The Amazonian fish Colossoma macropomum harbors high myxosporean diversity: A description of three novel species from a fish farm.

The farming of Colossoma macropomum has intensified in recent years, leading to an increased need for research into the health of the fish. We therefore investigated the diversity of myxosporeans (Cnidaria: Myxozoa) infecting C. macropomum in a breeding system in the municipality of Rio Branco, in the state of Acre, Brazil. Twenty-four fish specimens were examined from June to August 2018. Our results revealed a high prevalence of infection, with 23 specimens (95.8%) exhibiting myxosporean plasmodia. Morphological analysis, based on light and electron microscopies, and molecular analysis (small subunit ribosomal DNA [SSU rDNA] sequencing) revealed the occurrence of three novel species of the genus Myxobolus. Plasmodia of Myxobolus guttae n. sp. were found in the fins of 75% of the specimens, and the myxospores were pear-shaped, measuring 12.3 ± 0.6 (10.3-13.5) µm in length, 8.1 ± 0.3 (7.1-8.6) µm in width, and 5.1 ± 0.6 (4.5-6.5) µm in thickness. The polar capsules were elongated and equal in size, measuring 6.8 ± 0.5 (5.8-7.6) µm in length and 2.5 ± 0.3 (1.8-3.1) µm in width, exhibiting polar tubules with 9-10 coils. The plasmodia of Myxobolus longus n. sp. were found in the gills of 45.8% of the C. macropomum specimens, and the myxospores were fusiform, measuring 16.4 ± 0.6 (14.7-17.3) µm in length, 7.1 ± 0.2 (6.8-7.7) µm in width and 5.5 ± 0.6 (4.4-6.6) µm in thickness. The polar capsules occupied more than half of the myxospore, exhibiting different sizes, the largest measuring 9.2 ± 0.5 (7.3-10.1) µm in length and 2.5 ± 0.3 (2.0-3.1) µm in width, while the smallest measured 8.5 ± 0.4 (7.1-9.1) µm in length and 2.4 ± 0.2 (1.9-3.0) µm in width. Both polar capsules contained polar tubules with 10-12 coils. For Myxobolus tambaquiensis n. sp., plasmodia were found in the opercular cavity of 41.7% of the fish specimens, and the myxospores had an oval shape, measuring 10.0 ± 0.4 (9.5-11.3) µm in length, 6.5 ± 0.2 (6.1-7.1) µm in width, and 4.6 ± 0.4 (3.9-5.6) µm in thickness. The polar capsules were elongated and equal in size, measuring 4.9 ± 0.2 (4.4-5.3) µm in length and 1.9 ± 0.2 (1.5-2.2) µm in width, closing with 8-9 coils of the polar tubule. The morphological and sequencing data of the SSU rDNA showed that the three species studied herein remain unknown to science, increasing the diversity of myxosporeans infecting C. macropomum, an iconic fish in South American freshwater fish farming. The SSU rDNA based phylogenetic analysis revealed that Myxobolus spp. parasites of C. macropomum did not have a monophyletic origin, identifying different times and pathways of the acquisition of parasites by this host species.

Avaliação da cavidade orofaríngea da tartaruga da Amazônia, Podocnemis expansa (Schweigger, 1812) / Evaluation of the oropharyngeal cavity of Giant South American turtle Podocnemis expansa (Schweigger, 1812)

Os quelônios são importantes como fonte alimentar e econômica para as comunidades da região amazônica. Sendo assim, a caça, a pesca e a procura por ovos destes animais tem ocorrido frequentemente. Podocnemis expansa (Tartaruga da Amazônia) é o maior quelônio de água doce da América do Sul. É uma espécie largamente distribuída, porém, nota-se que aspectos anatômicos da espécie são insuficientemente descritos. O objetivo desse estudo foi descrever a cavidade orofaríngea desses quelônios. Foram utilizadas 12 cabeças de P. expansa adultas, de ambos os sexos, com idade entre 3 a 8 anos, com peso corpóreo de 5 a 22kg (média de 7,5kg). P. expansa conta com a presença de rafontecas afiadas e bem desenvolvidas que, associadas à musculatura potente da mandíbula e à língua volumosa e bem distribuída no assoalho da orofaringe, atuam na apreensão e deglutição do alimento, garantindo uma maior adaptação em diversos ambientes...

Turtles are important as food and economic resources for the Amazon communities and there is a large demand on its meat and eggs. Podocnemis expansa (Giant South American turtle) is the largest freshwater chelonian of South America. This turtle is a widely distributed specie, however its anatomical features are poorly described. The objective of this study was to describe the oropharyngeal cavity of the turtle. Twelve heads of 3 to 8-year-old female and male P. expansa turtles with an average body weight of 7.5kg were used. P. expansa has a sharp and well developed rhamphotheca, which together with a powerful jaw muscles and a large tongue uniformly distributed on the oropharynx floor works for the apprehension and swallowing of food, what ensures good adaptation in different environments...