Ultrastructural morphology and phylogeny of Henneguya gilbert n. sp. (Myxozoa) infecting the teleostean Cyphocharax gilbert (Characiformes: Curimatidae) from Brazil

Morphological, histopathological, ultrastructural and phylogenetic analysis of Henneguya archosargus n. sp. (Cnidaria, Myxosporea) infecting the sparid fish Archosargus probatocephalus in Brazilian waters

The introduction of new fish species to the aquaculture industry is essential to halt the progressive decline of natural fish stocks. The sheepshead Archosargus probatocephalus is a commercially valuable sparid fish with potential for breeding in captivity, but with limited information regarding parasitic infections that could pose a significant threat for its sustainable production. Thus, the present study aimed to study the myxozoan diversity infecting A. probatocephalus. A novel Henneguya sp. was detected forming plasmodia in the gill lamellae of specimens inhabiting the Brazilian coast, and is characterized based on morphological, histopathological, ultrastructural, molecular, and phylogenetic data. Myxospore total length was 21.3 ± 0.8 μm, with myxospore body 10.0 ± 0.5 μm long, 6.2 ± 0.3 μm wide, and 4.8 ± 0.5 μm thick. Caudal appendages were 10.3 ± 0.5 μm long and did not present any type of coating. Two pyriform polar capsules, 3.4 ± 0.3 μm long and 1.5 ± 0.2 μm wide, each containing an isofilar polar tubule with 4-5 coils. Histopathological analyses showed large intralamellar polysporic plasmodia associated with vascular congestion of the gill filament and gill lamellae, as well as epithelial hyperplasia causing partial or total fusion of gill lamellae. Maximum likelihood and Baysesian inference SSU rDNA-based phylogenetic analyses showed the novel sequence grouped within the marine clade of Henneguya spp. that mostly parasitize fishes belonging to Eupercaria incertae sedis.

Synopsis of the species of Henneguya Thélohan, 1892 (Cnidaria: Myxosporea: Myxobolidae) described since 2012

The genus Henneguya Thélohan, 1892 (Cnidaria: Myxosporea: Myxobolidae) encompasses a large number of species that mostly infect freshwater fish belonging to 71 families of Actinopterygii. A synopsis of Henneguya species described between 2012 and 2022 is herein presented. It includes 57 species described during the last decade, and one species missing from the previous synopses, adding to a total of 254 species that have been formally described within this genus. Biological characters and myxospore morphometry are presented for each species record.

Description of Two Novel Henneguya (Cnidaria: Myxosporea) Infecting Curimatid Fish, Using Morphological, Histological, and Molecular Analyses

PURPOSE

We describe two new Henneguya spp. (Myxobolidae) found parasitizing Cyphocharax modestus from Pardo river, Paraná river basin, municipality of Botucatu, São Paulo State, Brazil: Henneguya fastigata n. sp. from gill lamellae and Henneguya pardensis n. sp. from gill arches. We based the descriptions on myxospore morphology, histology, and small subunit ribosomal DNA sequences.

METHODS

In this investigation, 50 specimens of Cyphocharax modestus were examined between July and December 2020 for myxozoan infections. Morphological characterization was based on the mature myxospores. The small subunit ribosomal DNA sequences were used for molecular and phylogenetic study.

RESULTS

Phylogenetic analysis provided the evolutionary position of these new species with other myxobolids species. Myxospores of the two species had similar morphology and morphometrics, but differed in spore body width and length, and ssrDNA sequences differed by 7.2%. These data supported the diagnosis of the parasites as distinct and novel species. The phylogenetic analysis showed a well-supported subclade formed by species that parasitize curimatid fishes, with Henneguya gilbert as a sister species of Henneguya fastigata n. sp., and Henneguya pardensis n. sp. as a sister species of both species.

CONCLUSION

Our analysis was consistent with previous studies suggesting that orders and families of the hosts are strongly correlated with phylogenetic signals in the Myxobolidae. These are the first species of myxozoans described in the Pardo river.

Description of a new species of myxobolid parasite, Henneguya pindaibensis n. sp. (Cnidaria: Myxosporea), infecting the gills of Boulengerella cuvieri (Spix and Agassiz, 1829) from Brazil

