Juvenile Colossoma Macropomum Research Articles

Behavioral and electrophysiological study in Colossoma macropomum treated with different concentrations of Nepeta cataria oil in an immersion bath revealed a therapeutic window for anesthesia.

The purpose of this study was to characterize the activity of essential oils from Nepeta Cataria (EON) at concentrations of 125 L-1, 150 L-1, 175 L-1, and 200 L-1 on the behavior of loss of the posture reflex and recovery of the posture reflex and electrocardiographic activity and recording of the opercular beat of Colossoma macropomum during immersion bathing for a period of 5min, in order to obtain a window for safe use during anesthesia. The fish (23.38 ± 3.5g) were assigned to the following experiments: experiment 1 (latency to loss and recovery of the posture reflex): (a) 125 L-1, (b) 150 L-1, (c) 175 L-1, and (d) 200 L-1 (n = 9) per group. Experiment 2 (electrocardiographic and heartbeat recordings): (a) control group; (b) vehicle control group (2ml of alcohol per liter of water), (c) 125 L-1, (d) 150 L-1, (e) 175 L-1, and (f) 200 L-1 (n = 9), per group. All the concentrations used showed efficacy in inducing loss of the posture reflex and reversibility with recovery of the posture reflex, but the electrocardiographic recordings indicated morphographic changes such as bradycardia during induction and p wave apiculation during recovery at the highest concentrations tested. In this way, we suggest a safe use window for short-term anesthesia with EON in the concentration range of 125 to 150 L-1 for juvenile Colossoma macropomum.

Blood cell alterations in Colossoma macropomum juveniles caused by silver nanoparticles.

This study evaluated the median lethal concentration of silver nanoparticles and their effects in fish tambaqui Colossoma macropomum. Therefore, an acute toxicity assay was carried out in completely randomized design evaluating six different concentrations of silver nanoparticles on blood parameters of tambaqui. The silver nanoparticles were produced by chemical reduction with polyvinyl alcohol (AgNP-PVA). The lethal concentration 50% (LC50) was estimated using probit regression. The blood was collected, analyzed and the data were submitted to T-test (dying x surviving fish) and Tukey test (surviving fish). An increase in glucose, hematocrit, total plasma protein, hemoglobin, erythrocytes, leukocytes, monocytes, and neutrophils as well as reduced MCV (mean corpuscular volume) in dying fish compared to surviving fish were observed. Survived fish exposed to 187.5 µg/L showed an increase in hematocrit, MCV, and MCH and a reduction in erythrocytes, total numbers of leukocyte, thrombocyte, lymphocyte, and neutrophil. The fish exposed to concentrations below 125 µg/L, had returned the blood parameter to baselines compared to control. The estimated LC50 was 165.09 µg/L and was classified as highly toxic for the fish tambaqui. In higher concentrations, it causes an acute respiratory toxicity, but in concentrations below 125 µg/L, the fish can adapt to the stressing agent.

Crude glycerin in feed for Colossoma macropomum fish: evaluation of histopathological effects on the liver and kidney

The present study aimed to verify whether the use of crude glycerin in the diet of juvenile Colossoma macropomum could promote histopathological changes in the liver and kidneys. 150 juveniles were used, divided into 15 tanks of 1000 liters (five treatments and three repetitions, n = 10). Five different diets with inclusion of crude glycerin (0%; 7.5%; 10%; 12.5%; 15%) were used in exchange for soybean oil and partial replacement of corn bran. The animals were fed to satiation for 60 days. After this period, liver and kidney samples from each group were submitted to histological processing and histopathological analysis. The semi-quantitative method was used to assess the lesions: calculation of Mean Alteration Values (MVA), which assess the occurrence of the lesion, and the Histopathological Alterations Index (HAI), which allows assessing the severity of the lesions. The results indicated significant non-harmful effects, but adaptive responses to the diet. In conclusion, the inclusion of up to 15% crude glycerin can be used without causing significant liver and kidney changes in C. macropomum juveniles.

