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The use of anesthetic agents in the management of fish in fish farming or ornamental fish breeding aims to minimize stress and promote animal welfare. Therefore, this study aims to investigate behavioral, electrocardiographic, and ventilatory characteristics of tambaquis exposed to anesthetic baths with etomidate. The study was conducted with juvenile tambaquis (27.38 ± 3.5g) n = 99, at etomidate concentrations of 2-4 mg.L -1, analyzing induction and anesthetic recovery behavior (experiment I), electrocardiogram (experiment II), and opercular movement (experiment III). Fish exposed to high concentrations of etomidate reached the stage of general anesthesia faster, however, the recovery time was longer, characterizing a dose-dependent relationship. Cardiorespiratory analyzes demonstrated a reduction in heart rate (69.19%) and respiratory rate (40.70%) depending on the concentration of etomidate used during anesthetic induction. During the recovery period, there was cardiorespiratory reversibility to normality. Therefore, etomidate proved to be safe as an anesthetic agent for this species at concentrations of 2 to 3 mg.L -1 for short-term anesthesia, but at higher doses the animals showed slow reversibility of anesthesia in a gradual manner and without excitability. The hemodynamic effect due to the rapid decrease in heart rate includes a negative factor of using higher concentrations of etomidate for Colossome macropomum anesthesia.

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The present study investigated the best photoperiod for culturing pacu (Piaractus mesopotamicus) in recirculation aquaculture systems (RAS) based on its growth performance and hematological and oxidative stress responses. Juveniles (∼ 5 g) were subjected to five treatments (in triplicate): 24 L (light):0D (dark), 15 L: 09D, 12 L:12D, 9 L:15D, and 0 L:24D for 45 days. A total of 225 pacu individuals were randomly distributed among 15 tanks of 210 L (n = 15 per tank). Zootechnical, hematological (glucose, lactate, hematocrit, and hemoglobin), and antioxidant and oxidative stress parameters (glutathione S-transferase (GST), total antioxidant capacity against peroxyl radicals (ACAP), and lipid peroxidation (LPO) were analyzed. The zootechnical parameters (e.g., weight gain, Fulton's condition factor, and specific growth rate) were better and worse with 9 L:15D and 24 L:0D photoperiods, respectively. The hepatosomatic index was higher and lower in the 0 L:24D and 9 L:15D photoperiods. Blood lactate levels and antioxidant and oxidative stress responses were increased in the longest photoperiods (15 L:9D and 24 L:0D). In contrast, the treatments that showed lower oxidative damage (liver, gills, brain, and muscle) were 9 L:15D and 12 L:12D. In conclusion, manipulating artificial light is one way to improve fish growth and health, where the best photoperiod for pacu farming in RAS is 9 L:15D.

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This study evaluated the growth and physiological response of proactive and reactive Colossoma macropomum juveniles in a recirculating aquaculture system (RAS). In Phase 1 of the experiment (50 days of cultivation), juveniles, weighing 2.16 ± 0.52 g, were stocked in 12 28-L tanks to test the following treatments: proactive (PT), reactive (RT) and mixed (MT) composed of reactive (MRT) and proactive (MPT) animals. In Phase 2 of the experiment (40 days of cultivation), the animals were transferred to 175-L tanks with the same treatments as Phase 1. The animals were fed twice a day with commercial diet during both phases. After Phase 1, MPT animals showed higher growth than MRT animals (P < 0.05), and higher weight gain and daily weight than PT animals (P < 0.05). After Phase 2, PT animals showed higher weight gain and daily weight gain than RT and MT animals (P < 0.05), as did MPT animals compared to PT animals. Performance for RT animals was superior (P < 0.05) to that of MRT animals. Glucose (P < 0.04) and cholesterol (P < 0.01) were higher for RT animals compared to PT animals. Cholesterol was higher for MPT animals compared to MRT animals (P < 0.01), while plasma protein was lower (P < 0.001). Glucose (P < 0.001) and cholesterol (P < 0.01) were higher for MPT animals compared to PT animals and for MRT animals compared to RT animals (glucose P < 0.02, cholesterol P < 0.01). After 90 days of cultivation, proactive animals cultivated separately presented better performance. When cultivated together, reactive animals experienced a decrease in performance and both stress coping styles showed more signs of stress.

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The purpose of this study was to characterize the activity of essential oils from Nepeta Cataria (EON) at concentrations of 125 µ L  L-1, 150 µ L  L-1, 175 µ L  L-1, and 200 µ L  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 5 min, in order to obtain a window for safe use during anesthesia. The fish (23.38 ± 3.5 g) were assigned to the following experiments: experiment 1 (latency to loss and recovery of the posture reflex): (a) 125 µ L  L-1, (b) 150 µ L  L-1, (c) 175 µ L  L-1, and (d) 200 µ L  L-1 (n = 9) per group. Experiment 2 (electrocardiographic and heartbeat recordings): (a) control group; (b) vehicle control group (2 ml of alcohol per liter of water), (c) 125 µ L  L-1, (d) 150 µ L  L-1, (e) 175 µ L  L-1, and (f) 200 µ L  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 µ L  L-1 for juvenile Colossoma macropomum.

