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The accidental spill of petroleum asphalt cement (PAC) in São Raimundo (SR Harbor, located on the Rio Negro (Manaus, Amazonas, Brazil) was monitored through the analysis of polyciclic aromatic hydrocarbons (PAHs) in water and a set of biomarkers in fishes (exposure biomarkes: PAHs-type metabolites concentrations in bile; the activities of ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in liver. Effect biomarkers: lipid peroxidation concentration (LPO) in liver, acetylcholinesterase activity in brain, and genotoxic DNA damage in erythrocytes). Two fish species, Acarichthys heckelii and Satanoperca jurupari, were collected 10, 45, and 90 days after the PAC spill in São Raimundo. At the same time, fish were collected from the Tupé Sustainable Development Reserve (Tupé) which served as a reference area. The sampling periods were related to the rising waters of the natural flood pulse of the Rio Negro. Higher concentrations of PAHs in water were observed at 10 and 45 days and returned to the values of TP 90 days after the PAC spill, a period in which harbor waters rose about 0.2 m. Unlike the PAHs in water, biomarker responses in both fish species significantly increased following the PAC spill in SR. Hepatic ethoxyresorufin-O-deethylase (EROD), PAH-like metabolites in bile, and erythrocyte DNA damage increases, together with inhibition of acetylcholinesterase (AChE) activity in the brain were the most evident responses for both fish species. The calculated pyrolytic index showed mixed sources of PAHs (petrogenic and pyrolytic). The applied PCA-FA indicated important relationships between dissolved organic carbon (DOC) and PAHs concentrations in water, where DOC and PAHs concentrations contributed to biomarkers responses for both fish species in all collection periods.

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The objective of this study was to evaluate the immunopharmacological activity of doxycycline, administered orally in Nile tilapia (Oreochromis niloticus), during experimental infection by Aeromonas hydrophila, through the correlation between therapeutic efficacy and fish immune response. 160 Nile tilapia (±100 g) from the same spawning were distributed in 16 tanks (100 L, n = 10), constituting four treatments: control (infected and untreated); Infected and Treated with 20, 40 and 80 mg of doxycycline/Kg of b.w. Control fish and treated with the lowest dose of doxycycline (20 mg) exhibited typical signs of aeromonosis, including exophthalmos, fin erosion, hemorrhagic septicemia, corneal opacity and ascites. No clinical signs were observed in animals treated with 40 and 80 mg of doxycycline. There was a dose-response effect to the treatment with this tetracycline with relative percentage of survival (RPS) of 60, 73.3 and 93.3% for the treatments with 20, 40 and 80 mg/kg of b.w. when compared to control animals, as well as increased in the production of antibodies anti-A. hydrophila. Doxycycline treatment decreased monocytosis and reactive oxygen species (ROS) production observed in tilapia during A. hydrophila infection. Therefore, doxycycline administered orally to O. niloticus revealed the potential of this antimicrobial for use in tilapia farming, providing convincing results of the therapeutic efficacy against A. hydrophila. These results confirm the hypothesis that the antimicrobial action of doxycycline favored the defense mechanisms of tilapia treated mainly at a dose of 80 mg/kg. Although the exact mechanism of increased antibody response remains to be elucidated, the present observations demonstrate important practical significance for the sanitary management of tilapia farming.

