Effects of starvation on the pharmacokinetics and optimal dosages of florfenicol and associated serum biochemistry in Asian seabass (Lates calcarifer).

Starvation has influence on physiology and pharmacokinetic (PK) characteristics of many drugs in land animals. However, similar PK information in fish is lacking. The current study examined the effects of starvation on fish PK, taking florfenicol (FF) in Asian seabass as an example. FF was orally administered at a single dose of 10 mg/kg into 35-day starved fish reared at 25 and 30°C and the serum FF concentration was analyzed by HPLC-FLD. At 30°C, the absorption and elimination half-lives of the starved fish were increased by 30% (from 0.44 to 0.57 h) and 55% (from 7.2 to 11.18 h), respectively. The volume of distribution, clearance, and area under the curve were changed from 1.25 to 0.71 L/kg, 0.120 to 0.044 L/kg/h, and 88 to 228 h·µg/ml, respectively. Similar starvation-induced PK changes were also observed at 25°C. The serum biochemical parameters, mainly the alanine aminotransferase, aspartate aminotransferase, and glucose levels, were significantly reduced in the starvation group. Overall, FF absorption, distribution, and elimination rates were reduced by starvation, resulting in four to five times lower optimal dosage than the non-starved fish. Drug treatment in starved fish should be treated with caution as overdosing and/or tissue residues could perceivably occur.

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.

Myxobolus spp. (Cnidaria: Myxobolidae) in the circulating blood of fishes from Goiás and Mato Grosso States, Brazil: case report / Myxobolus spp. (Cnidaria: Myxobolidae) no sangue circulante de peixes dos estados de Goiás e Mato Grosso, Brasil: relato de caso

Myxosporidiosis is an infectious disease caused by myxozoans of the Phylum Cnidaria, Class Myxosporea, and Order Bivalvulida, considered a common parasite in fresh and saltwater fishes that parasitize many organs, especially gills. In the present study, 49 specimens of fishes belonging to eight genera: Tetragonopterus, Leporinus, Myleus, Pirinampus, Rhapiodon, Pygocentrus, Ageneiosus, and Serrasalmus were collected and blood smears were made, fixed with absolute methanol, and stained with Giemsa 10% to survey hemoparasites. However, myxospores were found in the circulating blood of five (10.20%) fishes belonging to genus Tetragonopterus, Myleus, and Pygocentrus. Two morphological types of Myxobolus spp. were identified in all the five fish specimens analyzed. Usually, investigations on myxozoans in fish are carried out with the search for plasmodia or cysts in the fish organs and observation of the cavity of organs. Nevertheless, this study highlights the importance of also examining the blood of these animals, since these parasites can cause severe pathogenic diseases in fish. Thus, the blood analyses can proportionate preventive sanitary control for commercial fish avoiding economic loss.

A mixosporidiose é considerada uma doença infecciosa causada por mixozoários pertentences ao Filo Cnidaria, Classe Myxosporea e Ordem Bivalvulida, considerados parasitos comuns de peixes de água doce e salgada, parasitando vários órgãos, principalmente as brânquias. No presente estudo, 49 espécimes de peixes pertencentes a oito gêneros: Tetragonopterus, Leporinus, Myleus, Pirinampus, Rhapiodon, Pygocentrus, Ageneiosus and Serrasalmus foram coletados e extensões sanguíneas foram feitas com a finalidade de encontrar hemoparasitos. Entretanto, mixoesporos foram observados em cinco (10.20%) espécimes de peixes, pertencentes aos gêneros Tetragonopterus, Myleus e Pygocentrus. Dois morfotipos de Myxobolus spp. foram identificados parasitando esses peixes. Normalmente, as investigações sobre mixozoários em peixes é realizada com a procura de plasmódios ou cistos nos órgãos dos peixes e observação da cavidade de órgãos. Porém, esse trabalho ressalta a importância de se examinar também o sangue desses animais, já que esses parasitos podem ocasionar patogenias severas em peixes. Sendo assim, a análise sanguínea pode proporcionar controle sanatório preventivo para peixes comerciais e evitar perdas econômicas.

Antarctic teleosts with and without hemoglobin behaviorally mitigate deleterious effects of acute environmental warming.

