Trace metal accumulation is infrapopulation-dependent in acanthocephalans parasites of the white mullet (Mugil curema) from an estuarine environment of southeastern Brazil coast.

Here, in an estuarine canal in southeast Brazil, we evaluated the potential for trace metal accumulation of the acanthocephalan parasite Floridosentis mugilis, which infects the fish host Mugil curema. The quantities of the trace metals were quantified using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), which was used to analyze samples of the fish's muscle, intestine, and liver as well as the parasites. The parasites and the host's tissues had significantly different trace metal concentrations, according to our data. Furthermore, some metals have quite high bioconcentration factors, including Al, Cr, Ni, and Cd. We also found that the trace metal concentrations in the parasites were impacted by the sizes of the parasitic infrapopulations, with smaller infrapopulations tending to accumulate more metals. This study shows this acanthocephalan species' effective ability to store metals and is the first to investigate metal accumulation using it as a model.

Oncoceratium amphidactylum n. gen. n. sp. (Monogenoidea: Gyrodactylidae) from Hoplosternum littorale (Hancock) (Siluriformes, Callichthyidae) from southeastern Brazil.

Oncoceratium n. gen. is proposed to accommodate Oncoceratium amphidactylum n. gen. n. sp. (Monogenoidea, Gyrodactylidae). Although the proposed genus is monotypic, the differences presented in the diagnosis clearly establish it as distinct from species from other genera, such as Gyrodactylus von Nordmann, 1832 and especially those that occur exclusively in the Neotropical region. The new genus is diagnosed by the presence of a bulbous male copulatory organ, with one row of spinelets of similar sizes and shapes, while the only spine usually found in the gyrodactylids is absent or not differentiated; a haptor with anchors presenting points folded outwards, and superficial and deep roots continuous and indistinguishable; the absence of a deep bar; and hooks in two bilateral clusters of eight hooks. Oncoceratium amphidactylum n. gen. n. sp. is described from the tamboatá fish, Hoplosternum littorale (Hancock) (Callichthyidae), and is characterized by the presence of a pair of horn-shaped anchors with the point turned outwards, a superficial bar shield and absent deep bar, hooks disposed in bilateral lobes, and a MCO with no spine or with a row with large spinelets visible in place of the spine. In addition to the morphological features, distance analysis and Bayesian inference, based on 5.8s and partial ITS2, support placing the new species in a new genus, and not including it in a cluster of species of Gyrodactylus and near to Gyrodactyloides bychowskii Albova, 1948, Ieredactylus rivuli Schelkle et al., 2011 and Laminiscus gussevi (Bychowsky & Polyansky, 1953) Pálsson & Beverely-Burton, 1983.

Bioaccumulation and health risk assessment of trace metal contamination in the musculature of the trahira fish (Hoplias malabaricus) from two neotropical rivers in southeastern Brazil.

BACKGROUND: Fish are an important source of nutrition for humans. Artisanal fishing plays a fundamental role in Brazil fish production. In Brazil, the unrestrained increase, diffusion, and little importance for environmental causes of other economic activities, such as the agricultural industry, has caused irreparable damage, leading to the contamination of water bodies. Among the countless pollutants that reach water bodies, trace metals are extremely problematic. Here, we evaluated the bioaccumulation and health risk of trace metal contamination in the musculature of the trahira fish (Hoplias malabaricus), collected from two rivers in southeastern Brazil. METHODS: During the period from May 2017 to November 2019, 90 fish were collected, 45 from each river. River water samples were also taken during the same collection periods. From fish, muscle tissue samples were taken, and together with river water samples, analyzed for the recovery of trace metals (Al, Cr, Mn, Fe, Ni, Cu, As, Cd, and Pb) through the technique of Inductively Coupled Plasma Mass Spectrometry (ICP-MS). RESULTS: In general, fish as well as the waters of the Jacaré-Guaçú River had higher concentrations of metals. The elements Al, Cr and Cd stood out from the others analyzed metals for having a hazard index (HQ) above 1 (Al), for being up to 10 times above the concentrations allowed by Brazilian legislation (Cr) and for having a high bioconcentration factor (Cd), indicating a biomagnification process through the food chain. CONCLUSION: In general, trace metal concentrations in the waters and fish of the Jacaré-Guaçú were higher than in the Jacaré-Pepira, which shows that the Jacaré-Guaçú is the one that suffers more anthropogenic action between the two rivers. In addition, some elements such as Al, Cr and Cd, due to its high concentrations, should receive some attention as they can pose risks to the health of fish, which can jeopardize the survival of their populations, and especially to humans who use these animals as a food source.

