Austrodiplostomum Compactum Research Articles

Endoparasitic helminth fauna and diet of Geophagus sveni (Pisces) in Upper Paraná River basin.

In freshwater ecosystems, parasite infection patterns are influenced by factors including spatial-temporal variations, host diet, and habitat. Fish often change diets, affecting their parasite communities. This study focused on non-native host fish Geophagus sveni, aiming to characterize diet and endoparasitic helminth fauna patterns in the invaded area, investigating spatial and seasonal possible differences of endoparasite infections and correlating with host diet, in São José dos Dourados River and Tietê River areas. The host fish were collected in these areas during the dry and rainy season using gillnets. The endoparasites were collected and preserved in alcohol and identified using taxonomic methods, and stomach contents were examined for diet analysis. Parasitism descriptors were calculated and evaluated spatially and seasonally by ANOVA and the Kruskal-Wallis tests. PERMANOVA assessed G. sveni diet differences, and RDA correlated the endohelminth abundance with the host diet. Two endoparasites were recorded: metacercariae of Austrodiplostomum compactum (Trematoda) and larvae and adults of Raphidascaris (Sprentascaris) lanfrediae (Nematoda). Spatial differences were observed for the mean abundance and prevalence of R. (S.) lanfrediae and A. compactum prevalence. Seasonal variations of parasitic descriptors occurred for the nematode in the Tietê River area. The detritus and aquatic insects were the most consumed items by G. sveni. Detritus consumption positively correlates with nematode abundance. The findings indicate that factors such as artificial channels and rainfall, which can influence resource availability, may affect the fish's diet and potentially influence the structure of its endoparasite community. The study emphasizes the importance of understanding trophic chain-transmitted parasites and calls for further research in Neotropical environments.

Diversity of helminths parasitizing Phalacrocorax brasilianus (Gmelin, 1789) in the Brazilian Amazon.

This study was carried out in northern Brazil to determine the prevalence of helminth parasites that infect Phalacrocorax brasilianus (Gmelin, 1789). Between July 2020 and July 2023, adult and larvae parasites were collected from the respiratory and gastrointestinal tract of 30 birds that died in fishing nets and in fishing corral in the municipality of Soure on Marajó Island. The identified parasites included the nematodes Contracaecum sp., Contracaecum australe, Contracaecum rudolphii sensu lato, Contracaecum microcephalum, Contracaecum multipapillatum, Syncuaria squamata, Desportesius invaginatus, Tetrameres sp., Aplectana sp., Cyathostoma sp., Eucoleus contortus, Baruscapillaria spiculata, Baruscapillaria appendiculata; the trematodes Drepanocephalus spathans, Austrodiplostomum mordax, Austrodiplostomum compactum, Hysteromorpha triloba; the cestodes Paradilepis caballeroi; and the acanthocephalans Andracantha sp., Southwellina hispida and Southwellina macracanthus. The whole prevalence was 96.66% (29/30) and the most frequent helminths were nematodes (96.66%; 29/30), followed by acanthocephalans (66.66%; 20/30). These data increase the knowledge about helminths in cormorants widely distributed to Marajó Island.

Fauna of metazoan parasites of Pterygoplichthys pardalis (Castelnau, 1855) sold at fairs in the city of Manaus, state of Amazonas, Brazil

Pterygoplichthys pardalis is an endemic as well as economically important fish species in the Amazon basin. Thirty P. pardalis specimens were purchased at assorted fairs in the city of Manaus. Fish were necropsied, and then, had their organs investigated for parasites. The identified parasites were observed under Light bright field microscopy and that of Scanning Electron Microscopy (SEM). Through the analyses it was observed 219 metazoan parasite specimens, belonging to four taxonomic groups: Monogenoidea, Digenea, Acanthocephala, and Copepoda. Six metazoan parasitic species were identified: Monogenoidea Unilatus unilatus Mizelle and Kritsky, 1967 and Copepoda Therodamas elongatus (Thatcher, 1986) from the gills, Digenea Austrodiplostomum compactum (Lutz, 1928), Megacoelium spinicavum Szidat, 1954 and Diplostomum sp. from the eyes, stomach, and gonads, respectively, and Acanthocephala Gorytocephalus elongorchis Thatcher, 1979 from the intestine. Gorytocephalus elongorchis was the one presenting the highest prevalence value, followed by digeneans M. spinicavum, Diplostomum sp., and A. compactum. The present study has come to provide the very first SEM M. spinicavum, G. elongorchis, and T. elongatus images, thus improving on the up to now available data addressing P. pardalis parasitic fauna, which has been found to be infecting, the fish species presently being marketed in Manaus. Moreover, the current survey has demonstrated the identified parasite species pose no public health concern at all.

