Recent studies of the forces behind the diversification of parasite assemblages have shed light on many aspects of parasite biodiversity. By using only parasite species richness as their measure of diversity, however, previous investigations have ignored the relatedness among parasite species and the taxonomic structure of the assemblages, which contain much information about their evolutionary origins. Here, we performed a comparative analysis across 50 species of fish from the coast of Brazil ; we evaluated the effects of several host traits (body size, social behaviour, feeding habits, preference for benthic vs. pelagic habitats, depth range, and ability to enter brackish waters) on the diversity of their assemblages of metazoan parasites. As measures of diversity, we used parasite species richness, as well as the average taxonomic distinctness of the assemblage and its variance ; the latter measures are based on the average taxonomic distance between any two parasite species in an assemblage. Unlike parasite species richness, taxonomic distinctness was unaffected by the number of host individuals examined per species. Fish body length proved to be the main predictor of parasite species richness, even when controlling for the confounding influences of host phylogeny and sampling effort, although it did not correlate with measures of parasite taxonomic distinctness. Predatory fish also had higher parasite species richness than planktivores, but this trend could not be confirmed using phylogenetically independent contrasts between host taxa. The main host feature associated with the taxonomic diversity of parasites was schooling behaviour, with schooling fish having more taxonomically diverse parasite assemblages than those of their non-schooling relatives. When focusing on endoparasite species only, both predatory feeding habits and a broad depth range were associated with the taxonomic distinctness of parasites. Our results suggest that certain host traits (i.e. body size) determine how many parasite species a host can accumulate over evolutionary time, whereas different host features influence the processes causing the taxonomic diversification of parasite assemblages.

Although research on parasite biodiversity has intensified recently, there are signs that parasites remain an underestimated component of total biodiversity in many regions of the planet. To identify geographical hotspots of parasite diversity, we performed qualitative and quantitative analyses of the parasite-host associations in fishes from Latin America and the Caribbean, a region that includes known hotspots of plant and animal biodiversity. The database included 10,904 metazoan parasite-host associations involving 1660 fish species. The number of host species with at least 1 parasite record was less than 10% of the total known fish species in the majority of countries. Associations involving adult endoparasites in actinopterygian fish hosts dominated the database. Across the whole region, no significant difference in parasite species richness was detected between marine and freshwater fishes. As a rule, host body size and study effort (number of studies per fish species) were good predictors of parasite species richness. Some interesting patterns emerged when we included only the regions with highest fish species biodiversity and study effort (Brazil, Mexico and the Caribbean Islands). Independently of differences in study effort or host body sizes, Mexico stands out as a hotspot of parasite diversity for freshwater fishes, as does Brasil for marine fishes. However, among 57 marine fish species common to all 3 regions, populations from the Caribbean consistently harboured more parasite species. These differences may reflect true biological patterns, or regional discrepancies in study effort and local priorities for fish parasitology research.

A comparative analysis was performed to seek large-scale patterns in the relationships between a set of fish species traits (body size, type of environment, trophic level, schooling behaviour, depth range, mean habitat temperature, geographical range, ability to enter brackish waters and capability of migration) and the diversity of their metazoan parasite assemblages among 651 Neotropical fish species. Two measurements of parasite diversity are used: the species richness and the taxonomic distinctness of a fish's parasite assemblage, including all metazoan parasites, ectoparasites only, or endoparasites only. The results showed that, on this scale, the average taxonomic distinctness of parasite assemblages was clearly more sensitive to the influence of host traits than parasite species richness. Differences in the taxonomic diversification of the parasite assemblages of different fish species were mainly related to the fish's environment (higher values in benthic-demersal species), trophic level (positive correlation with increasing level), temperature (positive correlation with temperature in marine ectoparasites, negative in endoparasites; positive for all groups of parasites in freshwater fishes) and oceanic distribution (higher values in fish species from the Pacific Ocean than those of the Atlantic). The results suggest that, among Neotropical fish species, only certain key host traits have influenced the processes causing the taxonomic diversification of parasite assemblages.

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

Parasite infracommunities were studied in 202 specimens of Astronotus ocellatus collected from a freshwater lake in the State of Amapá, northern Brazil. Relationships between some host attributes (i.e., ontogeny, sex, and body size) and parasite infections were analyzed, but the primary focus was the seasonal variation in the parasite fauna. In total, 6,308,912 parasites belonging to 11 different taxa were found. Protozoa were the most abundant and dominant taxa, but monogeneans, trematode metacercariae, and nematode larvae were also prevalent and abundant. Fish ontogeny had a weak influence on parasite infection rates; juveniles were more parasitized by Dolops nana and Posthodiplostomum sp. The abundances of all parasite species were weakly correlated with host body size (low r(2) values), except D. nana, Contracaecum sp., and Posthodiplostomum sp., which exhibited no correlation between abundance and host body size. Prevalence and abundance were different between flood and drainage seasons for all parasite species, except for D. nana and the 2 metacercarial species. Astronotus ocellatus may represent a link in food-web transmissions for parasites because it is used both as definitive and intermediate host. The parasite fauna of A. ocellatus was composed primarily of ectoparasites, and this could be considered typical of fishes that inhabit lentic waters. Seasonality was a strong determinant in the parasite community structure.

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One hundred and eighty specimens of sigmodontine rodents living in sympatric conditions were collected in the Atlantic Forest in the state of Rio de Janeiro, Brazil (25 Akodon cursor, 98 Akodon montensis and 57 Oligoryzomys nigripes) to examine whether the helminth structure and component communities can be characterized among these three closely related rodents. The parasite species richness was 9 in A. cursor, 12 in A. montensis and 12 in O. nigripes. Five species were common to the three rodent species, and eight were common to A. cursor and A. montensis. The trichostrongylids - Stilestrongylus eta in A. cursor, S. aculeata in A. montensis and S. lanfrediae in O. nigripes - were the species with highest dominance frequency and determined the characterization of individual community structures. The prevalence and abundance of concurrent helminth species among rodents were significantly different. Canonical multivariate analysis demonstrated a similar helminth community structure between A. cursor and A. montensis but a high discrepancy between Akodon spp. and O. nigripes. Thus, the data indicated that small rodents such as A. cursor, A. montenis and O. nigripes that are sympatric and phylogenetically related have a different community structure, but similar component community, suggesting the role of helminth specificity and the hosts' habitats as determinants in structuring their helminth communities.

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