Morphological and molecular characterization of Hysterothylacium spp. parasitizing Pomatomus saltatrix and Pagrus pagrus of the State of São Paulo, Brazil.

Raphidascarid nematodes have been the focus of several studies, mainly due to the zoonotic potential of some species, even though the cases are underreported. Due to the difficulty in identifying their larvae, the use of diagnostic techniques involving morphological and molecular analyses has grown in the last 20 years. The present study had as objective the morphological and molecular characterization of the L3 larval types of Hysterothylacium collected in Pomatomus saltatrix and Pagrus pagrus from the Brazilian coast, close to the municipality of Santos, State of São Paulo. Twenty specimens of P. saltatrix were necropsied and Hysterothylacium type V (n = 257) and Hysterothylacium type X (n = 5) larvae were found. Five specimens of P. pagrus were necropsied and all were parasitized by Hysterothylacium type V larvae. The analyses showed a genetic proximity relationship between Hysterothylacium types V with other Hysterothylacium V and with H. deardorffoverstreetorum, although this is a species inquirenda. Haplotypes for Hysterothylacium type X found in the present study formed a monophyletic group with other Hysterothylacium X, H. amoyense, and H. zhoushanense. Through this study, new hosts and localities were registered for Hysterothylacium type V and Hysterothylacium type X.

Taxonomy and Systematics of Two New Species of Myxobolus (Cnidaria: Myxobolidae) Parasitizing the Gills of Mugil curema (Mugilidae) from the Brazilian Coast.

PURPOSE: We describe two new species of Myxobolus (Myxobolidae) found parasitizing Mugil curema from two locations in Brazil: Myxobolus curemae n. sp. from gill arch and rays and Myxobolus maceioensis n. sp. from gill lamellae. METHODS: We based the descriptions on myxospore morphology, histology, and small-subunit ribosomal DNA sequences. RESULTS: Myxospores of the two new species had similar morphology and morphometry but differed in spore body width and length, and ssrDNA sequences differed by 10.5%. These data supported the diagnosis of the parasites as distinct and novel species. The phylogenetic analysis showed a subclade formed by species that parasitize Mugiliformes, with M. maceioensis n. sp. as a sister species of Myxobolus episquamalis and Myxobolus bizerti, while there is a group of six species that are sister related to M. curemae n. sp. Our analysis was consistent with previous studies suggesting that orders of the hosts are strongly correlated with phylogenetic signals in the Myxobolidae. CONCLUSIONS: Myxobolus curemae n. sp. and M. maceioensis n. sp. are new species identified parasitizing M. curema.

Morphology and molecular phylogeny of Hoferellus jutubensis n. sp. (Cnidaria: Myxozoa) found parasitising Ageneiosus inermis (Siluriformes: Auchenipteridae), in the Brazilian Amazon region.