Growth Performance and Histomorphology of Intestine, Skin, Gills and Liver of Juvenile Colossoma macropomum Fed Diets Containing Different Levels of the Essential Oil of Nectandra grandiflora

The present study evaluated different levels of the essential oil of Nectandra grandiflora (EONG) in the diet of juvenile Colossoma macropomum. The juveniles (0.75 ± 0.05 g) were fed four experimental diets with differing levels of EONG (0, 0.5, 0.75, and 1.50 mL/kg). After 20 days, the weight, daily weight gain, specific growth rate, and daily feed consumption per fish were highest for the fish fed 0.5 mL EONG/kg, while after 30 days, only the weight and daily feed consumption per fish for that diet remained highest. The viscerosomatic index was highest for the fish fed 0.5 mL EONG/kg while the hepatosomatic index was higher for the groups that received dietary EONG for 30 days. The juveniles fed 1.5 mL EONG/kg showed a proliferative response of the mucous cells in the gills, but the proliferation of these lysozyme- and immunoglobulin-secreting mucosal cells was higher for the skin of the fish of all EONG levels, compared to that of the control fish. The fish fed 0.5 mL EONG/kg had the greatest height and width of intestinal villi. The two highest levels of dietary EONG supplementation (0.75 and 1.50 mL/kg) reduced the hepatocyte dimensions but did not modify the centrolobular vein area. Dietary supplementation with 0.5 mL EONG/kg improved the growth, gut health, and immune response of juvenile C. macropomum.

Oxidative stress in juvenile tambaqui (Colossoma macropomum) after different periods of air exposure

This study evaluated the response of juvenile Colossoma macropomum to oxidative stress when exposed to air for different periods of time. Fifty-four juveniles weighing 74.8 ± 17.4 g were randomly transferred to nine 30-L tanks in a recirculating aquaculture system and acclimatized to experimental conditions for 15 days. The fish were subsequently fasted for 24 h, after which a group of animals (n = 6) was sampled immediately at the beginning of the experiment to determine baseline levels (without air exposure). Another group (n = 24) was exposed to air for 30 min (30E) and the rest of the fish (n = 24) were exposed to air for 60 min (60E). Oxidative damage and antioxidant defenses were determined immediately after air exposure (IAE; n = 6) and at 1, 24 and 48 h after air exposure (1hAE, 24hAE, and 48hAE; n = 6 animals/per exposure time) by euthanizing fish and immediately removing the gills, liver, kidney, and brain. The interaction between factors (air exposure time x collection time) had an effect on reduced glutathione in the liver (P < 0.0001) and kidney (P = 0.0252). The highest concentrations for reduced glutathione in the gills was for treatment 60E (P = 0.0294), while that for the brain was for treatment 30E (P = 0.0012). Air exposure time had an effect on liver (P < 0.0001) and kidney (P < 0.0001) superoxide dismutase, with the highest values for 60E and 30E, respectively. The interaction between factors had an effect on liver protein levels (P = 0.0029), with the highest value for 30E at 24hAE. Treatment 60E had higher protein degradation in the gills, kidneys and brain than treatment 30E (P < 0.05). Treatment 30E had lower TBARS concentrations in the liver (P = 0.0284) and gills (P = 0.0012), but without damage to the kidney (P = 0.9396) and brain (P = 0.5277). Therefore, air exposure caused changes in antioxidant defenses in the liver, kidney, brain, and gills of C. macropomum juveniles.

Levamisole hydrochloride as an anthelmintic against Neoechinorhynchus buttnerae in juvenile Colossoma macropomum.

Acanthocephalosis is caused by the endoparasite Neoechynorhyncus buttnerae and affects fish farmed in the Amazon. This study assessed the efficacy of therapeutic levamisole hydrochloride (LVC) baths against N. buttnerae and its effects on juvenile tambaqui blood parameters. In vitro and in vivo tests were carried out, the latter employing two experimental therapeutic LVC bath protocols. Concerning in vitro efficacy, the T75 (75 mg.L-1 LVC) and T100 (mg.L-1 LVC) treatments were 100% effective in 15 min, while the T50 (50 mg.L-1 LVC) and T25 (25 mg.L-1 LVC) treatments required parasite exposure for 45 and 60 min, respectively. During exposure, the parasites displayed reduced motility, proboscis retraction, coiling into a spiral shape, body rigidity and swelling. The LVC LC50-72h for juvenile tambaqui was 115 mg.L-1 . Regarding in vivo efficacy for Protocol I (8-h bath), the T125 resulted in 82% effectiveness, while in Protocol II (two 8-h baths with a 24-h interval), the T115 treatment (115 mg.L-1 LVC) achieved 95.6% effectiveness without clinical intoxication signs, despite behavioural changes. No significant changes were observed in fish blood parameters. LVC was, therefore, highly effective both in vitro and in vivo in controlling the acanthocephalan N. buttnerae without compromising tambaqui juvenile homeostasis.