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Abstract Introduction: The digestive tract of Neotropical cichlids has not been deeply studied, and it is a fundamental topic for understanding fish physiology, nutrition, trophic associations, and evolution. Objective: To describe anatomically and histologically the digestive tract of the Neotropical cichlid fish Cichlasoma dimerus and to immunolocalize the orexigenic peptide (Npy) along the intestine. Methods: We euthanized 14 adult individuals and fixed the organs in Bouin´s solution; we stained 7 μm thick paraffin sections for general description and with Alcian Blue (pH = 2.5, AB) and Periodic acid-Schiff (PAS) to identify acid or neutral glycoconjugates, respectively. Additionally, we performed immunohistochemistry for Npy in 3 adult individuals. We manually counted PAS- and AB-positive cells, and Npy-immunoreactive cells per fold. Results: There is a short oesophagus, a sac-like stomach, and a tubular intestine with two loops. The oesophagus has a stratified epithelium with a high density of PAS- and AB-positive goblet cells and striated muscle fibers in the tunica muscularis. The stomach mucosa is formed by simple columnar epithelium. The intestine has a simple columnar epithelium, with brush border and interspersed PAS- and AB-positive goblet cells, and Npy-immunoreactive cells. There is an ileorectal valve in the transition between the posterior intestine and the rectum. This last gut portion has goblet cells and a thicker tunica muscularis. Conclusions: C. dimerus shares features with other Neotropical cichlids, but the goblet cells and gastric glands distribution seems to be unique for the species. To our understanding, this is the first work to describe Npy-immunoreactive cells distribution in the intestine of a Neotropical cichlid fish.

Resumen Introducción: El tracto digestivo de los cíclidos neotropicales no ha sido profundamente estudiado y es un tema fundamental para entender la fisiología, nutrición, asociaciones tróficas y evolución de los peces. Objetivo: Describir anatómica e histológicamente el tracto digestivo del pez cíclido neotropical Cichlasoma dimerus e inmunolocalizar el péptido orexigénico (Npy) a lo largo del intestino. Métodos: Sacrificamos 14 individuos adultos y fijamos los órganos en solución de Bouin; teñimos secciones de parafina de 7 μm de espesor para una descripción general y con azul alcián (pH = 2.5, AB) y ácido periódico-Schiff (PAS) para identificar glicoconjugados ácidos o neutros, respectivamente. Además, en 3 individuos adultos se realizaron inmunohistoquímicas contra Npy. Contamos manualmente las células PAS y AB positivas, y las células inmunorreactivas a Npy por pliegue. Resultados: Hay un esófago corto, un estómago en forma de saco y un intestino con dos vueltas. El esófago tiene un epitelio estratificado con una alta densidad de células caliciformes PAS- y AB- positivas y fibras esqueléticas estriadas en las capas musculares. La mucosa del estómago está revestida por epitelio simple cilíndrico. El epitelio intestinal es simple cilíndrico con chapa estriada y células caliciformes PAS- y AB- positivas intercaladas, y células inmunorreactivas a Npy. Hay una válvula ileorrectal en la transición entre el intestino posterior y el recto. Esta última porción intestinal tiene células caliciformes y una túnica muscular más gruesa. Conclusiones: C. dimerus comparte características con otros cíclidos neotropicales, pero la distribución de las células caliciformes y las glándulas gástricas, serían rasgos propios de esta especie. A nuestro entender, este es el primer trabajo que describe la distribución de células inmunorreactivas a Npy en el intestino de un pez cíclido neotropical.

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To identify activation pathways and effector mechanisms of innate immunity in fish has become relevant for the sanitary management of intensive fish farming. However, little is known about the blocking of cysteinyl leukotrienes receptors (CysLTRs) and their effects in teleost fish. Our study evaluated the anti-inflammatory effect of 250 and 500 µg zafirlukast (antagonist of CysLTRs)/kg b.w., administered orally in the diet, during acute inflammatory reaction induced by Aeromonas hydrophila bacterins in Oreochromis niloticus. 80 tilapia were distributed in 10 aquariums (100L of water each, n = 8) to constitute three treatments: Control (inoculated with A. hydrophila bacterin and untreated); Treated with 250 µg or 500 µg of zafirlukast/kg b.w. and inoculated. To be evaluated in three periods: 6, 24 and 48 h post-inoculation (HPI), totaling nine aquariums. A tenth group was sampled without any stimulus to constitute reference values (Physiological standards). Tilapia treated with zafirlukast demonstrated dose-response effect in the decrease of accumulated inflammatory cells, strongly influenced by granulocytes and macrophages. Zafirlukast treated-tilapia showed decrease in blood leukocyte counts (mainly neutrophils, and monocytes) and reactive oxygen species production. Treatment with zafirlukast resulted in down-regulation of ceruloplasmin, complement 3, alpha2-macroglobulin, transferrin and apolipoprotein A1, as well as up-regulation of haptoglobin. Our study provided convincing results in the pathophysiology of tilapia inflammatory reaction, considering that treatment with zafirlukast, antagonist of cysteinyl leukotriene receptors, resulted in a dose-response effect by suppressing the dynamics between leukocytes in the bloodstream and cell accumulation in the inflamed focus, as well as modulated the leukocyte oxidative burst and the acute phase protein response.

