First assessment of the metazoan parasite community of Gymnogeophagus balzanii (Cichliformes: Cichlidae) from Pantanal wetlands, State of Mato Grosso do Sul, Brazill

Gymnogeophagus is a genus of fish from the family Cichlidae present in freshwaters from Southern South America, and the knowledge on its parasite communities is rather scarce. Therefore, the present study evaluated, for the first time, the parasite community of G. balzanii. Fish were collected in the Pantanal wetlands, State of Mato Grosso do Sul, Brazil and analysed for metazoan parasites. Ten taxa (larvae and adult) were found including Nematoda (3), Digenea (5), Copepoda (1) and Monogenea (1). All taxa were aggregated within the host population, few showed high prevalence and all had low abundance. The parasite community was composed by few specialists and several generalist and characterised by low richness, diversity and, consequently high dominance of few species and low evenness. These characteristics are typical of isolationist parasite communities. The predominance of larval forms indicates that G. balzanii occupies a lower position within the food chain, acting as an important link for trophic relations. Host length and weight were strong determinants in the parasite community, making fish sex also important since males were significantly longer and heavier than females. Generally, the parasite fauna did not influence host body condition, indicating no apparent debility. Presence of Clinostomum metacercariae is important for human health issues.