Hemoparasite Analysis and Hematological Parameters of Four Freshwater Turtle Species (Testudines: Podocnemididae) from the Brazilian Amazon.

METHODS: Sampling was performed at three sites in the Tapajós River mouth, Pará State, Brazil, and an aliquot of blood was collected from each turtle by post-occipital dorsal vein puncture. The aliquots were used for the determination of hematological parameters and for the study of hemoparasites in the blood samples. RESULTS: A total of 37 turtles were sampled: 21 Podocnemis expansa, three P. sextuberculata, nine P. unifilis, and four P. erythrocephala. Parasitological analyses showed inclusions in erythrocytes compatible with Haemogregarina sp., representing an overall prevalence of parasitized animals of 64.8% with an average of 94,789 parasites/ml of blood. In this study, the evolutionary forms of Haemogregarina spp. from trophozoites, pre-meronts, meronts, and mature and immature gamonts were observed in three species of freshwater turtle species, and one morphotype of the parasite with high similarity to Haemogregarina podocnemis has been observed. CONCLUSION: Despite recent research on freshwater turtles, this study provides new information on the intensity of blood parasite infection and hematological parameters of free-living animals, highlighting the need for studies on infected and uninfected animals from the same population.

Evolutionary morphology of haptoral anchors in monogenoids (Dactylogyridae) of marine catfish (Siluriformes: Ariidae) from the Atlantic coast of South America.

Exploring the phylogenetic signal of morphological traits using geometric morphometry represents a powerful approach to assess the relative weights of convergence and shared evolutionary history in shaping species' forms. We evaluated the phylogenetic signal in shape and size of ventral and dorsal haptoral anchors of 10 species of monogenoids (Hamatopeduncularia, Chauhanellus and Susanlimocotyle) occurring in marine catfish (Siluriformes: Ariidae) from the Atlantic coast of South America. The phylogenetic relationships among these species were mapped onto the morphospaces of shape and size of dorsal and ventral anchors. Two different tests (squared change-parsimony and Kmult) were applied to establish whether the spatial positions in the phylomorphospace were influenced by phylogenetic relationships. A significant phylogenetic signal was found between anchor form and parasite phylogeny. Allometric effects on anchor shape were non-significant. Phylogenetically distant species on the same host differed markedly in anchor morphology, suggesting little influence of host species on anchor form. A significantly higher level of shape variation among ventral anchors was also found, suggesting that the evolutionary forces shaping ventral anchor morphology may operate with differing intensities or exhibit distinct mechanisms compared to their dorsal counterparts. Our results suggest that phylogenetic relationships were a key driver of changes in shape (but not size) of anchors of monogenoids of South American ariids. However, it seems that the emergence of the digitiform haptor in Hamatopenducularia and in some species of Chauhanellus played an important role in the reduction in anchor size and may cause secondary losses of anchors in other groups of monogenoids.

A new freshwater Ceratomyxa species (Myxozoa: Ceratomyxidae) parasitizing a sciaenid fish from the Amazon Basin, Brazil.

Myxozoans of Ceratomyxidae Doflein, 1899 are common coelozoic parasites of marine life, and are also found less frequently in freshwater fish. The present study describes Ceratomyxa ranunculiformis n. sp. as a new freshwater myxosporean species infecting the gall bladder of the Amazonian sciaenid Plagioscion squamosissimus. The new Ceratomyxa was described based on its host, myxospore morphology, ribosomal rDNA gene sequencing, parasite distribution, and phylogenetic analysis. Immature and mature plasmodia were tadpole-shaped or pyriform, and exhibited slow undulatory motility. The myxospores were elongated and crescent-shaped in the frontal view, with a sutural line between two valves, which had rounded ends. The measurements of the formalin-fixed myxospores were: average length 4.9 (4.0-6.6) µm, average thickness 37.6 (32.4-43.9) µm, average posterior angle 165° (154°-173°). Two ovoid polar capsules of equal size, average length 2.0 (1.4-3.0) µm and average width 1.9 (1.4-2.4) µm, were located adjacent to the suture and contained polar filaments with 2-3 coils. The integrated comparative analysis of the morphological characteristics and molecular analyses of the ribosomal rDNA genes supported the identification of a new species of coelozoic Ceratomyxa. Maximum likelihood analyses showed the new species clustering within a well-supported clade, together with all the other Amazonian freshwater ceratomyxids.

Phylogenetic and host-parasite relationship analyses of Henneguya caquetaia sp. nov (Myxosporea: Myxobolidae) infecting an Amazonian cichlid fish.