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BACKGROUND: Astaxanthin, classified as a xanthophyll, has antioxidant properties about 500 times greater than α-tocopherols and ten times greater than ß-carotenes. Based on the antioxidant activity of this carotenoid, this study aimed to evaluate the shelf-life of tilapia fillets (Oreochromis niloticus) fed with astaxanthin, by determining the microbiological quality (colimetry, counts of mesophilic and psychrotrophic microorganisms), physicochemical analyses (colorimetry, pH, thiobarbituric acid reactive substances (TBARS)) and sensory analysis. RESULTS: Tilapia supplemented with astaxanthin presented a reduction in the counts of microorganisms (mesophiles and psychrotrophics) and lower lipid oxidation index (TBARS), when compared to fillets of control fish. Colorimetric changes of fillet degradation were observed, associated with increased pH during storage, as well as loss of brightness and texture in addition to worsening of appearance and odor. These deteriorating changes were minimized using astaxanthin. CONCLUSION: Our results demonstrate the beneficial performance of astaxanthin in the shelf-life of tilapia fillets stored under refrigeration. Therefore, dietary supplementation with astaxanthin (100 and 200 mg kg-1 of feed) improves the microbiological and physicochemical quality of tilapia fillets during 50 days of shelf-life. © 2022 Society of Chemical Industry.

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This study aimed to evaluate the clinical safety of doxycycline treatment (Sandoz Pharmacetical Industry from Brazil Ltd.), administered orally incorporated into the feed of Nile tilapia, Oreochromis niloticus. For this purpose, 75 Nile tilapia (±300g) from the same spawning were randomly distributed in 15 tanks (n=5), containing 100 L of water each, supplied with running water free from chlorine, to establish the following treatments: TO (Control - not treated with doxycycline); T1, T2, T3 and T4 (treated with 10, 20, 40 and 80mg of doxycycline/kg of body weight, respectively), in which 5 animals per treatment were sampled in 3 periods: 2, 4 and 8 days post-treatment (DPT). Blood samples were collected for hemogram determination and serum biochemical evaluation, as well as spleen, liver and kidneys (cranial and caudal) for somatic and histopathological evaluation. The results showed no significant difference among treatments in the serum values of creatinine, total protein, cholesterol, triglycerides, globulin, glycemia and alkaline phosphatase enzyme activity. However, serum levels of AST (aspartate aminotransferase) were significantly higher (P<0.05) in animals treated with 80 mg of doxycycline in the longest period of treatment (8 days). In the hematological evaluation of tilapia treated with doxycycline, no significant changes (P>0.05) were observed in erythrocyte counts, hematocrit, MCV, HCM and CHCM values. Doxycycline-treated tilapia did not present significant difference in the somatic analysis of spleen, liver and kidney when compared to control group. Therefore, the results demonstrated the clinical safety of oral treatment with doxycycline at doses of 10, 20, 40 and 80 mg/kg of b.w., although transient changes in liver functionality were observed after eight days of treatment with the dose of 80mg/kg.

