Oxidative responses in small juveniles of Colossoma macropomum anesthetized and sedated with Ocimum gratissimum L. essential oil.

This study evaluated the use of essential oil of Ocimum gratissimum (EOOG) for anesthesia and in transport of Colossoma macropomum. Experiment 1, Test 1, anesthesia induction and recovery times were determined using different EOOG concentrations (0, 20, 50, 100, 200, 300 mg L-1), with two size classes: Juveniles I (0.86 g) and Juveniles II (11.46 g) (independent tests in a completely randomized design). Based on the results of Test 1, in Test 2 Juveniles II were exposed to EOOG concentrations: 0, 20, 100 mg L-1. Tissue samples were collected immediately after induction and 1 h post-recovery, to assess oxidative status variables. Experiment 2, Juveniles I (0.91 g) and Juveniles II (14.76 g) were submitted to transport in water with different concentrations of EOOG (0, 5, 10 mg L-1) (independent tests in a completely randomized design). The effects on oxidative status variables were evaluated. Concentrations between 50 and 200 mg L-1 EOOG can be indicated for Juveniles I, while concentrations between 50 and 100 mg L-1 EOOG for Juveniles II. The concentration of 100 mg L-1 EOOG was able to prevent oxidative damage in the liver. In Experiment 2, the concentrations of 5 and 10 mg L-1 EOOG added to the transport water caused sedation for both studied size classes of juveniles and did not cause oscillations in water quality variables nor any mortality. The concentration of 10 mg L-1 EOOG improved the oxidative status. It can be concluded that EOOG can be used for anesthesia and transport of C. macropomum.

Sensitivity of different organs and tissues as biomarkers of oxidative stress in juvenile tambaqui (Colossoma macropomum) submitted to fasting.

The present study was conducted to evaluate the effects of fasting on responses of oxidative biomarkers and antioxidant defenses using different organs and tissues of Colossoma macropomum. The fish were divided into two groups: fed (control) and fasting (7 days). After 7 days, the fish were sampled for assessment of oxidative stress biomarkers (MDA-lipid peroxidation and PCO-protein carbonyl) and antioxidant defenses (SOD-superoxide dismutase; CAT-catalase; GPX-glutathione peroxidase; and GST-glutathione-S -transferase) in the liver, intestine, gills, muscle, brain, and plasma. The results showed an increase in MDA, PCO, SOD, and GPX concentrations in the liver and intestine of fasting fish. In contrast, in the branchial tissue, there was a reduction in the activity of SOD and CAT enzymes in fasting fish. There was also a reduction in CAT activity in the muscle of fasting fish, while in the brain, there were no changes in oxidative stress biomarkers. Plasma showed a relatively low antioxidant response. In conclusion, our results confirm that a 7-day fasting period induced tissue-specific antioxidant responses, but the increase in antioxidant responses was only for the SOD and GPX enzymes of the liver and intestine. Additionally, the liver and intestine were the most responsive tissues, whereas the plasma was the least sensitive to oxidative stress.

Hematological, biochemical and oxidative responses induced by thermal shock in juvenile Tambaqui (Colossoma macropomum) and its hybrid Tambatinga (Colossoma macropomum x Piaractus brachypomus).