The present study describes Hoferellus jutubensis n. sp., a myxozoan parasite found in the urinary bladder of the driftwood catfish Ageneiosus inermis, captured on Jutuba Island in the state of Pará, northern Brazil. A total of 30 A. inermis specimens were examined, of which 26 (86.7%) had myxospores and polysporic plasmodia of varying shapes and sizes dispersed in the lumen of the urinary bladder, either floating freely or attached to the epithelium. In the apical view, the myxospores of Hoferellus jutubensis n. sp. are rounded, 6.1 ± 0.2 (5.7-6.3) µm long and 5.5 ± 0.3 (5.2-6.0) µm wide, with two sub-spherical polar capsules, equal in size and shape, 2.5 ± 0.2 (2.3-2.7) µm long and 1.7 ± 0.2 (1.4-2.2) µm wide. The phylogenetic analysis of a partial sequence of the SSU rDNA gene, indicated that the new species is the sister taxon of Hoferellus azevedoi, with these two species forming a Brazilian lineage of Hoferellus. The comparison of the morphological and molecular data with those of the existing members of the genus confirmed the species status of Hoferellus jutubensis n. sp., which adds one further Hoferellus taxon to the known myxosporean diversity of the Amazon basin.

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.

A new species of Phanerothecium (Monogenea, Oogyrodactylidae), in Hypostomus regani (Loricariidae) from southeast Brazil / Uma nova espécie de Phanerothecium (Monogenea, Oogyrodactylidae), de Hypostomus regani (Loricariidae) do sudeste do Brasil

Abstract: A new species of Phanerothecium Kritsky & Thatcher, 1977 (Oogyrodactylidae Harris, 1983) is described from locariid fish from southeast Brazil. Phanerothecium macrosomum n. sp. (Oogyrodactylidae) is described from the body surface of Hypostomus regani (Ihering, 1905) (Loricariidae). It is characterized by an armed male copulatory organ containing spines of different size from proximal to distal extremity, short peduncle and robust haptor.

Resumo: Uma nova espécie de Phanerothecium Kritsky & Thatcher, 1977 (Oogyrodactylidae Harris, 1983) é descrita em peixes locariídeos do sudeste do Brasil. Phanerothecium macrosomum sp. n. (Oogyrodactylidae) é descrito da superfície corporal de Hypostomus regani (Ihering, 1905) (Loricariidae) e é caracterizado pela presença de órgão copulador masculino armado contendo espinhos de diferentes tamanhos da extremidade proximal à distal, pedúnculo curto e haptor robusto.

Qualitative and quantitative study of parasites of Pimelodus maculatus and Rhamdia quelen from the Jacaré-Pepira River, state of São Paulo, Brazil.

In the freshwater ecosystems of Brazil can be found high biodiversity of fish, about 5160 species. However, the Jacaré-Pepira River, located in the state of São Paulo, Brazil, presents a diversity of fish still to be explored in ichthyological studies. Metazoan parasites of Pimelodus maculatus and Rhamdia quelen were qualitatively and quantitatively diagnosed. Ten species of parasites (Demidospermus sp., D. majusculus, D. bidiverticulatum, D. paravalenciennesi, Ameloblastella paranaensis, Scleroductus sp., Riggia sp., Austrodiplostomum compactum, Helobdella sp. and Neochinorhynchus pimelodi) were collected in P. maculatus and eight species of parasites (Aphanoblastella robustus, A. mastigatus, Phyllodistomum rhamdiae, Crocodilicola pseudostoma, Henneguya jundiai, Contracaecum sp., Rhabdochona sp. and Capillariidae gen. sp.) were collected in R. quelen. All parasites presented aggregate distribution. A significant correlation was observed in P. maculatus concerning the weight with the prevalence of ectoparasite D. majusculus; however, R. quelen showed a relation to the length and weight with the abundance of ectoparasite A. mastigatus and endoparasites. The parasitic community of P. maculatus and R. quelen was characterized by high diversity, high richness, and low uniformity.

Morphological and molecular data of new species of Characithecium and Diaphorocleidus (Monogenea: Dactylogyridae) from Neotropical characid fishes.