Recent studies forecast that many ectothermic animals, especially aquatic stenotherms, may not be able to thrive or even survive predicted climate change. These projections, however, generally do not call much attention to the role of behavior, an essential thermoregulatory mechanism of many ectotherms. Here we characterize species-specific locomotor and respiratory responses to acute ambient warming in two highly stenothermic Antarctic Notothenioid fishes, one of which (Chaenocephalus aceratus) lacks hemoglobin and appears to be less tolerant to thermal stress as compared to the other (Notothenia coriiceps), which expresses hemoglobin. At the onset of ambient warming, both species perform distinct locomotor maneuvers that appear to include avoidance reactions. In response to unavoidable progressive hyperthermia, fishes demonstrate a range of species-specific maneuvers, all of which appear to provide some mitigation of the deleterious effects of obligatory thermoconformation and to compensate for increasing metabolic demand by enhancing the efficacy of branchial respiration. As temperature continues to rise, Chaenocephalus aceratus supplements these behaviors with intensive pectoral fin fanning which may facilitate cutaneous respiration through its scaleless integument, and Notothenia coriiceps manifests respiratory-locomotor coupling during repetitive startle-like maneuvers which may further augment gill ventilation. The latter behaviors, found only in Notothenia coriiceps, have highly stereotyped appearance resembling Fixed Action Pattern sequences. Altogether, this behavioral flexibility could contribute to the reduction of the detrimental effects of acute thermal stress within a limited thermal range. In an ecologically relevant setting, this may enable efficient thermoregulation of fishes by habitat selection, thus facilitating their resilience in persistent environmental change.

A new experimental model for the investigation of sequential hermaphroditism.

The stunning sexual transformation commonly triggered by age, size or social context in some fishes is one of the best examples of phenotypic plasticity thus far described. To date our understanding of this process is dominated by studies on a handful of subtropical and tropical teleosts, often in wild settings. Here we have established the protogynous New Zealand spotty wrasse, Notolabrus celidotus, as a temperate model for the experimental investigation of sex change. Captive fish were induced to change sex using aromatase inhibition or manipulation of social groups. Complete female-to-male transition occurred over 60 days in both cases and time-series sampling was used to quantify changes in hormone production, gene expression and gonadal cellular anatomy. Early-stage decreases in plasma 17ß-estradiol (E2) concentrations or gonadal aromatase (cyp19a1a) expression were not detected in spotty wrasse, despite these being commonly associated with the onset of sex change in subtropical and tropical protogynous (female-to-male) hermaphrodites. In contrast, expression of the masculinising factor amh (anti-Müllerian hormone) increased during early sex change, implying a potential role as a proximate trigger for masculinisation. Collectively, these data provide a foundation for the spotty wrasse as a temperate teleost model to study sex change and cell fate in vertebrates.

Evidence for a Novel Antiviral Mechanism of Teleost Fish: Serum-Derived Exosomes Inhibit Virus Replication through Incorporating Mx1 Protein.

Exosomes are associated with cancer progression, pregnancy, cardiovascular diseases, central nervous system-related diseases, immune responses and viral pathogenicity. However, study on the role of exosomes in the immune response of teleost fish, especially antiviral immunity, is limited. Herein, serum-derived exosomes from mandarin fish were used to investigate the antiviral effect on the exosomes of teleost fish. Exosomes isolated from mandarin fish serum by ultra-centrifugation were internalized by mandarin fish fry cells and were able to inhibit Infectious spleen and kidney necrosis virus (ISKNV) infection. To further investigate the underlying mechanisms of exosomes in inhibiting ISKNV infection, the protein composition of serum-derived exosomes was analyzed by mass spectrometry. It was found that myxovirus resistance 1 (Mx1) was incorporated by exosomes. Furthermore, the mandarin fish Mx1 protein was proven to be transferred into the recipient cells though exosomes. Our results showed that the serum-derived exosomes from mandarin fish could inhibit ISKNV replication, which suggested an underlying mechanism of the exosome antivirus in that it incorporates Mx1 protein and delivery into recipient cells. This study provided evidence for the important antiviral role of exosomes in the immune system of teleost fish.

Pharmacokinetics and pharmacodynamics of single and multiple-dose levamisole in belugas (Huso huso): Main focus on immunity responses.