The present study describes a new species of Henneguya infecting the ornamental fish Caquetaia spectabilis from the Brazilian Amazon. Fish specimens were collected where the Tapajós and Amazon rivers merge, municipality of Santarém in the State of Pará, Brazil. Infections were intense, with several plasmodia spread on the opercula, fins and eye. Phylogenetic characterization and host-parasite relationship studies of the new Henneguya species used a combination of small subunit ribosomal DNA (ssrDNA) and morphological (photonic and transmission electron microscopy) analyses. Plasmodia were white round to ellipsoidal measuring up to 1.8 mm. The myxospores body measured 20.5 ± 3.9 (15-27) in length, 7.9 µm (6.2-10.8) in width, 6.7 µm (6.0-7.6) in thickness, 20.5 µm (14.4-32.3) in caudal appendages length, and 40.6 µm (34.2-54.6) in total length. The two polar capsules were elongated and equal in size, measuring 4.3 µm (3.3-5.4) in length and 2.1 µm (1.3-2.8) in width. Histological analysis revealed the parasite development in connective tissues of the fins, eyes and opercula. The skin of the fins and opercula presented detachment of the epidermis, however, no inflamatory infiltrate was observed. In the eye were observed inflammatory infiltratate in the epithelium and stroma of the cornea. Ultrastructure analysis showed the connective tissue capsule composed by an inner cellular layer with fibroblasts and outer layer where collagen fibers arranged transversely yet interspersed by layers of fibers arranged longitudinally. Numerous invaginations and extensive pinocytotic channels were observed in the plasmodial membrane. A layer of microfilament-like microfilament-like material was observed in the ectoplasm area and along to the internal surface of the plasmodial membrane. Generative cells and early stages of sporogenesis were seen more internally. The ssrDNA based phylogeny showed the South American species grouped in two lineages and the new species arises in a well-sustained subclade as sister branch of the clade composed by Henneguya spp. parasites of cichlids fish.

Diversification processes between monogenoids (Dactylogyridae) and their marine catfish (Siluriformes: Ariidae) from the Atlantic coast of South America.

Due to their high specificity, monogenoids from fish provide an interesting model to study historical associations of hosts and parasites. High agreement between host and parasite phylogeny is often interpreted as evidence of cospeciation. However, cophylogenetic signal may also arise from other, either adaptive or non-adaptive, processes. We applied the recently developed Cophylospace Framework to better understand the evolutionary relationship between monogenoids and marine catfish from the Atlantic coast of South America. The associations between 12 marine catfish and 10 monogenoid species were assessed. Molecular data of host and parasite species were used for phylogenetic reconstruction. We used anchor morphology based on Procrustes coordinates to evaluate whether closely related hosts are associated with morphologically similar parasites. To assess the association between parasite phylogeny and host morphology, we produced a distance matrix based on morphological characters of catfishes. Agreement between phylogenies and between phylogeny and morphology was measured using Procrustes R2 computed with PACo. The parasite phylogeny obtained in this study represents the first complete phylogenetic hypothesis of monogenoids parasitizing ariids from South America. The Cophylospace analysis suggested that phylogenetic and morphological distance of monogenoids contributes similarly to explain the pattern of host­parasite associations, whereas parasite phylogeny is more strongly associated with the morphological traits of the hosts than with host phylogeny. This evidence suggests that cospeciation is not a major force accounting for diversification in the monogenoids studied. Rather host morphological traits seem to be a more important driver, which conforms with evidence from other host‒monogenoid systems.

Integrative Taxonomy Reveals a Panmictic Population of Henneguya longisporoplasma n. sp. (Cnidaria: Myxozoa) in the Amazon Basin.