Composition and structure of the parasitic fauna of Hypostomus spp. (Loricariidae: Hypostominae) from a Neotropical river in Brazil.

Hypostomus are abundant in Brazilian rivers and streams. In the Ivaí River, the loricariids represent 20.3% of the total species of the basin. Of these 13 species belong to Hypostomus. However, to date, there are no studies on these fish parasitic fauna. Thus, this research aimed to analyze the distribution of the parasitic infracommunity of six species of Hypostomus from the Ivaí River and investigate how the infracommunity is structured in these hosts. One hundred and twenty-eight fish were analyzed, belonging to six sympatric species of Hypostomus (Hypostomus hermanni, H. cochliodon, H. albopunctatus, H. regani, Hypostomus sp.1, and Hypostomus sp.2); of these, 92.9% were parasitized with at least one taxon, totaling 1478 specimens of parasites. The parasitic fauna was composed of the ectoparasites Trinigyrus anthus, T. carvalhoi, Unilatus unilatus (monogeneans), and Placobdella spp. (hirudinea), and the endoparasites Austrodiplostomum compactum (digenean) and Procamallanus annipetterae (nematode). The parasites exhibited similar patterns of infection in all hosts, including a low number of species, low diversity, and numerical dominance of a group of parasites. However, permutational multivariate analysis of variance (PERMANOVA) showed different parasite species compositions among the hosts. Hypostomus cochliodon and H. regani had the highest parasite richness, while Hypostomus sp.1 and Hypostomus sp.2 showed low abundance and intensity of parasitic infections. However, Hypostomus sp.1 showed the highest values of evenness, although the parasite composition in both species did not differ. The results presented herein contribute to increasing the knowledge about the parasitic fauna of Hypostomus spp. from the Ivaí River by presenting new hosts and locality records.

Molecular phylogeny of Diplostomum, Tylodelphys, Austrodiplostomum and Paralaria (Digenea: Diplostomidae) necessitates systematic changes and reveals a history of evolutionary host switching events

The Diplostomidae Poirier, 1886 is a large, globally distributed family of digeneans parasitic in intestines of their definitive hosts. Diplostomum and Tylodelphys spp. are broadly distributed, commonly reported, and the most often sequenced diplostomid genera. The majority of published DNA sequences from these genera originated from larval stages only, which typically cannot be identified to the species level based on morphology alone. We generated partial large ribosomal subunit (28S) rRNA and cytochrome c oxidase subunit 1 (cox1) mtDNA gene sequences from 14 species/species-level lineages of Diplostomum, six species/species-level lineages of Tylodelphys, two species/species-level lineages of Austrodiplostomum, one species previously assigned to Paralaria, two species/species-level lineages of Dolichorchis and one unknown diplostomid. Our DNA sequences of 11 species/species-level lineages of Diplostomum (all identified to species), four species/species-level lineages of Tylodelphys (all identified to species), Austrodiplostomum compactum, Paralaria alarioides and Dolichorchis lacombeensis originated from adult specimens. 28S sequences were used for phylogenetic inference to demonstrate the position of Paralaria alarioides and Dolichorchis spp. within the Diplostomoidea and study the interrelationships of Diplostomum, Tylodelphys and Austrodiplostomum. Our results demonstrate that two diplostomids from the North American river otter (P. alarioides and a likely undescribed taxon) belong within Diplostomum. Further, our results demonstrate the non-monophyly of Tylodelphys due to the position of Austrodiplostomum spp., based on our phylogenetic analyses and morphology. Furthermore, the results of phylogenetic analysis of 28S confirmed the status of Dolichorchis as a separate genus. The phylogenies suggest multiple definitive host-switching events (birds to otters and among major avian groups) and a New World origin of Diplostomum and Tylodelphys spp. Our DNA sequences from adult digeneans revealed identities of 10 previously published lineages of Diplostomum and Tylodelphys, which were previously identified to genus only. The novel DNA data from this work provide opportunities for future comparisons of larval diplostomines collected in ecological studies.

