Michele Velasco

Morphology and Phylogeny of Thelohanellus marginatus n. sp. (Myxozoa: Myxosporea), a Parasite Infecting the Gills of the Fish Hypophthalmus marginatus (Teleostei: Pimelodidae) in the Amazon River

Thelohanellus marginatus n. sp., a new myxosporean parasite infecting the primary gill filaments of the teleost fish Hypophthalmus marginatus (Pimelodidae) in the Amazon River, is described on the basis of microscopic and molecular procedures. The parasite forms whitish and ellipsoidal cysts up to 250 μm in diam. Myxospores ellipsoidal with a slightly more pointed anterior end, measuring 17.1 ± 0.6 μm in length, 6.9 ± 0.4 μm in width, and 5.1 ± 0.5 μm in thickness. A single pyriform polar capsule, 9.0 ± 0.3 μm long and 6.1 ± 0.4 μm wide, positioned slightly right to the medial plane in valvular view, contains a polar filament arranged in 4–5 coils. Molecular analysis of the SSU rRNA gene by Maximum Parsimony, Neighbor‐Joining, and Maximum Likelihood revealed the parasite clustering among other myxobolids, namely Henneguya and Myxobolus. Host affinity is supported as an important evolutionary signal for the phylogeny of myxobolids. The parasite here described represents the first record of the genus Thelohanellus Kudo, 1933 from the South American fauna.

Infection of the heart of Pimelodus ornatus (Teleostei, Pimelodidae), by Myxobolus sp. (Myxozoa, Myxobolidae)

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.

Gobioides broussonnetii (Gobiidae): a new host for Pterobothrium crassicolle (Trypanorhyncha) on Marajó Island, northern Brazil.

In the present study, the cestoid Pterobothrium crassicolle Diesing, 1850 (Trypanorhyncha), was observed parasitizing specimens of the violet goby (Gobioides broussonnetii Lacepède, 1800) collected from the estuary of the Paracauarí River on Marajó Island in the north of the Brazilian state of Pará, between January 2009 and December 2010. Tissue samples were analyzed, which led to identification of blastocysts containing plerocercoid larvae. These larvae were processed for scanning electron microscopy. Sixty G. broussonnetii specimens were dissected, and P. crassicolle was found in 48 (80%) of them. The violet goby, G. broussonnetii, is a new host for P. crassicolle.

Infection by Henneguya sp. (Myxozoa) in the bone tissue of the gill filaments of the Amazonian catfish Hypophthalmus marginatus (Siluriformes)

This study describes aspects of the infection caused by the myxosporean genus Henneguya, which forms cysts in the bony portion of the gill filaments of Hypophthalmusmarginatus. Specimens of this catfish were acquired dead from artisanal fishermen near the town of Cametá, state of Pará, northern Brazil, between July 2011 and May 2012. They were transported in refrigerated containers to the Carlos Azevedo Research Laboratory at the Federal Rural University of Amazonia, in Belém, where analyses were performed. After confirmation of parasitism by the genus Henneguya, observation were made using optical and differential interference contrast (DIC) microscopy. The histological technique of embedment in paraffin was used. Ziehl-Neelsen staining was applied to the histological sections. Necropsy analyses on specimens of H. marginatus showed that 80% of them (40/50) had cysts of whitish coloration inside the bony portion of the gill filaments, filled with Henneguya spores. The present study found inflammatory infiltrate in the vicinity of the cysts. Furthermore, the special Ziehl-Neelsen staining technique made it possible to mark the Henneguya sp. cysts in the bone tissue and in spore isolates in the gill tissue structure. The descriptions of these histopathological findings show that this parasite is very invasive and causes damage to its host tissues.

Kudoa spp. (Myxozoa) infection in musculature of Plagioscion squamosissimus (Sciaenidae) in the Amazon region, Brazil

Ninety specimens of Plagioscion squamosissimus captured using fishing tackle in the Outeiro district, state of Pará, were examined. Fish were placed in plastic bags containing water, under conditions of artificial aeration, and transported live to the Carlos Azevedo Research Laboratory (LPCA), in Belém, Pará. They were anesthetized, euthanized and necropsied; small fragments of the epaxial and hypaxial muscles were removed for examination of fresh histological sections by means of optical microscopy. In 100% of the specimens analyzed, parasitic pseudocysts were seen to be interspersed within and between the skeletal muscle. These contained pseudoquadrate and/or star-shaped spores that presented four valves and four polar capsules, which were identified from their morphology as belonging to the genus Kudoa. This is the first report of Kudoa in P. squamosissimus in the Amazon region, Pará, Brazil.