The pharmacokinetics of levamisole were determined in the belugas after single intravascular (IV), and single and multiple-dose oral by feed administrations. Also, the effect of levamisole (LVM) on the stress and immune responses of belugas were assessed. One hundred-fourteen healthy belugas in 4 different groups received single LVM administration at the doses of 50 and 100 mg/kg via IV and oral routes. A separate group of 24 belugas were administered oral LVM at the dose of 100 mg/kg for 5 days. Blood samples were collected at different time points after administrations to measure plasma concentrations of LVM by a validated high-performance liquid chromatography (HPLC) assay. For immunological evaluations, a total of 126 belugas received 50 and 100 mg/kg LVM via medicated feed for 5 days or served as the control without any medication; blood samples were recovered on day 0, 1, 3, 5, 7, 10, and 14 to measure hemolytic activity of the complement system (HAC50), serum lysozyme activity, serum antibacterial activity, glucose, cortisol, total protein, albumin and C3 contents. In the single-dose administration, quantified LVM concentrations were dose-dependent and the oral bioavailability was in the range of 43.2-49.6%. In the multiple-dose administration, the peak plasma concentration at the steady state was 45.2 mg/ml, and accumulation ratio was calculated as 3.6. In the immunological study, LVM especially at the dose of 100 mg/kg increased HAC50, lysozyme and antibacterial activity in the sera of treated fish. No significant effect of LVM on glucose and albumin content was observed, but cortisol levels decreased and C3 content was increased, more significantly by LVM at the dose of 100 mg/kg. Our results indicate that LVM is well absorbed after oral administration and reached to concentrations that can affect stress indicators and improve immune responses in belugas.

Combined effects of enzymes and probiotics on hemato-biochemical parameters and immunological responses of juvenile Siberian sturgeon (Acipenser baerii).

A 10-week feeding trial was run to investigate the separate and simultaneous effects of exogenous enzymes (Enz), probiotics (Pro), and Pro-Enz mixtures on the hematology indices, serum biochemical parameters, and innate-immunity status of juvenile Siberian sturgeon. The fish (138.06 ± 3.64 g) were randomly dispersed into 12 tanks (20 individuals per tank) and fed with Enz (Phytase, protease, and xylanase), Pro (Pediococcus pentosaceus and Lactococcus lactis), and Pro-Enz cocktail. At the end of the feeding bioassay, the highest values of red blood cell count, hemoglobin concentration, hematocrit level, and lymphocyte percentage followed by the lowest neutrophil percentage were obtained in Pro-Enz treatment (P < 0.05). Despite a significantly lower level of alkaline phosphatase in the fish fed with Pro supplemented diet (P < 0.05), no significant difference was found in the serum level of alanine aminotransferase and aspartate aminotransferase among the experimental groups (P > 0.05). Total protein content was significantly upregulated in serum and skin mucus samples from those fed with supplemented diets compared to the control group (P < 0.05). In both serum and skin mucus samples, higher immune responses in terms of lysozyme activity, immunoglobulin M, total protein was seen in Pro-Enz treatment compared to the control group followed by the serum complement components (P < 0.05). The results indicate that the combinational supplementation of Siberian sturgeon diet with the exogenous enzymes and probiotics modulates the physiometabolic responses and innate immune system to a higher grade than their individual supplementation.

The effects of bisphenol A on liver proteome and mucus vitellogenin in comparison to plasma as a non-invasive biomarker in immature Siberian sturgeons (Acipenser baerii).

This study was done to evaluate the effects of Bisphenol A (BPA) on Siberian sturgeon (Acipenser baerii). As liver is the main organ in the homeostatic adjustments to stress, we used a proteomics method to address molecular response in this tissue. Also, we compared the levels of vitellogenin in plasma and mucus to propose that the last one be a non-invasive method to analyze this biomarker. The fish received 1, 10, and 100 µg g-1 week-1 BPA intraperitoneally for two weeks. The samples were taken on days 0, 7, and 14. Plasma vitellogenin level increased as the highest value was recorded in the group with 100 µg g-1 week-1 of BPA. Changes in the mucus and blood vitellogenin showed a similar pattern, suggesting that mucus could be used for evaluating the changes in blood vitellogenin. Comparative proteomics was used to determine the proteome of the liver of A. baerii in the highest dose of BPA in comparison with the control. Sixteen proteins were identified that their expression changed at least twice between the studied groups. The proteomic results showed that BPA increased the expression of proteins involved in the detoxification and metabolism, activated glycolysis, and produced necrosis in the liver.