The present study describes three new species of monogenean parasites of characid fishes from the Upper Paraná River basin, Brazil: Characithecium paranapanemense n. sp. on Psalidodon paranae and Psalidodon bockmanni, Diaphorocleidus magnus n. sp. on Astyanax lacustris and Psalidodon fasciatus, and Diaphorocleidus neotropicalis n. sp. on Astyanax lacustris and P. bockmanni. An amendment for Diaphorocleidus is proposed, since additional characters observed in the new species required to extend the generic diagnostic features mainly to include: articulation process connecting the base of the MCO with accessory piece present or absent, and accessory piece with variable shapes (plate-like, pincer-shaped, wrench-shaped, sheath-shaped), divided or not into subunits. Characithecium paranapanemense n. sp. can be distinguished from other congeners by the morphology of its MCO and accessory piece. Diaphorocleidus magnus n. sp. differs from most of its congeners by the morphology of its accessory piece, the presence of articulation process connecting the base of the MCO with accessory piece, and the morphology of the sclerotized structures of the haptor. Diaphorocleidus neotropicalis n. sp. can be easily distinguished from its congeners by the morphology of the accessory piece, the sclerotized structures of the haptor and the morphology of the vagina. Molecular data of the new species (partial 28S rDNA and mitochondrial cytochrome oxidase I) were obtained and the first phylogenetic analysis based on 28S rDNA gene sequences for species of Characithecium and Diaphorocleidus are provided. Although Diaphorocleidus and Characithecium share some morphological similarities, phylogenetic analysis indicates that species of these two genera are not closely related.

Morphological and molecular analysis of Henneguya tietensis n. sp. (Cnidaria: Myxosporea), parasitizing the gill filaments of Prochilodus lineatus (Valenciennes, 1837) from Brazil.

The present study describes Henneguya tietensis n. sp. parasitizing Prochilodus lineatus (Valenciennes, 1837) from Brazil, through morphological and molecular analysis. Myxospores were found in the gill tissue of P. lineatus with a prevalence of 10%. The myxospores consisted of two elongate, elliptical shell valves each with a long, tapering caudal appendage. The morphology was consistent with Henneguya and the myxospore measured as follows (mean ± SD): total length 55.5 ± 2.1 µm, body length 16.2 ± 1.1 µm, body width 5.5 ± 0.1 µm, caudal appendages length 39.0 ± 2.0 µm. The polar capsules were 7.3 ± 0.2 µm long, 1.7 ± 0.2 µm wide and contained a polar filament coiled 11 to 13 turns. Histological analysis showed the plasmodia developing in the middle region of each gill filament and caused a focally extensive distension by forming a space-occupying mass within the gill filament. The ultrastructural analysis allowed the observation of the presence of mature myxospores throughout the plasmodium. Phylogenetic analysis with the SSU rDNA gene showed Henneguya tietensis n. sp. as a sister species of the subclade formed by Henneguya piaractus and Henneguya brachypomus that infect fishes of the genus Piaractus. The genetically closest species was H. piaractus, which showed a similarity of 82.4%. Using molecular and morphological characterization, the myxozoan parasite described herein represents a new species of the genus Henneguya.

Morphological and molecular analysis of Henneguya lagunensis n. sp. (Cnidaria, Myxosporea) parasitizing the gills of Eugerres brasilianus from Brazil.

Plasmodia containing myxospores belonging to the genus Henneguya Thélohan, 1892 were found in the gills of Eugerres brasilianus (Cuvier, 1830). Despite the economic importance, few parasitological studies have been done with this species. We describe Henneguya lagunensis n. sp. using morphological and molecular data. The mature myxospores were rounded, measuring 29.1 ± 2.2 µm in total length, 8.2 ± 1.0 µm in body length, 7.9 ± 0.2 µm in body width, 20.7 ± 2.4 µm in tail length and 4.8 ± 1.0 µm in thickness. The polar capsules measured 3.3 ± 0.4 in length and 1.7 ± 0.3 µm in width. Polar filaments had 4-5 turns, helical. Phylogenetic analysis showed Henneguya lagunensis n. sp. as a sister species of Henneguya cynoscioni Dyková, Buron, Roumillat and Fiala, 2011, within a clade that contained mostly Henneguya species that parasitize marine fish of the order Perciformes. This is the first report of a species of Henneguya parasitizing Eugerres brasilianus.