The effects of thermal shock on hematological, biochemical and antioxidant responses were evaluated in liver tissue of juvenile tambaqui (Colossoma macropomum) and tambatinga (♀ C. macropomum × â™‚ Piaractus brachypomus). Forty juveniles of tambaqui and 40 juveniles of tambatinga, of the same age and with an initial weight of 23.3 ± 6.7 g, were randomly distributed in eight 28L circular tanks. A tank (n = 10 fish) of tambaqui and a tank (n = 10 fish) of tambatinga were then used to obtain basal data. The other animals were subjected to thermal shock with sudden temperature reduction from 28 to 18 ºC. Blood and tissue were then collected after 1, 6 and 24 h from the onset of thermal shock. No mortality was observed during the experimental period. Thermal shock increased triglyceride levels after 24 h of stress for tambaqui and reduced values for tambatinga. There was an effect on plasma glucose only for fish group (P < 0.0001) and collection time (P < 0.0001) with a peak observed for the hybrid after 6 h. The interaction of factors for SOD indicated greater activity for tambatinga at the 6 h collection and lower at basal and 1 h collections. There was an interaction for CAT (P = 0.0020) with less activity for tambatinga at 1 h. However, thermal shock and hybridization did not influence GST and TBARS levels in liver tissue. Therefore, the results suggest that the hybrid, tambatinga, is more efficient at promoting adjustments of biochemical responses and antioxidant enzymes during thermal shock.

Starvation-induced autophagy modulates spermatogenesis and sperm quality in Nile tilapia.

Spermatogenesis is a finely regulated process that involves the interaction of several cellular mechanisms to ensure the proper development and maturation of germ cells. This study assessed autophagy contribution and its relation to apoptosis in fish spermatogenesis during starvation. To that end, Nile tilapia males were subjected to 0 (control), 7, 14, 21, and 28 days of starvation to induce autophagy. Testes samples were obtained for analyses of spermatogenesis by histology, electron microscopy, immunohistochemistry, and western blotting. Sperm quality was assessed using a computer-assisted sperm analysis (CASA) system. Data indicated a significant reduction in gonadosomatic index, seminiferous tubule area, and spermatozoa proportion in fish subject to starvation compared to the control group. Immunoblotting revealed a reduction of Bcl2 and Beclin 1 associated with increased Bax and Caspase-3, mainly after 21 and 28 days of starvation. LC3 and P62 indicated reduced autophagic flux in these starvation times. Immunolabeling for autophagic and apoptotic proteins occurred in all development stages of the germ cells, but protein expression varied throughout starvation. Beclin 1 and Cathepsin D decreased while Bax and Caspase-3 increased in spermatocytes, spermatids, and spermatozoa after 21 and 28 days. Autophagic and lysosomal proteins colocalization indicated the fusion of autophagosomes with lysosomes and lysosomal degradation in spermatogenic cells. The CASA system indicated reduced sperm motility and velocity in animals subjected to 21 and 28 days of starvation. Altogether, the data support autophagy acting at different spermatogenesis stages in Nile tilapia, with decreased autophagy and increased apoptosis after 21 and 28 days of starvation, which results in a decrease in the spermatozoa number and sperm quality.

Edwardsiella tarda in Tambaqui (Colossoma macropomum): A Pathogenicity, Antimicrobial Susceptibility, and Genetic Analysis of Brazilian Isolates.

Edwardsiella tarda is a crucial pathogenic bacterium in tropical aquaculture. This bacterium was recently isolated from tambaqui (Colossoma macropomum), a commercially important fish species in Brazil. This study assessed the antimicrobial susceptibility, pathogenicity, and genetic diversity of the tambaqui-derived E. tarda isolates. Fourteen bacterial isolates isolated from tambaqui were identified as E. tarda by using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry and dnaJ gene sequencing. Antimicrobial susceptibility tests were conducted against seven drugs using the disc diffusion assay. The pathogenicity test conducted by intraperitoneal injection of 2.4 × 107 colony-forming units (CFU) fish-1 of E. tarda (ED38-17) into tambaqui juveniles eventually revealed that neither clinical signs nor death were present. However, splenomegaly and whitish areas in the spleen and kidneys were observed. The histological investigation also revealed granulomatous splenitis, nephritis, and hepatitis occurring internally. Repetitive extragenic palindromic-PCR fingerprinting separated the 14 isolates into three genetic groups. The antibiogram revealed that all E. tarda isolates were wild-type (WT) to florfenicol (FLO), norfloxacin (NOR), neomycin (NEO), erythromycin (ERY), and oxytetracycline (OXY); however, some were non-wild-type to sulfamethoxazole/trimethoprim (7.1%) and amoxicillin (21.4%). Therefore, through experimental infection, E. tarda ED38-17 could induce pathogenic effects in C. macropomum. Additionally, three distinct genetic types were found, and the E. tarda isolates were WT to FLO, NOR, NEO, ERY, and OXY. These findings raise awareness of a bacteria causing unseen lesions, a pathogen that will potentially impact tambaqui aquaculture in the future.