The evolution of red blood cell shape in fishes.

The size and shape of red blood cells (RBCs) provide key information on life-history strategies in vertebrates. However, little is known about how RBC shape evolved in response to environmental factors, body size and the role of evolutionary rate. Here, we analysed RBC morphometrics in a set of Teleostei (bony fishes) and Elasmobranchii (sharks and rays) species testing the hypothesis that phylogenetic relationship explains species occupation of morphospace. We collected data on cell and nucleus area and volume, nucleus:cytoplasm ratio and shape factor for 65 species belonging to 28 orders. Then, we built phylomorphospaces separately for bony fish and sharks and rays. To test whether phylogenetic relationships predicted phenotypic similarity, we calculated multivariate phylogenetic signal. We also estimated the evolutionary rate of RBC shape for each node and tip using ridge regression. Finally, we tested whether habitat and body size influenced RBC shape using a PGLS. We found a significant phylogenetic signal in RBC shape for bony fish, but not sharks and rays. Saltwater teleost species were more clustered than freshwater ones in the phylomorphospace, suggesting clade disparity. Accordingly, the rate of evolution was highly heterogeneous, with significant decrease in Acanthopterygii. Neither habitat nor body size influenced RBC shape. In conclusion, RBC shape seems to have evolved in fishes in response to multiple selective pressures independent of life-history characters.

Teleost red blood cells actively enhance the passive diffusion of oxygen that was discovered by August Krogh.

In the early 20th century, August and Marie Krogh settled one of the most controversial questions in physiology, showing through elegant experiments that oxygen (O2) uptake at the lung is driven by passive diffusion alone. Krogh's later work, on the regulation of local blood flow and capillary recruitment at the tissues, was awarded with the Nobel Prize in 1920. A century later it is still undisputed that O2 moves across tissues by diffusion, however, animals use active mechanisms to regulate and facilitate the passive process. Teleost fishes have evolved a mechanism by which adrenergic sodium-proton-exchangers (ß-NHEs) on the red blood cell (RBC) membrane actively create H+ gradients that are short-circuited in the presence of plasma-accessible carbonic anhydrase (CA) at the tissue capillaries. The rapid acidification of the RBC reduces the O2 affinity of pH-sensitive haemoglobin, which increases the O2 diffusion gradient to the tissues. When RBCs leave the site of plasma-accessible CA, ß-NHE activity recovers RBC pH during venous transit, to promote renewed O2 loading at the gills. This mechanism allows teleosts to unload more O2 at their tissues without compromising O2 diffusion gradients and therefore, to use the available O2 carrying capacity of the blood to a greater degree. In Atlantic salmon, ß-NHE short-circuiting reduces the requirements on the heart by up to 30% during moderate exercise and even at rest, with important ecological implications. Thus, in some teleosts, the RBCs participate in regulating the systemic O2 flux by actively altering the passive diffusion of O2 that Krogh discovered.

Gonadal steroid fluctuations and reproduction results of European grayling (Thymallus thymallus L.) from broodstock farmed in a recirculation aquaculture system.

The initial experiment of this study was conducted to determine whether sex steroid concentrations varied before, during and after the reproductive season of European grayling (Thymallus thymallus L.) farmed broodstock confined in a recirculation aquaculture system (RAS). The results indicated that the plasma sex steroid (testosterone - T, progesterone - P4 and estradiol - E2) concentrations varied (P < 0.05) during these reproductive periods. There were greater concentrations of T, P4 and E2 before and during the grayling reproductive season indicating there are important functions of these steroid hormones associated with gonadal maturation, gamete production and reproductive behavior during the spawning period. In the second experiment of this study, the effectiveness of European grayling controlled reproduction treatment regimens was analyzed and there were 34.69 % and 68.18 % having ovulations in the 2 and 3-year-old broodfish, respectively. Of the embryos developing to the eyed-egg stage, there were 3.70 % and 6.87 % derived from eggs of 2- and 3-year-old grayling females, respectively. Proportions of embryos developing from the eyed-egg stage to hatching were 38.1 % and 52.1 % from eggs of 2- and 3-year-old grayling females, respectively, when there was culturing in a RAS. The results indicate that with grayling broodfish there is greater efficacy in induction of reproduction when there is imposing of the controlled reproduction treatment regimen on 3- rather than 2-year-old broodfish.

