Community structure of metazoan parasites from Pimelodus blochii in two rivers of the Western Brazilian Amazon: same seasonal traits, but different anthropogenic impacts

Abstract

The present investigation evaluated the influence of seasonality and locality on the structure of the parasite community of the catfish Pimelodus blochii. A total of 160 fish were collected from two rivers in the State of Acre, western Brazilian Amazon: 80 fish in River Acre and 80 in River Iaco, with 40 in each season (rainy and drought). The overall prevalence was 78.7% and 1461 parasite specimens (adults and larvae) were allocated in 22 taxa: 5 of Monogenea, 10 of Nematoda, 3 of Digenea, 1 of Cestoda and 3 of Crustacea. In drought season, Procamallanus (Spirocamallanus) pimelodus and Demidospermus peruvianus were more prevalent in River Acre and Iaco, respectively. The parasite diversity (Brillouin index) as well as the prevalence and abundance of the monogeneans D. peruvianus, D. striatus, Demidospermus sp. and Ameloblastella sp. were higher in River Acre. The parasite community structure were dissimilar among rivers, and seasonally in River Iaco. These results suggest that environmental traits may overshadow seasonal influences on the parasite community structure, which may be related to the higher anthropization in River Acre. Furthermore, seasonality exerted less influence on the parasite community than expected, probably because the two rivers have different hydrological traits than those of other rivers in the Brazilian Amazon. New host and locality records expanded our knowledge of parasite biodiversity of P. blochii.

Helminth diversity in Pimelodus blochii Valenciennes, 1840 (Osteichthyes: Pimelodidae) in two Amazon Rivers

“…As P. (S.) pimelodus, O. moraveci also stands out from the other species in the community, as it was the most prevalent and abundant species in the Acre River and the second most prevalent in the Xapuri River. These results differ from the study of Negreiros et al (2018), which reported this species in low prevalence and abundance rates. The pathogenicity of fish parasites is mostly associated with the species of the genera Procamallanus and Cucullanus.…”

“…Except for the trematode D. oxycephala, all the other adult specimens were nematodes. The nematodes are among the most abundant endohelminths in Pimelodus spp., as reported in the studies at Mogi Iguaçu River, São Paulo State (Kohn and Fernandes 1987), Itajaí-Açu River, Santa Catarina State (Bachmann et al 2007), São Francisco River, Minas Gerais State (Sabas and Brasil-Sato 2014), and Iaco and Acre Rivers, Acre State (Negreiros et al 2018), corroborating the results of the present study.…”

“…However, this species was found in only one fish caught in the Acre River. This helminth species was reported in this host with a prevalence of 3.8% in the same river by Negreiros et al (2018).…”

“…The occurrence of only two female specimens of P. acreanensis only in the Acre River may indicate that possible intermediate hosts are restricted to the Acre River. Negreiros et al (2018) also found few specimens of this helminth in P. blochii in the same river. Those authors also found more local environmental than seasonal influence in the Acre River, and seasonal differences were clearer in the most preserved river (Negreiros et al 2018).…”

“…Concerning helminth parasites, most of the studies carried out for this host were species lists (Kohn et al 2007;Luque and Tavares 2007;Luque et al 2011;Martins 2018) or species descriptions (Gil de Pertierra 2004; Mendoza-Palmero and Scholz 2011; Orélis-Ribeiro and Bullard 2015; Cavalcante et al 2017;Cavalcante et al 2018;Negreiros et al 2019a;Negreiros et al 2020). There are only two studies which investigated the helminth community structure of P. blochii (Negreiros et al 2018(Negreiros et al , 2019b. The former compared the parasitic fauna in the Acre and Iaco Rivers in the Amazon region, reporting 22 taxa with a dissimilar parasite community structure between rivers; the latter evaluated the temporal changes in the community structure also in the Iaco River for 5 years.…”