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This study aimed to verify the effect of different feeding and stocking conditions during 14 days on the gene expression of several hormones and enzymes related to the stress cascade and metabolic parameters in silver catfish Rhamdia quelen under the following experimental conditions: 1) fed at low stocking density (2.5 kg m-3, LSD-F); 2) fed at high stocking density (32 kg m-3, HSD-F); 3) food-deprived at LSD (LSD-FD); and 4) food-deprived at HSD (HSD-FD). Fish from LSD-F and HSD-F groups were fed daily (1 % of their body mass), while fish from food-deprived groups (LSD-FD and HSD-FD) were not fed during the experimental time. Plasma metabolic parameters (glucose, lactate, triglycerides, and proteins) and hepatosomatic index (HSI) were evaluated. In addition, mRNA expression of genes related to the stress axis (crh, pomca, pomcb, nr3c2, star, hsd11b2 and hsd20b), heat shock protein family (hsp90 and hspa12a), sodium-dependent noradrenaline transporter (slc6a2), and growth axis (gh and igf1) were also assessed. Specific growth rate and HSI decreased in food-deprived fish regardless of stocking density. The HSD-FD group showed weight loss compared to the HSD-F, LSD-F, and LSD-FD groups. Plasma glucose and triglycerides were reduced in food-deprived groups, while lactate and protein levels did not change. The expression of key players of the stress response (crh, pomca, pomcb, hsd11b2, nr3c2, and hsp90b) and growth (gh and igf1) pathways were differently regulated depending on the experimental condition, whereas no statistical difference between treatments was found for hsd20b, scl6a2, hspa12a, and star mRNAs expression. This study suggests that LSD acts as a stressor affecting negatively the physiological status of fed fish, as demonstrated by the reduction in growth rates, altered metabolic orchestration, and a higher crh mRNA expression. In addition, food deprivation also increased mRNA expression of other assessed genes (nr3c2, hsp90b, pomca, and pomcb) in fish fr

Advances in fisheries and aquaculture science often follow the introduction of new tools or analytic methods [...]

Advances in fisheries and aquaculture science often follow the introduction of new tools or analytic methods [...]

Exposure to acidic and alkaline pHs results in an ionic imbalance. Cellular responses involved in osmoregulation in silver catfish exposed to different pHs (5.5, 7.5, and 9.0) for 24 h were evaluated. The gills and kidney were collected to measure Na+/K+-ATPase (NKA) and H+-ATPase (V-ATPase) activities and to evaluate the expression of ion transporter-related genes: NKA (atp1a1), H+-ATPases (atp6v0a1b, atp6v0a2a, atp6v0a2b), Na+/H+ antiporter (slc9a3), K+/Cl− symporters (slc12a4, slc12a6, slc12a7a, slc12a7b), Na+/K+/2Cl− symporter (slc12a2), and ammonium transporter Rh type b (rhbg). The gills presented greater responses to pH changes than the kidney. The pH alterations changed the atp1a1 gene expression and NKA activity, whereas the H+-ATPase activity increased in the gills in alkaline water, probably to maintain ionic balance. The slc9a3 and slc12a2 genes play more prominent roles in the ion uptake at acidic pH than H+-ATPase. The slc12a7a was the only isoform of this transporter affected by pH. The rhbg is apparently related to ammonia excretion through the gills and kidney (minor scale). Exposure to alkaline pH seems to be battled by impairment of NKA and H+-ATPase activities in the gills, whereas the expression of some ion transporters in silver catfish changes during both acidic and alkaline pHs.

