Franmir Rodrigues Brandão

The tambaqui (Colossoma macropomum) is a species of great economic importance for fish farming in the Brazilian Amazon, and acanthocephaliasis caused by Neoechinorhynchus buttnerae (Golvan 1956) represents an obstacle to its production due to it causing severe morphological damage to the intestinal mucosa, thus impairing the absorption of nutrients and causing weight loss in the fish. Therefore, the establishment of in vitro protocols for evaluation of anthelmintic drugs is the first step to development of effective measures for in vivo control of this endoparasite. The present study evaluated the in vitro survival of N. buttnerae maintained in Eagle’s minimum essential medium under different culture conditions. Three assays were carried out to evaluate whether temperature, supplementation with the antibiotics penicillin and streptomycin, and culture medium replacement or no replacement would influence the motility and morphology of the acanthocephalans. The results of the Kaplan-Meier analysis indicated that the use of culture in minimum essential medium together with penicillin and streptomycin prolonged the parasite’s survival when kept at temperatures of 24 °C or 28 °C. We describe herein for first time an alternative protocol that is ideal for the in vitro culture of N. buttnerae. As such, this protocol ensures greater reliability in further in vitro studies with N. buttnerae.

The aim of this study was to determine the acute toxicity of the essential oils (EOs) of Aloysia triphylla, Lippia gracilis and Piper aduncum in juvenile tambaqui (Colossoma macropomum), and evaluate the possible histopathological alterations in their gills. For the acute toxicity tests, juvenile tambaqui (n=24/treatment) were distributed in six treatments with three replicates, which comprised the control and five EO concentrations of A. triphylla (60, 80, 100, 120 and 140 mg L^-1), L. gracilis (35, 40, 45, 50 and 55 mg L^-1) and P. aduncum (42.5, 45, 47.5, 50 and 52.5 mg L^-1), with an exposure period of 4 h. The mortality rate and severity of damage to the tambaqui gills were proportional to the increase in the concentration of the EO, with LC₅₀-4 h values estimated at 109.57 mg L ^-1 for A. triphylla, 41.63 mg L ^-1 for L. gracilis and 48.17 mg L ^-1 for P. aduncum. The main morphological damages observed in the gills of the tambaqui exposed to the three EOs, were Grade I: hypertrophy and hyperplasia of lamellar epithelial cells, lamellar fusion, epithelial detachment, capillary dilation and constriction, proliferation of chloride cells and mucosal cells and edema; in low frequency Grade II damage as epithelial rupture and lamellar aneurysm. Necrosis (Grade III damage) was observed only in gill lamellae exposed to P. aduncum EO (47.5, 50.0 and 52.5 mg L^-1). Concentrations of EOs below LC₅₀-4 h can be used sparingly, for short periods of exposure for the treatment of diseases in tambaqui breeding.

The aim of this study was to determine the chemical composition of Lippia alba and two genotypes of L. origanoides, L. origanoides A and L. origanoides B (syn. Lippia sidoides) essential oils(EOs) and to investigate the antibacterial activity against 27 Aeromonas spp. isolated from tambaqui (Colossoma macropomum). The activity of the antibiotics Florfenicol and Oxytetracycline was also compared. The EOs were obtained by hydrodistillation and their composition determined by CG-MS. Antibacterial activity was assessed based in the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using microdilution method. The main compounds identified were carvone (55.9%) and limonene (21.9%) in L. alba EO, carvacrol (35.6%) and p‐cymene (15.7%) in L. origanoides A EO and thymol (53.5%) and p‐cymene (15.5%) in L. origanoides B EO. The Lippia species showed bacteriostatic and bactericidal action against Aeromonas isolates with MICs and MBCs ranging from 104.17 to 16,666.67 μg.mL⁻¹. Among the tested EOs, the best performance was obtained by that of the L. origanoides B genotype, followed by L. origanoides A and L. alba respectively. Among antibiotics, the best performance was of oxytetracycline (MICs and MBCs ranging from 0.195 to 0.78 μg.mL⁻¹) compared to florfenicol (MICs and MBCs ranging from 0.195 to 3.12 μg.mL⁻¹).