Patterns of distribution and accumulation of trace metals in Hysterothylacium sp. (Nematoda), Phyllodistomum sp. (Digenea) and in its fish host Hoplias malabaricus, from two neotropical rivers in southeastern Brazil.

Here we evaluated the potential for trace metal accumulation of two parasitic species, Hysterothylacium sp. (Nematoda) and Phyllodistomum sp. (Digenea), found parasitizing Hoplias malabaricus, a characiform fish also known as trahira, collected from two neotropical rivers, Jacaré-Pepira and Jacaré-Guaçú, in southeastern Brazil. Fish were collected between July 2017 and July 2019, totaling 90 fish specimens analyzed, 45 from each river. From fish, we take samples of three different tissues: muscle, intestine and liver. Along with the parasite samples taken from fish hosts, tissue samples were analyzed by an Inductively Coupled Plasma Mass Spectrometer (ICP-MS) for obtaining the trace metal (Al, Cr, Mn, Fe, Ni, Cu, As, Cd e Pb) concentrations. All elements were found in statistically higher concentrations in the parasites, both nematodes and digeneans, than in the host tissues, but in comparison, was observed that Hysterothylacium sp. had higher concentrations than those obtained in Phyllodistomum sp. We also found that uninfected fish had statistically higher concentrations of metals than infected ones. And in those who are infected, the size of the parasitic infrapopulations correlated negatively with the concentrations of trace metals obtained in the hosts tissues, that is, the concentrations in fish showed a tendency to decrease as the parasitic infrapopulations increased, or vice versa. In addition, our results show that the influence of the parasitic infrapopulations on metal concentrations in the fish host is not affected in cases of mono-infection or co-infection.

A new species, Henneguya lacustris n. sp. (Cnidaria: Myxosporea), infecting the gills of Astyanax lacustris from Brazil.

The present study describes Henneguya lacustris n. sp. parasitizing Astyanax lacustris (Lütken 1875), from the Tietê River, State of São Paulo, Brazil, through morphological and molecular analysis. Myxospores of the parasites were found in the gills of A. lacustris with 13% prevalence of infection. The myxospores were oval and presented as measures (mean ± standard deviation): total length 18.3 ± 2.2 µm, body length 10.4 ± 1.6 µm, body width 4.9 ± 0.9 µm, tail length 7.2 ± 2.5 µm. The polar capsule was 4.8 ± 0.3 µm long and 1.5 ± 0.2 µm wide. The polar tubules, present inside the polar capsules, had 6 to 7 turns. The ultrastructural analysis allowed the observation of the asynchronous development of the myxospores. Phylogenetic analysis showed H. lacustris n. sp. as a sister species of H. chydadea Barassa and Cordeiro 2003 in a subclade formed by species that parasitize the gills of Characiform fish from Brazil. Using molecular and morphological characterization, this parasite was identified as a new species of the genus Henneguya Thélohan 1892.

Molecular characterization of the progenetic metacercariae Crocodilicola pseudostoma parasitizing Rhamdia quelen (Siluriformes, Heptapteridae) in Brazil.

The trematodes have developed several adaptations and strategies to complete their life cycle in the intermediate host, without even reaching the definitive host. Thus, metacercariae through progeny can produce viable eggs by self-fertilization in the second intermediate host. We analyzed 30 specimens of Rhamdia quelen Quoy & Gaimard 1824 (Siluriformes, Heptapteridae) collected in the Jacaré-Pepira River, Ibitinga. Among the specimens analyzed, only one host was parasitized by the progenetic metacercariae of Crocodilicola pseudostoma Willemoes-Suhm 1870 (Digenea: Proterodiplostomidae) presenting prevalence of 3.3%, mean intensity of 68.0 ± 12.4 and mean abundance of 2.3 ± 0.4. This is the first record of progenesis in the metacercariae of C. pseudostoma in the Jacaré-Pepira River, as well as the first partial sequence of COI gene obtained from this species in Brazil.