This study aimed to verify whether dietary quercetin protects against the detrimental effects induced by oxytetracycline (OTC) administration in silver catfish (Rhamdia quelen). Fish were divided into different experimental groups that received OTC and/or quercetin, either during 14 or 21 days. To determine the endocrine system stress response, we have measured the brain mRNA expression levels of corticotropin-releasing hormone (crh), proopiomelanocortins (pomca and pomcb) and some of the pituitary hormones (growth hormone [gh], somatolactin [sl], and prolactin [prl]). We have also quantified the levels of cortisol as well as some metabolites (glucose, glycogen, lactate, and triglycerides) in the plasma. Moreover, the enzymatic activity of hexokinase, phosphorylase (active GPase), fructose-biphosphatase (FBP), glycerol-3-phosphate dehydrogenase, glucose-6-phosphate dehydrogenase, and glutamate dehydrogenase (GDH) and gill Na+/K+-ATPase were measured. The results demonstrated that OTC activates the silver catfish stress response by increasing the plasma cortisol and decreasing the glucose levels at 14 and 21 days. Additionally, OTC also altered the fish hepatic metabolic status as demonstrated by an increase in triglycerides levels and the enzymatic activity of both FBP and GDH after 14 days. OTC also stimulated Na+/K+-ATPase activity in the gill after 14 days and altered the hypophyseal expression of gh (at 14 and 21 days) and prl (at 14 days). The co-treatment with 1.5 g of quercetin could prevent most of the alterations caused by OTC, strongly suggesting quercetin as a beneficial compound when added to the fish diet.

Stress responses in teleosts include the release of hormones into the bloodstream. Their effects depend on the species and on the environmental conditions. The Amazon basin collects waters of diverse chemical composition, and some fish are able to inhabit several of them. However, the effects of these waters on the stress axis are still unknown. Here we show how acute air-exposure differently affects stress biomarkers in tambaqui (Colossoma macropomum), a tropical model species, when acclimated to two Amazonian waters (Rio Negro -RN- water rich in humic acids and poor in ions, and groundwater -IG- with no humic acids and higher concentration of ions). This study described primary and secondary stress responses after air exposure including plasma cortisol, energy metabolites, pH and ions, skin mucus energy metabolites, as well as gills and kidney Na+/K+-ATPase and Na+/H+-exchanger (NHE) activities. Several differences were described in these stress biomarkers due to the acclimation water. The most remarkable ones include increased mucus glucose only in RN-fish, and mucus lactate only in IG-fish after air exposure. Moreover, an inverse relationship between plasma cortisol and Na+ concentrations as well as a direct relationship between plasma ammonia and branchial NHE activity were observed only in RN-fish. Our results demonstrate how important is to study stress responses in fish acclimated to different environments, as physiological differences can be magnified during episodes of high energy expenditure. In addition to having a direct application in aquaculture, this study will improve the management of critical ecosystems such as the Amazon.

In teleost fish, stress initiates a hormone cascade along the hypothalamus-pituitary-interrenal (HPI) axis to provoke several physiological reactions in order to maintain homeostasis. In aquaculture, a number of factors induce stress in fish, such as handling and transport, and in order to reduce the consequences of this, the use of anesthetics has been an interesting alternative. Essential oil (EO) of Lippia alba is considered to be a good anesthetic; however, its distinct chemotypes have different side effects. Therefore, the present study aimed to investigate, in detail, the expression of genes involved with the HPI axis and the effects of anesthesia with the EOs of two chemotypes of L. alba (citral EO-C and linalool EO-L) on this expression in silver catfish, Rhamdia quelen. Anesthesia with the EO-C is stressful for silver catfish because there was an upregulation of the genes directly related to stress: slc6a2, crh, hsd20b, hspa12a, and hsp90. In this study, it was also possible to observe the importance of the hsd11b2 gene in the response to stress by handling. The use of EO-C as anesthetics for fish is not recommended, but, the use of OE-L is indicated for silver catfish as it does not cause major changes in the HPI axis.

The effects of diet supplemented with Myrcia sylvatica essential oil (EOMS) on growth and stress tolerance to different stocking densities were assessed in Sparus aurata. Initially, three experimental groups were established: (i) control, (ii) 1.0 and (iii) 2.0 ml EOMS/kg dry feed. After 90 days, nine fish per group were anaesthetized, weighed and sampled for metabolic analysis. The remaining fish were divided into two different conditions: low (LD—5 kg/m3) and high (HD—40 kg/m3) stocking densities, constituting a final experimental setup with six treatments. After 22 days, 10 individuals per treatment were anaesthetized and sampled for biochemical analysis. EOMS feeding for 90 days did not interfere with growth, although it was effective in reducing cortisol levels and the activation of lipid and carbohydrate metabolism. The HD interfered in growth performance, increased the lactate levels in the control group, reducing also hepatic glycogen levels without dependence on diet supplementation. The 2.0 ml EOMS + LD group increased the growth parameters and decreased the cortisol and triglycerides levels. Additionally, metabolism adjustment was observed to provide energy during LD and HD conditions, indicating that diets supplemented with EOMS produce metabolic reorganization to maintain body homeostasis, suggesting its use as a beneficial supplement in fish.