Effects of live prey concentration, salinity, and weaning age on larviculture of Piaractus brachypomus reared in a recirculating aquaculture system.

This study evaluated the effects of live prey concentration (nauplii of Artemia sp.), water salinity, and weaning age on survival, growth, and stress resistance rate (Rs) of Piaractus brachypomus under larviculture in a recirculating aquaculture system (RAS). Larvae aged 6 days post-hatching (1.64 ± 0.11 mg) were distributed in 28-L tanks (five larvae L-1), in two RASs. The experiment was carried in a 2 × 2 × 2 factorial arrangement, as follows: two feeding strategies (sudden transition from live food to commercial food after 10 (FT10) and 20 (FT20) days of larviculture with Artemia); two daily initial prey concentrations (P350 = 350 and P700 = 700 nauplii larva-1, these being increased every 5 days); and two water salinities (S0 = fresh water and S2 = 2 g of salt L-1). Weight (W), total length (TL), and daily specific growth rate (SGR) were evaluated after 10, 20, 30, and 40 days of larviculture. After 40 days of larviculture, survival was evaluated and a test of air exposure was performed to determine stress resistance rate (Rs). Noteworthy results during this period are the lowest specific daily growth rate (SGR) after weaning for FT10 and the best growth results for S2 and P700. After 40 days, weight (W) and total length (TL) showed effects of P, FT, and S with higher values for P700, FT20, and S2 (P < 0.05). The interaction P × FT × S also had effects on survival and Rs at the end of the experiment, with higher survival and Rs for P700FT20S2 (P < 0.05). Larviculture of P. brachypomus in RAS, in association with the three managements-live prey concentration P700, salinity S2, and age at feed transition FT20-promotes maximization of survival, growth, and stress resistance rate of the animals. The larviculture of P. brachypomus in RAS must be carried out with an initial concentration of live prey of 700 nauplii larva-1, at a salinity of 2 g of salt L-1 and with the feeding transition starting in 20 days of larviculture, for maximization intensive larviculture of this species.

Anesthetic and sedative efficacy of essential oil of Hesperozygis ringens and the physiological responses of Oreochromis niloticus after biometric handling and simulated transport.

This study aimed to evaluate different concentrations of the essential oil of Hesperozygis ringens (EOHR) and its effects on anesthesia and transport of Oreochromis niloticus. Experiment I evaluated the concentrations of 0, 150, 300, 450, and 600 µL L-1 EOHR for times of induction and recovery from anesthesia and ventilatory frequency (VF) of O. niloticus (26 g), with 10 repetitions each in a completely randomized design. Based on the results of Experiment I, Experiment II submitted fish (25 g) to three treatments-control (clean water), ethanol (5 mL ethyl alcohol), and 600 µL L-1 EOHR-and then handling for biometry. Blood was collected 1 and 24 h after exposure and handling to analyze hematological and biochemical parameters in a completely randomized design in a factorial arrangement (3 × 2). Experiment III submitted fish (35 g) to simulated transport (4.5 h) with 0, 10, or 20 µL L-1 EOHR and determined the effects on blood variables. Concentrations of 450 and 600 µL L-1 EOHR provoked deep anesthesia in juvenile O. niloticus and provided induction and recovery times within the limits considered ideal for fish. However, this essential oil was not able to attenuate the effects of stress caused by biometric handling. EOHR was able to attenuate the effects of stress from simulated transport, with 10 µL L-1 EOHR being responsible for causing a decrease in protein, triglycerides, and cholesterol values immediately after transport of O. niloticus.

