Parasites in Leporinus macrocephalus (Anostomidae) of four fish farms from the western Amazon (Brazil).

This study evaluated the presence of metazoan parasites in Leporinus macrocephalus from four fish farms from the western Amazon (Brazil). In 160 fish examined, prevalence was 61.9%, and parasites found were: Urocleidoides paradoxus, Urocleidoides eremitus, Tereancistrum parvus, Jainus leporini, Procamallanus (Spirocamallanus) inopinatus, Rhabdochona (Rhabdochona) acuminata, Dolops discoidalis and Ergasilus sp., but U. paradoxus was the dominant parasite. Jainus leporini and Ergasilus sp. occurred only in L. macrocephalus from one fish farm, while U. paradoxus, U. eremitus and T. parvus were found in fish from three fish farms. Dolops discoidalis, P. (S.) inopinatus and R. (R.) acuminata occurred only in L. macrocephalus from two fish farms. Higher infection levels were caused by U. paradoxus, U. eremitus and P. (S.) inopinatus, which had an aggregated dispersion. There was positive correlation between abundance of parasites and the length of hosts. No difference in the condition factor of parasitized and non-parasitized fish were found. Such differences between fish farms were attributed to differences in management and quality of cultivation environments, and data indicate the need to adopt prophylactic measures in the fish farms to prevent diseases in the future. This was the first report of D. discoidalis and Ergasilus sp. for L. macrocephalus.

Dadaytrema oxycephala (Digenea: Cladorchiidae) in definitive host Pimelodus blochii (Pisces: Pimelodidae), with morphological and geographic distribution data in fishes from the South America.

The aim of this study was to describe structural and ultrastructural morphological data of Dadaytrema oxycephala (Diesing, 1836) Travassos, 1931 in Pimelodus blochii Valenciennes, 1840 from western Amazon (Brazil), besides geographic distribution in host fishes from South America. Of 160 P. blochii examined in the rivers Acre and Iaco, 15% were infected by D. oxycephala with mean intensity of 6.5 ± 1.9 and mean abundance of 1.0 ± 5.1. All parasites were found in the intestine of the infected hosts. The structural and ultrastructural characteristics of the developmental stages of D. oxycephala are presented and discussed. Dadaytrema oxycephala has a wide geographic distribution in South America, parasitizing fish species of Characiformes and Siluriformes from Brazil, Venezuela, Argentina, Peru and Paraguay. We elucidated part of life cycle of D. oxicephala in P. blochii, which is a definitive host for this digenean.

Monogeneans of the catfish Pimelodus blochii Valenciennes (Siluriformes: Pimelodidae) from the Brazilian Amazon, with a description of a new species of Ameloblastella Kritsky, Mendoza-Franco & Scholz, 2000 (Monogenea: Dactylogyridae).

Ameloblastella amazonica n. sp. (Monogenea: Dactylogyridae) collected on the gills of Pimelodus blochii Valenciennes (Siluriformes: Pimelodidae) from Rivers Acre and Iaco, State of Acre (Brazil) is described. The new species differs from the congeners mainly by the morphology of the dorsal bar, i.e. slightly U-shaped bearing a posteriorly directed flap, arising from the anterior edge of its middle third. The most morphologically similar congeners, A. paranaensis (França, Isaac, Pavanelli & Takemoto, 2003) and A. satoi Monteiro, Kritsky & Brasil-Sato, 2010, resemble A. amazonica n. sp. regarding the general structure of the copulatory complex; however, besides other features, they also differ from the new species because their hooks are similar in size (vs hooks with three different sizes). In addition to the dorsal bar lacking a flap, A. amazonica n. sp. can be differentiated from all congeners based on the combination of the following features: size of hooks (one or two different sizes), shape of the dorsal bar (other than slightly U-shaped), anchor points largely passing the level of superficial root (vs not or slightly passing it), number of MCO rings (other than 3-4) and structure of the articulation between the MCO base and the accessory piece (other than thick, medium-sized, smooth and tubular). Demidospermus leptosynophallus Kritsky & Gutierrez, 1998 and Scleroductus yuncensi Jara & Cone, 1989 were also found infesting P. blochii, both representing new host and locality records.

First description of the male of Philometroides acreanensis and phylogenetic assessment of Philometridae (Nematoda: Dracunculoidea) suggest instability of some taxa.

The male of Philometroides acreanensis, parasitic in the anterior intestine external wall of the freshwater catfish Pimelodus blochii, from the Brazilian Amazon, is described for the first time. Additional data on the morphology of females is given. The new morphological data strengthened the validity of the species as well as its first genetic characterization, using three nuclear genetic markers (18S and 28S of the rDNA and ITS1-58S-ITS2), confirmed the high genetic resemblance of male and female specimens. Philometroides acreanensis shows morphological features of the generic diagnosis of Neophilometroides, Alinema, Philometra and Philometroides. Phylogenetic analyses using sequences of the18S rDNA from representatives of Dracunculoidea confirmed the validity of P. acreanensis and its close relatedness with Alinema rather than with other genera. The validity of Philonemidae was confirmed, as was the monophyly of Philometridae and Clavinema. However, Dentiphilometra, Philometra and Philometroides appear not to be monophyletic. Host taxa, habitat and geographic occurrence seem to have some relationship with the evolutionary traits of certain phylogenetic assemblages of philometrids, which were highly supported in the phylogentic reconstructions. Even though interesting aspects of the phylogeny and taxonomy of Philometridae came to light, further integrative approaches should be used that include additional genetic markers, due to the loose boundaries between some genera as observed here.

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

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.