The objectives of this experiment were to (i) determine the efficacy of essential oils of clove (CO) and Lippia alba (EOLA) to induce deep anaesthesia in juvenile specimens (49.0 ± 6.2 g body mass, 16.6 ± 0.8 cm; n = 8 per treatment) of meagre (Argyrosomus regius); and (ii) study the feasibility of these substances, together with 2‐phenoxyethanol (2‐PHE), as potential sedatives [low concentration: (i) EOLA: 12 mg L−1; (ii) CO: 1 mg L−1; and (iii) 2‐PHE: 33 mg·L −1; n = 8 per treatment] for live fish transport of this species. All test were performed at a constant temperature (18°C). Thus, the main primary stress indicator (plasma cortisol) and secondary factors (plasma metabolites) were evaluated. In addition, growth hormone (GH) mRNA expression was also evaluated in the pituitary gland. The results indicated that EOLA is considered to be effective for deep anaesthesia when the concentration is close to 160 mg L−1, while CO produces the same effect when lower concentrations are added (40–50 mg L−1). Regarding sedative concentrations, a significant ~3‐fold increase in plasma cortisol levels was detected in the EOLA group when compared to control specimens. In addition, glucose levels were not reduced and significantly increased (~1.6‐fold) for 2‐PHE in relation to the control fish. None of the anaesthetics promoted a significant difference for GH expression with respect to the control group, but a significant ~2‐fold increase for 2‐PHE treatment with respect to the EOLA exposition was found in this gene expression. Results show that none of the anaesthetics analysed, at least in the ranges of concentrations used in this study (EOLA 12 mg L−1, CO 1 mg L−1, 2‐PHE 33 mg L−1), are recommended for live fish transport, as shown by the absence of inhibition on the stress parameters assessed.

[ES] Unas condiciones de cultivo inadecuadas (por ejemplo la alta densidad), causan estrés a los peces, afectando el metabolismo de lípidos, hidratos de carbono y proteínas. El objetivo de este estudio fue evaluar los efectos de la adición de aceite esencial de Myrcia sylvatica (AEMS) en la dieta de ejemplares de Sparus aurata en situaciones de baja y alta densidad. Los juveniles de dorada fueron distribuidos y alimentados con tres dietas experimentales durante tres meses: i) control, ii) 1,0 mL AEMS/kg de pienso, y iii) 2.0 mL AEMS/kg de pienso. Transcurrido este tiempo, cada grupo experimental fue dividido en dos nuevas condiciones: baja y alta densidad de carga (BD, 5 kg/m3 y AD, 40 kg/m3, respectivamente) para tener un total de seis grupos experimentales: i) control-BD, ii) control-AD, iii) 1,0 mL-BD, iv) 1,0 mL-AD, v) 2,0 mL-BD, y vi) 2,0 mL-AD). Después de 22 días bajo estas condiciones, 10 individuos de cada tratamiento fueron anestesiados y se extrajeron muestras de sangre e hígado para el análisis de cortisol y metabolitos. Nuestros resultados muestran que la adición de AEMS disminuye los niveles de cortisol en condiciones de BD y AD. Además, se observa que dietas suplementadas con dosis cercanas a 2,0 mL AEMS/kg de pienso originan una reorganización metabólica para poder afrontar la situación de estrés producido por la alta densidad de carga., [EN] Inadequate stocking densities (e.g. high stocking density) activated stress system, affecting the metabolism of lipids, carbohydrates and proteins. The aim of this study was to evaluate the effects of adding essential oil of Myrcia sylvatica (EOMS) in the diet of Sparus aurata juveniles held at different stocking densities. Juvenile specimens were distributed into the three experimental groups, feeding three different diets during three additional months: i) control, ii) 1.0 mL EOMS/kg of feed, and iii) 2.0 mL EOMS/kg feed. After that, each experimental group was divided in two different conditions: low and high stocking densities (LD-5 kg/m3 and HD-40 kg/m3, respectively) constituting a total of six different treatments: i) control-LD, ii) control-HD, iii) 1.0 mL-LD, iv) 1.0 mL-HD, v) 2.0 mL-LD, and vi) 2.0 mL-HD). After 22 days under these conditions, 10 individuals from each treatment were anesthetized and sampled for plasma and liver. These samples were analysed for cortisol and metabolites analysis. Our results shown that EOMS decreased plasma cortisol levels under LD and HD conditions. Moreover, it is observed that diets supplemented with 2.0 mL EOMS/kg of food originates a metabolic reorganization to cope with the stressful situation produced by higher stocking densities.