Biodiversity of parasites found in the trahira, Hoplias malabaricus (Bloch, 1794), collected in the Batalha River, Tietê-Batalha drainage basin, SP, Brazil.

Eighty-one Hoplias malabaricus specimens were collected between February 2014 and June 2016. A total of 29 species of metazoan parasites were found, 13 of which were identified as monogeneans, seven were digenean species, seven of which were nematodes, and two of which were from the subclass Hirudinea. The highest prevalence values ​​were presented by Contracaecum sp. and Tylodelphys sp. The highest mean abundance and mean intensity was recorded by Tylodelphys sp.; the values were ​​36.7 ± 61.8 and 55.65 ± 69.1, respectively. The abundance of the monogenean Urocleidoides cuiabai was found to be positively correlated with host weight. The abundance of Bucephalidae gen. sp. exhibited significant positive correlations with host weight and length. For Contracaecum sp., a significant negative correlation was found between its abundance and host length and weight. No significant differences between the diversity indexes (Margalef, Pielou and Shannon) of the parasites collected in the two points were found. The Sorensen similarity index, with a value of 0.82 between the two sampling points revealed that the parasitic diversity between them is similar. The findings from this study represent new records of occurrence of H. malabaricus, as well as of Urocleidoides margolisi, Scleroductus sp. and Helobdella sp.

A new species of Tereancistrum (Monogenea: Dactylogyridae), parasite of Prochilodus lineatus (Characiformes: Prochilodontidae) from southeast Brazil.

A new species of Tereancistrum Kritsky, Thatcher & Kayton, 1980 collected of Prochilodus lineatus gills from the Batalha River, Tietê-Batalha basin, São Paulo State, Brazil is described. The new species can be distinguished from its congeners mainly by the configuration of the ventral bar, which has an anvil-shaped characteristic with corrugated anterior projection. Tereancistrum takemotoi n. sp. is morphologically similar to T. toksonum Lizama, Takemoto & Pavanelli, 2004 in terms of their dorsal bars (Y-shaped), their dorsal anchors with divergent roots (superficial and deep) wherein their deep root rather elongated, and by the fact that they both have the male copulatory organ counterclockwise. However, only T. takemotoi n. sp. presents the male copulatory organ with 2» rings and shows undulations in the anterior margin of the dorsal bar. These undulations are absent in T. toksonum (which only has 1» rings). This is the fourth Tereancistrum species described for P. lineatus and the first described for the region from the Tietê-Batalha basin.

First record of Hysterothylacium fabri (Rudolphi 1819) Deardorff and Overstreet 1980 from Scomber Colias of the South Atlantic waters.

Among several marine pelagic species of the Brazilian coast, Scomber colias Gmelin, 1789 (Perciformes: Scombridae) stands out for having great economic importance, since it is widely used as a food resource and presents moderate vulnerability. Twenty specimens of S. colias were purchased from October 2015 to October 2016 from the coast of Santa Catarina, Brazil. In the present study, we recorded Hysterothylacium fabri (Rudolphi, 1819) (Deardorff and Overstreet, Proc Biol Soc Wash 93(4):1035-1079 1980) from the S. colias intestine using an integrative taxonomy approach, where morphological data are used in combination with partial sequences of the ITS gene, to validate the taxonomic status of the species and establish their relationships with other members of the genus. This species is being recorded for the first time in the South Atlantic and S. colias. The specimens of H. fabri collected in this study parasitizing S. colias presented morphology similar to the other specimens already registered parasitizing other hosts. The distance matrix generated showed that the partial sequences obtained in this study were more similar to sequences of Hysterothylacium sp. collected in China. In phylogenetic analysis, the two detected haplotypes of this study were grouped with H. fabri haplotypes deposited in GenBank in a monophyletic subclade.