Dietary lysine requirements of Colossoma macropomum (Cuvier, 1818) based on growth performance, hepatic and intestinal morphohistology and hematology.

This study aimed to determine the dietary lysine requirements of juvenile Colossoma macropomum tambaqui based growth performance, hepatic and intestinal morphohistology and hematology. Tambaqui were fed with levels of 6.60, 9.72, 12.84, 15.96, 19.08, and 22.20 g/kg of total lysine and those who received 15.96 g/kg dietary lysine showed higher final weight (p= 0.001) and optimized feed conversion ratio (p= 0.001). Morphohistological modifications (presence of fat droplets) were present in livers of fish fed with low levels of lysine. In the morphohistology of the intestine, the diets influenced the density of the intestinal, cell layers, height and perimeters of the villi and acid mucin secretion by the goblet cells. In the proximal intestine, mucosa layer density was greater at the level of 15.96 g/kg (p= 0.001). In the middle intestine, height (p= 0.001) and perimeter (p= 0.001) of the villi were greater at low levels of lysine (respectively, 9.72 and 12.84 g/kg dietary lysine). No differences were found for the hemoglobin, hematocrit, erythrocytes, MCV, MCH, MCHC, thrombocytes and leukocytes differentiated of fish fed with experimental diets (p>0.05). The biochemical responses were affected by the diet, both in plasma concentration (protein and cholesterol; p<0.05), and in muscle (ash and moisture; p<0.05). In conclusion, the dietary requirement for lysine for tambaqui juveniles was estimated to be 15.4 - 15.6 g/kg of diet (5.7% -5.8% dietary protein).

CRESCIMENTO DE TAMBAQUI COLOSSOMA MACROPOMUM (CUVIER 1816) EM SISTEMA DE RECIRCULAÇÃO DE ÁGUA

This study provided was carried out with the objective of determining the ideal stocking density for the rearing of tambaqui juveniles Colossoma macropomum, a fish native to the northern region of the Brazil that has favorable zootechnical and market characteristics for the development of regional fish farming. For this purpose, three stocking densities (100 fish per m³, 200 fish per m³ and 300 fish per m³) in triplicate, were evaluated in a completely randomized design for 68 days. The fish, with an initial average weight of 077 ± 0.01 g, were fed daily according to the feeding rate. Regarding the results, the growth variables showed a significant difference (P&gt; 0.05), except for survival and feed conversion, with the treatment with animals stored in 100 fish per m³ showing the best performance between treatments. The stocking density of tambaqui juveniles is inversely proportional to weight gain, specific growth rate and average feed consumption. Therefore, it is suggested to cultivate the tambaqui juveniles in a water recirculation system at the stocking density of 100 fish per m³.

Physiological responses of juvenile Colossoma macropomum after different periods of air exposure

The objective of this work was to evaluate the physiological responses of juvenile Colossoma macropomum exposed to air for different periods of time. Juveniles weighing 74.78 ± 17.39 g were acclimated for 15 days in 30-L tanks in a recirculating aquaculture system (RAS) at a density of 6 animals/tank. The animals were then fasted for 24 h prior to the air exposure test and six juveniles were captured for blood collection to establish basal levels of the parameters. Next, 24 animals were exposed to air for 30 min and the other 24 for 60 min. Blood samples were taken from six animals of each exposure treatment immediately after exposure (IAE), and the other animals returned to their tanks. Subsequent blood samples were taken for six animals (n = 6) per exposure time at 1 h (1hAE), 24 h (24hAE) and 48 h (48hAE) after air exposure. No mortality was recorded. Hematocrit and hemoglobin did not vary according to air exposure time, collection time or the interaction between these two factors. There was an interaction of the factors times of exposure to air and times of collection for glucose where was higher for the 60 min exposure compared to the 30 min exposure at the 1hAE collection, while after 24hAE the levels did not differ from basal. For lactate there was also an interaction between the factors being higher for the 60 min exposure compared to the 30 min exposure at IAE and 1hAE. Blood pH varied among the collections, with a lower value at 1hAE for the 60 min exposure. The parameters PvCO2 (venous carbon dioxide partial pressure) and PvO2 (venous oxygen partial pressure) were inversely proportional; while PvCO2 increased, PvO2 decreased after collection 1hAE. Values of HCO3− (bicarbonate) differed between exposure times and varied among collections. The electrolytes Cl− (Chloride) and K+ (Potassium) varied among collections in relation to basal, however, they did not differ between exposure times. The value for Na+ (Sodium) for the 60 min exposure at IAE was higher than basal, and only 24hAE was different from basal for both exposures. Ca2+ (Calcium) values differed between exposure times (30 and 60 min) in the 24hAE collection, however, values did not differ from basal. Exposure to air caused physiological, biochemical, gasometric and electrolytic in juvenile C. macropomum. These animals can be considered resistant to this stress due to their ability to restore physiological.

