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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 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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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.

NOTA CIENTÍFICA RESUMO: O gênero Calyptospora possui espécies parasitas de peixes de água doce e marinha, e são frequentemente encontrados no fígado do hospedeiro. Este trabalho relata uma nova ocorrência e aspectos morfológicos de um coccídio hepatopancreático, em Cichla temensis da região nordeste paraense. Setenta espécimes do peixe C. temensis foram coletados no Rio Tocantins (Cametá-PA) e transportados ao Laboratório de Pesquisa Carlos Azevedo, sendo anestesiados e necropsiados para pesquisa de parasitos. Os fragmentos de tecidos parasitados foram fixados e processados para microscopia de luz (ML) e microscopia eletrônica de varredura (MEV). Os aspectos histológicos evidenciaram oocistos agrupados e isolados no parênquima hepático e pancreático. Diante dos achados macro e microscópicos da parasitose, apesar da grande carga parasitária presente na região hepatopancreática, não foi observado reação inflamatória significativa pelo hospedeiro. Este é o primeiro registro da ocorrência do parasitismo por Calyptospora sp. em hepatopâncreas de C. temensis no nordeste paraense.