[ES] Las actividades acuícolas producen situaciones de estrés que disminuyen el bienestar de los peces cultivados. El objetivo de este estudio fue evaluar los efectos de la adición del aceite esencial de Myrcia sylvatica (AEMS), una sustancia que mitiga la activación del sistema de estrés en otras especies de teleósteos, en la dieta de la dorada (Sparus aurata). Los juveniles de dorada fueron proporcionados por los Servicios Centrales de Investigación de Cultivos Marinos (SCI-CM, Universidad de Cádiz), aclimatados durante un mes en tanques de 1000 L y distribuidos en 9 tanques de 80 L (densidad de carga inicial: 2,76 ± 0,013 g/L) que constituyeron los tres grupos experimentales por triplicado: i) control, ii) 1,0 mL AEMS/kg de pienso, y iii) 2,0 mL AEMS/kg de pienso. Tras 90 días, los peces (n = 9 por grupo experimental) fueron anestesiados, medidos y pesados. Posteriormente, se extrajeron muestras de sangre e hígado para el análisis de cortisol y metabolitos. La adición en la dieta de AEMS disminuyó los niveles de cortisol y triglicéridos en plasma, así como del glucógeno hepático. Por tanto, nuestros resultados sugieren que la adición de AEMS en la dieta (dosis entre 1,0-2,0 mL AEMS/kg de pienso) podría mejorar el bienestar animal de esta especie durante su cultivo., [EN] Aquaculture activities promote stress situations that decrease fish welfare. In this sense, the objective of this study was to evaluate the effects of adding essential oil of Myrcia sylvatica (EOMS), a substance that has been used to mitigate activation of stress system in other teleost, in the diet of gilthead sea bream (Sparus aurata). Juveniles specimens were provided by the Servicios Centrales de Investigación de Cultivos Marinos (SCI-CM, University of Cadiz), acclimated for one month in 1000 L-tanks and distributed in 9 tanks of 80 L (initial stocking density: 2.76 ± 0.013 g/L), which constituted the three experimental groups in triplicate: i) control, ii) 1.0 mL EOMS/kg food, and iii) 2.0 mL EOMS/kg food). After 90 days, fish (n = 9 fish per group) were anesthetized measured and weighed. Subsequently, blood and liver samples were extracted for cortisol and metabolites analysis. The addition of EOMS in diet decreased plasma cortisol levels and plasma triglycerides, as well as liver glycogen. Therefore, our results suggest that the addition of EOMS in the diet (doses between 1.0-2.0 mL EOMS/kg food) could promote fish welfare of this specie in culture.

This study investigated the effects of prolonged exposure of silver catfish (Rhamdia quelen) to the essential oil (EO) of Hesperozygis ringens. Ventilatory rate (VR), stress and metabolic indicators, energy enzyme activities, and mRNA expression of adenohypophyseal hormones were examined in specimens that were exposed for 6 h to 0 (control), 30 or 50 µL L−1 EO of H. ringens in water. Reduction in VR was observed in response to each treatment, but no differences were found between treatments. Plasma glucose, protein, and osmolality increased in fish exposed to 50 µL L−1. Moreover, lactate levels increased after exposure to both EO concentrations. Plasma cortisol levels were not changed by EO exposure. Fish exposed to 30 µL L−1 EO exhibited higher glycerol-3-phosphate dehydrogenase (G3PDH) activity, while exposure to 50 µL L−1 EO elicited an increase in glucose-6-phosphate dehydrogenase (G6PDH), fructose-biphosphatase (FBP), and 3-hydroxyacyl-CoA-dehydrogenase (HOAD) activities compared with the control group. Expression of growth hormone (GH) only decreased in fish exposed to 50 µL L−1 EO, while somatolactin (SL) expression decreased in fish exposed to both concentrations of EO. Exposure to EO did not change prolactin expression. The results indicate that GH and SL are associated with energy reorganization in silver catfish. Fish were only slightly affected by 30 µL L−1 EO of H. ringens, suggesting that it could be used in practices where a reduction in the movement of fish for prolonged periods is beneficial, i.e., such as during fish transportation.

