Nematodes as indicators of environmental changes in a river with different levels of anthropogenic impact.

Considering that changes in the biodiversity of parasite communities can be used as indicators of ecosystem health, the aim of this study was to investigate the potential use of Geophagus brasiliensis parasites as bioindicators of environmental changes. We established three sample points in the Iguaçu River, each presenting different degrees of environmental impact. Out of the 69 G. brasiliensis specimens analyzed, 32 (46.3%) were parasitized by at least one parasite. We collected a total of 56 specimens of endoparasites belonging to the phylum Nematoda. Fishes collected in point 3 presented a significantly higher abundance of nematode species (moderately degraded) (Kruskal-Wallis2;69 = 8.62; p = 0.01) and species compositions between points were significantly different (F = 6.95, p = 0.002). No significant difference in relative condition factor (Kn) among the points (F2;66 = 2.54; p = 0.08) or correlation in Kn and abundance of nematodes (rs = 0.1; p = 0.4) were indicated. The results presented in this study indicate that the parasitic community of G. brasiliensis is characterized by low diversity in polluted locations, which explains the absence of certain parasite species and the occurrence of nematode species with varied responses to the pollution gradient.

Microcotylidae (Monogena) parasites of snappers (Perciformes: Lutjanidae) collected from the northeast coast of Brazil.

Monogeneans are a diverse group of flatworms, being ectoparasites of marine and freshwater fish, with great morphological and ecological variety. Analyzes of monogenetics in fish with great habitat diversity such as snappers are scarce in the literature, which already emphasizes the need for an update in this regard. The presente study found, morphologically characterized and mapped the geographic distribution and in known hosts the species Microcotyloides incisa and Microcotyloides impudicus, describing the first occurrence of these monogeneans for South America and in new hosts. The survey of hosts in the literature shows that M. incisa seems to have a greater Affinity with congener species of Lutjanidae and fish from other families, which may indicate a preference or specificity for fish of this family because they are congeners of their host type. The introduction of these parasites into South American waters may have occurred due to the migratory behavior of snappers, which are well distributed along the Mexican coast, where the parasites are usually reported. Here, we also bring the first occurrence of M. incisa for Lutjanus analis and Lutjanus jocu and M. impudicus for Ocyurus chrysurus and Lutjanus synagris, helping in the mapping and distribution of these monogenetic species in the Americas.

Abundance of Procamallanus (Spirocamallanus) inopinatus (Nematoda: Camallanidae) in Characiformes fish and associated factors in Midwest Brazil.

The success of Procamallanus (Spirocamallanus) inopinatus infection in fish involves a complexity of variables. This study aims to evaluate the relationship between abundance of P. (S.) inopinatus with biometric and somatic parameters, sex, relative condition factor (Kn) and hosts diet, as well as to evaluate length relationship of the parasites and the hosts. The fishes were collected by the mesh method and data, length, weight, sex, gonad and liver weight, Gonadosomatic index (GSI) and hepatosomatic index (HSI), Kn and stomach content were recorded. Twenty-seven specimens of P. (S.) inopinatus were collected in the intestine from Serrasalmus rhombeus and 52 from Leporinus friderici. In general, the prevalence, mean intensity and mean abundance of infection was higher in L. friderici. The total abundance was explained by the variables GSI, HSI total length, gonad and liver weight. Fish relative condition factor (kn) and sex were not influenced by the infection, being that the parasite infection did not impair the body condition of the hosts. There is no relationship between host length and parasite length in any of the evaluated fish species. On average, S. rhombeus parasites are 0.69 cm larger than L. friderici parasites.

New arrangement of three genera of fish tapeworms (Cestoda: Proteocephalidae) in catfishes (Siluriformes) from the Neotropical Region: taxonomic implications of molecular phylogenetic analyses.

