Exploring the mitochondrial genomes and phylogenetic relationships of trans-Andean Bryconidae species (Actinopterygii: Ostariophysi: Characiformes).

Comparative mitogenomics and its evolutionary relationships within Bryconidae remains largely unexplored. To bridge this gap, this study assembled 15 mitogenomes from 11 Bryconidae species, including five newly sequenced. Salminus mitogenomes, exceeding 17,700 bp, exhibited the largest size, contrasting with a median size of 16,848 bp in the remaining species (Brycon and Chilobrycon). These mitogenomes encode 37 typical mitochondrial genes, including 13 protein-coding, 2 ribosomal RNA, and 22 transfer RNA genes, and exhibit the conserved gene arrangement found in most fish species. Phylogenetic relationships, based on the maximum-likelihood method, revealed that the trans-Andean species (found in northwestern South America) clustered into two main sister clades. One clade comprised the trans-Andean species from the Pacific slope, Brycon chagrensis and Chilobrycon deuterodon. The other clade grouped the trans-Andean species from the Magdalena-Cauca Basin Brycon moorei and Salminus affinis, with their respective cis-Andean congeners (found in eastern South America), with Brycon rubricauda as its sister clade. Since the current members of Brycon are split in three separated lineages, the systematic classification of Bryconidae requires further examination. This study provides novel insights into mitogenome characteristics and evolutionary pathways within Bryconidae, standing as crucial information for prospective phylogenetic and taxonomic studies, molecular ecology, and provides a valuable resource for environmental DNA applications.

Etomidate as an anesthetic in Colossoma macropomum: Behavioral and electrophysiological data complement each other as a tool to assess anesthetic safety.

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.

Effects of the replacement corn meal by whole mango meal on tambaqui (Colossoma macropomum) diet: Digestibility, growth performance, biochemical, and hematological responses.

This study evaluated the digestibility of whole mango (Mangifera indica) meal (WMM) and determined the growth performance, intestinal enzyme activity, and metabolic and hematologic responses of tambaqui (Colossoma macropomum) juveniles fed diets containing different proportions of corn meal (CM) substitution by WMM. Fish fed with graded levels of WMM (0 (control), 80, 160, 240, and 320 g kg diet-1), replacing part of the dietary CM. The apparent digestibility coefficients of WMM were above 96%. Diets with WMM did not affect growth performance or intestinal enzyme activity. However, they showed a positive linear effect on plasma glucose, amino acids, and albumin levels and a negative linear effect on hepatic aspartate aminotransferase activity and hepatic glycogen, plasma cholesterol, and hemoglobin levels. Increased erythrocyte values and decreased plasma triglyceride levels were verified in fish fed 80 and 160 g WMM kg diet-1. In conclusion, the WMM may be a viable alternative to the tambaqui juveniles' diet, and WMM could replace up to 16% of CM without harming the growth and health of tambaqui juveniles.

Influence of urbanization on size and biomass of a small-sized characid fish (Diapoma alburnum) in a subtropical river basin of southern Brazil.

The coastal lagoons of the Tramandaí River basin are dynamic ecosystems characterized by high biodiversity. They provide important ecosystem services, such as water supply for human consumption, industry, agriculture, animal husbandry, leisure activities, tourism and fishing. Constant increases in the human population and the use and occupation of the land around the lagoons has brought growing demands for their resources, resulting in increased pressure that compromises these ecosystems. Understanding how biological populations respond to these anthropogenic pressures is essential. This study examined whether the degree of urbanization around 23 lagoons in the Tramandaí River basin influences the size and biomass of the characid fish species Diapoma alburnum. Specimens were collected between 2009 and 2012 using standardized drag nets. All specimens were measured for standard length to determine average length (size) per lagoon, while all fish collected per lagoon were weighed together to determine average biomass per lagoon by dividing by the number of specimens. Urbanization around the lagoons was measured using satellite images representing artificial nocturnal light as a proxy for urbanization. Nocturnal light intensity was measured within 1 km, 3 km, and 5 km buffers around each lagoon. The resulting urbanization index ranged 6 - 44% for the 5 km buffer, from 3 - 55% for the 3 km buffer and 1 - 65% for the 1 km buffer. Regression analyses showed a significant positive relationship with increasing urbanization around lagoons for D. alburnum average biomass in the 3 km and 5 km buffers and for D. alburnum average length in the 3 km buffer. Although urbanization around the lagoons is not fully established, the results indicate its impact on the size and biomass of D. alburnum.