Bacterial diseases are important factors that limit productivity in aquaculture. To reduce negative economic impacts, fish farmers use antimicrobials, often indiscriminately, and this action has led to bacterial resistance to drugs. The objectives of this study were to isolate and identify the main putative pathogenic bacterial species in tambaqui (Colossoma macropomum), establish the profile of resistance to antimicrobials by the methods of disc diffusion, and determine the minimum inhibitory concentration (MIC) values. Two hundred and ninety asymptomatic fish were collected between March and November 2015 from ten fish farms in the Amazonas state (Brazil). Of the total strains recovered from tambaqui, seven were identified as Aeromonas spp. by sequencing the 16S rRNA gene. These seven isolates showed resistance to ampicillin, 28% to erythromycin, and 28% to sulfonamide. Additionally, the seven isolates showed a MIC higher than the range evaluated for amoxicillin, penicillin, novobiocin, tylosin tartrate, and clindamycin, and 85% showed resistance to erythromycin. The results of this study indicate the need to increase the awareness of fish farmers and, most importantly, the government, about the lack of drug regulations for use in aquaculture, and good management practices, so the indiscriminate prophylactic and systemic use of antimicrobials be inhibited.

The objective of this study was to investigate the parasites occurrences and to determine the rates of infestation/parasitic infection in juvenile Arapaima gigas from seven fish farms in the state of Amazonas, relating to the characteristics of these fish farms. Of the 70 A. gigas evaluated, 43 were infested/infected, with a total of 133 parasites collected. Three fish farms (2, 4, 6) showed the highest levels of prevalence of parasites (100%, 70%, 70%), mean intensity (4.1±2.6, 8.1±9.2, and 2.1±1.3), and mean abundance (4.1±2.6, 5.7±8.1, and 1.5±1.5), respectively. Prevalence ranged from 30% to 100%, mean intensity from 1.0 to 8.1 and mean abundance from 0.3 to 5.7. Monogenea, Digenea, Nematoda (Hysterothylacium sp. and Spirocamallanus sp.) and Acanthocephala (Neoechinorhynchus sp. and Polyacanthorhynchus sp.) were identified. The parasites Hysterothylacium sp. and Neoechinorhynchus sp. were the most prevalent parasites with 31.43% and 15.71%, respectively. The fish presented negative allometry in growth and constant condition factor. Measures to prevent and control the parasitic diseases diagnosed are discussed as well prophylactic practices that contribute to the biosecurity of the farms.

Óleos essenciais podem ser usados como anestésicos naturais para peixes em diversos procedimentos laboratoriais ou de rotina da piscicultura. Vários são considerados seguros tanto para os peixes como para o ambiente. Entretanto, os seus efeitos como redutores de estresse em peixes necessitam ser avaliados. O transporte é uma das práticas de manejo da piscicultura mais estressantes. O estresse nos peixes pode induzir a consequências indesejáveis como manifestações de doenças e mortalidades. Este estudo avaliou os efeitos do óleo essencial de Ocimium gratissimum em parâmetros fisiológicos de estresse em Colossoma macropomum submetidos ao transporte. Os peixes foram transportados em sacos plásticos sob diferentes concentrações do óleo essencial (0, 5, 10, 15 e 20 mg L-1) por 4 h. Amostras de sangue foram coletadas antes e depois do transporte. As concentrações de glicose e amônia plasmáticas aumentaram e o lactato diminuiu depois do transporte com o óleo essencial diluído na água. Os níveis de proteína plasmática e glicogênio hepático apresentaram variações muito amplas. Os parâmetros sanguíneos não mostraram diferenças entre os tratamentos. Os peixes apresentaram-se recuperados 24 h após o transporte. As concentrações avaliadas do óleo essencial de O. gratissimum não foram eficientes como mitigadores de estresse em tambaqui submetido ao transporte. Estudos adicionais são necessários para avaliações de outras concentrações, bem como a associação com outros produtos e procedimentos.