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Why do some clades diversify more than others? And what are the roles of abiotic and biotic factors in driving such unequal diversification? To explore this, Burns et al. (2024) investigate variation in body morphology in a group of freshwater fish, Characiformes, across South America and Africa. They find that habitat features such as slope, elevation, and flow rates have played a major role in the diversification of morphological variation in the Characiformes. The Neotropical lineages residing in significantly more diverse slope and elevation habitats were found to display more body shape diversity than African lineages. The authors also report that competition might have limited the morphological variation in African Characiformes compared to the Neotropical lineages. This study highlights the importance of exploring both abiotic and biotic factors when examining diversification.

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A new miniature species of Characidium is described from the midde rio Guaporé, rio Madeira basin, Rondônia, Brazil. The new species can be readily distinguished from all congeners by the sexual dichromatism, with females having narrow dark bars on body absent in males, and by the presence, in both sexes, of a black midventral dashed line extending from area between contralateral pectoral fins to at least the anal-fin origin. It can also be diagnosed from congeners by having strongly tricuspid teeth, with well developed and similar sized cusps in the premaxilla and outer series of dentary, and short lateral line with 6­8 perforated scales. Morphological novelties to Characidium observed in the new species include a rounded process on the first pleural rib near the vertebra, three or four haemal spines of the first caudal vertebrae distinctly elongate, neural and haemal spines of the antepenultimate vertebra not reaching origins of dorsal and ventral procurrent rays nor the origin of the caudal-fin rays.(AU)

Uma nova espécie miniatura de Characidium é descrita do médio rio Guaporé, bacia do rio Madeira, Rondônia, Brasil. A nova espécie pode ser facilmente distinguida de todas as congêneres pelo dicromatismo sexual, com barras escuras estreitas no corpo das fêmeas ausentes nos machos, e por ter uma linha preta mediana ventral tracejada em ambos os sexos, que se estende da área entre as bases das nadadeiras peitorais até pelo menos a origem da nadadeira anal. A espécie também pode ser diagnosticada das congêneres por ter dentes fortemente tricúspides, com cúspides bem desenvolvidas e de tamanho semelhante no pré-maxilar e série externa do dentário, e linha lateral curta com 6­8 escamas perfuradas. Novidades morfológicas para Characidium observadas na nova espécie incluem presença de um processo arredondado na primeira costela pleural próximo à vértebra, três ou quatro espinhos hemais das primeiras vértebras caudais distintamente alongados, espinhos neurais e hemais da antepenúltima vértebra não atingindo as origens dos raios procorrentes dorsal e ventral, nem a origem dos raios da nadadeira caudal.(AU)

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The goal of this study was to determine the essential fatty acids of the total lipids of the fillet, head and orbital cavity tissue from farmed tambaqui (Colossoma macropomum) fish from a Brazilian Amazon area. The tambaqui were acquired from different fish farms in the Roraima state, located at Western Brazilian Amazon. The meat, the head and the fatty tissue from orbital cavity were dissected for lipid extraction and analysis of fatty acids by gas chromatography. The fatty acids were quantified in mg g-1of total lipids using C23:0 as an internal standard. The nutritional quality of the lipids was determined by using the atherogenicity and thrombogenicity indices, and also by the ratio between hypocholesterolemic / hypercholesterolemic fatty acids. The orbital cavity tissue had the higher concentration amount of linoleic and α-linolenic acid, whereas the fillet had higher docosahexaenoic acid (DHA). The eicosapentaenoic acid (EPA) concentration was: 1.28, 0.97, 1.71 mg g-1of total lipids, in the filet, in head, and in orbital cavity tissue,respectively. All essential fatty acids were detected in the three parts analyzed. The nutritional quality of the total lipids from the head and from the orbital cavity tissue was similar to the fillet.(AU)

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The aimed of this study was to evaluate the mineral composition in commercial cuts of tambaqui (Colossoma macropomum) and pirarucu (Arapaima gigas). Were compared to the minimum values of daily consumption of minerals recommended by the World Health Organization (WHO). The experimental design was completely randomized, with processing performed in triplicate. Data were submitted to ANOVA. If ANOVA appeared statistically significant (α=0.05), the means were compared by Tukey's Test. There was a difference (p<0.05) between commercial cuts of the tambaqui for different minerals. Tambaqui ribs and band presented the highest values of total iron 1.08 ± 0.12 mg/100g compared to other commercial cuts. The mineral elements Na+, K+, Ca2+ and Mg2+ expressed the highest values for the tambaqui steak, 301.00 ± 80.58, 457.00 ± 129.33, 36.00 ± 4.36 and 46.90 ± 4.68 mg/100g, respectively. There was a difference (p<0.05) between commercial cuts of the pirarucu for different minerals. The mineral elements Total Iron, Na+, K+ and Ca2+ expressed the highest values for pirarucu loin, 0.80 ± 0.07, 406.00 ± 117.50, 529.30 ± 130.58 and 32.00 ± 5.12 mg/100g, respectively. However, Mg2+ expressed a higher value for pirarucu tail fillet 37.10 ± 4.99 mg/100g. The tambaqui steak and pirarucu loin were the cuts that best met the minimum needs for mineral supply.(AU)