Lophiosilurus alexandri, a sedentary bottom fish, adjusts its physiological parameters to survive in hypoxia condition.

We investigated blood gas, hematological and biochemical parameters, and gill morphology of Lophiosilurus alexandri juveniles submitted to hypoxia for 48 h, followed by recovery for 48 h. A total of 48 juveniles (360.0 ± 141.6 g) were distributed among eight tanks (120 L) and subjected to hypoxia condition (water with dissolved oxygen at 2.12 ± 0.90 mg L-1) or normoxia (at 5.60 ± 0.31 mg L-1). Blood gas values (pH, PvCO2, PvO2, sO2, HCO3-, stHCO3-, and base excess) in hypoxia were significantly different from normoxia, while for lactate and the electrolytes (K+, Na+, Cl-, and Ca2+) there was no significant change among treatments. The erythrocytes differed significantly between normoxia and hypoxia at 72 h (24 h of recovery), while for hemoglobin and hematocrit there were no significant differences. There was a significant difference in glucose, triglycerides, and cholesterol for both normoxia and hypoxia, while plasma protein remained unchanged. All gill components (epithelial cells, erythrocytes, pillar cells, mucous cells, ionocytes, undifferentiated cells, and blood capillary lumen) differed significantly between normoxia and hypoxia. A reduction in the length of the primary lamella was observed in the hypoxia and recovery treatments, when compared to normoxia. The secondary branchial lamella showed no significant difference for both treatments. Juveniles of Lophiosilurus alexandri adapted well to hypoxia for 48 h, as they were able to adjust most of their physiological variables to survive this stress condition. After 48 h of hypoxia recovery, fish showed parameters similar to animals in normoxia. Thus, the present study shows that the tolerance to hypoxia conditions of L. alexandri, together with other important beneficial characteristics of the species, such as the high meat quality and high commercial value, demonstrates its great potential for production among regional species.

Essential oil of Ocimum gratissimum (Linnaeus, 1753): efficacy for anesthesia and transport of Oreochromis niloticus.

This study aimed to evaluate the essential oil of Ocimum gratissimum L. (EOOG) for anesthesia and in the transport of Oreochromis niloticus. Experiment I determined the time of anesthesia induction and recovery during anesthesia of O. niloticus exposed to different concentrations of EOOG (0, 30, 90, 150, and 300 mg L-1). Based on data from Experiment I, Experiment II evaluated the effect of 0, 30, and 90 mg L-1 EOOG on blood parameters and oxidative stress immediately after anesthesia induction and 1 h after recovery. Experiment III evaluated the effect of 0, 5, and 10 mg L-1 EOOG on blood variables immediately after 4.5 h of transport of juveniles. Concentrations between 90 and 150 mg L-1 EOOG were efficient for anesthesia and recovery. The use of 90 mg L-1 of EOOG prevented an increase in plasma glucose. Other changes in blood parameters and oxidative stress are discussed. The use of 10 mg L-1 EOOG in transport increased plasma glucose and decreased hematocrit values immediately after transport. It is concluded that the use of 90 and 150 mg L-1 EOOG causes anesthesia and recovery in O. niloticus within the time intervals considered ideal. The use of 90 mg L-1 EOOG favored stable plasma glucose soon after anesthesia induction and 1 h after recovery, but caused changes in the antioxidant defense system by increasing hepatic and kidney ROS. The transport of 12 g O. niloticus for 4.5 h can be performed with concentration of 5 mg L-1 of EOOG.

Physiological and metabolic responses in juvenile Colossoma macropomum exposed to hypoxia.