Este estudo teve por objetivo avaliar a segurança clínica do tratamento com doxiciclina (Sandoz do Brasil Indústria Farmacêutica Ltda.), administrada via oral incorporada à ração em tilápias do Nilo, Oreochromis niloticus. Para tal, foram utilizadas 75 tilápias no Nilo (±300g) oriundas da mesma desova foram distribuídas aleatoriamente em 15 tanques (n=5), contendo 100 L de água cada, abastecidos com água corrente desprovida de cloro, para constituir os seguintes tratamentos: TO (Controle - não tratado com doxiciclina); T1, T2, T3 e T4 (tratados com 10, 20, 40 e 80mg de doxiciclina/kg de p.v., respectivamente. 5 animais por tratamento foram amostrados em 3 períodos: 2, 4 e 8 dias pós-tratamento (DPT). Foram coletadas amostras de sangue para determinação do hemograma e avaliação do bioquímico sérico, além de órgãos como baço, fígado e rins (cranial e caudal) para avaliação somática e histopatológica. Os resultados não mostraram diferença significativa entre os tratamentos nos valores séricos de creatinina, proteína total, colesterol, triglicerídeos, globulina, glicemia e atividade da enzima fosfatase alcalina. No entanto, os níveis séricos de AST (aspartato aminotransferase) foram significativamente maiores (P<0,05) nos animais tratados com 80 mg de doxiciclina no período mais longo de tratamento (8 dias). Na avaliação hematológica de tilápias tratadas com doxiciclina, não foram observadas alterações significativas (P>0,05) nas contagens de eritrocitos, valores de hematocrito, VCM, HCM e CHCM. Tilápias tratadas com doxiciclina não apresentaram diferença significativa na análise somática do baço, fígado e rim quando comparadas aos animais do grupo controle. Portanto, os resultados demonstraram a segurança clínica do tratamento oral com doxiciclina nas doses de 10, 20, 40 e 80 mg/kg de peso corporal, embora alterações transitórias na funcionalidade hepática tenham sido observadas após oito dias de tratamento com a dose de 80mg/kg.

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Lincomycin is a broad-spectrum antimicrobial acting against Gram-positive bacteria, widely used in veterinary medicine. In fish, there are only limited in vitro data, thus requiring the design of effective therapeutic protocols for their use in aquatic organisms. In this context, the objective was to evaluate the clinical safety of lincomycin treatment, administered orally in tilapia, through hematological, biochemical and somatic index evaluation. A total of 136 tilapia (+100g) were randomly distributed in 17 tanks (100L of water, n=8) to constitute the following treatments: TO (control group, not treated with lincomycin); T1, T2, T3 (treated with 10, 20 and 40mg/kg¹ of lincomycin b.w., respectively) and T4 physiological standard (reference values). Eight animals were sampled per treatment in 4 periods: 2, 4 and 8 days post-treatment (DPT), and a group that was treated for 8 days with the drug and then treated only with commercial feed until the 12th day (recovery period). Tilapia treated with lincomycin had no difference in the hematological and leukocyte evaluation, in the hepatic, renal and splenic somatic index. However, they presented a transient increase in the values of ALT, AST, cholesterol, triglycerides and creatinine, which returned to normal levels after the period of recovery (12DPT). Furthermore, an increase in total protein, albumin and globulin levels was observed in treated animals. It is concluded that although there were some transient changes during the experiment, lincomycin has a good clinical safety margin at doses of 10, 20 and 40mg/Kg¹ b.w. for Nile tilapia.

A lincomicina é um antimicrobiano de amplo espectro atuando contra bactérias gram-positivas, amplamente utilizada na medicina veterinária. Em peixes existem apenas dados limitados in-vitro, necessitando assim, de delineamento de protocolos terapêuticos eficazes para seu uso em organismos aquáticos. Desse modo, objetivou-se avaliar a segurança clínica do tratamento com lincomicina, administrada por via oral em tilápias, por meio da avaliação hematológica, bioquímica e indice somático hepático, renal e esplênico. Foram utilizadas 136 tilápias (±100g), distribuídas aleatoriamente em 17 tanques (100L de água, n=8) para constituir as repetições dos diferentes tratamentos: TO (grupo controle, não tratado com lincomicina); T1, T2, T3 (tratados com 10, 20 e 40mg/kg de p.v. de lincomicina, respectivamente) e T4 padrão fisiológico (valores de referência). Oito animais foram amostrados por tratamento em 4 períodos: 2, 4 e 8 dias pós-tratamento (DPT) com lincomicina, e um grupo que foi tratado por 8 dias com o fármaco e após isso tratado apenas com ração comercial até o 12º dia (período de recuperação). Tilápias tratadas com lincomicina não tiveram diferença na avaliação hematológica e leucocitária, no índice somático hepático, renal e esplênico, entretanto, apresentaram um aumento transitório nos valores de ALT, AST, colesterol, triglicérides e creatinina, que retornaram aos níveis normais após o período de recuperação (12DPT). Ademais, foram observados um incremento nos níveis de proteína total, albumina e globulina nos animais tratados. Conclui-se que embora tenha ocorrido algumas alterações transitórias ao decorrer do experimento, a lincomicina apresenta boa margem de segurança clinica nas doses de 10, 20 e 40mg/Kg¹ p.v para tilápia do Nilo.

