The aim of the present study was to provide a current survey of the species of parasites found in the Upper Paraná River floodplain, as well as to investigate which strategies and mechanisms used by parasites, are favored and which environmental factors influence the parasite community in the studied environments. During a seven-year period from February 2000 to September 2007, 3,768 fish belonging to 72 species were collected and analyzed for the purpose of studying the parasite fauna. A total of 337 species of parasites were reported, including 12 new descriptions: one myxosporid, Henneguya paranaensis Eiras, Pavanelli and Takemoto Keywords: ichthyoparasites, biodiversity, helminthes, crustaceans, parasite ecology. Diversidade dos parasitos de peixes da planície de inundação do Alto Rio Paraná, BrasilResumo O objetivo do presente trabalho foi realizar um novo levantamento das espécies de parasitos encontradas na planície de inundação do Alto Rio Paraná, bem como investigar quais estratégias e mecanismos utilizados pelos parasitos são mais favorecidos e quais fatores ambientais estão influenciando a comunidade parasitária nos ambientes estudados.

No abstract

Materials and MethodsThe list of parasitic crustaceans of fishes in Brazil was based on extensive search of published records. This bibliographic review of the crustacean species reported from fishes in Brazilian waters was complemented with information from the Zoological Record, Biological Abstracts, Web of Knowledge, Google Scholar, Aquatic Sciences and Fisheries Abstracts, Biological and Agricultural Index Plus and the Scopus. Data were compiled until March, 2013. In the case of parasitic copepods, only information not presented in the checklist of Copepoda parasites of fishes from Brazil by Luque and Tavares (2007) was included. The number of parasitic associations was calculated from the sum of the richness of species of parasites on each host species.The checklist follows the classification and systematic arrangement proposed by Boxshall and Halsey (2004) for Copepoda, and Young (1998) and Martin and Davis (2001) for other crustacean groups.The species of crustaceans are arranged according to taxonomic categories, within which the species are presented in alphabetical order, followed by hosts (specific name), site of infection, habitat, localities and references (between parentheses, in chronological order). In addition, the checklist also includes crustacean species identified only at the genus level and undetermined species. Crustacean names presented in the checklist follow the most recent taxonomic literature, but validity of individual taxa or reliability of their records was not critically examined by the present authors. Host species were arranged in taxonomic and then alphabetical order.The key to identification of the genera of parasitic crustaceans from fishes in Brazil has been produced on the basis of those by Delaney

Summary1. 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 Parana´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.

Diplostomum (Austrodiplostomum) compactum (Lutz, 1928) metacercariae (Platyhelminthes, Digenea) were found in six fish species, belonging to two orders (Characiformes and Perciformes) and three families (Erythrinidae, Sciaenidae and Cichlidae). A total of 477 individuals were collected, from August 1999 to May 2001, in the upper Paraná River floodplain, Brazil. The metacercariae were infecting the eyes of six host species and the brain of five of them. Plagioscion squamosissimus, Satanoperca pappaterra and Cichla monoculus presented the highest values of prevalence, mean intensity and mean abundance. Diplostomum (A.) compactum was over-dispersed in the population of Hoplias aff. malabaricus, S. pappaterra, P. squamosissimus, Crenicichla britskii and C. monoculus. No significant difference was observed in the metacercariae distribution in the right and left eyes. The abundance of D. (A.) compactum metacercariae was positively correlated with the host's relative condition factor in H. aff. malabaricus and S. pappaterra. No significant difference of the abundance of parasitism between the sex of the hosts was evidenced. In relation to the prevalence, significant difference was observed only in C. britskii. Positive correlations were verified between the prevalence of infection and the standard length of the specimens in C. britskii and the intensity of infection and the standard length of the hosts in P. squamosissimus and C. monoculus. In relation to parasite abundance and the standard length class of the host, significant differences were observed in P. squamosissimus, C. britskii and C. monoculus.

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Specialized interactions tend to be more common in systems that require strong reciprocal adaptation between species, such as those observed between parasites and hosts. Parasites exhibit a high diversity of species and life history strategies, presenting host specificity which increases the complexity of these antagonistic systems. However, most studies are limited to the description of interactions between a few parasite and host species, which restricts our understanding of these systems as a whole. We investigated the effect of the developmental stage of the parasite on the structure of 30 metazoan fish-parasite networks, with an emphasis on the specificity of the interactions, connectance and modularity. We assessed the functional role of each species in modular networks and its interactions within and among the modules according to the developmental stage (larval and adult) and taxonomic group of the parasites. We observed that most parasite and host species perform a few interactions but that parasites at the larval stage tended to be generalists, increasing the network connectivity within and among modules. The parasite groups did not differ among each other in the number of interactions within and among the modules when considering only species at the larval stage. However, the same groups of adult individuals differed from each other in their interaction patterns, which were related to variations in the degree of host specificity at this stage. Our results show that the interaction pattern of fishes with parasites, such as acanthocephalans, cestodes, digeneans and nematodes, is more closely associated with their developmental stage than their phylogenetic history. This finding corroborates the hypothesis that the life history of parasites results in adaptations that cross phylogenetic boundaries.

(Wood land. 1935 ) was lhe only species Ihal presel1led a relalion ship helween lhe illlensily of infeclion and lhe environmenl. ln S. borelli only Cllcllllal/lIs pil/I/oi Travassos. Anigas & Pereira. 1928 rrcsel1led a relalionship wilh lhe env ironmenl. ln lhis case lhe mea n illlensi ly was grea ler in kl1lic env ironmel1l s. The high va lue s of lhe similarily ind ex in lhe lhrec environlllel1ls sludied indicale a considerable homoge neily of lhe endohelminths' species wilh regard 10 P. corruscol/S and S. borelli. This is probably due lO whal occurs wilh environmellls eluring lhe high waler period when lhey are interlinked . The hyelro log ical level was a le ss intluential variahle in endoparasilic infrapopulalions of lhe hOSlS studied . ln P. corruscal/s only lhn:e species. S. spillll/ifera, NO/lli/l/osco/e.r SlIdobi/l/ Woodland . 1934 aml MegalhrloC/(,I'