Molecular identification of Austrodiplostomum sp., an eye parasite among farmed tambaqui in Amazonia.

Austrodiplostomum Szidat & Nani, 1951 is a genus of parasitic digenetic trematodes widely distributed in the Neotropical region. Infects a wide variety of species, families and requests for freshwater fish. We identify samples of Austrodiplostomum sp, based on metacercariae isolates from eyes of tambaqui (Colossoma macropomum), a fish of high commercial importance in Brazil, and widely consumed by the population of the northern region. The sequences obtained clustered with A. compactum. This is the first report of the occurrence of diplostomids in farmed tambaqui in Amazonia.

Distribution of the acanthocephalan Neoechinorhynchus buttnerae and semiquantitative analysis of histopathological damage in the intestine of tambaqui (Colossoma macropomum).

In this paper, we have described for the first time a semiquantitative method to evaluate histopathological damage, taking the degree of Neoechinorhynchus buttnerae attachment to the intestinal wall of the tambaqui (Colossoma macropomum), an important species in Brazilian aquaculture, into account. Twelve specimens of tambaqui were collected from a fish farm. Their bowels were removed and divided into seven morphologically distinct portions according to density and distribution of the parasite studies. Fragments from each fraction were histologically processed and analyzed. There was a clear preference on the part of N. buttnerae for the intermediate regions of the intestinal tube, where the highest densities were recorded. The intensity of damage to the host, estimated by calculating the Histopathological Alteration Index (HAI), showed severe and irreversible changes only where the parasite had its proboscis penetrated into the intestine wall.

A Perspective of Molecular Cytogenomics, Toxicology, and Epigenetics for the Increase of Heterochromatic Regions and Retrotransposable Elements in Tambaqui (Colossoma macropomum) Exposed to the Parasiticide Trichlorfon.

Rex retroelements are the best-known transposable elements class and are broadly distributed through fish and also individual genomes, playing an important role in their evolutionary dynamics. Several agents can stress these elements; among them, there are some parasitic compounds such as the organochlorophosphate Trichlorfon. Consequently, knowing that the organochlorophosphate Trichlorfon is indiscriminately used as an antiparasitic in aquaculture, the current study aimed to analyze the effects of this compound on the activation of the Transposable Elements (TEs) Rex1, Rex3, and Rex6 and the structure of heterochromatin in the mitotic chromosomes of the tambaqui (Colossoma macropomum). For this, two concentrations of the pesticide were used: 30% (0.261 mg/L) and 50% (0.435 mg/L) of the recommended LC50-96 h concentration (0.87 mg/L) for this fish species. The results revealed a dispersed distribution for Rex1 and Rex6 retroelements. Rex3 showed an increase in both marking intensity and distribution, as well as enhanced chromosomal heterochromatinization. This probably happened by the mediation of epigenetic adaptive mechanisms, causing the retroelement mobilization to be repressed. However, this behavior was most evident when Trichlorfon concentrations and exposure times were the greatest, reflecting the genetic flexibility necessary for this species to successfully adapt to environmental changes.

A fast and practical method for initial diagnosis of Piscinoodinium pillulare outbreaks: piscinootest / Um método rápido e prático para o diagnóstico inicial de surtos de Piscinoodinium pillulare: piscinootest

ABSTRACT: The dinoflagellate Piscinoodinium pillulare is a parasite with low parasitic specificity and unspecific geographical distribution. This research reported a simple and practical method - the principle of spontaneous sedimentation - to identify the presence of P. pillulare during massive infestations which does not require using precision equipment. Agitation in water of the gill arches of infested fish will elicit, after a period of rest, recording the accumulation of trophonts in the bottom of flasks. The method was applied during outbreaks of P. pillulare in tambaqui, Colossoma macropomum and matrinxã, Brycon amazonicus, in fish farms of the Amazon region and proved to be effective.

RESUMO: O dinoflagelado Piscinoodinium pillulare é um parasita com baixa especificidade parasitária e distribuição geográfica não específica. Este trabalho reporta um método simples e prático - o princípio da sedimentação espontânea - para identificar a presença de P. pillulare durante infestações maciças, que não requer o uso de equipamentos de precisão. A agitação em água dos arcos branquiais de peixes infestados permite, após um período de repouso, registrar o acúmulo de trofontes no fundo dos frascos. O método foi aplicado durante os surtos de P. pillulare em tambaqui, Colossoma macropomum e matrinxã, Brycon amazonicus, em pisciculturas comerciais da região Amazônica e provou ser eficaz.