PURPOSE: Henneguya Thélohan, 1892 is one of the most species-rich genera of myxosporean parasites and infects fish around the world. The present study describes a new species infecting the gill filaments, fins, and kidneys of Plagioscion squamosissimus (Heckel, 1840), an economically important freshwater fish distributed in watersheds in the north of South America. METHODS: A total of 108 P. squamosissimus specimens were examined from three geographic localities in the Amazon basin: the Lago Grande do Curuai, a marginal lake of the Amazon River; the Tapajós River, in the state of Pará; and the Solimões River, in the state of Amazonas, Brazil. The analyses were based on the myxospore morphology, ribosomal DNA sequencing, phylogeny, prevalence, and geographic distribution of the host and its parasite. RESULTS: Parasite prevalences were 50% in both the Tapajós and Solimões rivers, and 35.4% in the Lago Grande do Curuai. In terms of the site of infection, the prevalence total was 23.1% in the gill filament, 29.6% in the fins, and 1.8% in the kidney. Regarding gender, the prevalence was 59.5% for males, 32.5% for females, and 21.7% for undetermined sex. The specimens found here were both morphologically and molecularly identical regardless of the infected organ and geographic locality, but distinct from all other Henneguya species, revealing that the parasite reported represents a novel species named Henneguya longisporoplasma n. sp. Despite the sampling being carried out in three different geographic localities of the Amazon basin, no population-level genetic variation was observed, even in the typically more variable ITS-1 region, revealing a panmictic population of H. longisporoplasma n. sp. in this large watershed. Maximum likelihood and Bayesian analyses showed the novel Henneguya clustered as a sister branch of the subclade formed of Henneguya that infect fish belonging to the family Cichlidae. CONCLUSIONS: A novel Henneguya species was identified parasitizing P. squamosissimus. The parasite presented wide geographic distribution in the Amazon basin and genetic analyses showed it as revealing a panmictic population.

Occurrence of the host-parasite system Rhaphiodon vulpinus and Ceratomyxa barbata n. sp. in the two largest watersheds in South America.

While around world, species of the genus Ceratomyxa parasite majority marine hosts, growing diversity has been reported in South American freshwater fish. The present study reports Ceratomyxa barbata n. sp. parasitizing the gallbladder of the Rhaphiodon vulpinus fish from the Amazon and La Plata basins. Morphological (light and transmission electron microscopy), molecular (sequencing of small subunit ribosomal DNA - SSU rDNA), and phylogenetic analyses were used to characterize the new species. Worm-like plasmodia endowed with motility were found swimming freely in the bile. The myxospores were elongated, lightly arcuate, with rounded ends and had polar tubules with 3 coils in the polar capsules. Ultrastructural analysis revealed plasmodia composed of an outer cytoplasmic region, where elongated tubular mitochondria, a rough endoplasmic reticulum, sporogonic stages, and a large vacuole occupying the internal area were observed. Phylogenetic analysis, based on SSU rDNA, found that among all South America freshwater Ceratomyxa species, C. barbata n. sp. arises as an earlier divergent species. The present study reveals the occurrence of this host-parasite system (R. vulpinus/C. barbata n. sp.) in the two largest watersheds on the continent.

Morphological and functional structure of two Ergasilidae parasites determine their microhabitat affinity on the gills of an Anostomidae fish from the Amazon.

The aim of this study was to investigate the microhabitat affinities of Ergasilus sp. and Therodamas longicollum on the gills of Leporinus fasciatus ("aracu-piau"), an anostomid fish from the Amazon. A total of 143 specimens of L. fasciatus were examined, of which 35% had their gills parasitized by at least one ergasilid species. A total of 159 specimens of Ergasilus sp. and 97 specimens of T. longicollum were recovered. Both ergasilids species exhibited a greater affinity for attachment in arch 1 of the gills of the host. There was a negative correlation between the abundance of Ergasilus sp. and the abundance of T. longicollum within each gill arch. Analysis of distribution along the gill arch showed a higher occurrence of Ergasilus sp. in Section 5, while T. longicollum occurred mainly in Section 3 of the gills. There was a positive correlation between the abundance of these ectoparasites and the size of the gill arch. Ergasilus sp. occurred only on the filament of the gill arch and exhibited affinity for the proximal region, while T. longicollum occurred only in the gill arch itself. The results reveal that these two parasite species compete in the gills of the host without the overlapping of their niches.

Relationship of the parasite Rhadinorhynchus plagioscionis (Acanthocephala) with Plagioscion squamosissimus host and its specificity of occurrence in the Brazilian Amazon.

Objective was the relationship of the parasite Rhadinorhynchus plagioscionis with its host Plagioscion squamosissimus, providing morphological and morphometric data to prove the specificity of this parasite with its host, with reports occurring only in rivers in the Brazilian Amazon. Rhadinorhynchus plagioscionis infected P. squamosissimus captured in the municipal region of Santarém, in the state of Pará, in the eastern Brazilian Amazon. The specimens were analyzed by light and scanning electron microscopy. Morphological data obtained confirmed conspecificty with R. plagioscionis and supplemental information was added to the morphological concept of this species. The body of R. plagioscionis is cylindrical and milky-coloured with dorsal curvature, a long proboscis displaying ventral curvature with 12 longitudinal rows containing 22 to 24 hooks, which are larger and more prominent towards the end of the ventral curvature, and decrease in size in the posterior extremity of the proboscis. The present study describes, in addition to the morphological and morphometric characteristics of R. plagioscionis, which have host specificity for P. squamosissimus, a relationship being reported exclusively in the Brazilian Amazon.

