<b>Endoparasitic fauna of <i>Serrasalmus</i> spp. (Characidae: Serrasalminae) in a neotropical floodplain

Abstract

ABSTRACT. Floodplains systems present complex biodiversity and upper Paraná river floodplain retains a wide variety of terrestrial and aquatic species. Serrasalmus marginatus (nonindigenous species) and Serrasalmus maculatus (native species) are part of this biodiversity component and can be infected by trophic transmission. In order to understand the ecological processes within the upper Paraná river floodplain, endoparasite fauna of those two hosts species were analyzed, considering prevalence, abundance, intensity and richness variables to determine this relationship. So, abundance of acantocephalan Echinorhynchus sp. was positively correlated to S. marginatus length, while Kritskyia annakohnae (Monogenea) prevalence and S. marginatus length presented a negative correlation. S. marginatus relative condition factor (Kn) was negatively and significantly associated to the abundance of K. annakohnae, and Kn of infected fish by that species is lower compared with the non-infected fish. Since hosts are in the context of the introducing of species, the research of endoparasites ecological variables allows to understansd infracommunity and component community as a way of analyzing the consequence of these parasites distribution in the native and non-native species.Keywords: neotropical floodplain, parasite ecology, invasive species, piranha.Fauna endoparasitária de Serrasalmus spp. (Characidae: Serrasalminae) de uma planície de inundação neotropical RESUMO. Sistemas de inundação possuem uma complexa biodiversidade. Por causa desta característica, a planície de inundação do alto rio Paraná abriga uma gama muito grande de espécies aquáticas e terrestres. Serrasalmus marginatus (espécie introduzida) e Serrasalmus maculatus (espécie nativa) compõem a ictiofauna desta área, e estes hospedeiros podem ser infectados por endoparasitos pela transmissão trófica. A fauna endoparasitária das duas espécies de peixes foi analisada por meio da prevalência, abundância, intensidade e riqueza para averiguar a relação destas com as variáveis dos hospedeiros. Observou-se que a abundância do acantocéfalo Echinorhynchus sp. está positivamente correlacionada com o comprimento de S. marginatus, enquanto existe uma correlação negativa e significativa entre a prevalência de Kritskyia annakohnae (Monogenea) e o comprimento de S. marginatus. O fator de condição relativo (Kn) de S. marginatus está relacionado negativa e significativamente com a abundância de K. annakohnae, e o Kn dos peixes parasitados por esta mesma espécie é mais baixo se comparado com os peixes não parasitados. Como os hospedeiros estão no contexto de introdução de espécies, as investigações das variáveis ecológicas dos endoparasitos possibilitam o conhecimento de cada infracomunidade e comunidade componente, como forma de delimitar a atuação dos parasitos na mediação da relação ecológica entre a espécie nativa e não nativa.Palavras-chave: planície de inundação neotropical, ecologia parasitária, espécie invasora, piranha.

Infection pattern of Echinorhynchus salobrensis (Acanthocephala) in congeneric species of piranha from a Neotropical floodplain region

“…Although it has been observed that larger fish may have a greater abundance of parasites (Lehun et al 2023), we found that parasite index values were higher in S. marginatus, which has a shorter mean standard length when compared to S. maculatus. Casali and Takemoto (2016) found a positive correlation between the abundance of E. salobrensis and the length of S. marginatus, but this correlation was not significant in our study.…”

Parasites and diet of Serrasalmus maculatus in a hydroelectric reservoir in Brazil

“…Several authors have reported rich endoparasite fauna for S. maculatus in the Upper Paraná River floodplain, whereas endoparasites were completely absent in the present study, and the richness of ectoparasites was low (Pavanelli et al, 1997;Pavanelli et al, 2004;Takemoto et al, 2009;Casali & Takemoto, 2016 see Table 1). It is possible that the dynamics of parasitic infections are negatively affected by abiotic and biotic homogenisation in artificial habitats (Agostinho et al, 2007), such as hydroelectric reservoirs, especially for endoparasites with heteroxenous life cycles.…”

“…The dietary components of S. maculatus identified in the present study were like the findings of previous studies in the Upper Paraná floodplain, including the Ibicuí River, Rio Grande do Sul state, and a lower stretch of the Sorocaba River basin, São Paulo state, Brazil (Agostinho & Marques, 2001;Agostinho et al, 2003;Behr & Signor, 2008;Villares et al, 2008). Serrasalmus maculatus is piscivorous, preferentially ingesting fish fragments (instead of ingesting the host's entire body), and its feeding behaviour includes the mutilation of prey scales, fins, and muscle tissue, which we infer can hinder the ingestion of endoparasites (Sazima & Pombal-Jr, 1988;Sazima & Machado, 1990;Casali & Takemoto, 2016). In the present study, the dietary components of S. maculatus were fish fragments, terrestrial plants, and decapods (Macrobrachium sp.).…”

“…In summary, the richness of the component parasite community of S. maculatus in the Ilha Solteira hydroelectric reservoir in Brazil was low, in contrast to what has been previously reported in other water environments Braz J Vet Parasitol 2022; 31(1): e019221 24/28 Parasites and diet of Serrasalmus maculatus (Pavanelli et al, 1997(Pavanelli et al, , 2004Takemoto et al, 2009;Casali & Takemoto, 2016). These findings provide insight into the relationships between S. maculatus diet, social behaviour, and parasite fauna and the distribution and infection patterns of the observed parasite taxa.…”

“…Most studies of the parasitology of S. maculatus have focused on populations in the Upper Paraná River floodplain region (Pavanelli et al, 1997(Pavanelli et al, , 2004Takemoto et al, 2009;Casali & Takemoto, 2016;Moreira et al, 2019), and few studies have examined this species ecology or parasitology in artificial environments. In addition, considering the diet is an important factor in host-parasite interactions and hosts with more diverse diets tend to be more susceptible to endoparasite infections (Lima et al, 2016), we aimed (i) document the parasitic fauna and (ii) characterize the diet of S. maculatus in a hydroelectric reservoir in Brazil.…”