Albendazole is effective in controlling monogeneans in Colossoma macropomum (Serrasalmidae): therapeutic baths and their physiological and histopathological effects.

In aquaculture worldwide, most of the chemotherapeutic agents used for disease control and treatment are unregulated chemical products derived from agriculture. In this study, we investigated the efficacy of therapeutic baths with albendazole against the monogeneans Anacanthorus spathulatus, Notozothecium janauachensis and Mymarothecium boegeri, which infest the gills of Colossoma macropomum, and the hematological and histopathological effects of this anthelmintic agent on these fish. Albendazole at a concentration of 500 mg/L was used in three baths of 24 hours each, with intervals of 24 hours between these baths. Three replications of this treatment were used, and the control group consisted of water from the cultivation tank. Afterwards, hematological, histopathological and parasitological analyses were conducted. We found that the therapeutic baths with albendazole at 500 mg/L presented high efficacy (94.9%) against monogeneans de C. macropomum and caused few physiological or histopathological alterations. Therefore, baths with albendazole at 500 mg/L, as used in this strategy, can be recommended for controlling and treating infections by monogeneans in C. macropomum.

Can photoperiod improve growth performance and antioxidant responses of pacu (Piaractus mesopotamicus) reared in recirculation aquaculture systems?

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.

Hematological and anthelminthic responses of tambaqui (Colossoma macropomum) supplemented with Artrhospira platensis and Chlorella vulgaris.

The present study evaluated the hematological, antiparasitic and growth responses in tambaqui (Colossoma macropomum) fed with diets supplemented with the microalgae Arthrospira platensis and Chlorella vulgaris (0%; 10% A. platensis; 10% C. vulgaris; and 5% A. platensis+5% C. vulgaris). Tambaqui (n=60, 62.57 ± 8.76 g) were fed for 20 days with experimental diets. Blood samples collection was done to determine hematological parameters, and gills were removed to identify and count monogenetic parasites. Supplementation with A. platensis 10% reduced red blood cells count, in consequence mean corpuscular volume and mean hemoglobin concentration increased. Total leukocyte, monocyte, eosinophil, and basophil counts reduced with the use of A. platensis. Higher monocytes, eosinophil, and basophil numbers in tambaqui fed with diet supplemented with 10% C. vulgaris were observed and may have been due to the presence of immunostimulants in this microalga composition. Reduction on total cholesterol in tambaqui that received both microalgae (A. platensis 5%+C. vulgaris 5%) may indicate that combined supplementation presented greater benefits to the health for C. macropomum than separately. Both microalgae were efficient against monogenetic parasites of tambaqui. Thus, the dietary use of the microalgae A. platensis and C. vulgaris provided immunostimulant and antiparasitic efficacy in C. macropomum.

Effects of trichlorfon on ecotoxicological biomarkers in farmed Colossoma macropomum (tambaqui).

Producers of fish have been looking for viable alternatives for the management of Colossoma macropomum (tambaqui) in confinement systems in order to avoid the harm and subsequent losses caused by parasitic diseases. One alternative used by farmers is pesticides, such as trichlorfon, which has a genotoxic effect. Thus, this study aimed to evaluate the changes in gene expression due to the side effects of trichlorfon in tambaqui. Two treatments were used based on LC50-96h of 0.870 mg/L using 30% and 50% trichlorfon with exposure periods of 48, 72 and 96 h. For differential expression of the genes in the liver, real-time PCR was performed for the AChE, GST, CYP2J6, CYP2C8, 18S and GAPDH genes. After 96 h of exposure to trichlorfon, an alteration in the gene expression profile of the antioxidant defense system (GST) of the tambaqui was observed. It was also observed that this organophosphate did not affect the expression of genes related to the isoenzymes that are responsible for the biotransformation of xenobiotics in phase I (2J6 and 2C8) and cholinesterase AChE. It was concluded that the reduction in gene expression of GST suggests a decrease in metabolization capacity in phase II.