Tapeworms (Cestoda: Proteocephalidae) are the dominant component of communities of intestinal parasites in pimelodid and other catfishes (Siluriformes) from South America. Even though these parasites have been studied intensively over more than one century, molecular taxonomy and phylogenetics have questioned their morphology-based classification, thus raising doubts about the systematic value of traits commonly used to circumscribe individual taxa. In the present study, members of three morphologically well-characterized genera of proteocephalids from pimelodid (Hemisorubim platyrhynchos and Sorubim lima) and auchenipterid (Ageneiosus inermis) catfishes from the Paraná or Amazon River basins were subjected to DNA sequencing of the large subunit nuclear ribosomal RNA (lsrDNA) and complete mitochondrial cytochrome c oxidase subunit I (COI). Phylogenetic analyses revealed the sister relationship between Manaosia bracodemoca and Mariauxiella piscatorum, and among Mariauxiella pimelodi and Ageneiella brevifilis. As a result, Mar. piscatorum and A. brevifilis are transferred to Manaosia and Mariauxiella, respectively, as Manaosia piscatorum n. comb. and Mariauxiella brevifilis n. comb., and the genus Ageneiella is suppressed. Diagnoses of Manaosia and Mariauxiella are amended. In addition, the present study revealed misidentification of tapeworms whose sequences are deposited in the GenBank database.

The first record of Centrocestus formosanus (Trematoda: Heterophyidae) in southern Brazil supported by molecular data.

Centrocestus formosanus is a digenean parasite first described from Asia, which parasitizes Melanoides tuberculata (Gastropoda: Thiaridae) at the first intermediate stage, and different fish species as second intermediate host. C. formosanus was previously recorded in Brazilian states, but never before in the southern region of this country. Recording and identification of digenean species through morphological identification is a taxonomic challenge. In light of this, we use an integrative taxonomic approach to report the occurrence of cercariae and metacercariae of C. formosanus in molluscs and fish, respectively, in an urban park located in southern Brazil. Specimens of M. tuberculata and the fishes Poecilia reticulata and Xiphophorus sp. (Poeciliidae) were collected for screening for parasites and molecular analyses using partial fragments of the 28S rDNA gene. The identification of C. formosanus obtained from molluscs and fish specimens permitted us to partially solve the life cycle of this parasite for the first time in the studied environment, demonstrating the necessity of monitoring and controlling molluscs populations. Nevertheless, our results will support future studies aiming to elucidate the life-cycle of C. formosanus in this region, since all sampled hosts' species are invasive in this environment.

Behavioral changes in host foraging: Experiments with Clinostomum (Trematoda, Digenea) parasitizing Loricariichthys platymetopon (Loricariidae).

Complex life cycle parasites can manipulate the behavior of intermediate hosts in order to reduce their fitness and increase the chance of completing life cycle. In order to understand the effects of the trematode parasites of the genus Clinostomum on host fish Loricariichthys platymetopon, a filmed experiment was carried out to quantify the foraging activity of hosts with different intensities of infection. The results suggest that hosts with higher parasite intensities reduced foraging activity early in the morning when compared to hosts with low intensities. This period may be critical for hosts since birds, the target hosts of such trematodes, forage intensively at dawn.

Phylogenetic position of Diplostomum spp. from New World herons based on complete mitogenomes, rDNA operons, and DNA barcodes, including a new species with partially elucidated life cycle.

Diplostomum ardeae Dubois, 1969 has seldom been reported since its description from the great blue heron (Ardea herodias L., 1758) in the USA. Sequences obtained in this study from the barcode region of cytochrome c oxidase 1 (CO1) in diplostomids from black-crowned night heron (Nycticorax nycticorax (L., 1758)) in Puerto Rico matched data from D. ardeae from A. herodias in the type region. We also obtained DNA barcodes from morphologically similar diplostomids from a rufescent tiger heron (Tigrisoma lineatum (Boddaert, 1783)) and from metacercariae from eye lenses of Trachelyopterus galeatus (Linnaeus, 1766) from the Paraná River basin in Argentina and Brazil, respectively. Barcodes matched (97-100% identity) in these South American adult and larval specimens as well as in recently published sequences from metacercariae from 11 other siluriform fishes from the same region. Barcodes from the South American species, which we describe as Diplostomum lunaschiae n. sp., differed from those of D. ardeae by 7.2-9.8%, and the new species differs from D. ardeae in its size, pharynx:oral sucker length ratio, egg:body length ratio, and distribution of vitellaria. As in prior phylogenetic analysis of CO1 sequences, both D. ardeae and D. lunaschiae n. sp. were not associated with Diplostomum. In more character-rich analyses of nuclear rDNA and of mitochondrial genomes, D. ardeae was an early divergent member of clades of species of Diplostomum. Consequently, we continue to consider D. ardeae and D. lunaschiae n. sp. members of Diplostomum, in contrast to recent suggestions that these species may belong to a different genus.

