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The world population is estimated to reach close to 10 billion inhabitants by 2050, thus increasing the global demand for energy, drinking water and food (ONU, 2019). Given this scenario and the decline of natural fish stocks, aquaculture has been the subject of rapid development. Aquaculture has grown faster than other major food production sectors as it contributes to the supply of animal protein of high biological value for human consumption, job creation and income, thereby boosting the economic development of several countries (FAO, 2018).However, aquaculture activities around the world have suffered from outbreaks of parasitic diseases, which cause losses in production and affect profitability and sustainability (Assefa & Abunna, 2018).Losses in aquaculture caused by parasitic diseases are estimated at US $ 1.05-9.58 billion/years (Shinn et al., 2015). Losses from parasitic diseases are also attributed to stressful handling conditions, high stocking densities and inadequate water quality during the cultivation.Parasitic diseases in fish farming include those caused by monogeneans, which are ectoparasites with simple and direct life cycle.These ectoparasites can cause significant losses in farmed fish for

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This study investigated for the first time the anthelmintic efficacy of therapeutic baths with Copaifera reticulata oleoresin and nanoemulsion with this oleoresin against monogeneans of Colossoma macropomum, as well as the haematological and histological effects in this fish. In the therapeutic baths of three consecutives were used 100 mg/L of C. reticulata oleoresin or 250 mg/L of nanoemulsion containing C. reticulata oleoresin. Therapeutic baths with 100 mg/L of C. reticulata oleoresin had anthelmintic an efficacy of 48.5% against monogeneans (Anacanthorus spathulatus, Notozothecium janauachensis and Mymarothecium boegeri), while baths with nanoemulsion of C. reticulata oleoresin had not anthelmintic efficacy, which was discussed. Baths for 1 h with 100 mg/L of C. reticulata oleoresin or 2 h with 250 mg/L of C. reticulata nanoemulsion increased levels of plasma total protein and glucose, mean corpuscular volume (MCV) and neutrophils number in C. macropomum and decreased in the number of total leucocytes and lymphocytes. In the gills of fish exposed and controls occurred detachment of the epithelium, hyperplasia and hypertrophy, resulting in moderate fusion of the secondary lamellae. Therefore, therapeutic baths with C. reticulata oleoresin and nanoemulsion of C. reticulata oleoresin have a low toxicity to C. macropomum, as there were few changes to the blood parameters.

The present study describes light microscopy, transmission electron microscopy, and molecular analyses of a myxosporid found parasitizing the gill region of the teleost fish Cichla temensis, collected from the Tocantins River, near Cametá, Pará State, Brazil. The prevalence of infection was 60 %. The spore-containing cysts that were located in the gill lamellae were oval and whitish. The spores had a mean length of 42.3 ± 0.65 μm; fusiform body, 12.8 ± 0.42-μm long and 8.6 ± 0.32-μm wide; each of the two valves exhibited a tapering tail of 29.5 ± 0.73 μm length. The spores had two polar capsules, 7.4 ± 0.16-μm long by 2.6 ± 0.08-μm wide, containing a polar filament with 5-7 twists. The spores differ from the species previously described, and phylogenetic analysis based on spore morphology and molecular aspects indicated that the fish parasite Henneguya sp. has a strong trend to form clades mainly based on the environment and host order/family. Thus, we conclude that the species belongs to the family Myxobolidae, genus Henneguya, which comprises a new species: Henneguya paraensis n. sp.

The phylum Myxozoa Grassé, 1970, consists of a heterogenous group of around 50 genera that are worldwide disseminated in a wide variety of aquatic media. In the present study, 43 specimens of Pimelodus ornatus were collected from an adjacent area to the Cachoeira do Arari municipality on Marajó Island, in the Brazilian state of Pará, in 2013. Macroscopic analysis showed the presence of whitened plasmodia located in the cardiac muscle and also in the region between the bulbus arteriosus and atrium cordis. Microscopic analysis on the parasitized tissues revealed spores that were typically piriform, with the anterior portion slightly narrower than the posterior end. The spore valves were symmetrical. The present species is placed in the genus Myxobolus Butschli, 1882, because of the presence of a pair of equal polar capsules in each spore. The prevalence of parasitism observed was 13.9% (6/43). This research note reports the first occurrence of Myxobolus as a parasite of the heart in the teleostean fish P. ornatus in the Amazon region and confirms the occurrence of secondary myocarditis in this fish, caused by parasitism by Myxobolus sp. The rarity of this parasitic species of Myxobolus at this tissue site, associated with other spore morphology characteristics in the fish, suggests that it is an undescribed species.

Aspidogastreans are commonly found infecting freshwater and marine molluscs, teleosts fishes and freshwater turtles. The subclass comprises four families - Rugogastridae Schell 1973, Stichocotylidae Faust & Tang 1936, Multicalycidae Gibson & Chinabut 1984 and Aspidogastridae Poche 1907 - and it is characterized by the presence of a ventral adhesive disc divided into rows of alveoli. In the current work, using light and scanning electron microscopy and molecular approaches, a new species of Aspidogastridae of the genus Rohdella Gibson & Chinabut, 1984, is described as a parasite of Colomesus psittacus in Brazil. The new taxon is distinguishable by the presence of oesophageal glands, teguments covered by ciliated papillae, and the position and shape of the hermaphroditic duct. The present work describes the third species of the genus Rohdella, thereby adding new morphological and molecular data regarding Aspidogastridae.