O objetivo do estudo foi avaliar a composição mineral em cortes comerciais de tambaqui (Colossoma macropomum) e pirarucu (Arapaima gigas). Foram comparados aos valores mínimos de consumo diário de minerais recomendados pela Organização Mundial da Saúde (OMS). O delineamento experimental foi inteiramente casualizado, com processamento realizado em triplicata. Os dados foram submetidos à ANOVA. Caso a ANOVA parecesse estatisticamente significativa (α=0,05), as médias foram comparadas pelo Teste de Tukey. Houve diferença (p<0,05) entre cortes comerciais de tambaqui para os diferentes minerais. A costela e a banda de tambaqui apresentaram os maiores valores de ferro total 1,08 ± 0,12 mg/100g em relação aos demais cortes comerciais. Os elementos minerais Na+, K+, Ca2+ e Mg2+ expressaram os maiores valores para posta de tambaqui, 301,00 ± 80,58, 457,00 ± 129,33, 36,00 ± 4,36 e 46,90 ± 4,68 mg/100g, respectivamente. Houve diferença (p<0,05) entre cortes comerciais de pirarucu para diferentes minerais. Os elementos minerais Ferro Total, Na+, K+ e Ca2+ expressaram os maiores valores para o lombo de pirarucu, 0,80 ± 0,07, 406,00 ± 117,50, 529,30 ± 130,58 e 32,00 ± 5,12 mg/100g, respectivamente. No entanto, o Mg2+ expressou maior valor para filé da cauda de pirarucu 37,10 ± 4,99 mg/100g. Em destaque, a posta de tambaqui e o lombo de pirarucu foram os cortes que mais atenderam às necessidades mínimas de suprimento mineral. (AU)

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Landscape changes and hydrologic alterations associated with dam construction have greatly hindered reproductive success and the recruitment of migratory species. However, little is known about the flow conditions that are necessary for the reproductive success of migrators. We aimed to analyze one of the important migrants of the Paraná River, the curimba, Prochilodus lineatus(Valenciennes, 1836), to determine the minimum velocities necessary for egg drift and analyze the behavior of larvae at different flow velocities. Thus, we experimentally evaluated the behavior of eggs and larvae released in a drift simulator channel (DSC) under four flow velocities. Additionally, we investigate the swimming ability of larvae in relation to certainmorphometric measures of their bodies. We also performed morphometry and calculations of larval body and fin proportions to determine which structures influence swimming ability. The results indicated that environments with flow velocities greater than 0.081 m s-1were favorable for egg drift and increased the chances of successful transportof eggs to downstream areas. We also observed that soon after hatching, the larvae positioned themselves against the flow, indicating that they had a perception of position and orientation. The larvae were able to maintain and disperse against the flow within the channel 32h after hatching at all velocities, which was mainly due to the development of pectoral and caudal fins that were actively involved in the swimming process, as well as the reduction in the dimensions of the yolk sac, which reduced drag.(AU)

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In the present study, two approaches were followed to evaluate the metabolic responses of tambaqui (Colossoma macropomum), a frugivorous species, to intraperitoneal (IP) administration of glucose (GLU) and fructose (FRU) in fed (FED) and 10-day fasted (FAST) fish. Glucose and fructose tolerance tests were performed to assess the carbohydrate utilization and complementary NMR-metabolomics analyses were done to elucidate the impacts of sugar mobilization on the metabolic profile of plasma, liver and muscle. Blood was sampled from FED groups at 0, 3, 6 and 24 h; and at 0 and 24 h from FAST groups. Significant differences were observed in the hyperglycaemic peak between sugars at 3 h (GLU - 13.7 ± 2.0 mM vs. FRU - 8.7 ± 1.1 mM; saline 6.3 ± 0.6 mM) and on the return to normoglycaemia (GLU - 8.5 ± 2.2 mM vs. FRU - 5.2 ± 0.9 mM; saline 4.9 ± 0.6 mM) 6 h after IP on the FRU fish. The NMR-metabolomics approach allowed to conclude that tambaqui seems to be more responsive to the feeding regime (FED vs. FAST) than to the injected sugar (FRU vs. GLU). From the studied tissues, plasma showed no significant variations between feeding regimes at 24 h after IP, while muscle and liver revealed some variations on the final metabolome profile between FED and FAST groups. The metabolome variations between feeding regimes are indicative of changes on the amino acid utilization. Fish from FAST group seem to utilize amino acids as energy source rather than for protein synthesis and muscle growth. Variations on glucose concentration in muscle can also indicate different utilization of the sugars depending on the feeding regime.

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