A novel Ceratomyxa species (Myxozoa: Cnidaria) infecting an Amazonian catfish.

Parasites are important organisms for the health of ecosystems. While the Amazon Basin is home to a great diversity of ichthyofauna, our knowledge of myxozoan diversity in the biome remains relatively limited. The present study describes a new myxozoan species, Ceratomyxa mandii n. sp., parasitizing the gallbladder of the Amazonian catfish Pimelodina flavipinnis (Pimelodidae) from the Solimões River, in the region of Manaus, Brazil. Light and electron microscopy,  small subunit ribosomal DNA (SSU rDNA) sequencing and phylogenetic analysis were performed. The new species exhibited worm-like plasmodia with undulatory motility. The SSU rDNA based phylogenetic analysis revealed it to be a sister taxon of C. gracillima, which also parasitizes an Amazonian pimelodid fish, possibly reflecting a host-parasite co-speciation process. This study contributes to our understanding of this little sampled group of organisms.

Two novel species of Myxobolus parasitizing the gills of Semaprochilodus insignis in the Brazilian Amazon.

The present study describes two new Myxobolus species infecting the gills of Semaprochilodus insignis, the most consumed freshwater fish species in the Brazilian Amazon. The fish specimens were caught in the Tapajós River, in the state of Pará, and the morphological, ultrastructural, small subunit ribosomal DNA (ssrDNA), and phylogenetic data of the myxosporean species were obtained. Two species of Myxobolus were found in the gills of S. insignis. Myxobolus maiai n. sp. developed in the gill filaments, and mature myxospores were round-shaped from the frontal view, measuring 12.5-14.8 (13.9 ± 0.5) µm in length, 11.4-13.8 (12.3 ± 0.5) µm in width, and have a thickness of 6.4-7.7 (6.9 ± 0.6) µm in the lateral view, with symmetric values. Its polar capsules were 4.4-6.6 (5.5 ± 0.5) µm in length and 2.3-3.7 (3.0 ± 0.3) µm in width, and the polar tubules had 4 - 5 coils. Myxobolus iarakiensis n. sp. was found infecting the gill arch. Mature myxospores were oval-shaped from the frontal view, and measured 6.7-8.6 (8.0 ± 0.4) µm in length, 4.5-6.3 (5.6 ± 0.4) µm in width, and had a thickness of 2.7-4.7 (3.8 ± 0.5) µm in the lateral view, with symmetric values. Its polar capsules were 2.1-3.7 (2.9 ± 0.3) µm in length and 1.1-2.0 (1.5 ± 0.2) µm in width, and its polar tubules had 4 - 5 coils. The ssrDNA based phylogeny showed these two novel species as grouping in a clade composed of parasite species of Prochilodontidae hosts.

Morphology and molecular phylogeny of Pauciconfibuloides amazonica gen. n. sp. n. (Platyhelminthes, Monogenoidea) parasitizing the Amazonian croaker Plagioscion squamosissimus.

An integrative study was performed to understand the phylogenetic relationships of an undescribed, freshwater species of microcotylid parasitizing Plagioscion squamosissimus from the Amazon River Basin. Based on morphological and molecular analysis (18S rDNA and partial 28S rDNA genes), a new genus is proposed to accommodate this new species, Pauciconfibuloides amazonica gen. n. sp. n. The new genus is closely related to Protastomicrocotylinae and Pauciconfibula by sharing the vagina, male copulatory organ, and genital atrium all unarmed. However, Pauciconfibuloides gen. n. can be distinguished from those taxa by the prostatic system and position of the vaginal pore. Molecular phylogenetic inference suggests a sister relationship with species of Polylabris (Prostatomicrocotylinae), but to date, there are no available 18S or 28S rDNA sequences of Pauciconfibula to be compared. This is the first report of a microcotylid parasitizing a freshwater sciaenid from South America.

Expanding the geographic distribution of the freshwater parasite Ceratomyxa (Cnidaria: Myxozoa) with vermiform-type plasmodia.