This study aimed to evaluate hematological, biochemical, and gasometric parameters of tambaqui juveniles (Colossoma macropomum) exposed to hypoxia and subsequent recovery. Six animals were subjected to normoxia (basal) treatment with dissolved oxygen (DO) 6.27 ± 0.42 mg L-1. Water flow and aeration were reduced for 3 days (hypoxia), during which DO was 0.92 ± 0.37 mg L-1. Water flow and aeration were then reestablished with DO remaining similar to basal. The treatments were as follows: normoxia (basal); 24 h after initiating hypoxia (24H); 72 h after initiating hypoxia (72H); 24 h after reestablishing normoxia (24R); 48 h after reestablishing normoxia (48R); and 96 after reestablishing normoxia (96R). The highest glucose level was recorded at 24H (P < 0.05); the highest lactate level was at 72R; and the highest blood pH was at 24H and 72H (P < 0.05). The highest concentration of PvCO2 was at 24H (P < 0.05), while at 96R it was equivalent to basal (P > 0.05). The variable PvO2 was only higher than basal at 24R (P < 0.05). Juvenile C. macropomum managed to reestablish the main stress indicators (glucose and lactate) at 96R, while the other indicators varied during the study, with homeostatic physiology being reestablished during the recovery period.

Rearing and maturation of Lophiosilurus alexandri (Steindachner, 1876) in controlled conditions: First reports and future perspective.

Lophiosilurus alexandri is a freshwater carnivorous fish for which there is fishing pressure in its natural environment, yet the species has potential for captive rearing. Information on growth and sexual development for the species is scarce, and age and size at first maturation have yet to be determined. A total of 400 fish, therefore, were reared from hatching to 968 days after hatching (DAH). Fish gonads were histologically analyzed throughout the rearing period, and growth, the hepatosomatic index and the gonadosomatic index were compared between males and females. Estradiol, testosterone and 17α-hydroxyprogesterone concentrations were quantified at 845 and 968 DAH to compare sexually mature males and females. Weight and length did not differ between males and females (P >  0.05). Males were sexually mature at 593 DAH, with body lengths of 29.88 ±â€¯1.76 cm and weights of 444.1 ±â€¯77.03 g, while females were sexually mature at 845 DAH, with lengths of 36.51 ±â€¯1.06 cm and body weights of 783.05 ±â€¯48.57 g. The results provided important information regarding the minimum capture size of L. alexandri for identifying the appropriate period to begin reproductive management of the species.

Response of juvenile Lophiosilurus alexandri to osmotic and thermic shock.

The objective of the present study was to evaluate the physiological responses of juvenile Lophiosilurus alexandri submitted to osmotic and thermic shock. Thirty juveniles were used for each test, of which 10 were not subjected to stress and remained in normal conditions (fresh water at 28.0 °C). The others were submitted to stress shock (saline water of 10.0 g of salt/L or water cooled to 18.0 °C). Blood samples were taken at 0 h (no exposure to the stress factor) and 1 h and 24 h after the tests. At 24 h, the survivorship was 100% in both tests. In both the osmotic and thermic shock tests, cortisol and glucose levels were higher at 1 h but then decreased after 24 h. Lactate dehydrogenase showed differences in the temperature test, but there was no difference between 1 and 24 h after exposure to osmotic shock (P > 0.05). The difference was recorded in blood gas variables (pH, PvCO2, PvO2, hemoglobin, sO2, BE, tCO2, HCO3-, and stHCO3-) and electrolytes (Na+, Ca++, nCa++, and K+) in both experiments. With regard to hematology and blood biochemistry, exposure to thermal shock did not affect (P > 0.05) ALP, total plasma protein, hematocrit, and ALT and AST at 1 h and 24 h. ALP and total protein in the blood of fish submitted to the osmotic shock were lowest (P < 0.05) at 24 h. Leukocyte and erythrocyte counts exhibited differences after osmotic shock, in contrast to erythrocyte counts of the temperature test, which did not change in 24 h (P > 0.05). Juveniles of L. alexandri were able to reestablish the main indicators of stress (cortisol, glucose), while the others (hematological, biochemical, and gasometric) varied in compensation for normal physiological reestablishment.