Growth and physiological response of proactive and reactive juvenile "tambaqui" (Colossoma macropomum) in a recirculating aquaculture system.

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.

Parasites of Astyanax lacustris (Pisces, Characiformes) from Brazilian streams.

Astyanax lacustris is a small characid fish widely distributed in Brazil, with fast-growing and omnivorous feeding habits. Although the species presents economic and ecological importance, little is known about its parasitological fauna in stream environments. This study aimed to characterize the parasitic fauna of A. lacustris in two streams in the state of Paraná, Brazil. Fifty-two specimens of A. lacustris were collected, 22 from the Carolina stream (Lower Iguaçu River) and 30 from the Carreira stream (Upper Paraná River), in July and September 2018. In both streams, there was a low richness of parasites, and the structure of the parasitic community was predominantly composed of monogeneans. These findings may be associated with the gregarious behavior of the host species. Moreover, the low occurrence of endohelminths, may be associated with the fact that in streams, the energy flow is low, and depends directly on the input of allochthonous matter, which favors the formation of shelters for the establishment of macroinvertebrates, which represent important sources of food for the ichthyofauna, and may act as intermediate and paratenic hosts of parasites. These environments require further studies to support conservation measures aimed at maintaining the balance of ecological relationships in these preserved ecosystems.

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.

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 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.

Histopathology and changes in the expression of metallothioneins, heat shock proteins and inducible nitric oxide synthase in Prochilodus costatus from a neotropical river contaminated by heavy metals.

The most recent dam rupture in Brazil released tons of mining tailings into the upper course of the Paraopeba River, affecting this river in an unprecedented way. The present study aimed to evaluate the influence of heavy metals on Prochilodus costatus, an important commercial species in Brazil, four years after the dam colapse. To this end, biomarkers of heavy metals, oxidative stress, and environmental stress were analyzed, and histological analyses of target organs were performed. The results demonstrated critical contamination of fish from the Paraopeba River. Increased expression of Metallothioneins - MTs, Heat Shock Protein - HSP70, and inducible nitric oxide synthase - iNOS, as well as greater rates of histological changes in the liver, spleen, and gonads, were observed in P. costatus. These findings demonstrate that, despite past contamination, the metals present in mining tailings have significantly increased the contamination of the Paraopeba River basin.

Chromosomal mapping of repetitive DNA and retroelement sequences and its implications for the chromosomal evolution process in Ctenoluciidae (Characiformes).

Ctenoluciidae is a Neotropical freshwater fish family composed of two genera, Ctenolucius (C. beani and C. hujeta) and Boulengerella (B. cuvieri, B. lateristriga, B. lucius, B. maculata, and B. xyrekes), which present diploid number conservation of 36 chromosomes and a strong association of telomeric sequences with ribosomal DNAs. In the present study, we performed chromosomal mapping of microsatellites and transposable elements (TEs) in Boulengerella species and Ctenolucius hujeta. We aim to understand how those sequences are distributed in these organisms' genomes and their influence on the chromosomal evolution of the group. Our results indicate that repetitive sequences may had an active role in the karyotypic diversification of this family, especially in the formation of chromosomal hotspots that are traceable in the diversification processes of Ctenoluciidae karyotypes. We demonstrate that (GATA)n sequences also accumulate in the secondary constriction formed by the 18 S rDNA site, which shows consistent size heteromorphism between males and females in all Boulengerella species, suggesting an initial process of sex chromosome differentiation.

Integrative Taxonomy of Urocleidoides spp. (Monogenoidea, Dactylogyridae) Parasites of Pseudanos trimaculatus (Characiformes: Anostomidae) from Eastern Amazon, Brazil.