Dietary Euterpe oleracea Mart. attenuates seizures and damage to lipids in the brain of Colossoma macropomum.

The Amazonian açai fruit (Euterpe oleracea) has shown promising anticonvulsant properties, comparable to those of diazepam (BDZ) in in vivo models submitted to pentylenetetrazole (PTZ). PTZ is a classic convulsant agent used in studies for the purpose of screening anticonvulsants and investigating the mechanisms of epilepsy. Herein, we aimed to determine, for the first time, the effect of dietary administration of lyophilized E. oleracea (LEO) on PTZ-induced seizures, using juvenile Colossoma macropomum fish (9.1 ± 1.5g) as a model. A control diet (0.00% LEO) and two levels of LEO inclusion were established: 5.00% and 10.0% LEO (w/w). Fish were divided into five groups (n = 5): control (0.9% physiological solution; i.p.), PTZ (PTZ 150mgkg-1; i.p.), PTZ LEO 5.00%, PTZ LEO 10.0%, and BDZ-PTZ (BDZ: diazepam 10mgkg-1; i.p.). In addition to the electroencephalography (EEG), the lipid peroxidation (TBARS) was quantified in the brain, along with the characterization of behavioral responses. Fish receiving PTZ showed intense action potential bursts (APB), which overlapped with a hyperactive behavior. In PTZ LEO 5.00% and 10.0% groups, convulsive behavior was significantly reduced compared to the PTZ group. Fish fed 5.00% or 10.0% LEO and exposed to PTZ showed less excitability and lower mean amplitude in tracings. The inclusion of 10.0% LEO in the diet prevented the increase in mean amplitude of the EEG waves by 80%, without significant differences to the quantified mean amplitude of the BDZ-PTZ group. TBARS concentration was reduced by 60% in the brain of fish fed 10.0% LEO-enriched diets relative to the PTZ-administered group. The results of this study demonstrated the anticonvulsant and protective roles of LEO to the brain, and the dietary inclusion of LEO seems to be promising for the formulation of functional diets. Results of this study may boost the interest on the anti-seizurogenic properties of Euterpe oleracea, including the development of new approaches for the prevention of seizures in humans and animals with low epileptic threshold.

Effect of multi‐species probiotic administration in Colossoma macropomum juvenile rearing: supplementation and bioremediation

Brazil major probiotics and bioremediators have proven their effectiveness in the cultivation of exotic species. The aim of the study was to evaluate the effects of a commercial multi-species probiotic suitable for shrimp and fish in the feed and as biocontrol in tambaqui rearing through zootechnical performance, water quality, clinical and laboratory alterations and innate immunity evaluations. Colossoma macropomum juveniles were used, distributed: Control (C)—without any probiotic addition; Probiotics added to water (G2)—.004 g/L of probiotics added to each experimental unit; Probiotics in feed (G3)—5 g/kg of probiotics added to the feed. The use of probiotics during the tambaqui breeding phase was proven safe. However, the use of multi-species did not result in any complementary benefit when added to the water or to the feed for 60 consecutive days regarding zootechnical performance, water quality and tambaqui health under the applied experimental conditions. The findings demonstrate the need for further in vitro and in vivo tests regarding microorganism screening and protocols analyses for each culture species, since several factors influence the effects of the administration of probiotics on aquaculture production and health.