Effect of formalin in early stages of the freshwater neotropical catfish, Lophiosilurus alexandri.

The objective of this study was to evaluate the acute toxicity of formalin and its level of therapeutic safety in early stages of Lophiosilurus alexandri. Experiment 1, larvae 7 days after hatching (DAH) were exposed to 43.2, 86.4, 172.8, 345.6, 691.2, 1404.0 mg/L of formalin. Experiment 2, juveniles with 22 DAH exposed to 54, 108, 216, 432, 648 mg/L. Experiment 3, 45 DAH exposed to 86.4, 172.8, 345.6, 691.2, 1036.8 mg/L. The experiments had a control without addition of formalin and all were carried out in duplicate. The LC50-12 h were: Experiment 1 = 108.86 mg/L; 2: 152.74 mg/L; 3: 244.38 mg/L of formalin. The respective safety levels were: Experiment 1 = 66.22 mg/L (1 h), 10.89 mg/L (12 h); 2 = 49.17 mg/L (2 h), 15.27 mg/L (12 h); 3 = 68.89 mg/L (2 h), 24.44 mg/L (12 h). The results showed that the developmental stage influenced the sensitivity of animals to formalin.

Effects of starvation and refeeding cycles on spermatogenesis and sex steroids in the Nile tilapia Oreochromis niloticus.

Food restriction is part of the life cycle of many fish species; however, nutritional deficiency may negatively influence gametogenesis and gonadal maturation. The aim of this study was to evaluate the effects of food restriction on the spermatogenesis of Nile tilapia. For this, adult males were submitted to starvation and refeeding cycles (alternating periods of starvation and feeding) for 7, 14, 21, and 28 days. After 7 days of starvation, glycaemic and lipid levels were significantly reduced, followed by reduction of plasma testosterone (T) and 11-ketotestosterone (11-KT). In addition, reduced proliferation of spermatogonia and increased apoptosis of spermatocytes, spermatids, and spermatozoa was observed in starvation groups. In the refeeding groups, the sex steroids and the proportion of germ cells had no significant alterations compared to the control group, except for spermatozoa. In this sense, the present study suggests that starvation after 7 days progressively reduces T and 11-TK, resulting in damage to the production of spermatogenic cells, while refeeding may delay spermatogenesis but does not lead to testicular impairment.

Low salinity negatively affects early larval development of Nile tilapia, Oreochromis niloticus: insights from skeletal muscle and molecular biomarkers.

The present study evaluated the effects of low salinity on the early larval development of Oreochromis niloticus, specifically histological damage to white muscle, morphology of the yolk-sac surface and trunk area, and molecular expression of apoptosis and cell proliferation biomarkers. Newly hatched larvae were submitted to four salinity treatments for a period of 48 or 72 h, in duplicate: (S0) freshwater, (S2) 2 g l-1, (S4) 4 g l-1, and (S6) 6 g l-1NaCl. Larval development was examined using histology, electron microscopy, enzyme-linked immunosorbent assay (ELISA), and morphometry. At the yolk-sac surface, larvae of S4 and S6 displayed alterations to the apical opening of chloride cells that may be related to osmotic expenditure caused by the increased salinity. Caspase-3 expression did not differ significantly among treatments, however significantly lower proliferating cell nuclear antigen (PCNA) expression (P < 0.05) suggested minor cell proliferation in larvae of S4 and S6 compared with S0 and S2. Furthermore, there was a significant reduction in both trunk area and percentage of normal white muscle fibres (WF) in larvae of S4 and S6. Vacuolated areas and myofibrils concentrated at the cell periphery and found in the white muscle from larvae exposed to saline environments suggested disturbance to muscle development. Oedema and mononuclear infiltrate were also observed in the white muscle of S4 and S6 larvae. Together these results indicated that treatments with 4 and 6 g l-1 NaCl may cause osmoregulation expenditure, morphological alterations to the yolk-sac surface and histological damage to skeletal muscle that negatively affected the early larval development of O. niloticus.