First record of Dichelyne (Dichelyne) bonacii (Nematoda, Cucullanidae) parasitizing the intestine of two species of lutjanid fish (Perciformes, Lutjanidae) on the northeast Brazilian coast.

Lutjanids are marine fish and commonly inhabit coral reefs, which have migratory habits and feed in a general way, due to these characteristics, are susceptible to infections by parasites, such as cuculanid nematodes. This work aimed to report for the first time, the occurrence of Dichelyne (Dichelyne) bonacii in Brazil, in two new hosts, Lutjanus analis and Rhomboplites aurorubens, acquired from local artisanal fishermen at the Aracaju city public fishing terminal (10 ° 54'17 "S37 ° 2'56" W), northeast coast of Brazil. Adult nematodes were collected from the intestinal tract of the hosts, clarified in Aman's Lactophenol and were briefly described here. Three adult males and five gravid females were found, indicating that the two species of fish acted as definitive hosts. Currently, this species of parasite has been reported only from fish collected in the coast of Mexico, which makes this work the first record of this parasite in Brazilian coastal waters. The results show that probably the range of hosts and the distribution of D. (Dichelyne) bonacii is not as restricted as data pointed in the literature, being a little wider, extending also to waters that bathe the Brazilian coast.

Behavioral changes caused by Austrodiplostomum spp. in Hoplias malabaricus from the São Francisco River, Brazil.

Traira (Hoplias malabaricus) is a neotropical fish that is widely distributed in freshwater environments in South America. In the present study, we documented the occurrence of metacercariae of Austrodiplostomum spp. (Diplostomidae) in the eyes and cranial cavity of H. malabaricus and described parasite-induced behavioral changes in the host. The fish were collected from the upper São Francisco River, in the Serra da Canastra mountain range, Minas Gerais, transported alive to the laboratory, observed for 2 weeks, and subsequently examined for parasites. Of the 35 fish examined, 28 (80 %) had free metacercariae in the vitreous humor (mean intensity=95.4; mean abundance=76.3), and 24 (68.57 %) had free metacercariae in the cranial cavity, mainly concentrated below the floor of the brain, at the height of the ophthalmic lobe (mean intensity=12.91; mean abundance=8.85). Specimens of H. malabaricus with a high intensity of infection in the brain displayed changes in swimming behavior.

Parasites of the fish Cichla piquiti (Cichlidae) in native and invaded Brazilian basins: release not from the enemy, but from its effects.

The enemy release hypothesis is frequently used to explain the success of invaders, postulating that introduced species have escaped from their native enemies, including parasites. Here, we tested this hypothesis for the tucunaré (Cichla piquiti), a predatory cichlid, and its endoparasites. First, the parasites and their influence on the condition of the hosts in the native environment, the Tocantins River (TO), were compared to an environment where the fish was introduced, the Paraná River (PR). Then, comparisons of the abundances of Diplostomidae eye flukes and Contracaecum sp. larval nematodes were made between the introduced tucunaré and two predators native to the PR, Hoplias malabaricus and Raphiodon vulpinus. Nine species of endoparasites were recorded in total, five of which occurring in both localities. Total species richness did not differ between localities, and fish condition was negatively affected by the cestodes Sciadocephalus megalodiscus only in the TO. In the PR, abundance of Contracaecum sp. did not differ between natives and invaders; however, eye flukes were more abundant in the native fish H. malabaricus, which may represent an advantage to the invader if they were competing for prey. These results did not support the idea that the escape from parasites favoured the establishment of C. piquiti in the PR. Instead, the escape from the parasites' effects seems a better explanation, and further studies examining effects on host physiology and/or fitness in the native and introduced ranges are needed.