Host diversity, phylogenetic relationships and local environmental factors drive infection patterns of a non-native parasite in tropical floodplain fish assemblages

Biodiversity, biological traits of potential host species, and environmental conditions may mediate the emergence of new diseases. We assessed the relative influence of such factors on patterns of infection by Austrodiplostomum compactum (Digenea, Diplostomidae) in fish assemblages of the Upper Parana River floodplain, Brazil. Multiple infection parameters were modeled at the community and species levels using phylogenetic diversity (PD), abundance (total and for a main reservoir species Plagioscion squamosissimus), local environmental conditions and phylogenetic distance from P. squamosissimus (Dis_Plag). In total, 108 fish species were collected and 28 were infected. At the community level, mean parasite abundance and mean infection intensity were positively associated with PD and the interaction between PD and environmental conditions, whereas host richness was negatively associated with PD. The complementary results indicate a biodiversity sampling effect rather than dilution effect. Environmental conditions often had the strongest coefficients in community-level models and mediated associations between infection parameters and other factors. At the species level, consistent negative associations between infection parameters and Dis_Plag indicate phylogenetic niche conservatism of parasites. Integration of community and species-level analyses demonstrates that phylogenetic diversity can affect host–parasite interactions in multiple ways, but that the associations depend on phylogenetic relationships and environmental conditions.

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.

Metazoan parasites of Plagioscion squamosissimus (Osteichthyes: Sciaenidae) of two rivers from the eastern Amazon (Brazil).

Plagioscion squamosissimus, commonly known as "white hake" or "corvina", is among the most commercially important fish in the Amazon and host to a great diversity of endoparasites. The aim of the present study was to compare the communities and infracommunities of metazoan parasites that infect P. squamosissimus in two rivers from the eastern Brazilian Amazon. A total of 75 specimens of P. squamosissimus were collected from Lago Grande do Curuái and the mouth of the Tapajós River. Morphological analysis revealed the presence of 16 parasite species, three myxozoans (Myxobolus sp., Ceratomyxa sp., Henneguya sp.), two trematodes (Austrodiplostomum compactum, Digenea gen. sp. (metacercariae), two monogeneans (Diplectanum sp., Euryhaliotrema sp.), three nematodes (Procamallanus (S.) sp., Anisakis sp., Pseudoproleptus sp. (larva), two acanthocephalans (Rhadinorhynchus plagioscionis and Neoechinorhynchus sp.), one Cestoda Ptychobothriidae gen. sp. and three crustaceans (Therodamas sp., Ergasilus sp., Dolops sp.). Six new records of parasites of P. squamosissimus were made, of which three were myxozoan species, one nematode species and two crustacean species. There were differences in the component communities of parasites of both rivers studied and these were discussed.

Metacercariae of Austrodiplostomum compactum (Trematoda, Diplostomidae) in non-native fish species in Brazil: a possible explanation for the high rate of parasitic infection.