Two new species of Urocleidoides are described from the gills of Pseudanos trimaculatus (Characiformes: Anostomidae) from the coastal drainages of the Eastern Amazon, Brazil. Urocleidoides itabocaensis n. sp. is characterized by having a sclerotized, tubular, sigmoid male copulatory organ (MCO), a circular sclerotized tandem brim associated with the base of the MCO; an accessory piece articulated with the MCO, a V-shaped, divided into two subunits, distal subunit spoon-shaped; and a vaginal pore dextroventral with opening marginal. Urocleidoides omphalocleithrum n. sp. is characterized by presenting a C-shaped or sigmoid MCO; an accessory piece articulated with the MCO, L-shaped, divided into two subunits, distal subunit gutter-shaped; a vaginal pore dextroventral with opening marginal; and a ventral bar broadly V-shaped, with anteromedial projection. Molecular phylogenetic analysis based on partial 28S rDNA and COI mtDNA genes indicate that U. itabocaensis n. sp. and U. omphalocleithrum n. sp. are closely related and appear as a sister group to other Urocleidoides species (U. paradoxus, U. digitabulum and U. sinus) parasitizing anostomid fishes. This study represents the first record of monogenoids from the gills of P. trimaculatus for the Eastern Amazon.

Updated distribution and morphological variation of the genus Pseudanos in the Río de la Plata basin (Characiformes: Anostomidae).

Pseudanos is a fish genus with cis-Andean distribution in South America. Pseudanos trimaculatus is originally known from the Amazon and Orinoco basins. Three decades ago, a few specimens collected in the Río de la Plata basin were identified as P. trimaculatus, what remained to be confirmed and understood. The aim of this contribution is to analyze these specimens. Consequently, the morphological variation of P. trimaculatus is discussed and updated. Morphometric and meristic data were taken from the specimens and compared with those of the type and non-type specimens of the species. Multivariate analyses of the size-corrected measurements were used to explore the morphological variation. Size-corrected PCA revealed that the specimens collected in the Río de la Plata basin nested with the remaining specimens, being slightly closer to those from the Guaporé, Napo and Uatumã rivers. Measurements such as caudal peduncle depth, body depth, and body width affected more heavily the first components. Cluster analysis did not show well-defined groups based on the hydrogeographic basins. The studied specimens from the Río de la Plata basin are herein confirmed as conspecific with P. trimaculatus. The species is added to the list of fish species shared between the Amazon and Río de la Plata basins.

Ocimum gratissimum essential oil in the transport water of Brycon hilarii: implications at water quality, blood parameters and residues in tissue and plasma.

Transporting live fish is a common practice in fish farming, and is certainly one of the main problems that affect fish homeostasis. In this scenario, the use of natural additives has shown promise in improving fish resistance to adverse situations. This study aimed to assess the impact of Ocimum gratissimum L. essential oil (OGEO) on water quality, hematological parameters, and residue levels in the plasma, fillet, and liver of juvenile piraputanga (Brycon hilarii) during a two-hour transportation period. The fish were divided into plastic bags (4 L) and exposed to three different OGEO concentrations (10, 20, and 30 mg L-1), while a control group received no OGEO (three repetitions each). After the two-hour transportation, blood samples were collected, as well as portions of the fillet and liver for quantifying essential oil compounds, which were also measured in the plasma. Oxygen levels remained high throughout the transportation period, in all groups, while the pH decreased. Hemoglobin, MCHC, and MCH increased in fish exposed to OGEO concentrations of 20 and 30 mg L-1, compared to the control group. However, lymphocyte counts and the concentrations of essential oil compounds in plasma, fillet, and liver increased with higher OGEO concentrations. The use of 10 mg L-1 OGEO in the two-hour transport water is promising to ensure the survival and well-being of Brycon hilarii juveniles (weighing 16 g), showing to be safe and effective. The residual concentration of eugenol the major compound of OGEO in the fillet remains below the maximum limit of the recommended daily intake.