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The amazon fishes' responses to hypoxia seem to be related to the Amazon basin diversity of aquatic environments, which present drastic daily and seasonal variations in the dissolved oxygen concentration. Among these fishes' adaptation to hypoxia, behavioral, metabolic, physiological, and biochemical responses are well known for some species. In this work, we aimed to identify how two different aquatic environments, normoxic forest streams and hypoxic lakes, dictate the responses to hypoxia for two cichlid species, Mesonauta festivus and Aequidens pallidus. In our results, we found that A. pallidus is less tolerant to hypoxia, which seems to be related to this animal's natural normoxic environment. Even though this species modulated the mitochondrial respiration in order to improve the oxygen use, it also showed a lower decrease in metabolic rate when exposed to hypoxia and no activation of the anaerobic metabolism. Instead, M. festivus showed a higher decrease in metabolic rate and an activation of the anaerobic metabolism. Our data reveal that the natural dissolved oxygen influences the hypoxia tolerance and the species' tolerance is related to its ability to perform metabolic depression. The interest results are the absence of mitochondrial respiration influences in these processes. The results observed with A. pallidus bring to light also the importance of preserving the forests, in which streams hold very specialized species acclimated to normoxia and lower temperature. The importance of hypoxia tolerance is, thus, important to keep fish assemblage and is thought to be a strong driver of fish biodiversity.

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Procamallanus is a species-rich genus of parasitic nematodes of marine, brackish, and freshwater fishes, occurring also occasionally in amphibians and reptiles. In the Neotropical region, this genus is highly diverse, with species described from a wide range of fish families. In this study, we reassess the taxonomic status of Procamallanus rebecae with molecular and morphological data and describe a new species endemic to Nicaragua and Costa Rica. We analyzed all Procamallanus isolated from fish from the Nicaraguan lakes and some rivers in Costa Rica after an exhaustive analysis of their freshwater fish endoparasite fauna. Procamallanus rebecae is a host-specific parasite of Middle American cichlids, previously reported in southern Mexico, Nicaragua, and Costa Rica. We therefore compared these Central American specimens with individuals of P. rebecae collected in cichlids from southeastern Mexico using two genomic regions (28S rDNA and mitochondrial cytochrome oxidase subunit 1, COI). We found high levels of sequence divergence between Procamallanus from the two geographical regions, with up to 9.8 and 10.5% for both genetic markers, respectively. We also analyzed their morphology and found conspicuous differences in the shape of the mouth and the structure of the female cauda. We therefore describe the specimens of Procamallanus from Central American cichlids as a new species. Both Procamallanus species occur in different cichlid species and are allopatrically distributed. The host specificity and ancient association patterns between cichlids and Procamallanus and the jointly colonization of both hosts and parasites during their northern dispersal from South America are briefly discussed.

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During focal observations carried out in the Olho dÁgua River, upper Paraguay River basin, Brazil, we registered the defensive behaviour of one pair of Crenicichla lepidota attempting to protect their offspring from conspecific and non-specific predators. Adults exhibited substrate-guarding behaviour and displayed primary and secondary anti-predation mechanisms. The primary mechanisms (e.g., fin flicking and flaring, gill extending) were ineffective against conspecific predators or against other species. Secondary mechanisms included charging would-be predators of the offspring, and this tactic was successful against non-specifics. This record confirms, in the wild, agonistic behaviour as an effective secondary defence mechanism used in parental care in Crenicichla lepidota.(AU)

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