Increasing the known biodiversity of cnidarian parasites of bryconid fishes from South America: two novel Myxobolus species with ultrastructure and ssrDNA-based phylogeny.

This study increases the known biodiversity of cnidarian parasites in neotropical bryconid fishes. Two novel Myxobolus species are described based on morphology, ultrastructure and small subunit ribosomal DNA (ssrDNA) sequencing: Myxobolus vetuschicanus n. sp. infecting fins of Salminus franciscanus and Myxobolus mineirus n. sp. infecting the mesentery of Brycon orthotaenia from the São Francisco River basin, Minas Gerais State, Brazil. Ultrastructural analysis of the two species revealed an asynchronous sporogenesis process, with germinative cells and young developmental stages of myxospores in the periphery of the plasmodia. In M. vetuschicanus n. sp., the plasmodia were surrounded by a layer of fibroblasts and in M. mineirus n. sp., the plasmodial membrane had direct contact with the host tissue. The phylogenetic analysis based on the ssrDNA of Henneguya/Myxobolus species showed that the two novel Myxobolus species grouped in subclades together with other parasite species of bryconid fishes.

Morphology and molecular data of two novel cnidarian myxosporean (Myxobolidae) infecting Piaractus brachypomus from the Amazon basin.

The objective of this study was reports, through morphological and small subunit ribosomal DNA (SSU rDNA) sequencing, two novel myxobolid myxosporeans infecting Piaractus brachypomus, an economicaly important Amazonian fish popularly known as "pirapitinga". Of a total of 25 specimens of P. brachypomus examined 68% had the gill filament parasitized by Henneguya tapariensis n. sp. and 16% had infection of Myxobolus arapiuns n. sp. in the pyloric cecum. The morphological analysis revealed H. tapariensis n. sp. myxospores with an ellipsoid shape and caudal process larger than the length of the body. The polar capsules of same size were elongated and occupied less than half the body. Sequencing of the SSU rDNA generated a partial sequence of 1946 bp. In M. arapiuns n. sp. the myxospores had oval-shaped body and polar capsules of the same size, occupying less than half the body. Sequencing of the SSU rDNA generated a partial sequence of 1950 bp. Phylogenetic analysis revealed a cluster according to the order/family of the host, where H. tapariensis n. sp. was grouped in a subclade with Henneguya brachypomus and Henneguya piaractus and M. arapiuns grouped in a subclade with Myxobolus colossomatis, Myxobolus matosi and Myxobolus pirapitingae.

Novel myxosporean species parasitizing an economically important fish from the Amazon basin.

This paper provides morphological and phylogenetic analyses of two new myxobolid species found infecting Piaractus brachypomus from the Amazon basin. The fish were caught in the Tapajós River, in the municipality of Santarém, in the state of Pará, Brazil. The plasmodial development of Henneguya brachypomus n. sp. occurred in the gill lamellae while Myxobolus pirapitingae n. sp. developed in the pyloric cecum. Morphological analyses did not identify inflammatory infiltrate for either species, but H. brachypomus n. sp. induced stretching of the epithelium, compression of the adjacent tissues, and displacement and deformation of the neighboring lamellae. The mature myxospores of H. brachypomus n. sp. were ellipsoid, with a length of 11.7-13.8 µm, a width of 4.0-4.6 µm, and a thickness of 3.5-4.3 µm. The polar capsules were elongated, with a length of 5.6-7.3 µm and a width of 1.3-2.0 µm, and each contained a polar filament with 8-9 coils. The caudal process was 40.5-48.1 µm long and the total length of the myxospore was 52.4-61.6 µm. Myxobolus pirapitingae n. sp. exhibited rounded mature myxospores measuring 10.0-11.1 µm in length, 7.0-7.6 µm in width, and 5.4-6.3 µm in thickness. The polar capsules were of equal size and occupied less than half the myxospore, measuring 3.5-4.0 µm in length and 2.0-2.6 µm in width, with each containing a polar filament with 6-7 coils. Phylogenetic analysis based on partial small subunit ribosomal DNA (ssrDNA) sequences showed that H. brachypomus n. sp. clustered as a sister species of Henneguya piaractus, while M. pirapitingae n. sp. was grouped in a sub-clade together with Myxobolus matosi and Myxobolus colossomatis.

Taxonomy, phylogeny and host-parasite interaction of two novel Myxobolus species infecting Brycon orthotaenia from the São Francisco River, Brazil.