Autophagy and Cathepsin D mediated apoptosis contributing to ovarian follicular atresia in the Nile tilapia.

Follicular atresia is a hormonally controlled degenerative process involving apoptosis of the somatic and germ cells. Since different signaling pathways can induce cell death, the aim of the present study was to investigate cell death signaling and crosstalk between autophagic, apoptotic, and lysosomal proteins during follicular atresia in Nile tilapia. For this, females were kept in controlled conditions for 21 days, and ovary samples were collected weekly. The atretic follicles (AF) were analyzed in three regression phases: Early, advanced, and late. Under electron microscopy, the follicular cells exhibited numerous protein synthesis organelles in the early AF. Immunoreactivity for Bcl2, Beclin1, Lc3, and Cathepsin D increased significantly in advanced AF (p < .001), when follicular cells were in intense yolk phagocytosis. In this phase, autophagosomes and autolysosomes were frequently observed. In the late AF, follicular cells had a markedly electron-lucid cytoplasm and immunoreactivity for Bax and TUNEL assay indicated an elevated apoptosis rate. Colocalisation of Lamp1/Cathepsin D and Lc3/Caspase-3 suggests dynamic crosstalk between the autophagy, apoptosis, and lysosome pathways. Taken together, the data indicate that autophagy plays a role in the homeostasis and clearance of the follicular cells preceding Cathepsin D mediated apoptosis during follicular atresia in Nile tilapia.

Influence of salinity on spermatogenesis in adult Nile tilapia (Oreochromis niloticus) testis.

Continental waters salinisation is a global threat that has grown because of climate change and human activities, but little is known about how and what biological tracts are affected. The aim of this study was to investigate the influence of different water salinities on the expression of HSP70, PCNA and caspase-3 during spermatogenesis of Nile tilapia. Adult males were submitted to four salinity treatments: (S0) fresh water, (S7) 7 g L-1, (S14) 14 g L-1, and (S21) 21 g L-1 for 1, 4, and 9 days. All specimens were in spermatogenic activity and the highest values of the gonadosomatic index (GSI) occurred in the S0 and S7. In the morphometric analysis, spermatocytes were the most frequent germ cell detected in all treatments (>50%) and spermatids achieved about 20% of the testicular proportion, with few variations among treatments. Spermatozoa were significantly reduced only in S14 compared to S7. Leydig cells were significantly increased in S14 when compared to S7 but plasma concentrations of 11-KT showed no significant difference among treatments. ELISA assay showed higher testicular expression of HSP70 at 1 day in all groups, followed by a significant decrease at days 4 and 9 in S14 and S21. The expression of PCNA was significantly lower while the activity of caspase-3 was higher in S14 and S21 when compared to S0 and S7. These results indicate that higher salinities in S14 and S21 interfere with the relationship between testicular HSP70, PCNA, and caspase-3, but with few effects over spermatogenesis dynamics of Nile tilapia.

Temperature-induced changes in reproductive variables in the teleost fish Lophiosilurus alexandri.

The present study evaluates whether increased water temperature induces reproduction by Lophiosilurus alexandri under controlled conditions, and investigates the effects of this procedure on sexual steroids, hematological profile and behavior. A 44-week experiment was performed with four wild males and 12 wild females that had been acclimatized to captive conditions. Water temperature was maintained at 24.4 ±â€¯1.0 °C for weeks 1-22, and then at 29.0 ±â€¯1.1 °C for weeks 22-44. Spawn weight, number of eggs/spawn and hatching rate were satisfactory and ranged 27.5-127.5 g, 1209-5183 and 83-89%, respectively. Hematocrit, leukocytes and glucose were not influenced by increased water temperature, while higher values for erythrocytes were observed for both sexes. The lowest value for plasma protein was for females maintained at 29.0 °C, while the lowest value for testosterone was obtained at the end of the study period at a temperature in 29.0 °C. Serum values of 17ß-estradiol were higher in females than in males, however, there was no evidence of variation as a function of experimental temperature or interaction with sex. The reproductive behavior of L. alexandri in captivity is described for the first time. The present study demonstrates that adult individuals are able to maintain a stable hematological profile during an increase in mean water temperature from 24.4 °C to 29.0 °C, even during the reproductive period, and still produce good quality larvae. Nonetheless, whether spawning was associated with increased 17ß-estradiol levels could not be determined.