Metacercariae of Diplostomidae are widely distributed in America and may cause diplostomiasis, an ocular disease in fishes. The aim of this study is to report the occurrence of metacercariae of Austrodiplostomum compactum in Plagioscion squamosissimus (non-native fish species) from Nova Avanhandava Reservoir, Tietê River, Brazil and an explanation for the high infection rates with this parasite in the Paraná River Basin is proposed. Eyes of 70 hosts were examined, the metacercariae were preserved and identified. The prevalence (P), mean intensity of infection (MII) ± standard deviation, mean abundance (MA) ± standard deviation, were calculated and a bibliographic review was performed. There was no difference in parasitism between male and female hosts. The values of P = 80%, MII = 21.55 ± 3.25 and MA = 17.24 ± 2.91 were high, as in most studies in areas where P. squamosissimus were introduced, while these values were low in areas of natural occurrence. This may be explained by the genetic susceptibility of the host to the parasite. The entire population of P. squamosissimus from the Upper Paraná has been founded by a few specimens, resulting in very low genetic variability. Consequently, the population may be highly susceptible to A. compactum.

Occurrence of metacercariae of Austrodiplostomum compactum (Lutz, 1928) (Trematoda, Diplostomidae) in Pimelodus platicirris in the Ilha Solteira Reservoir, São Paulo, Brazil

This study reports the occurrence of metacercariae of Austrodiplostomum compactum in Pimelodus platicirris from a Neotropical reservoir in the Grande River, SP, Brazil. A total of 164 fish were collected, of which 12.80% were infected with metacercariae in the eyes. The mean intensity of infection and mean abundance were 1.52±0.14 (1‒3) and 0.23±0.05 (0‒3), respectively. The presence of this parasite with a high intensity of infection can cause exophthalmos, retinal displacement, opacity of the lens, blindness or even death. This is the first record of ocular metacercariae for P. platicirris, thus increasing the number of hosts for A. compactum.

Molecular, morphological and experimental-infection studies of cercariae of five species in the superfamily Diplostomoidea (Trematoda: Digenea) infecting Biomphalaria straminea (Mollusca: Planorbidae) in Brazil

Trematodes belonging to the superfamily Diplostomoidea have complex life cycles involving birds, mammals and reptiles as definitive hosts, and gastropods and different groups of invertebrates and vertebrates as intermediate hosts. Molecular studies of these parasites are numerous, but data from larval stages in molluscs remain scarce, particularly in South America. The present study focused mainly on five morphotypes of longifurcate cercariae found in Biomphalaria straminea (Dunker, 1848) from Belo Horizonte, Minas Gerais, Brazil, collected between 2009 and 2017. In each morphotype, nuclear internal transcribed spacer (ITS1-5.8S ITS-2) rDNA and mitochondrial cytochrome c oxidase 1 (COI) genes were sequenced. Laboratory-reared fish, Poecilia reticulata Peters, 1859 or snails, Biomphalaria glabrata (Say, 1818) were exposed to cercariae to obtain metacercariae. The morphology of cercariae, experimentally obtained metacercariae, and phylogenetic analyses led to the identification of three species of Diplostomidae [Austrodiplostomum compactum (Lutz, 1928), Crassiphialinae gen. sp. and Hysteromorpha sp.] and two species of Strigeidae (Cotylurus sp., Apharyngostrigea sp.). Previously published sequences allowed species-level identification for only A. compactum, although provisional identifications were possible in two cases. First, the COI from cercariae of Apharyngostrigea sp. in Brazil matched those of metacercariae from naturally infected Cnesterodon decemmaculatus (Jenyns, 1842) in Argentina; although a positive identification is not possible, the material presents morphological similarities with larval stages previously described for A. simplex. Secondly, Cotylurus sp. resembles C. lutzi. Our analysis of previously published COI sequences suggests that Cotylurus cornutus (Rudolphi, 1808) has a Holarctic distribution. Both the morphology of experimentally obtained metacercariae and COI sequences indicate that Hysteromorpha sp. in Brazil is distinct from congeners in North America [Hysteromorpha corti (Hughes, 1929)] and Europe [Hysteromorpha triloba (Rudolphi, 1819)].