The influence of stocking density and food deprivation on energy metabolism, stress processes and the pituitary endocrine system of silver catfish (Rhamdia quelen) was investigated after a period of 14 days, in which plasmatic and hepatic parameters and the mRNA expression of prolactin (PRL), growth hormone (GH) and somatolactin (SL) were assessed. The fish were subjected to four experimental conditions: (1) fed under high stocking density (32 kg/m3, HSD); (2) fed under mean stocking density (16 kg/m3, MSD); (3) fed under low stocking density (8 kg/m3, LSD); and (4) food-deprived under low stocking density (8 kg/m3, LSD-FD). After 14 days, plasma and liver samples were obtained to analyze the metabolite levels and enzymatic activities related to metabolism, and pituitary glands were obtained to analyze hormone expression (PRL, GH and SL). Liver weight and the hepato-somatic index (HSI) revealed that specimens maintained at HSD and/or MSD had higher hepatic stores, which were observed in the triglyceride and glycogen levels in this tissue, than animals submitted to the LSD and LSD-FD groups. Triglyceride levels in the plasma and liver revealed the consumption of fatty acid reserves in the fasting group. Enzymatic activities, such as glutamate dehydrogenase (GDH), phosphorylase (GPase), pyruvate kinase (PK), aspartate transaminase (AST) and glycerol-3-phosphate dehydrogenase (G3PDH), indicated an increase in gluconeogenic pathways in the HSD group and an increase in glycolitic metabolism in the LSD groups. The expression of PRL was not affected by stocking density and/or food deprivation and GH decreased with increased density and increased in fasting conditions. A negative effect of density and fasting was observed on the expression of SL. Overall, the data suggested that juvenile silver catfish reared at stocking densities of 16 to 32 kg/m3 were better maintained than those maintained at the lowest density.