A new species of Tereancistrum (Monogenea: Dactylogyridae), parasite of Prochilodus lineatus (Characiformes: Prochilodontidae) from southeast Brazil / Uma nova espécie de Tereancistrum (Monogenea: Dactylogyridae), parasito de Prochilodus lineatus (Characiformes: Prochilodontidae) do sudeste do Brasil

Abstract A new species of Tereancistrum Kritsky, Thatcher & Kayton, 1980 collected of Prochilodus lineatus gills from the Batalha River, Tietê-Batalha basin, São Paulo State, Brazil is described. The new species can be distinguished from its congeners mainly by the configuration of the ventral bar, which has an anvil-shaped characteristic with corrugated anterior projection. Tereancistrum takemotoi n. sp. is morphologically similar to T. toksonum Lizama, Takemoto & Pavanelli, 2004 in terms of their dorsal bars (Y-shaped), their dorsal anchors with divergent roots (superficial and deep) wherein their deep root rather elongated, and by the fact that they both have the male copulatory organ counterclockwise. However, only T. takemotoi n. sp. presents the male copulatory organ with 2» rings and shows undulations in the anterior margin of the dorsal bar. These undulations are absent in T. toksonum (which only has 1» rings). This is the fourth Tereancistrum species described for P. lineatus and the first described for the region from the Tietê-Batalha basin.

Resumo É descrita uma nova espécie de Tereancistrum Kritsky, Thatcher & Kayton, 1980, coletada das brânquias de Prochilodus lineatus do rio Batalha, bacia do Tietê-Batalha, estado de São Paulo, Brasil. A nova espécie pode ser diferenciada de seus congêneres, principalmente pela configuração da barra ventral, que tem o formato de bigorna e apresenta uma projeção anterior com ondulações. Tereancistrum takemotoi n. sp. é morfologicamente semelhante a T. toksonum Lizama, Takemoto & Pavanelli, 2004, em termos de suas barras dorsais (em forma de Y), suas âncoras dorsais com raízes divergentes (superficiais e profundas) sendo que a raiz profunda é bastante alongada, e pelo fato de ambos terem o órgão copulatório masculino no sentido anti-horário. No entanto, apenas T. takemotoi n. sp. apresenta o órgão copulatório masculino com 2» anéis e também exibe ondulações na margem anterior da barra dorsal, diferentemente do T. toksonum (que possui apenas 1» anel em seu órgão copulatório masculino). Essa é a quarta espécie de Tereancistrum descrita para P. lineatus e a primeira descrita para a região da bacia do Tietê-Batalha.

A new myxozoan species Henneguya unitaeniata sp. nov. (Cnidaria: Myxosporea) on gills of Hoplerythrinus unitaeniatus from Mato Grosso State, Brazil.

On the basis of morphological and molecular analyses, a new myxozoan parasite is described from the gills of the fish Hoplerythrinus unitaeniatus, collected in the municipality of Nova Xavantina, Mato Grosso State, Brazil. Plasmodia of Henneguya unitaeniata sp. nov. were oval and whitish and were found surrounded by collagen fibers forming plasmodia wall between gill filaments on the gill arch. The spores were ellipsoidal with two similar polar capsules. Morphometric analysis showed a total spore mean length of 23.8 ± 1.5 µm, spore body mean length of 14.5 ± 0.7 µm, caudal appendage mean length of 10.3 ± 1.4 µm, thickness mean length of 4.3 ± 0.3 µm, polar capsule mean length of 4.2 ± 0.5 µm, polar capsule mean width of 1.8 ± 0.3 µm, spore mean width of 4.8 ± 0.4 µm, and 4-5 polar filament coils. Phylogenetic analysis showed Henneguya unitaeniata sp. nov. as a basal species in a subclade formed by myxozoans that parasitize bryconid fishes.