Assessing the Taxonomic Validity of Austrodiplostomum spp. (Digenea: Diplostomidae) through Nuclear and Mitochondrial Data

Adults of the genus Austrodiplostomum are parasites in cormorants of the New World, whereas metacercariae are parasites from eye globe and brain of freshwater and brackish water fishes. In this study, specimens of Austrodiplostomum mordax from South America (type-species) were analyzed together with other specimens of Austrodiplostomum spp. collected from several locations across Middle America and North America. Partial DNA sequences of the mitochondrial gene cytochrome c oxidase subunit I ( COI), the internal transcribed spacers ( ITS1, ITS2, and 5.8S gene), and the D2-D3, domains of the large subunit ( LSU) of nuclear ribosomal DNA, were generated for both developmental stages and compared with available sequences of Austrodiplostomum spp. Phylogenetic analyses inferred with each molecular marker using maximum likelihood and Bayesian inference revealed the existence of 4 lineages representing 2 described species, A. mordax and Austrodiplostomum compactum (syn. Austrodiplostomum ostrowskiae) and 2 undescribed species of Austrodiplostomum recognized in previous studies. The COI haplotype network inferred with 172 sequences detected 28 haplotypes divided into 4 clusters, separating each other by 33 and 40 substitutions and with a genetic divergence ranging from 9 to 12%. The largest group included specimens identified as A. compactum plus those identified as A. ostrowskiae, supporting the synonymy of both species. As a result, we conclude that A. compactum is widely distributed across the Americas, in locations of the United States, Mexico, El Salvador, Honduras, Costa Rica, Venezuela, Peru, and Brazil. The other 2 undescribed species of the genus Austrodiplostomum were previously recorded in the United States and now are reported in Mexico. These 2 species cannot be described because adult forms have not been found in their definitive hosts. Finally, the species A. mordax has been found only in some lakes from Argentina, and it was validated in this study through molecular analyses.

<b>Biodiversity and ecology of the parasitic infracommunities of <i>Loricaria prolixa</i> (Siluriformes: Loricariidae) from the Tietê-Batalha Basin, SP, Brazil

The parasitic biodiversity of the Loricaria prolixa , an endemic fish from the Parana and Prata basins was studied and analyzed the parasitic’s communities dynamics and their ecological relations with this host. Samples were collected in the Batalha River and 39 specimens were analyzed from 2014 to 2016. All fishes were parasitized. The component community was composed by twelve species with 8694 metazoan found on the surface, gills, eyes, brain, intestine and blood of the hosts. Demidospermus spirophallus, Diplostomidae gen. sp., Rhabdochona kidderi and Oligobdella sp. showed higher values for the parasitism's ecological descriptors, and were centrals and dominants species. The infracommunities were characterized by specific richness smaller in relation to diversity, and both superior to equitability (H’ = 0.94; J = 0.6; d = 0.83). There was a significant positive correlation between the host standard length and the parasite abundance of D. spirophallus , Diplostomidae gen. sp. and Oligobdella sp., while Procamallanus ( Spirocamallanus ) inopinatus presented a significant negative correlation. This is the first contribution concerning the parasite biodiversity of L. prolixa. Clinostomum detruncatum , Diplostomidae gen. sp., Austrodiplostomum compactum , R. kidderi , P. ( S. ) inopinatus , P. ( S. ) rebecae , Cucullanus pinnai pinnai , Oligobdella sp. and Trypanosoma sp. were first recorded in this host.

Digenea parasites of Acestrorhynchus falcirostris (Osteichthyes, Acestrorhynchidae) in the state of Amazonas, Brazil.

This study presents the helminthofauna of digenean parasites of Acestrorhynchus falcirostris in the state of Amazonas (Brazil). Eight species belonging to four families were recovered: Metacercariae of Austrodiplostomum compactum (Diplostomidae) and Clinostomum marginatum (Clinostomidae) and mature specimens of Bellumcorpus majus, Prosorhynchoides carvajali, Rhipidocotyle santanaensis (Bucephalidae); Prosthenhystera obesa (Callodistomidae); Genarchella genarchella (Derogenidae) and Phyllodistomum spatula (Gorgoderidae). Examining specimens belonging to the genus Bellumcorpus collected from A. falcirostris, were observed a great variation in the size and shape of testes, which also could be observed in the type specimens of Bellumcorpus majus and B. schubarti. Considering the similar morphology and morphometric characteristics of both species, in this paper B. schubarti is considered synonym of B. majus. Acestrorhynchus falcirostris is a new host records for all these species of digenean, except to A. compactum and C. marginatum. Prosorhynchoides carvajali is referred for the first time in Brazil.