Effects of stocking density on survival, growth and stress resistance of juvenile tambaqui (Colossoma macropomum) reared in a recirculating aquaculture system (RAS)

The effects of different stocking densities (StDs) on growth and stress resistance rate (Rs) to air exposure (to evaluate the health condition of fish) of juvenile Colossoma macropomum in a recirculating aquaculture system (RAS) were investigated. A total of 1064 juveniles (0.35 ± 0.10 g) were stocked in 0.5 (D0.5), 1 (D1), 3 (D3), and 5 animals/L (D5) in four different RASs of four circular tanks (28 L) each, and fed at 10% biomass/day. Growth and survival were assessed at 15, 30, 45 and 60 days. After 60 days, a 75-min air exposure test was conducted for each StD treatment and Rs determined. Regression analyses were performed for growth parameters. At 15 days, weight (W), weight gain (WG), daily weight gain (DWG), feed intake (FI), feed conversion rate (FCR), and specific growth rate (SGR) were highest for D3. At 30 days, FI was highest at the StD values estimated through the derivation of the equation of 3.55 animals/L. At 45 days, WG, DWG, and SGR decreased with increasing StD. At 60 days, W was inversely proportional to StD. Biomass was directly related to StD at the end of all periods. Air exposure stress test found that after 48 h, 72 h, and 96 h, Rs values for D3 and D5 were highest and for D0.5 lowest. Stocking densities of between 3 and 4 animals/L are recommended for the first 30 days, while higher StDs affected weight between 30 and 60 days. Animals at StDs between 3 and 5 animals/L are more resistant.

Growth performance and physiological parameters of Colossoma macropomum in a recirculating aquaculture system (RAS): Importance of stocking density and classification

Tambaqui (Colossoma macropomum) is the main freshwater species produced in South American aquaculture and is also produced in several Asian countries. The objective of the present study was to evaluate the growth and physiology of juvenile Colossoma macropomum submitted to different stocking densities and classified by size in a recirculating aquaculture system (RAS) to maximize the production and enable the fish rearing in colder regions. In Phase I, juveniles (34.88 ± 0.60 g) were stocked at densities of D0.5 = 0.5, D1.0 = 1.0 and D1.6 = 1.6 kg/m3 for 53 days, and in Phase II, juveniles (150.61 ± 0.58 g) were stocked at densities of D1.5 = 1.5, D3.0 = 3.0 and D4.5 = 4.5 kg/m3 for 60 days. In Phase III, the animals were classified according to size as S = 300–400 g; M = 400–500 g and L ≥500 g for 60 days with an initial biomass of 3.9 kg/m3 for each class. After the first 30 days of Phase I, final weight (FW) and daily weight gain (DWG) were highest for D0.5, but feed conversion rate (FCR) was lowest. Daily feed intake (DC) was the lowest for D1.6 and the highest for D0.5. At 53 days, FW, DC and DWG were highest for D0.5 and lowest for D1.6. From day 31 to day 53 there was a decrease in hemoglobin (Hg) and hematocrit (Htc) and an increase in the hepatosomatic index (HSI) for D0.5. After the first 30 days of Phase II, FW, DWG and DC were highest for D1.5. After 60 days, D1.5 had the highest FW and HSI and lowest values for glucose, triglycerides and Htc (P < 0.05). In Phase III, after 30 days FW, DWG and DC were highest for class L (P < 0.05), and FW remained highest for class L after 60 days. The HSI was highest for class S and lowest for class L (P < 0.05) while triglycerides, cholesterol, total proteins and Hg were lowest for classes S and M (P < 0.05). Stocking density must be evaluated according to the size of the individuals and, despite the best performance found for the lowest densities (phases I and II), higher densities produced greater biomass. The classification of animals is an important management strategy to maintain uniformity for commercialization because different densities and sizes of animals can interfere with some hematological and biochemical parameters, which can be used as indicators of animal welfare.