Hematological alterations caused by high intensity of L3 larvae of Contracaecum sp Railliet & Henry, 1912 (Nematoda, Anisakidae) in the stomach of Hoplias malabaricus in lakes in Pirassununga, São Paulo.

The objective of the present study was to discover the hematological indices of Hoplias malabaricus infected by larvae of Contracaecum sp. A total of 105 fish were collected from two lakes located in the municipal district of Pirassununga, São Paulo, Brazil, of which 95.2% were infested by L3 larvae of Contracaecum sp., with an average intensity of 348.7 ± 231.55 helminths/fish. A total of 76 fish were analyzed to establish hematological parameters. Following analysis, it was found that there was a significant difference between hematological parameters Hct, erythrocytes (Er), thrombocytopenia (p = 0.01), and Hb (p = 0.02) in lakes A and B, while there was no significant difference for leukocyte (p = 0.68), mean corpuscular volume, mean corpuscular hemoglobin (p = 0.06), and mean corpuscular hemoglobin concentration (p = 0.47). The intensity of infection correlated negatively with Er (r(s) = -0.42; p < 0.01) and positively for (r(s) = 0.48; p < 0.01). The high intensity of infection by Contracaecum sp. in H. malabaricus did not affect the health of the fish despite causing alterations in hematological variables.

Infective pentastomid larvae from Pygocentrus nattereri Kner (Pisces, Characidae) from the Miranda River, Pantanal, Mato Grosso do Sul State, Brazil, with notes on their taxonomy and epidemiology.

During parasitological surveys of freshwater fish from the Miranda River, Brazil, 199 Pygocentrus nattereri Kner (Characidae) were caught. Two pentastomid families, Subtriquetridae Fain, 1961, represented by its single genus Subtriquetra Sambon, 1922, and Sebekidae Sambon, 1922, represented by three genera, were present. Free-living larvae of Subtriquetra subtriquetra (Diesing, 1835) were collected from the swim bladder. Encysted larvae of Alofia Giglioli, 1922 were found in the abdominal cavity, chambers of the heart, musculature, on the surface of the gonads and swim bladder. Some Alofia larvae were moving freely in the swim bladder. Larvae of Sebekia Sambon, 1922 were encysted in the musculature. Some larvae of Leiperia Sambon, 1922 were found encysted in the musculature and on the surface of the pyloric caeca, whereas others occurred free in the abdominal cavity. In some of the latter, the head was buried deep in the wall of the intestine, stomach or ovaries, whereas the rest of their body remained free. Infective pentastomid larvae were present throughout the year with an overall prevalence of 77%. Both prevalence and intensity were higher in members of the Sebekidae than in Su. subtriquetra, possibly due to the latter's mode of transmission and its high pathogenicity. No sex-related, statistically significant differences (p > 0.05) in prevalence or abundance were found. Fish weight and length had significant but weak positive correlations (r < or = 0.27) with the abundance of pentastomid larvae, possibly reflecting an increased likelihood of prior exposure in older fish. Parasite abundance had no significant effect on host body condition (p > or = 0.69). A higher prevalence and monthly mean abundance of pentastomids were seen in the dry season and might be due to increased host densities as habitats dry up. Pygocentrus nattereri represents a new intermediate host record for the genera Alofia, Leiperia and Subtriquetra.

Patterns of interactions of a large fish-parasite network in a tropical floodplain.

1. Describing and explaining the structure of species interaction networks is of paramount importance for community ecology. Yet much has to be learned about the mechanisms responsible for major patterns, such as nestedness and modularity in different kinds of systems, of which large and diverse networks are a still underrepresented and scarcely studied fraction. 2. We assembled information on fishes and their parasites living in a large floodplain of key ecological importance for freshwater ecosystems in the Paraná River basin in South America. The resulting fish-parasite network containing 72 and 324 species of fishes and parasites, respectively, was analysed to investigate the patterns of nestedness and modularity as related to fish and parasite features. 3. Nestedness was found in the entire network and among endoparasites, multiple-host life cycle parasites and native hosts, but not in networks of ectoparasites, single-host life cycle parasites and non-native fishes. All networks were significantly modular. Taxonomy was the major host's attribute influencing both nestedness and modularity: more closely related host species tended to be associated with more nested parasite compositions and had greater chance of belonging to the same network module. Nevertheless, host abundance had a positive relationship with nestedness when only native host species pairs of the same network module were considered for analysis. 4. These results highlight the importance of evolutionary history of hosts in linking patterns of nestedness and formation of modules in the network. They also show that functional attributes of parasites (i.e. parasitism mode and life cycle) and origin of host populations (i.e. natives versus non-natives) are crucial to define the relative contribution of these two network properties and their dependence on other ecological factors (e.g. host abundance), with potential implications for community dynamics and stability.