Physiological and metabolic responses of juvenile Lophiosilurus alexandri catfish to air exposure.

The present study aimed to evaluate the physiological and metabolic stress responses of juvenile Lophiosilurus alexandri submitted to an air exposure test. The subjects consisted of 72 juveniles. Blood samples were taken at: 0 h-fish not exposed to air; 0.5 h-fish shortly after exposure to air for 30 min (prior to returning to the tank); 1.5 h (90 min), 24, 48, and 96 h after the initiation of exposure to air for 30 min. After 96 h, survivorship was 100%. Cortisol and glucose levels were higher at 0.5 h, returning to baseline at 48 and 24 h, respectively. Lactate dehydrogenase levels were highest at 1.5 h after exposure to air, returning to normal values in 24 h. Several changes were recorded in gasometric blood values and electrolytes. With regard to hematology and blood chemistry, exposure to air did not affect globular volume and AST throughout the 96 h of the experiment. The values for alkaline phosphatase were highest at 0, 1.5, and 24 h. Total protein was similar between 0 and 1.5 h and lowest at 96 h, while ALT was highest at 0.5 h. Leukocytes were highest at 0.5, 1.5, 48, and 96 h, while erythrocytes were highest at 96 h. After 96 h, juvenile L. alexandri were able to reestablish the main indicators of stress (cortisol, glucose and lactate dehydrogenase), while other indicators (hematological, biochemical, and gasometric) exhibited compensatory variation for normal physiological re-establishment.

Daily rhythms of leukocytes populations, biochemical and enzymatic blood parameters in a carnivorous freshwater catfish (Lophiosilurus alexandri).

The aim of this study was to investigate the daily rhythms of hematological, biochemical and enzymatic parameters of the blood of a nocturnal model of fish (Lophiosilurus alexandri) bred in the laboratory (F1). Thirty-six juveniles were stocked in six tanks of a recirculation aquaculture system for 20 days. The fish were exposed to a light:dark cycle of 12:12 h and were fed 1% of biomass twice a day with commercial diet. The daily rhythms of hematological, biochemical and enzymatic parameters were then measured at six sampling times "zeitgeber time = ZT" at four-hour intervals under light:dark 12:12 h (lights on = ZT0, at 8.00 a.m). No differences were observed to alkaline phosphatase, glucose, cortisol, aspartate aminotransferase, superoxide dismutase, total protein and hematocrit (p > 0.05). However, white blood cell count, Lymphocytes (LYN), Neutrophils (NEU), Eosinophil and Neutrophils to Lymphocytes ratio were significant different between sample times (p < 0.05). Also, a significant difference in alanine transaminase was observed, with a peak of production at nighttime. In contrast, glutathione peroxidase peaked at 8:00. Uric acid, magnesium and Calcium (Ca++) showed statistically significant differences (p < 0.05). A significant difference was observed (p < 0.05), with a peak of albumin at 08:00 and triglycerides at 12:00, while cholesterol was low (p < 0.05) at 08:00 and higher from 12:00 to 04:00. Cosinor analysis revealed also rhythmicity to SOD, UA, Mg and Ca++, ALB and CHO (p < 0.05). In conclusion, the time of day must be considered a key factor when using blood parameters as biomarkers for disease, health and welfare in the L. alexandri aquaculture.