Although species of the genus Ceratomyxa Thélohan, 1892 mostly parasitize marine fish around the world, a surprising diversity of the genus has recently been reported from Amazonian freshwater fish. In this study, we report a freshwater Ceratomyxa species parasitizing Hemiodus orthonops (Hemiodontidae) from the Paraná River (La Plata Basin) in a watershed flowing into the southern part of South America, which expands the geographic distribution of this fish parasite in the freshwater resources of the continent. We applied a combination of morphological, small subunit ribosomal DNA (SSU rDNA), and phylogenetic analyses, and vermiform-shaped plasmodia endowed with motility were found swimming in the bile of the fish. The characteristics of the plasmodia and myxospores of the Ceratomyxa species found in the Paraná River resembled those of Ceratomyxa fonsecai, a parasite of the congeneric host Hemiodus unimaculatus from the Tocantins River basin in northern Brazil. Due to the close morphological and morphometric resemblances and the impossibility of genetic comparison, the parasite found in H. orthonops from the Paraná River was designated as Ceratomyxa cf. fonsecai, and the definition of its taxonomic status was left for further study. Maximum likelihood and Bayesian analyses showed Ceratomyxa cf. fonsecai clustering within a well-supported clade, together with other Amazonian freshwater ceratomyxids. The present study suggests that shifts of the complex host/parasite between marine and freshwater environments were facilitated by marine incursions into South America in the Early Miocene.

How to build single-celled cnidarians with worm-like motility: Lessons from Myxozoa.

Metazoans with worm-like morphologies across diverse and disparate groups typically demonstrate motility generated by hydrostatic skeletons involving tissue layers (muscles and epithelia). Here we present representative morphological, behavioural and molecular data for parasitic cnidarians (myxozoans) that demonstrate unprecedented variation in form and function, developing as cellular hydrostats. Motile elongate plasmodia characterise a remarkable radiation of species in the genus Ceratomyxa. The vermiform plasmodia inhabit gall bladders of a range of South American freshwater fish and exhibit undulatory motility reminiscent of nematodes but achieved at the cellular level. Collective insights from ultrastructure, confocal and light microscopy along with videos depicting movements highlight key features that we propose explain the unique motility of the plasmodia. These features include cytoskeletal elements (net forming microfilaments and microtubules), a large internal vacuole, a relatively rigid outer glycocalyx and peripherally arranged mitochondria. These constituents provide collective evidence for repurposing of the cnidarian epitheliomuscular cell to support worm-like motility at the cellular level. The apparent restriction of vermiform ceratomyxids to South American freshwaters suggests an origination via Cretaceous or Miocene marine transgressions and subsequent radiation.

Integrative taxonomy of a new species of Therodamas (Ergasilidae) infecting the Amazonian freshwater fish Leporinus fasciatus (Anostomidae).

Crustaceans of the subclass Copepoda are an important component of the invertebrate aquatic fauna. They occur in all aquatic environments and include some representatives that are free-living organisms and others that have a parasitic lifestyle. The genus Therodamas comprises marine and freshwater copepods whose females are parasites of fish in their adult phase, with only seven species described so far. During a field survey of fish parasites in the Jari River, a large tributary of the Amazon River system, in Brazil, we found a new species of the genus Therodamas infecting Leporinus fasciatus. Therodamas longicollum n. sp. is the second strictly freshwater species known. Phylogenetic analysis showed that the new species is grouped in the family Ergasilidae, and divergence estimates showed that T. longicollum n. sp. diverged from its ancestor at around 66.34 Ma, in the late Upper Cretaceous. Therodamas longicollum n. sp. differs from its congeneric in that it does not have lobes and/or expansion of the anterior neck region. Besides describing a new Therodamas species, thereby increasing the diversity of the genus to eight species, this study points out the existence of a lineage of these copepods that has adapted to the freshwater environment of the Amazon. This study also corroborates the genus Therodamas as part of the family Ergasilidae.

Morphological and molecular characterization of Ameloblastella pirarara sp. n. (Monogenoidea: Dactylogyridae) parasitizing the large Amazonian catfish Phractocephalus hemioliopterus.

In this study, integrative taxonomy is applied to describe a new dactylogyrid species, Ameloblastella pirarara sp. n. from the gills of Phractocephalus hemioliopterus, a commercially and ecologically important Amazonian catfish. Ameloblastella pirarara sp. n. can be distinguished from its congeners mainly by the morphology of the male copulatory organ (MCO), accessory piece, and anchors. The new species most resembles Ameloblastella unapi, from the Peruvian Amazon, but differs from it by the number of MCO rings, morphology of the vaginal canal and sclerotized structures of the haptor. Phylogenetic analyses based on sequences of the partial 28S rDNA (D1-D2 domains) gene placed the new species in a well-supported subclade of Ameloblastella spp. parasites of Neotropical siluriform fish, as a sister taxon to Ameloblastella unapioides. Thus, the new species described herein expands our knowledge of the diversity of monogenoid parasites from Amazonian freshwater fish.