A host-endoparasite network of Neotropical marine fish: are there organizational patterns?

Properties of ecological networks facilitate the understanding of interaction patterns in host-parasite systems as well as the importance of each species in the interaction structure of a community. The present study evaluates the network structure, functional role of all species and patterns of parasite co-occurrence in a host-parasite network to determine the organization level of a host-parasite system consisting of 170 taxa of gastrointestinal metazoans of 39 marine fish species on the coast of Brazil. The network proved to be nested and modular, with a low degree of connectance. Host-parasite interactions were influenced by host phylogeny. Randomness in parasite co-occurrence was observed in most modules and component communities, although species segregation patterns were also observed. The low degree of connectance in the network may be the cause of properties such as nestedness and modularity, which indicate the presence of a high number of peripheral species. Segregation patterns among parasite species in modules underscore the role of host specificity. Knowledge of ecological networks allows detection of keystone species for the maintenance of biodiversity and the conduction of further studies on the stability of networks in relation to frequent environmental changes.

Hysterothylacium larvae (Nematoda, Anisakidae) in the freshwater mussel Diplodon suavidicus (Lea, 1856) (Mollusca, Unioniformes, Hyriidae) in Aripuanã River, Amazon, Brazil.

Larvae of Hysterothylacium use various invertebrates as intermediate hosts. Definite hosts include fish, birds, reptiles or marine mammals. This study describes the occurrence of Hysterothylacium (Nematoda, Anisakidae) larvae parasitizing the pericardic cavity of Diplodon suavidicus (Unioniformes, Hyriidae) specimens collected in the Amazon basin, Brazil. This is the first record of this nematode parasitizing freshwater bivalves in South America. The high prevalence, medium intensity and medium abundance suggest that D. suavidicus acts as intermediate host for Hysterothylacium species in that environment.

Cysts and larvae of Strongyluris: A parasite of amphibians and reptiles found in an urban population of Lissachatina fulica (Férussac, 1821) in southern Brazil.

We report the finding of cysts and larvae of Strongyluris in specimens of L. fulica from an urban area of the municipality of Maringá in northern Paraná State, southern Brazil. Thirty-seven young adult snails were collected at three sites: 15 in riparian forest; 14 in a vegetable garden; and eight in a residential garden. We found a total of 16 cysts with nematode larvae in three of the 15 snails collected in riparian forest. The parasites were identified as larvae of the genus Strongyluris, which are parasites of the gastrointestinal tract of amphibians and reptiles. Lissachatina fulica is established in urban areas of 33% of the municipalities of the state of Paraná. The species has spread rapidly through the urban area of the municipality of Maringá, which may contribute to the transmission of nematode larvae of medical and veterinary interest to humans and other animals.

Occurrence of Isopods in Two Species of Snappers (Lutjanidae) from Northeast Brazil.

Parasitic isopod species are poorly known in the northeastern coast of Brazil. In this sense, this study presents novel records of Isopoda of the families Aegidae, Cymothoidae, and Corallanidae. A total 69 specimens of Lutjanus analis and 19 of Lutjanus jocu, of which 46 isopods from 3 different species were collected, i.e. Rocinela signata, Cymothoa excisa, and Excorallana richardsoni. The species R. siganata and E. richardsoni are reported for the first time in L. jocu. A significant relationship between the parasite R. signata and the size of the fish L. jocu was also observed. The isopod C. excisa is considered an incidental finding in L. analis. To the authors' knowledge, this is the first report of this species in fish from Brazil. The three species of isopods are new occurrences in the State of Sergipe, northeast region of the country. An additional morphological characteristic observed in the dorsal setae of pleotelson in specimens of E. richardsoni was that one end of this structure wws bifid. This information contributes to the current body of knowledge of the morphology of this particular species.