Cultivation of juvenile Colossoma macropomum in different colored tanks in recirculating aquaculture system (RAS): Effects on performance, metabolism and skin pigmentation

This study assessed the effects of different tank colors (white, blue, green and black) on the performance, metabolism and skin pigmentation of Colossoma macropomum cultivated in recirculating aquaculture system (RAS). In Phase 1 of the experiment, 224 juvenile C. macropomum (4.04 ± 0.32 g) were cultivated for a period of 30 days at a density of 0.5 juveniles/L. In Phase 2 of the experiment, the juveniles (34.32 ± 12.14 g) were cultivated within each treatment for another 20 days at a density of 0.25 juveniles/L. Biometrics were performed for all juveniles after 30 and 50 days of cultivation. Blood was also collected after 50 days of cultivation and skin pigmentation analysis and determination of the hepatosomatic index (HIS) and lipid concentration in the liver (HL) were performed. Juveniles grown in white tanks had the highest final weight (FW), total length (TL) and weight gain (WG) among treatments at the end of the both phases. At the end of Phase 2, juveniles grown in white tanks had higher levels of triglycerides (p < 0.05) than juveniles of the other treatments. Juveniles grown in black tanks had darker pigmentation and higher hemoglobin and total plasma protein (p < 0.05) than the other treatments. Tank color was found to affect the performance, pigmentation and metabolism of juvenile C. macropomum cultivated in RAS, with white tanks providing the best environment for cultivation and welfare.

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 ± 0.42mgL-1. Water flow and aeration were reduced for 3days (hypoxia), during which DO was 0.92 ± 0.37mgL-1. Water flow and aeration were then reestablished with DO remaining similar to basal. The treatments were as follows: normoxia (basal); 24h after initiating hypoxia (24H); 72h after initiating hypoxia (72H); 24h after reestablishing normoxia (24R); 48h 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.

Sedative and anesthetic potential of the essential oil and hydrolate from the fruit of Protium heptaphyllum and their isolated compounds in Colossoma macropomum juveniles

This study aimed to evaluate the sedative and anesthetic potential of the essential oil (PHEO) and hydrolate (PHH) from the fruit of Protium heptaphyllum and the isolated compounds (IC) of PHEO in tambaqui (Colossoma macropomum) juveniles. Fish were placed in aquaria with different concentrations of PHEO, PHH or IC (sabinene, terpinen-04-ol, γ-terpinene and α-pinene) to evaluate sedative and anesthetic efficacy. In another experiment, fish were transported for 22 h with 10% anesthetic concentrations added to the water of transport. No similarities regarding the major compounds of PHEO and PHH were observed. No mortality was observed during the experiments, and PHH did not show any sedative or anesthetic effect. PHEO induced sedation at 250 mg L−1 and deep anesthesia at 500, 750 and 1000 mg L−1. The recovery time increased with increasing concentration of PHEO. There was a significant difference in the time to induce deep anesthesia between PHEO and IC. Water conductivity and mucous cell density were lower in the transport with 50 mg L−1 PHEO. Tambaqui transported with 50 mg L−1 PHEO and 11.6, 17.4, and 23.2 mg L−1 terpinen-04-ol presented lower net whole body K+ and Cl− effluxes. PHEO is an alternative as sedative and anesthetic for tambaqui juveniles, and the concentration of 500 mg L−1 was the best for deep anesthesia. The use of 50 mg L−1 PHEO was effective for the transport of this species because it reduced net K+ and Cl− effluxes and did not stimulate proliferation mucous cells.

The use of Myrcia sylvatica hydrolate (G.MEY.) DC. (Myrtaceae) as a sedative under simulated conditions of transport of juvenile tambaqui (Colossoma macropomum)

ABSTRACT The objective of this work was to evaluate the use of Myrcia sylvatica Hydrolate (MSH) as a sedative under conditions of simulated transport of Colossoma macropomum juveniles. Simulated a 17 h transport of the load densities 30, 60, and 90 fish/L, with 2.5%, 5%, and 7.5% MSH and water-only control (W.C.). There was no significant difference in survival, temperature, hardness, and total and non-ionized ammonia between treatments and densities. The pH decreased as MSH concentration increased. Dissolved oxygen was lower and CO2 was higher in the end transport in relation initial. Alkalinity and total dissolved solids increased significantly as a function of density. We found lower levels of conductivity and ion flux (sodium, potassium, and Chloride) and a lower number of neutral and acidic gill mucous cells for 5% MSH at the highest bulk density. Therefore, suggest that 5% MSH may be an alternative sedative for the transport of tambaqui juveniles.