Hematology and Biochemistry Panel Reference Intervals for Captive Saddleback Clownfish Amphiprion polymnus and Tomato Clownfish A. frenatus.

Reference intervals of blood analytes are important diagnostic tools that clinicians use as a basis for making clinical decisions and that have been documented for many fish species. Although the effects of dietary supplementation on hematology and blood biochemistry variables in clownfish have been shown, there are no published reference intervals to date for routine hematology and blood biochemistry panels for these popular cultured marine fish (including Amphiprion spp.). The objective of this study was to establish de novo reference intervals for selected hemogram data and, using whole-blood analysis, commonly utilized chemistry analytes in two species of aquacultured clownfish: the Tomato Clownfish Amphiprion frenatus and Saddleback Clownfish A. polymnus. This study is based on blood samples from 25 clinically normal Tomato Clownfish and 38 clinically normal Saddleback Clownfish from two clownfish production facilities in Florida. Guidelines by the American Society for Veterinary Clinical Pathology were followed to generate robust reference intervals from the data collected. We report descriptive statistics and reference intervals for several hematology (n = 12) and biochemistry (n = 8) analytes using a small sample size and a small amount of blood per sample. The blood analyte data from this study are comparable with hematology and biochemistry data that have been reported in other teleost species. These results provide baseline health data for clownfish species that can be used in various clinical settings while also serving as a springboard for further research studies.

Immune Functions of Erythrocytes in Osteichthyes.

Red blood cells (RBCs)-erythrocytes-of Osteichthyes are primarily known for their involvement in the process of gas exchange and respiration. Currently, physiological properties of RCBs in fish should also include their ability to participate in defense processes as part of the innate and adaptive immune mechanisms. In response to viruses, bacteria, and fungi or recombinant nanoparticles, they can modulate expression of genes responsible for immune reactions, influence activity of leukocytes, and produce cytokines, antimicrobial peptides, and paracrine intercellular signaling molecules. Via the complement system (CR1 receptor) and owing to their phagocytic properties (erythrophagocytosis), RBCs of Osteichthyes can eliminate pathogens. In addition, they are probably involved in the immune response as antigen-presenting cells via major histocompatibility complex class II antigens.

Blood Biochemical and Erythrocytic Morpho-pathological Consequences of Naphthalene Intoxication in Indian Teleost, Anabas testudineus (Bloch).

Anabas testudineus (Bloch) was exposed to 0.71 mg/L and 1.42 mg/L (25 and 50% of LC50 value respectively) naphthalene, a polycyclic aromatic hydrocarbon (PAH), for 21 days. Blood biochemical parameters and erythrocytic morphological alterations were assessed to describe the naphthalene toxicity. Biochemical analysis showed a significant increase in glutamic pyruvic transaminase, GPT (576.7 ± 11.79 and 608.9 ± 12.08 U/L, respectively) and alkaline phosphatase, ALP (12.9 ± 0.69 and 13.4 ±â€¯0.64 U/L, respectively) activities under two doses compared with control. Protein and albumin (ALB) content in blood decreased significantly, in comparison with control value in the tune of 22.67 ±â€¯1.04 and 23.97 ±â€¯1.24 g/dl, respectively and 10.7 ±â€¯0.79 and 11.1 ±â€¯0.67 g/dl, respectively. Erythrocytes showed varied symptomatic morphological changes under naphthalene exposure, which included severe denaturation, swelling in cells, appearance of sickle and tear drop cells, and cellular vacuolation. In particularly, the changes were more prominent under higher naphthalene exposure. Following the results, it has been able to establish that GPT, ALP, protein and ALB, and the morphological manifestations of erythrocytes would be good tools of biomarker in monitoring toxicological paradigm, especially to naphthalene exposure in aquatic bodies.