The purpose of this study was to establish the optimal anesthetic concentration of eugenol for handling hybrid juvenile Pseudoplatystoma metaense by Leiarius marmoratus (PxL) and subsequent survival (24 hours). Forty juveniles youth PxL hybrid (9.3 ± 2.75 g and 9.08 ± 0.8 cm) from the ponds of IALL station obtained from the same spawning were exposed to eugenol (85% purity in oil base) (30, 50, 60 and 70 mg / L) and a control group (ethanol 0.8 ml / L). Specimens of each experimental group (n = 8 fish) were randomly selected and individually subjected to each treatment in an aquarium with a capacity of 10L and recovered in fresh water. The quality parameters determined for the experiment were: water temperature 28.3 ± 0.12°C, OD: 2.3 ± 8.0 mg / L and pH 5.4 ± 0.32. None of the treatments caused mortality (100% survival). Induction times measured for levels 50, 60 and 70 mg / L were significantly lower than those recorded for the concentration of 30 mg / L in which induction times were over 400 seconds. Although none of the concentrations produced damage to the recovery of the animals, in consideration of the time of induction of anesthesia-recovery, it is concluded that the concentration of 50 mg / L of eugenol is recommended for handling hybrid PxL., O objetivo deste estudo foi estabelecer a concentração anestésica ideal de eugenol para manuseio de juvenis do híbrido Pseudoplatystoma metaeense x Leiarius marmoratus (PxL) ea sobrevivência pós-anestesia (24 horas). Quarenta juvenis do híbrido PxL (9,3 ± 2,75 g e 9,08 ± 0,8 cm) foram obtidos a partir da mesma desova em tanques de cultivo no Iall e expostos a eugenol (85% de pureza em base de óleo) (30, 50, 60 e 70 mg / L) e um grupo control (etanol a 0,8 ml / L). Os exemplares de cada grupo experimental (n = 8 peixes) foram selecionados aleatoriamente e submetidos individualmente a cada tratamento em um aquário com capacidade de 10 L e recuperados em água corrente. Os parâme tros de qualidade determinados para a experiência foram: temperatura 28,3 ± 0.12°C, OD: 2,3 ± 8,0 mg / L e pH de 5,4 ± 0,32. Nenhum dos tratamentos causou mortalidade (100% de sobrevivência). Tempos de indução medidos para os níveis de 50, 60 e 70 mg / L foram significativamente menores que os registrados para a concentração de 30 mg / L, no qual o tempo de indução foi maior que 400 segundos. Embora nenhuma das concentrações tenha produzido dano para a recuperação dos animais, tendo em consideração o tempo de indução da anestesia e recuperação, conclui-se que a concentração de 50 mg / L de eugenol é recomendada para o manuseio de híbridos PxL., El objeto de ese trabajo fue establecer una concentración anestésica óptima de eugenol para la manipulación de los juveniles híbridos de Pseudoplatystoma metaense por Leiarius marmoratus (PxL) y determinar la sobrevivencia posterior a la anestesia (24 horas). Cuarenta juveniles del híbrido PxL (9,3 ± 2,75 g y 9.08 ± 0.8 cm) provenientes de los estanques de la estación IALL obtenidos de un mismo desove fueron expuestos al eugenol (85% de pureza en base oleosa) (30, 50, 60 y 70 mg/L) y un grupo control (etanol 0.8 ml/L). Los especímenes de cada grupo experimental (n= 8 peces), fueron seleccionados al azar y sometidos individualmente a cada tratamiento en un acuario con capacidad de 10L y recuperados en agua corriente. Los parámetros de calidad de agua determinados para el experimento fueron Temperatura 28, 3 ± 0.12°C, OD: 2,3 ± 8,0 mg/L y pH: 5,4± 0,32. Ninguno de los tratamientos causo mortalidad (100% de sobrevivencia). Los tiempos de inducción medidos para las concentraciones 50, 60 y 70 mg/L fueron significativamente inferiores a los registrados para la concentración de 30 mg/L en la cual se presentaron tiempos de inducción por encima de los 400 segundos. Aunque ninguna de las concentraciones produjo daños en la recuperación de los animales, en consideración con los tiempos de inducción-recuperación anestésica se concluye que la concentración de 50 mg/L de eugenol es la más recomendable para la manipulación de híbridos PxL.