Propofol and essential oil of Nepeta cataria induce anaesthesia and marked myorelaxation in tambaqui Colossoma macropomum: Implications on cardiorespiratory responses

This study aimed at characterizing the modulation of skeletal muscle contraction and cardiorespiratory response of tambaqui, Colossoma macropomum submitted to baths using anaesthetic concentrations (capable of inducing fast, i.e. < 5 min, and full body immobilization) of propofol (PRP) and essential oil of Nepeta cataria (EON). For the evaluation of electromyography, electrocardiographic data, and opercular beat intensity (OBI) and rate (OBR), fish (5.6 ± 1.8 g, 8.0 ± 0.3 cm, total length) were assigned to the following groups: a) control (basal recording), b) ethanol-exposed fish (vehicle control), c) fish submitted to induction with EON at 175 μL L−1 and subsequent recovery, and d) fish submitted to induction with PRP at 4 μL L−1 and subsequent recovery. Eight fish (n = 8) per group were used. Both products induced full body immobilization and suppressed (99.9%) dorsal muscle contraction power, determining a general anaesthesia-like state. During exposure to either anaesthetic, cardiac function was transiently affected, with decreased heart rates (42–43%) and a mild arrhythmia in PRP recovering fish. Moreover, ventilatory capacity was reduced with this drug (85.3% and 59.6% decrease in OBI and OBR, respectively), yet without mortality. On the other hand, EON did not alter ECG tracings, allowing for the maintenance of normal ventilation intensity during exposure, albeit a slight increment in OBR occurred during deep anaesthesia. This study confirms propofol anaesthesia in fish and presents N. cataria essential oil as a novel and safe natural anaesthetic for juvenile Colossoma macropomum and potentially for other teleost species.

Morphological and histochemical changes associated with massive infection by Neoechinorhynchus buttnerae (Acanthocephala: Neoechinorhynchidae) in the farmed freshwater fish Colossoma macropomum Cuvier, 1818 from the Amazon State, Brazil.

The study describes the morphological changes associated with parasitism by the intestinal acanthocephalan Neoechinorhynchus buttnerae in tambaqui juveniles Colossoma macropomum farmed in an excavated nursery, in Manaus (Amazon) in September 2013. After fish biometrics, analysis of macroscopic changes in morphology and counting of parasites, bowel fragments were fixed and submitted to histological and histochemical processing. All fish analyzed had acanthocephalans in the intestine; intestinal loops were milky white in color, with the presence of nodules with heavy parasitism. The changes in tissues that form the intestine varied according to the arrangement of the parasites: either free in the intestinal lumen or fixed by the proboscis on the organ wall. In the first case, the changes found were flaking, abrasion, compression, hypertrophy of goblet cells and disappearance of the villi on the mucosa, leukocytic cell infiltration in the submucosa, and muscle layer thickening. In the second case, in addition to these, other changes were observed as metaplasia in muscle tissue with its replacement by a loose connective tissue with severe leukocytic infiltration, edema in blood vessels, and necrotic foci. The histochemical analysis revealed that positive Alcian Blue mucosal cells (pH2.5) were more expressive in parasitized intestines than in intestines not parasitized by N. buttnerae.

Efficacy of Benzocaine as an Anesthetic in Juvenile Tambaqui Colossoma macropomum

Abstract.— The present study investigated the use of benzocaine as an anesthetic for juvenile Colossoma macropomum (tambaqui). In the first experiment, fish were exposed to various doses of benzocaine for 10 min at 24 C. The second experiment examined the effects of duration of exposure to 100 mg/L of benzocaine. In the third experiment, fish were exposed to 100 mg/L at temperatures of 24, 27, and 30 C. Benzocaine concentrations of 100–150 mg/L were considered ideal for quickly inducing total immobilization and fast recovery. Fish exposed to 350 mg/L benzocaine exhibited 30% mortality. No changes in hemat‐ocrit were recorded in fish exposed to different concentrations of benzocaine. Plasma glucose increased significantly when fish were exposed to benzocaine concentrations greater than 200 mg/L. Recovery time after a 30‐min exposure to 100 mg/L benzocaine was significantly greater than after an exposure for 10 and 20 min. No mortality was observed 96 h after exposure to 100 mg/L benzocaine for 10, 20, and 30 min. Dosages in the 100–150 mg/L range were effective for periods of up to 20 min of anesthesia. There was no effect of temperature on the time required for fish to lose equilibrium. However, recovery was significantly faster for fish anesthetized at 30 C. Benzocaine is an effective anesthetic agent for tambaqui juveniles, providing rapid immobilization and rapid recovery. Benzocaine is also less expensive than other available anesthetic compounds.