Exploring hidden diversity: Molecular insights into the Leporinus species of the rivers of the Brazilian states of Maranhão and Piauí.

The present study delved into the world of hidden diversity by examining specimens identified as Leporinus piau from the river basins of the northern Brazilian states of Maranhão and Piauí. Using genetic analyses that combined data from three mitochondrial markers and one nuclear marker, the study identified two well-supported groups, reinforcing the findings of previous publications. The first group, found in samples from the Itapecuru, Mearim, Turiaçu, and Pericumã basins, in Maranhão, appears to represent a relatively ancient diversification and the possibility of concealed cryptic diversity. The second group, comprising specimens from the Parnaíba (Piauí) and Mearim (Maranhão) basins, appears to have resulted from a more recent process of diversification and has a close relationship with Leporinus friderici from the type locality. Our findings not only confirm the existence of a complex scenario of cryptic diversity in the genus Leporinus from the study basins but also underscore the taxonomic inconsistencies within this group of fish. This study offers a comprehensive analysis of the species diversity of the Maranhão and Piauí basins, which are critical regions for the conservation of Amazonian fish, providing valuable insights for the sustainable management and conservation of these fish.

Essential Oil of Piper marginatum (Piperaceae) Against Monogeneans, and Its Hematological and Histopathological Effects on Colossoma macropomum.

PURPOSE: This study investigated the anthelmintic efficacy of therapeutic baths with the essential oil of Piper marginatum Jacq against the monogeneans Anacanthorus spathulatus Kritsky, Thatcher & Kayton, 1979, Notozothecium janauachensis Belmont-Jégu, Domingues & Laterça 2004, Mymarothecium boegeri Cohen & Kohn, 2005 and Linguadactyloides brinkmanni Thatcher & Krytsky, 1983 in Colossoma macropomum Cuvier, 1818, and its hematological and histopathological effects on this fish. METHODS: Short six therapeutic baths with 100 mg/L of the essential oil of P. marginatum and two control groups (water from the cultivation tank and water from the cultivation tank + 70% alcohol) were used for 20 min every two days. RESULTS: The therapeutic baths with 100 mg/L of the essential oil of P. marginatum had efficacy of 42.8% against monogeneans of C. macropomum gills. Toxicity was low for C. macropomum, because there were few physiological and histopathological changes that did not compromise the functioning of the gills of this fish. CONCLUSION: Short therapeutic baths with 100 mg/L of the essential oil of P. marginatum had low efficacy for controlling monogeneans in C. macropomum and thus cannot be recommended.

Efficacy of essential oil from ginger (Zingiber officinale) for anesthesia and transport sedation of pacu (Piaractus mesopotamicus).

This study evaluated the anesthetic and sedative effects of the essential oil of Zingiber officinale (EOZO) on juvenile pacu (Piaractus mesopotamicus). Experiment 1 evaluated concentrations of 0, 50, 100, 200 and 400 mg L-1 EOZO for times of induction and recovery from anesthesia. Furthermore, hematological responses and residual components of EOZO in plasma were determined immediately after anesthesia. Experiment 2 evaluated the effect of 0, 10, 20 and 30 mg L-1 EOZO on water quality, blood variables and residual components of EOZO in plasma and tissues (muscle and liver) immediately after 2 h of transport. Survival was 100%. The three main compounds of EOZO [zingiberene (32.27%), ß-sesquiphellandrene (18.42%) and ß-bisabolene (13.93%)] were observed in animal plasma and tissues (muscle and liver) after anesthesia and transport, demonstrating a direct linear effect among the evaluated concentrations. The concentration of 200 mg L-1 EOZO promoted surgical anesthesia of pacu and prevented an increase in monocyte and neutrophil levels, yet did not alter other hematological parameters. The use of 30 mg L-1 EOZO has a sedative effect on juvenile pacu, thereby reducing oxygen consumption during transport. Furthermore, the use of 30 mg L-1 EOZO in transport water prevented an increase in hemoglobin and hematocrit, with minimal influences on other blood variables.