Topological congruence between phylogenies of Anacanthorus spp. (Monogenea: Dactylogyridae) and their Characiformes (Actinopterygii) hosts: A case of host-parasite cospeciation.

Cophylogenetic studies aim at testing specific hypotheses to understand the nature of coevolving associations between sets of organisms, such as host and parasites. Monogeneans and their hosts provide and interesting platform for these studies due to their high host specificity. In this context, the objective of the present study was to establish whether the relationship between Anacanthorus spp. with their hosts from the upper Paraná River and its tributaries can be explained by means of cospeciation processes. Nine fish species and 14 monogenean species, most of them host specific, were studied. Partial DNA sequences of the genes RAG1, 16S and COI of the fish hosts and of the genes ITS2, COI and 5.8S of the parasite species were used for phylogenetic reconstruction. Maximum likelihood phylogenetic trees of the host and parasite species were built and used for analyses of topological congruence with PACo and ParaFit. The program Jane was used to estimate the nature of cospeciation events. The comparison of the two phylogenies revealed high topological congruence between them. Both PACo and ParaFit supported the hypothesis of global cospeciation. Results from Jane pointed to duplications as the most frequent coevolutionary event, followed by cospeciation, whereas duplications followed by host-switching were the least common event in Anacanthorus spp. studied. Host-sharing (spreading) was also identified but only between congeneric host species.

Parasitism by larval tapeworms genus Spirometra in South American amphibians and reptiles: new records from Brazil and Uruguay, and a review of current knowledge in the region.

Spargana are plerocercoid larvae of cestode tapeworms of the genus Spirometra, Family Diphyllobothriidae, parasitic to frogs, reptiles, birds and mammals. This parasitic disease in humans can be transmitted through the use and consumption of amphibians and reptiles. The available knowledge about Spirometra in South America is scarce, and there are only a few reports on the occurrence of sparganum in amphibians and reptiles, many of them published in old papers not easily available to researchers. In this work we present a review on this topic, provide new records in two species of amphibians and 7 species of reptiles from Brazil and Uruguay respectively. We also summarize current knowledge of Spirometra in the continent, along with an updated of host taxonomy. We could gather from the literature a total of 15 studies about amphibian and reptile hosts, published between 1850 and 2016, corresponding to 43 case reports, mostly from Brazil (29) and Uruguay (8), Argentina (3), Peru (2), and Venezuela (1); the majority of them related to reptiles (five lizards and 26 snake species), and 14 corresponded to amphibians (9 anurans). Plerocercoid larvae were located in different organs of the hosts, such as subcutaneous tissue, coelomic cavity, peritoneum, and musculature. The importance of amphibians and reptiles in the transmission of the disease to humans in South America is discussed. Relevant issues to be studied in the near future are the taxonomic characterization of Spirometra in the region and the biological risk of reptile meat for aboriginal and other rural communities.

The patterns of organisation and structure of interactions in a fish-parasite network of a neotropical river.

The use of the complex network approach to study host-parasite interactions has helped to improve the understanding of the structure and dynamics of ecological communities. In this study, this network approach is applied to evaluate the patterns of organisation and structure of interactions in a fish-parasite network of a neotropical Atlantic Forest river. The network includes 20 fish species and 73 metazoan parasite species collected from the Guandu River, Rio de Janeiro State, Brazil. According to the usual measures in studies of networks, the organisation of the network was evaluated using measures of host susceptibility, parasite dependence, interaction asymmetry, species strength and complementary specialisation of each species as well as the network. The network structure was evaluated using connectance, nestedness and modularity measures. Host susceptibility typically presented low values, whereas parasite dependence was high. The asymmetry and species strength were correlated with host taxonomy but not with parasite taxonomy. Differences among parasite taxonomic groups in the complementary specialisation of each species on hosts were also observed. However, the complementary specialisation and species strength values were not correlated. The network had a high complementary specialisation, low connectance and nestedness, and high modularity, thus indicating variability in the roles of species in the network organisation and the expected presence of many specialist species.