatments, indicating that both long-term and short-term feed treatments altered energy status. Plasma IGF-1 was higher in rockfish from the 9% ration than those in the 3% ration and was also higher in fed fish than fasted fish. Additionally, plasma IGF-1 related positively to individual variation in specific growth rate (SGR). The positive association between IGF-1 and SGR showed discordance in fish that had experienced different levels of food and growth over the long-term but not short-term, suggesting that long-term nutritional experience can influence the relationship between IGF-1 and growth in this species. Rockfish on the 3% ration showed a lower relative abundance of gene transcripts encoding igf1 in the liver, but higher hepatic mRNAs for IGF binding proteins igfbp1a and igfbp1b. Fasting similarly decreased the abundance of igf1 mRNAs in the liver of fish reared under both the 9% and 3% rations, while concurrently increasing mRNAs encoding the IGF binding proteins igfbp1a, -1b, and -3a. Hepatic mRNAs for igfbp2b, -5a, and -5b were lower with long-term ration variation (3% ration) and fasting. Fish that experienced long-term reduced rations also had higher mRNA levels for igfbp3a, -3b, and IGF receptors isoforms A (igf1rA) and B (igf1rB) in skeletal muscle, but lower mRNA levels for igf1. Fasting increased muscle mRNA abundance for igfbp3a, igf1rA, and igf1rB, and decreased levels for igfbp2a and igf1. These data show that a positive relationship between circulating IGF-1 and individual growth rate is maintained in copper rockfish even when that growth variation relates to differences in food consumption across varying time scales, but that long- and short-term variation in food quantity can shift basal concentrations of circulating IGF-1 in this species.

Inhibition of ovarian development and instances of sex reversal in genotypic female sablefish (Anoplopoma fimbria) exposed to elevated water temperature.

This study determined high temperature effects on ovarian development in a marine groundfish species, sablefish (Anoplopoma fimbria), with potential application in sex reversal or sterilization for aquaculture. Monosex female (XX-genotype) sablefish larvae (∼30 mm) were randomly divided into three groups and exposed to control (15.6 °C ±â€¯0.8 °C), moderate (20.4 °C ±â€¯0.5 °C), or high (21.7 °C ±â€¯0.5 °C) temperatures for 19 weeks. Treated fish were then tagged and transferred to ambient seawater (11.2 °C ±â€¯2.3 °C) for one year to determine whether temperature effects on reproductive development were maintained post-treatment. Fish were periodically sampled for gonadal histology, gene expression and plasma 17ß-estradiol (E2) analyses to assess gonadal development. Short-term (4-week) exposure to elevated temperatures had only minor effects, whereas longer exposure (12-19 weeks) markedly inhibited ovarian development. Fish from the moderate and high treatment groups had significantly less developed ovaries relative to controls, and mRNA levels for germ cell (vasa, zpc) and apoptosis-associated genes (p53, casp8) generally indicated gonadal degeneration. The high treatment group also had significantly reduced plasma E2 levels and elevated gonadal amh gene expression. After one year at ambient temperatures, however, ovaries of moderate and high treatment fish exhibited compensatory recovery and were indistinguishable from controls. Two genotypic females possessing immature testes (neomales) were observed in the high treatment group, indicating sex reversal had occurred (6% rate). These results demonstrate that extreme elevated temperatures may inhibit ovarian development or trigger sex reversal. High temperature treatment is likely not an effective sterilization method but may be preferable for sablefish neomale broodstock production.

Very high blood oxygen affinity and large Bohr shift differentiates the air-breathing siamese fighting fish (Betta splendens) from the closely related anabantoid the blue gourami (Trichopodus trichopterus).

The Siamese fighting fish, Betta splendens, and the blue gourami, Trichopodus trichopterus, are two closely related air-breathing anabantoid fishes. B. splendens is a sedentary facultative air breather frequenting often hypoxic waters, while T. trichopterus is a more active obligatory air-breather inhabiting better oxygenated waters. Despite their close taxonomic relationship, previous studies have shown inter-specific differences in both physiological and morphological plasticity. Consequently, we hypothesized that B. splendens would have the higher blood oxygen affinity characteristics typical of more hypoxia-tolerant fishes. Whole blood oxygen equilibrium curves were determined at 27 °C and pHs of 7.62, 7.44 and 7.25. At a pH of 7.62, the blood O2 affinity (P50) of B. splendens was just 2.9 mmHg, while that of T. trichopterus was ~5 times higher at 14.7 mmHg. There were no significant differences in P50 between males and females in either species. The Bohr coefficient in B. splendens and T. trichopterus was -1.79 and - 0.83, respectively. B. splendens, unlike T. trichopterus, showed a large Root effect. Hills cooperatively coefficient, n, was ~2 in both species, indicating a significant binding cooperative between oxygen and hemoglobin. Collectively, these differences in blood O2 transport characteristics in these two closely related species are likely correlated with the differing habitats in which they breed and inhabit as adults, as well as different activity levels. Finally, the very high blood O2 affinity of B. splendens is not extraordinary among air-breathing fish, as revealed by a review of the literature of blood oxygen affinity in air-breathing fishes.