Redescription of Austrodiplostomum compactum (Trematoda: Diplostomidae) from its Type Host and Locality in Venezuela, and of Austrodiplostomum mordax from Argentina.

Austrodiplostomum compactum from Nannopterum brasilianus, and its metacercaria from Geophagus sp. and Oreochromis mossambicus captured (1979) at its type locality, Valencia Lake, Venezuela, by the author, are redescribed. The adult is characterized by its large body size, and an oral sucker smaller than the pharynx. The metacercaria has a similar body size as the adult, and the small genital primordia occupy 4.1-7.3% of body length. Experimental infections in chickens with metacercariae of Diplostomulum mordax from brains of Odonthestes bonariensis, captured (2015) at Dique Paso de las Piedras, near Bahia Blanca City, Buenos Aires Province, Argentina, resulted in 10 adults 5 days postexposure. These adults correspond to Austrodiplostomum mordax as described from N. brasilianus at Lacombe Lagoon, Buenos Aires Province, and differ from A. compactum in their smaller body size, and an oral sucker larger than the pharynx. The metacercaria has a similar body size as the adult and differs mainly in that the larger genital primordia occupy 11.6-13.8% of body length. The status of earlier published Austrodiplostomum species in the American continent is discussed in view of available morphological and molecular data. A lectotype of A. mordax is here designated, and Austrodiplostomum ostrowskiae is considered as a new synonym of A. compactum.

Metacercariae of Austrodiplostomum compactum (Lutz, 1928) (Trematoda, Diplostomidae) infecting the eyes of Plagioscion squamosissimus (Heckel, 1840) (Perciformes, Scienidae) from Lake Catalão, Amazonas, Brazil

ABSTRACT Austrodiplostomum compactum is a digenetic trematode whith metacercariae that occur in the eyes of a wide variety of fish species. In Brazil, A. compactum metacercariae have been reported in many fish species, but there are only a few studies in the Amazon region. Due to the lack of information in the Amazon, the aim of this study was to report the occurrence of A. compactum metacercariae in the eyes of 15 specimens of Plagioscion squamosissimus from the Lake Catalão, in Amazonas, Brazil. Fishes were collected using gill nets placed randomly in the lake, euthanized in a field laboratory, and had their eyes dissected and examined under a stereomicroscope. A total of 801 metacercariae were registered infecting the eyes of the hosts with a parasitic prevalence of 100%. There was a significant positive correlation between the number of metacercariae recorded and the standard body length of fishes. No significant correlation was found between the number of metacercariae and the weight and relative condition factor (Kn) of the hosts. Values of the variance-to-mean ratio and Green's index suggested an aggregate distribution of the parasites in the hosts, with a low degree of aggregation. This is the first report of occurrence of A. compactum parasitizing a fish in the Lake Catalão.

Metazoan parasites of Plagioscion squamosissimus, an invasive species in the Tietê River, São Paulo, Brazil.

This study focused on the characterization and analysis of communities and infra-communities of metazoan parasites of Plagioscion squamosissimus caught in Promissão Reservoir in the Tietê River in Borborema (21°39'58"S, 49°8'49"W), state of São Paulo, Brazil. Fifty adult specimens caught by professional fishermen in March 2015 were necropsied. The fish presented an average standard length of 25.2 ± 2.2 cm and average weight of 328.82 ± 89.03 g. A total of 5,227 specimens of metazoan parasites were collected: 2,880 (55.1%) adult Diplectanum piscinarius (Monogenoidea: Diplectanidae) and 2,347 (44.9%) Austrodiplostomum compactum metacercariae (Digenea, Diplostomidae), both with 100% prevalence and mean abundance of 57.6 and 46.9, respectively. Parasite diversity was low (species richness = 2), with a Simpson index (D) equal to 0.505, and low values of Brillouin (HB = 0.687) and Margalef diversity (I = 0.117) indices. Berger-Parker's index of dominance (p = 0.551) indicated a slight dominance of the monogenean parasite D. piscinarius. There was a positive correlation, assessed by Pearson coefficient between parasite abundance of D. piscinarius and standard length (r = 0.43) and weight (r = 0.51) of hosts.