Haematology of Mugil curema from the north coast estuary of Santa Catarina state, Brazil / Hematologia de Mugil curema em estuário no litoral norte do estado de Santa Catarina, Brasil

Mugil curema is a teleost fish often found in coastal, estuarine and lagoon regions throughout the Brazilian coast. Blood parameters may be used as health and welfare indicators of the fish, as well as the environment they live in. The aim of this study was to verify the hematologic profile of the M.curema along 18 months in estuary waters from the north coast of the state of Santa Catarina in the south of Brazil. A total of 133 M. curema fish were captured from March 2016 to August 2017. Erythrogram, leukogram, thrombocytogram, hematocrit percentage, hemoglobin dosage, total plasma protein dosage, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and medium corpuscular hemoglobin concentration (MCHC) were analyzed. There was no significant difference (P>0.05) on the total number of erythrocytes between the fish gender. However, there was difference on the hematocrit between males and indefinite gender fish. The influences of temporal and geographical space, among the values of hematological parameters, in the different studies of the Brazilian coast are discussed.. The present research is an important contribution to establish a hematological pattern for M. curema. The local population of the studied fish has a proper behavior in hematological descriptors, which is different from other Brazilian coast studies with the same fish species.

Mugil curema é um peixe teleósteo, abundante em regiões costeiras, estuarinas e lagunares, em todo o litoral brasileiro. Os parâmetros sanguíneos podem ser usados como indicadores da saúde e do bem-estar dos peixes, bem como do ambiente onde estes vivem. O objetivo deste estudo foi verificar o perfil hematológico de M. curema ao longo de 18 meses, em águas estuarinas, no Litoral norte do estado de Santa Catarina, sul do Brasil. Um total de 133 peixes foram capturados, entre março de 2016 e agosto de 2017, para realização de eritrograma, leucograma, trombocitograma, porcentagem de hematócrito, dosagem de hemoglobina, dosagem de proteína plasmática total, volume corpuscular médio (VCM), hemoglobina corpuscular média (HCM) e concentração de hemoglobina corpuscular média (CHCM). Não houve diferença significativa (P>0,05) entre o número total de eritrócitos entre machos e fêmeas. No entanto, houve diferença no hematócrito, entre machos e peixes de sexo indeterminado. As influências do espaço temporal e geográfico, entre os valores dos parâmetros hematológicos, nos diferentes estudos do litoral brasileiro são discutidas. A presente investigação é importante contribuição para o estabelecimento de um padrão hematológico para M. curema. A população local de peixes estudada tem comportamento próprio em descritores hematológicos, diferenciado de outros estudos no litoral brasileiro para a mesma espécie.

Disturbance of oxidant/antioxidant status and impairment on fillet fatty acid profiles in Brycon amazonicus subjected to acute heat stress.

Amazon fish are vulnerable to climate change. Current temperature increases in Amazonian rivers are likely to continue in the coming years. Elevated temperatures impair homeostasis and subject fish to oxidative stress; nevertheless, the effects of elevated temperature on plasma and muscle oxidative stress as well as fillet fatty acid composition in matrinxã (Brycon amazonicus) remain unknown. Therefore, the aims of the present study were to determine whether antioxidant system is able to withstand acute thermal stress to avoid plasma and muscle oxidative damage and to determine the manner in which matrinxã adjust their muscle fatty acid metabolism in a response to acute heat stress. We exposed juvenile matrinxã to four temperatures (28 °C as control and 30, 32, and 34 °C) for 72 h and observed the effects on plasma and muscle oxidant/antioxidant status and on fatty acid composition. Plasma reactive oxygen species (ROS) and lipid peroxidation (LPO) levels were significantly higher in matrinxã exposed to 34 °C compared with the control group, while they were significantly higher in the muscle of matrinxã exposed to 32 °C and 34 °C compared with the control group. Superoxide dismutase (SOD) activity and total antioxidant capacity (TAC) levels were significantly lower in the plasma and muscle of matrinxã exposed to 34 °C compared with the control group. Plasma glutathione peroxidase (GPx) activity was significantly lower in matrinxã exposed to 32 and 34 °C compared with the control group, while it was significantly lower in the muscle of matrinxã exposed to 34 °C. The total content of saturated fatty acid (SFA) was significantly higher in the fillet of matrinxã exposed to 34 °C compared with the control group, while the total content of polyunsaturated fatty acid (PUFA) was significantly lower. Based on this evidence, we conclude that acute heat stress at 32 °C and 34 °C causes plasma and muscular oxidative stress, and the enzymatic and non-enzymatic antioxidant system is unable to prevent oxidative damage. Moreover, increased levels of total SFA and decreased levels of PUFA occur in an attempt to withstand heat stress and maintain membrane fluidity; nevertheless, these responses can represent negative impacts for consumers.