Effect of ration level on growth performance, body composition, intermediary metabolism and serum parameters in juvenile Patagonian blennie Eleginops maclovinus.

Eleginops maclovinus is an endemic species of the southern cone with beneficial physiological characteristics for aquaculture. However, this species has a low growth rate under captive conditions, and the optimal feed ration together with the metabolic process is unknown. This study aimed to determine the optimum feed ration during 90 days based on growth performance, body composition, intermediary metabolism, and serum parameters. For this, fish were randomly assigned to rations of 0.5, 1, 2 and 4% of body weight. No fish mortality was registered, but all fish, developed fatty liver. The results of weight, length, growth performance (WGR, SGR), and body parameters (HSI, VSI and K) followed a similar pattern, with the lowest values observed in the 0.5% and no significant differences between rations of 1, 2 and 4%. The feed intake and feces increased with the feed ration. However, the percentage of food consumed by the fish decreased with the ration size and the feed conversion ratio was lowest in the 1% ration. Total serum proteins and calcium were lowest in the 0.5% ration and presented no differences in the rations 1, 2 and 4%, while triglyceride content was significantly different only between the rations of 0.5 and 4%. Blood cortisol levels were significantly higher in the rations of 0.5 and 1%, and decreased in rations of 2 and 4%. The lipids, fiber, and energy of the total body mass increased with the feed ration, while dry matter, proteins, and ash of the body decreased to higher feed ration. In liver, triglyceride and protein levels decreased with a larger feed ration, amino acids increased in the rations of 0.5 and 4%, while glucose levels increased in rations of 2 and 4%. Liver enzymes Glucose-6-phosphate dehydrogenase and Glutamate dehydrogenase increased their activity at a higher feed ration, while Glycogen Phosphorylase, Aspartate aminotransferase and 3-Hydroxyacyl-CoA dehydrogenase presented their highest enzymatic activity only in the 4% ration. Fructose-1,6-bisphosphate showed low enzymatic activity in rations of 2 and 4% and Glycerol-3-phosphate dehydrogenase was significantly different only between the ration of 0.5 and 1%. Finally, our results suggests that optimal feed rations for E. maclovinus corresponds to 1% since this ration size produces the highest growth and metabolism with a minimum loss of food and feces present in the environment. Additionally, we recommend to reduce the percentage of fat in the diet to avoid the development of fatty liver.

Effects of predator exposure on baseline and stress-induced glucocorticoid hormone concentrations in pumpkinseed Lepomis gibbosus.

We compared baseline and maximal cortisol concentrations between predator exposure and prey blood samples in pumpkinseed Lepomis gibbosus, captured using a standardised fishing event underneath osprey Pandion haliaetus nests and away from osprey nests. We did not detect differences in cortisol or glucose between sites. These findings suggest that predictable sources of predation risk may not confer stress-related costs in teleosts.

Effect of long-term thermal challenge on the Antarctic notothenioid Notothenia rossii.

The thermal stability of the Antarctic Ocean raises questions concerning the metabolic plasticity of Antarctic notothenioids to changes in the environmental temperature. In this study, Notothenia rossii survived 90 days at 8 °C, and their condition factor level was maintained. However, their hepatosomatic (0.29×) index decreased, indicating a decrease in nutrient storage as a result of changes in the energy demands to support survival. At 8 °C, the plasma calcium, magnesium, cholesterol, and triglyceride concentrations decreased, whereas the glucose (1.91×) and albumin (1.26×) concentrations increased. The main energy substrate of the fish changed from lipids to glucose due to a marked increase in lactate dehydrogenase activity, as demonstrated by an increase in anaerobic metabolism. Moreover, malate dehydrogenase activity increased in all tissues, suggesting that fish acclimated at 8 °C exhibit enhanced gluconeogenesis. The aerobic demand increased only in the liver due to an increase (2.23×) in citrate synthase activity. Decreases in the activities of superoxide dismutase, catalase, and glutathione-S-transferase to levels that are most likely sufficient at 8 °C were observed, establishing a new physiological activity range for antioxidant defense. Our findings indicate that N. rossii has some compensatory mechanisms that enabled its long-term survival at 8 °C.

Different concentrations of Edwardsiella tarda ghost vaccine induces immune responses in vivo and protects Sparus macrocephalus against a homologous challenge.