Morphological, molecular, and histopathological characterization of a new species of Henneguya infecting farmed Astyanax lacustris in Brazil.

The present study describes the morphological, histopathological and SSU rDNA data of a new myxosporean species infecting farmed Astyanax lacustris fish from the state of São Paulo, Brazil. Henneguya lambariensis sp. nov. was found infecting the gills, and the plasmodial development resulted in displacement, blood congestion, compression, deformation and lamellar fusion, stretching of the epithelia, hyperplasia of the epithelial cells, edema, and mild infiltration of the mast cells and lymphocytes. The SSU rDNA sequencing resulted in the sequencing of 1804 nucleotides that did not correspond to any myxosporean sequences deposited in GenBank. The closest phylogenetic affinity of the new species was to the South American Henneguya loreotoensis and Henneguya guanduensis, which also parasite the gills. The present study suggests this new myxosporean species has considerable pathogenic potential, and health monitoring should be implemented in A. lacustris fish farms to ensure production.

Synopsis of the species of Myxobolus (Cnidaria, Myxozoa, Myxosporea) described between 2014 and 2020.

A synopsis of the species of Myxobolus Bütschli, 1882 (Cnidaria, Myxosporea, Myxobolidae) described from 2014 up till now is presented. It includes 122 nominal species described all over the world. For each of the species, the most relevant morphological and morphometric data, as well as data are provided related to the location in the host, type host and type locality. The GenBank accession numbers are provided whenever possible, and the spores were redrawn based on the original descriptions. The bibliography includes all the papers containing the species descriptions.

High prevalence and intensity of fish nematodes with zoonotic potential in the Brazilian Amazon, including a brief reflection on the absence of human infections

This study aimed to characterize the prevalence, mean abundance, and mean intensity of potential fish-borne zoonotic nematode larvae infecting the predator fish Hoplias aff. malabaricus from the Tapajós River, in the municipality of Santarém, in the Brazilian Amazon. After capture, the specimens of H. aff. malabaricus were analyzed for infection by Contracaecum sp. and Eustrongylides sp. third-stage larvae, and the prevalence, mean abundance, and mean intensity were calculated. A literature search was carried out to clarify the relationship between these indicators and eventual human cases of infection in the Amazon region. Third-stage larvae of nematodes of the Contracaecum and Eustrongylides genera were found in the specimens of H. aff. malabaricus sampled from the Tapajós River. The prevalence of Contracaecum larvae was 100%, while its mean abundance and mean intensity were both 54.8 larvae/fish. The prevalence of Eustrongylides larvae was 62.9%, and its mean abundance and mean intensity were 1.8 and 2.8 larvae/fish, respectively. Despite the high prevalence and intensity values, there are no cases of human infection by these nematode larvae in the Brazilian Amazon reported. The absence of human infections by these nematode larvae in the Brazilian Amazon despite the high prevalence/intensity of Contracaecum and Eustrongylides larvae and the high consumption of fish in the region, is most probably due to the fact that the local populations do not eat raw or undercooked fish. However, it is noteworthy that the absence of zoonotic cases in the region is based only on the examination of the available published papers. A better knowledge of the situation would require surveying hospitals and clinics, and data from the region's medical treatment facilities. However, the authors consider that cases of human infection, if any, are extremely rare, mainly due to the eating habits of the local population.

Morphological and molecular characterization of Udonella brasiliensis n. sp. (Monogenoidea), an epibiont on Caligus sp. parasite of Ariidae from the southeastern coast of Brazil.

The present study describes Udonella brasiliensis n. sp., an epibiont found on Caligus sp., a parasite the ariids Genidens barbus (Lacepède) and Aspistor luniscutis (Valenciennes), caught on the coast of the state of São Paulo, Brazil. Morphological and molecular analyses (partial 18S rDNA) were carried out. The morphological data showed that U. brasiliensis n. sp. can be distinguished from current valid species by its morphometric attributes (e.g., body, pharynx, ovary and testis), while the molecular information supports the proposal of a new species. The 18S rDNA phylogenetic analysis shows a close relationship between the new species and Udonella australis Carvajal & Sepulveda, in a subclade formed of species that parasitize South American fish. Finally, this study also discusses a scenario of initial irradiation for udonellids.