The purpose of this study was to establish the optimal anesthetic concentration of eugenol for handling hybrid juvenile Pseudoplatystoma metaense by Leiarius marmoratus (PxL) and subsequent survival (24 hours). Forty juveniles youth PxL hybrid (9.3 ± 2.75 g and 9.08 ± 0.8 cm) from the ponds of IALL station obtained from the same spawning were exposed to eugenol (85% purity in oil base) (30, 50, 60 and 70 mg / L) and a control group (ethanol 0.8 ml / L). Specimens of each experimental group (n = 8 fish) were randomly selected and individually subjected to each treatment in an aquarium with a capacity of 10L and recovered in fresh water. The quality parameters determined for the experiment were: water temperature 28.3 ± 0.12°C, OD: 2.3 ± 8.0 mg / L and pH 5.4 ± 0.32. None of the treatments caused mortality (100% survival). Induction times measured for levels 50, 60 and 70 mg / L were significantly lower than those recorded for the concentration of 30 mg / L in which induction times were over 400 seconds. Although none of the concentrations produced damage to the recovery of the animals, in consideration of the time of induction of anesthesia-recovery, it is concluded that the concentration of 50 mg / L of eugenol is recommended for handling hybrid PxL., O objetivo deste estudo foi estabelecer a concentração anestésica ideal de eugenol para manuseio de juvenis do híbrido Pseudoplatystoma metaeense x Leiarius marmoratus (PxL) ea sobrevivência pós-anestesia (24 horas). Quarenta juvenis do híbrido PxL (9,3 ± 2,75 g e 9,08 ± 0,8 cm) foram obtidos a partir da mesma desova em tanques de cultivo no Iall e expostos a eugenol (85% de pureza em base de óleo) (30, 50, 60 e 70 mg / L) e um grupo control (etanol a 0,8 ml / L). Os exemplares de cada grupo experimental (n = 8 peixes) foram selecionados aleatoriamente e submetidos individualmente a cada tratamento em um aquário com capacidade de 10 L e recuperados em água corrente. Os parâme tros de qualidade determinados para a experiência foram: temperatura 28,3 ± 0.12°C, OD: 2,3 ± 8,0 mg / L e pH de 5,4 ± 0,32. Nenhum dos tratamentos causou mortalidade (100% de sobrevivência). Tempos de indução medidos para os níveis de 50, 60 e 70 mg / L foram significativamente menores que os registrados para a concentração de 30 mg / L, no qual o tempo de indução foi maior que 400 segundos. Embora nenhuma das concentrações tenha produzido dano para a recuperação dos animais, tendo em consideração o tempo de indução da anestesia e recuperação, conclui-se que a concentração de 50 mg / L de eugenol é recomendada para o manuseio de híbridos PxL., El objeto de ese trabajo fue establecer una concentración anestésica óptima de eugenol para la manipulación de los juveniles híbridos de Pseudoplatystoma metaense por Leiarius marmoratus (PxL) y determinar la sobrevivencia posterior a la anestesia (24 horas). Cuarenta juveniles del híbrido PxL (9,3 ± 2,75 g y 9.08 ± 0.8 cm) provenientes de los estanques de la estación IALL obtenidos de un mismo desove fueron expuestos al eugenol (85% de pureza en base oleosa) (30, 50, 60 y 70 mg/L) y un grupo control (etanol 0.8 ml/L). Los especímenes de cada grupo experimental (n= 8 peces), fueron seleccionados al azar y sometidos individualmente a cada tratamiento en un acuario con capacidad de 10L y recuperados en agua corriente. Los parámetros de calidad de agua determinados para el experimento fueron Temperatura 28, 3 ± 0.12°C, OD: 2,3 ± 8,0 mg/L y pH: 5,4± 0,32. Ninguno de los tratamientos causo mortalidad (100% de sobrevivencia). Los tiempos de inducción medidos para las concentraciones 50, 60 y 70 mg/L fueron significativamente inferiores a los registrados para la concentración de 30 mg/L en la cual se presentaron tiempos de inducción por encima de los 400 segundos. Aunque ninguna de las concentraciones produjo daños en la recuperación de los animales, en consideración con los tiempos de inducción-recuperación anestésica se concluye que la concentración de 50 mg/L de eugenol es la más recomendable para la manipulación de híbridos PxL.

In this study, the protective effects of diphenyl diselenide [(PhSe)2] on quinclorac- induced toxicity were investigated in silver catfish (Rhamdia quelen). The fish were fed for 60 days with a diet in the absence or in the presence of 3.0 mg/Kg (PhSe)2. Animals were further exposed to 1 mg/L quinclorac for 8 days. At the end of experimental period, fish were euthanized and biopsies from liver and gills, as well as blood samples, were collected. The cortisol and metabolic parameters were determined in plasma, and those enzyme activities related to osmoregulation were assayed in the gills. In liver, some important enzyme activities of the intermediary metabolism and oxidative stress-related parameters, such as thiobarbituric acid-reactive substance (TBARS), protein carbonyl, catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), nonprotein thiols (NPSH) and ascorbic acid contents were also evaluated. Compared to the control group, quinclorac exposure significantly decreased hepatosomatic index and increased cortisol and lactate values in plasma. Moreover, the activities of fructose biphosphatase (FBPase), glucose-6-phosphate dehydrogenase (G6Pase), glycogen phosphorilase (GPase) and aspartate aminotransferase (AST) were significantly increased in liver. Quinclorac also induced lipid peroxidation while the activity of SOD, NPSH and ascorbic acid levels decreased in the liver. However, dietary (PhSe)2 reduced the herbicide-induced effects on the studied parameters. In conclusion, (PhSe)2 has beneficial properties based on its ability to attenuate toxicity induced by quinclorac by regulating energy metabolism and oxidative stress-related parameters.