Development of a giant grouper Luteinizing Hormone (LH) Enzyme-Linked Immunosorbent Assay (ELISA) and its use towards understanding sexual development in grouper.

A recombinant giant grouper Luteinizing Hormone (LH) consisting of tethered beta and alpha subunits was produced in a yeast expression system. The giant grouper LH ß-subunit was also produced and administered to rabbits for antibody development. The recombinant LH and its antibody were used to develop an Enzyme Linked Immunosorbent Assay (ELISA). This ELISA enabled detection of plasma LH levels in groupers at a sensitivity between 391 pg/ml and 200 ng/ml. Different species of grouper were assayed with this ELISA in conjunction with gonadal histology and body condition data to identify links between circulating LH levels and sexual development. We found that circulating levels of LH decreased when oocytes began to degenerate, and sex-transition gonadal characteristics were apparent when LH levels decreased further. When circulating LH levels were related to body condition (body weight/ body length), transitioning-stage fish had relatively high body condition but low plasma LH levels. This observation was similar across multiple grouper species and indicates that plasma LH levels combined with body condition may be a marker for early male identification in the protogynous hermaphrodite groupers.

Erythrocyte profile of circulating blood of Neogobius melanostomus (Pallas, 1814) under conditions of experimental hypothermia.

The influence of hypothermia on erythrocyte profile of thermophile teleost species round goby, Neogobius melanostomus (Pallas, 1814), has been studied. Fish were acclimated to temperature 1-2оС, 15-16оС and 19-20оС (control group) and held at given conditions for 5 days. The number of red blood cell precursors (pronormoblasts, basophilic and polychromatophilic normoblasts) in circulating blood has been estimated. Also, the number of abnormal erythrocytes, i.e. cells with micronuclei, nuclei invaginations, red blood cell shades, dacryocytes and cells undergoing amitosis has been determined on smears. The number of immature erythrocytes increased more than two times (p < 0,001) at 1-2оС. The number of low-differentiated precursors, pronormoblasts and early basophilic normoblasts, increased for the most part. The number of abnormal erythrocytes did not change substantially, The changes in cellular blood composition were accompanied with the increase of plasma lactate concentration, indicating hypoxic state of fish. The results of the present work indicate that hematopoietic tissue remains sensitive to controlling factors at hypothermia, such as hypoxia, and may enhance proliferation and differentiation of erythroid cells.

Stimulatory effects of short-term calcitonin administration on plasma calcium, magnesium, phosphate, and glucose in juvenile Siberian sturgeon Acipenser baerii.

Calcitonin (CT) has a potential function in calcium (Ca) regulation, but there are conflicting observations in fishes. Because of the lack of calcified endoskeleton, sturgeons have low Ca circulating compared with teleost fish and the function of CT on Ca in sturgeon is very less understood. The purpose of this study was to investigate the impact of injection of salmon CT on plasma Ca, magnesium (Mg), phosphate (PHO), and glucose levels of juvenile Siberian sturgeon Acipenser baerii. Sixteen-month-old fish (429.6 ± 12.1 g) were intraperitoneally injected with a single dose of CT (5 µg kg-1 BW) and saline solution as a control group. Thereafter, blood sampling was performed at 0, 1, 2, 4, 6, 12, 24, and 48 h after injection. CT produced marked increases in all variables measured. The highest levels of Ca (6.77 ± 0.53 mg dL-1), Mg (9.79 ± 0.16 mg dL-1) and PHO (1.74 ± 0.05 mg dL-1) were recorded at 2 h after CT injection and showed significant difference compared with control treatment (Ca 4.75 ± 0.12 mg dL-1; Mg 5.47 ± 0.16 mg dL-1 and PHO 1.23 ± 0.06 mg dL-1). It also likely produced hyperglycemia. However, the differences with the controls were not statistically significant, possibly due to interference with the hyperglycemia induced by the stress of injection. Our results showed that the injection of 5 µg kg-1 BW CT to Siberian sturgeon has an incremental effect on plasma Ca, Mg, and PHO. The increase in plasma Ca level indicated that CT has a potent hypercalcemic effect in sturgeon under laboratory condition, in contrast to the hypocalcemic effects reported for teleosts.