Bacterial ghosts (BGs) can be generated by the controlled expression of the PhiX174 lysis gene E in gram-negative bacteria. They are intriguing vaccine candidates since ghosts retain functional antigenic cellular determinants often lost during traditional inactivation procedures. Here we prepared Edwardsiella tarda ghost (ETG) and tested different concentrations in vaccination trials. The results showed that serum IgM antibody titers were significantly higher in three different concentration immunization groups than control group (P < 0.05), However, there was no significant (P > 0.05) difference between the immunized groups. The phagocytic percentage (PP) was significantly higher (P < 0.05) in ETG immunized groups than in the control group from 3 days post-treatment. The PP continued to rise with time until day 21, when the values of three ETG immunized groups were 45.7%,51.2% and 50.7%, respectively. In addition, phagocytic index (PI) was significantly higher (P < 0.05) in ETG immunized groups than in the control group after 7 days post-treatment. However, there was no significant (P > 0.05) difference of PP or PI between immunized groups. In addition, non-specific immune immunity, such as acid phosphatase, alkaline phosphatase, superoxide dismutase and lysozyme activities displayed a similar pattern in all immunized groups, all immunized fish showed significantly higher activities than control group fish (P < 0.05). Most importantly three ETG immunized groups were all significantly more protected against the E. tarda challenge (19/25, 76% survival), (21/25, 84% survival) and (20/25, 80% survival) respectively, compared to (9/25, 36% survival) survival in the control group, but there was no significant (P > 0.05) difference of survival rate (SR) or relative percent survival (RPS) between immunized groups. All these results suggest that an ETG could stimulate cellular and humoral immunity, and could be used as a vaccine candidate in S.m. In summary, ETG can protect fish from Edwardsiellosis, and there is no significant difference in SR and RPS when three different concentrations of ETG are used, so it can easily be developed as a vaccine for mechanical and artificial operations.

Cottonseed protein concentrate (CPC) suppresses immune function in different intestinal segments of hybrid grouper ♀Epinephelus fuscoguttatus×♂Epinephelus lanceolatu via TLR-2/MyD88 signaling pathways.

Cottonseed protein concentrate (CPC) has similar amino acid composition compared with fish meal, and has the characteristics of low gossypol and low toxicity. The present study was conducted to investigate the growth performance, antioxidant capacity and different intestinal segments immune responses of hybrid grouper to replacement dietary fish meal ofCPC. Six iso-nitrogenous (50% crude protein) and iso-lipidic (10% crude lipid) diets were formulated: a reference diet (FM) containing 60% fishmeal and five experimental diets (12%, 24%, 36%, 48 and 60%) in which fishmeal protein was substituted at different levels by CPC to feed fish (initial body weight: 11 ±â€¯0.23 g) for 8 weeks. Thena challenge test with injection of Vibrio parahaemolyticus was conducted for 7 days until the fish stabilized. The results showed that specific growth rate (SGR) was the highest with 24% replacement level and feed conversion ratio (FCR)was significantly increased when the replacement level reached 48% (P < 0.05). The content of malonaldehyde (MDA) in the serum was significantly increased when the replacement level reached 36% (P < 0.05). The plica height in the proximal, mid and distal intestine were significantly decreased with the replacement level up to 48% (P < 0.05). Hepatic fat deposition wasaggravatedwhen the replacement level reached 36% (P < 0.05). The expression of IL-6, TNF-α, and IL-1ß mRNAs were significantly up-regulated (P < 0.05). The hepcidin mRNA expression was significantly down-regulated (P < 0.05). In proximal intestine (PI) and mid intestine (MI), IFN-γ mRNA expression was significantly up-regulated (P < 0.05). These results suggested that the CPC decreased hybrid grouper growth performance and inflammation function, and different inflammation function responses in PI,MI, and distal intestine (DI) were mediated partly by the TLR-2/MyD88 signaling pathway. According to the analysis of specific growth rate, the dietary optimum replacement level and maximum replacement level were estimated to be 17% and 34%, respectively.

Expression patterns of sex differentiation-related genes during gonadal sex change in the protogynous wrasse, Halichoeres trimaculatus.

The three-spot wrasse, Halichoeres trimaculatus, can change sex from female to male (i.e. protogyny) due to sharp decrease in endogenous estrogen. During the sex change, ovarian tissue degenerates and testicular tissue arises newly. Finally, ovarian tissue disappears completely and replaces into mature testis. In order to predict the molecular mechanisms controlling the processes of sex change, we investigated the expression patterns of four genes (rspo1, figla, sox9b and amh), which have been thought to be associated with ovarian/testicular differentiation in vertebrates. Expression levels of rspo1 and figla, which play important roles for ovarian differentiation in vertebrates, were stable until the middle stage of the sex change, and subsequently down-regulated. Therefore, it was indicated that decrease in rspo1 and figla could result from ovarian degeneration. On the other hand, basis on the expression pattern, it was indicated that sox9b and amh, which are involved in testicular differentiation in vertebrates, were implicated in testicular formation and spermatogenesis during the sex change as well. The present results could be fundamental information for investigating the relationship between these factors and E2 depletion, which is crucial trigger for sex change.