Two new Myxobolus species were described infecting Brycon orthotaenia from the São Francisco River, in the state of Minas Gerais, Brazil. From a total of 39 B. orthotaenia collected, two specimens (5.1%) exhibited infection of the ovary and 12 specimens (30.8%) displayed infection of the liver. The plasmodia of both Myxobolus species were white and spherical measuring around 1 mm in length. The plasmodium found in the ovary showed mature myxospores, which were oval shaped from the frontal view and measured 9.2-11.0 (9.8 ± 0.4) µm in length, 5.9-6.9 (6.5 ± 0.3) µm in width and 4.6-5 (4.9 ± 0.1) µm in diameter. The two polar capsules were the same size and measured 3.9-6.2 (4.7 ± 0.5) µm in length and 1.8-2.4 (2.1 ± 0.2) µm in width. The polar tubules had 9 coils. The plasmodium found in the liver showed mature myxospores which were ellipsoidal in shape from the frontal view and measured 10.0-11.4 (10.7 ± 0.5) µm in length, 7.3-8.6 (8.1 ± 0.4) µm in width and 5.3-7.0 (6.8 ± 0.4) µm in diameter. The two polar capsules were the same size and measured 4.2-5.4 (4.9 ± 0.3) µm in length and 1.9-2.9 (2.7 ± 0.3) µm in width. The polar tubules had 8 coils. Ultrastructural analysis revealed an asynchronous sporogenesis process, with young developmental myxospore stages more often found in the periphery of the plasmodium and mature myxospores in the centre of the plasmodium. The plasmodial wall was formed by a single membrane which was not surrounded by a layer of host tissue. A thick layer of fibrous material was found in the peripheral ectoplasm close to the plasmodial wall of the plasmodium found in the ovary. Phylogenetic analysis based on the small-subunit ribosomal DNA - ssrDNA sequences and using the closest myxozoan sequences to each one of the species studied here based on previous GenBank data and Henneguya/Myxobolus/Thelohanellus species parasitizing fish from South American, revealed that the new species are grouped in a subclade together with other Myxobolus species parasitizing bryconid hosts.

Morphological, ultrastructural, and phylogenetic analysis of two novel Myxobolus species (Cnidaria: Myxosporea) parasitizing bryconid fish from São Francisco River, Brazil.

Twelve Myxobolus species have been previously described to parasitize Bryconidae fish in South America. Here, we describe two novel myxosporean species that parasitize economically important Bryconidae from the São Francisco River basin in Brazil. Myxospores morphometry, morphology, small-subunit ribosomal DNA - ssrDNA sequences, and other biological traits were used in the taxonomic analysis. Phylogenetic analysis was performed to assess the position of the new Myxobolus species among the closest Myxobolus/Henneguya. Myxobolus iecoris n. sp. was found infecting the liver of Salminus franciscanus (dourado). Myxospores were oval with the anterior region aculiform in frontal view and biconvex in lateral view and measured 11.4-14.2 (12.8 ±â€¯0.8) µm long, 7.7-9.9 (8.7 ±â€¯0.6) µm wide, 6.5-7.5 (6.9 ±â€¯0.4) µm thick. Two pyriform and equal-sized polar capsules measuring 4.9-7.4 (5.9 ±â€¯0.5) µm long and 2.3-3.5 (3.0 ±â€¯0.2) µm wide contained polar tubules with 8-9 turns. Myxobolus lienis n. sp. was found infecting the spleen of Brycon orthotaenia (matrinxã). Myxospores were round to oval in frontal view and biconvex in lateral view and measured 10.3-13.8 (12 ±â€¯0.6) µm long, 6.8-9.3 (8.3 ±â€¯0.5) µm wide, and 6.9-7.0 (7.0 ±â€¯0.6) µm thick. Two oval and equal-sized polar capsules measured 3.9-5.8 (4.6 ±â€¯0.5) µm long and 2.0-3.5 (2.8 ±â€¯0.3) µm wide contained polar tubules with 5-6 turns. Ultrastructural analysis revealed asynchronous sporogenesis with germinative cells and young sporogonic stages in the periphery of the plasmodia. A connective tissue capsule was observed surrounding Myxobolus lienis n. sp., but it was absent for Myxobolus iecoris n. sp. Maximum likelihood and Bayesian inferences showed the two novel species clustering in a well-supported subclade composed by Myxobolus spp. of bryconids. Myxobolus iecoris n. sp. appeared as a sister species of M. aureus and Myxobolus lienis n. sp. as sister to M. umidus.

Henneguya cuniculator sp. nov., a parasite of spotted sorubim Pseudoplatystoma corruscans in the São Francisco Basin, Brazil.

Henneguya cuniculator sp. nov. was found infecting spotted sorubim catfish Pseudoplatystoma corruscans from the São Francisco River, Minas Gerais, Brazil. The parasites form elongated plasmodia of up to 1 cm in length in the gill filaments. Mature spores were ellipsoidal from the frontal view, with total length of 29.4 ± 2.4 (mean ± SD, range 23.3-32.4) µm, body length of 12.1 ± 1.0 (10.0-14.7) µm, width of 4.8 ± 0.4 (4.0-5.9) µm, and tail length of 16.7 ± 2.0 (12.3-19.4) µm. From the lateral view, spores were biconvex, with thickness of 4.2 ± 0.7 (3.9-4.9) µm. The polar capsules were elongated and equal in size, 6.2 ± 0.3 (5.2-6.2) µm in length, and 1.8 ± 0.1 (1.4-1.9) µm in width. Ultrastructural analysis showed that the plasmodial wall had delicate projections towards the host tissue and a thin layer that prevented contact between the host cells and the parasite. In the ectoplasm, few mitochondria were observed, while generative cells, early stages of sporogenesis, and advanced spore development occurred in the plasmodial periphery, and more mature spores in internal regions. Histopathological analysis showed that plasmodia developed in the sub-epithelial connective tissue of gill filaments, causing compression of the adjacent tissues, deformation of gill filaments, and lamellar fusion. Phylogenetic analysis, based on 18S rDNA genes and using only Henneguya/Myxobolus species parasites of siluriform fish, showed grouping according to the fish family.