Here we provide a checklist of the crustacean species parasitizing both marine and freshwater fishes from Brazil. We list a total of 134 species of parasitic crustaceans associated with 205 species of fishes in Brazil. The data from this study added to the checklist of Copepoda in Brazilian fishes published in 2007 give a total of 251 species of parasitic crustaceans associated with 279 fish species currently known in Brazil. The majority of species of Crustacea listed as parasites of Brazilian fishes are Copepoda with 186 species registered. A total of 741 parasite-host associations were observed. Copepoda was the group with more host-parasite associations, totaling 419 associations. When comparing these data with those recorded for the fishes from other parasite hotspots of Neotropics (Mexico and Caribbean), it is possible to affirm that the fauna of parasitic crustaceans of Brazilian fishes is the richest in the region.

Summary: 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.

Parasites of 136 specimens of Hemisorubim platyrhynchos, popularly called jurupoca, were analyzed. Fourteen parasite species were recorded: four digeneans (Crocodilicola pseudostoma, one Gorgoderidae species, Sanguinicola platyrhynchi, and Sphincterodiplostomum sp.); three cestodes (Goezeella paranaensis, Spatulifer maringaensis, and Mariauxiella piscatorum); five nematodes (Contracaecum Type 1 larvae of Moravec, Kohn, & Fernandes, 1993; Contracaecum Type 2 larvae of Moravec, Kohn, & Fernandes, 1993; Cucullanus (Cucullanus) zungaro; Eustrongylides ignotus; and Goezia sp.); one acanthocephalan (Quadrigyrus machadoi), and one pentastomid (Sebekia sp.). Most of the helminth specimens were found in larval stages, confirming that H. platyrhynchos is a significant source of their transmission. No dominance was reported. With the exception of Contracaecum Type 2 (featuring random dispersion), the species had a clumped pattern of dispersion in the host sample. Evidence of competition among parasite species was not reported. Several species of parasites were correlated with host size and sex. This fact may be explained by increase in food content and possible behavioral modifications of male and female hosts. Infracommunity diversity was not related to host size or sex.

This study presents results from several expeditions in 1985, 1991-1995 and 2003 to the Medium Paraná River in the section that begins below the Itaipu Dam and ends at the trinational border of Brazil, Argentina and Paraguay, in the lotic and lentic zones of the reservoir of the Hydroelectric Power Station of “Itaipu Binacional” (localities Foz do Iguaçu, Santa Helena and Guaira). Ninety-eight species of freshwater fishes belonging to 22 families were examined for helminths. A host-parasite list based on Acanthocephala, Cestoda, Digenea, Monogenea and Nematoda collected from the region in question is provided. New host records are presented for Digenea and Nematoda. The Monogenea and Acanthocephala are being studied and will be published in a later paper, but are referred in the host-parasite list, in order to demonstrate the parasitism in the fishes of the reservoir. The results are compared with those presented by other authors from the Upper Paraná River.