Myxozoans are microscopic cnidarians that mainly parasitize fishes. The present study aimed to describe a new myxozoan parasite from the gills of Boulengerella cuvieri (Spix and Agassiz, 1829) by morphological and molecular analysis. The fish was collected in 2019 at the Pindaíba River, municipality of Cocalinho, Mato Grosso State, Brazil. Whitish and circular plasmodia were found in the primary gill filaments, occupying an intralamellar position, with an average of 0.5 mm in diameter. Henneguya Thélohan, 1892 myxospores found inside the plasmodia were elongated and ellipsoidal, consisting of two long and elliptical shell valves with two long, tapering caudal appendages. Morphometric measurements revealed a total spore length of 36.1 ± 2.0 μm; spore body length of 12.8 ± 0.5 μm; spore width of 4.9 ± 0.3 μm; tail length of 23.3 ± 1.6 μm; capsule length of 7.2 ± 0.4 μm; capsule width of 1.5 ± 0.2 μm; and 10 coils in the polar filament. Phylogenetic analysis showed that the isolates from this study were grouped into the main-clade of freshwater fishes, within a group of species parasitizing fishes from Brazil. Intergenotypic difference ranged from 23%-25.9% compared with other Brazilian myxozoan isolates. Using molecular and morphological characterization, this parasite was identified as a new species of the genus Henneguya.

Molecular and morphological analysis of Henneguya jundiai n. sp. (Cnidaria: Myxosporea), a new parasite of the gills of Rhamdia quelen in Brazil

Plasmodia containing spores of a new species of myxozoan, Henneguya jundiai n. sp., were found in the gill arches of Rhamdia quelen catfish. The present study describes H. jundiai n. sp. based on morphological and molecular analysis. The mature spores were elongated and measured 26.9 ± 1.9 (22.9-29.2) μm in total spore length, 9.5 ± 0.4 (8.8-10.0) μm in spore body length, 4.6 ± 0.4 (4.1-5.5) μm in spore body width, 17.3 ± 1.8 (14.1-19.8) μm in tail length, 4.9 ± 0.3 (4.6-5.5) μm in polar capsule length and 1.4 ± 0.2 (1.2-1.7) μm in polar capsule width. The polar filaments had 6-7 coils. Histological analysis revealed the formation of a large plasmodium connected to the gill arch through the epithelial tissue. Ultrastructural analysis revealed the presence of a binucleated sporoplasm, as well as the polar capsules and the coils of the polar filament. Phylogenetic analysis found that H. jundiai n. sp. is located within a subclade formed by species of Henneguya which parasitize siluriform fish from Brazil. Henneguya jundiai n. sp. appears as a sister species of H. quelen. The results of the analyzes clearly indicated the existence of a new species, H. jundiai.

Skin nodules associated with parasitism with Henneguya sp. (Cnidaria: Myxosporea) in the neotropical fish Cyphocharax modestus

A new myxozoan species, Henneguya sp., is described based on material from skin of Cyphocharax modestus. Mature myxospores are were elongate and ellipsoidal, measuring 21.4 ± 1.2 (19.4-23.2) μm in total length, 5.1 ± 0.3 (4.5-5.8) μm in width, 11.9 ± 0.5 (10.9-12.7) μm in body length and 9.6 ± 0.7 (8.4-10.5) μm in length of the caudal process. The polar capsules were elongated and had unequal sizes, with length of 5.1 ± 0.4 (4.5-6.0) μm and 5.6 ± 0.4 (4.9-6.3) μm for smaller and larger respectively and width of 1.8 ± 0.2 (1.4-2.0) μm. The larger polar capsule had 8 turns in polar filament while the smaller polar capsule had 5 turns in polar filament. The macroscopic analysis revealed the presence of large nodules, which were located before and after the dorsal fin of the hosts. The histopathological analysis showed the development of nodules filled with plasmodia, surrounded by loose connective tissue, developed in the dermis of the skin. Many cysts containing countless spores, as well as free spores, were located in the dermis and hypodermis of the hosts, causing the disorganization of the connective tissue that is responsible for the support. This is the first record of a Henneguya species in C. modestus.

A new species of Myxosporea, Henneguya quelen, from silver catfish Rhamdia quelen (Siluriforme: Pimelodidae) in the Amazonian region

Henneguya quelen n. sp. (Myxosporea) is described from the kidney of the silver catfish, Rhamdia quelen (Quoy & Gaimard, 1824), from Marajó Island. In all, 40% of the 57 silver catfish collected from the Paracauari River in the municipality of Salvaterra presented cysts in the kidney. The cysts were whitish, spherical, and 0.45 mm in diameter. The histological analyses revealed tubular renal compression and cellular degeneration in the area adjacent to the xenomas. The spores are ellipsoid, with well-marked valves, caudal projection, and two elongated polar capsules of equal size. The mature spores measure approximately 15.6 μm in length, with the caudal appendage split posteriorly; 24.3 μm in length, for a total spore length of 40.0 μm; and a width of 4.1 μm. The polar capsules are pyriform, 5.5 μm long and 1.7 μm wide. A phylogenetic analysis based on Bayesian inference confirmed that the specimens represented a new species, which was denominated Henneguya quelen n. sp.