Spontaneous multi-cystic peripheral ameloblastoma in the freshwater angelfish, from the Brazilian state of Pará

Este trabalho registra a ocorrencia espontânea de ameloblastoma em P. scalare. O tumor foi obtido a partir de um exemplar de Acara Bandeira, sendo fixado, seccionado, e os fragmentos processados para microscopia de luz e microscopia eletronica de varredura (MEV). O exame macroscopico evidenciou uma massa tumoral que se estendia do rebordo alveolar do maxilar superior a face externa labial. A MEV, a neoplasia apresentou uma serie de espiculas. Microscopicamente, percebia-se um processo neoplasico constituido por tecido conjuntivo de caracteristica mixoide, ricamente vascularizado, onde eram observados fragmentos de tecido osteoide. A amostra revelou proliferacao neoplasica do epitelio odontogenico, onde as celulas neoplasicas se organizavam na forma de palicada. Alteracoes histopatologicas em peixes tem sido uteis biomarcadores do efeito a exposicao a substâncias toxicas, sendo as neoplasias lesoes especificas, comumente encontradas em peixes de areas poluidas, revelando uma associacao entre as lesoes e a exposicao a irritantes.

Hepatic steatosis associated with microsporidiosis in teleost fishes from Marajó Island, Brazil

A total of 40 specimens of the teleost fish Gobioides grahamae Palmer & Wheeler, 1955 were obtained from the municipality of Salvaterra on Marajó Island in the Brazilian state of Pará. Their livers were removed and processed for light microscopy. Overall, 90% of the specimens presented some degree of steatosis of the liver, which was invariably associated with the presence of Microsporidium sp. The present study confirms the occurrence of steatosis in G. grahamae associated with parasitic infections by Microsporidium. The findings indicate that the condition of otherwise healthy fishes in their natural environment may be affected negatively by parasites.

Lymphocytic meningoencephalomyelitis associated with Myxobolus sp. (Bivalvulidae: Myxozoa) infection in the Amazonian fish Eigenmannia sp. (Sternopygidae: Gymnotiformes)

The genus Myxobolus, parasites that infect fishes, which cause myxobolosis, includes spore organisms belonging to the phylum Myxozoa and represents approximately 36% of all species described for the entire phylum. This study describes lymphocytic meningoencephalomyelitis associated with Myxobolus sp. infection in the brain and spinal cord (the central nervous system, CNS) of Eigenmannia sp., from the Amazon estuary region, in the Administrative District of Outeiro (DAOUT), Belém, Pará, Brazil. In May and June 2015, 40 Eigenmannia sp. specimens were captured from this region and examined. The fish were anesthetized, slaughtered and dissected for sexing (gonad evaluation) and studying parasites and cysts; after diagnosing the presence of the myxozoans using a light microscope, small fragments of the brain and spinal cord were removed for histological processing and Hematoxylin-Eosin and Ziehl-Neelsen staining. Histopathological analysis of the brain and spinal cord, based on histological sections stained with Hematoxylin-Eosin, pronounced and diffuse edema in these tissues, and congestion, degeneration, and focal necrosis of the cerebral cortex. The present study describes lymphocytic meningoencephalomyelitis associated with infection by Myxobolus sp. in the central nervous system of Eigenmannia sp.

An anatomopathological study of hepatic coccidiosis (Calyptospora sp.) in the Acará-pixuna, Aequidens plagiozonatus Kullander, 1984 from the Brazilian state of Pará

The present study focuses on the anatomopathological alterations provoked by parasitism by Calyptospora sp. in 40 specimens of Aequidens plagiozonatus collected in Para, Brazil. Examinations of the fresh material by compression of the hepatopancreas and histological sections showed immature forms and oocysts characteristic of the genus Calyptospora, in addition to a large quantity of melanomacrophagic centers spread throughout the organ. No significant inflammation of the hepatic tissue was observed. The melanomacrophagic centers and the compression of the hepatocytes are part of the response of the host to the parasite. This study represents the first record of parasitism by Calyptospora in A. plagiozonatus.