Austrodiplostomum compactum metacercariae (Digenea: Diplostomidae) in Schizodon intermedius (Characiformes: Anostomidae) from Jurumirim reservoir, Brazil.

This study reports the occurrence of Austrodiplostomum compactum metacercariae in the freshwater fish Schizodon intermedius (ximborê/piava) from a Neotropical reservoir in the Paranapanema River, state of São Paulo, Brazil. From a total of 75 fish collected, we found 38 infected with A. compactum metacercariae (prevalence = 50.67%) in the eyes. The mean intensity of infection and mean abundance were 9.05 ± 4.26 (1-155) and 4.59 ± 2.20 (0-155), respectively. Poulin's Discrepancy Index was 0.87 and four specimens presented more than 10 metacercariae in their eyes. No correlation was observed between parasite abundance and standard length, total weight and condition factor (p>0.05). These metacercariae are reported for the first time in S. intermedius.

Metazoan parasites of Geophagus brasiliensis (Perciformes: Cichlidae) in Patos Lagoon, extreme south of Brazil.

This study has evaluated the parasitic fauna of 79 pearl cichlids (Geophagus brasiliensis) from the estuary of Patos Lagoon (31° 57' S and 52° 06' W), Rio Grande do Sul, Brazil, during the months of May and June in 2011 and 2012. All the hosts analyzed were infected with at least one species of parasite. A total of eleven metazoa were identified in 459 specimens collected. The trematode Austrodiplostomum compactum (34.2%) and ergasilids Ergasilus lizae (32.9%) and Gauchergasilus lizae (32.9%) were the most prevalent species. The trematodes Thometrema overstreeti and Posthodiplostomum sp. had significantly higher prevalence in fish longer than 20 cm. The sex of the host had no effect on parasite prevalence and abundance. Pearl cichlids are registered as a new host for the trematodes Lobatostoma sp., Homalometron pseudopallidum and Thometrema overstreeti, for the ergasilids Ergasilus lizae and Gauchergasilus euripedesi and for the argulid Argulus spinolosus. The crustacean E. lizae is recorded in Rio Grande do Sul for the first time.

Parasite Community of Cichla kelberi (Perciformes, Cichlidae) in the Três Marias Reservoir, Minas Gerais, Brazil

A total of 112 specimens of yellow peacock bass, Cichla kelberi, were collected in the Três Marias Reservoir, upper São Francisco River, State of Minas Gerais, between 2004 and 2005. Twelve species of parasites were collected: two species of ectoparasites (the monogenetic Gussevia sp. and the copepod Ergasilus sp.); and ten species of endoparasites, including four species of adult endoparasites: the cestodes Proteocephalus macrophallus and P. microscopicus, and the nematodes: Capillostrongyloides sentinosa and Rhabdochona acuminata, and six species of larval endoparasites: the metacercariae of Austrodiplostomum compactum and the nematodes: Hysterothylacium sp., Contracaecum sp. Type 1, Procamallanus (Spirocamallanus) inopinatus, Spiroxys sp., and Goezia sp.. A significant positive correlation in the abundance of the two adult endoparasites species, P. macrophallus and P. microscopicus, may indicate that such associated species had the same ecological requirements. The positive correlations between the prevalence of the larval endoparasites, Hysterothylacium sp. and A. compactum, may indicate that there was opportunism for the two generalists species. Ergasilus sp., C. sentinosa, R. acuminata and Hysterothylacium sp. were recorded for the first time in C. kelberi, and this increased their list of known hosts. In addition, both proteocephalid species and C. sentinosa can extend their known biogeographical distribution to the Três Marias Reservoir.