Abstract Monogeneans are a diverse group of flatworms, being ectoparasites of marine and freshwater fish, with great morphological and ecological variety. Analyzes of monogenetics in fish with great habitat diversity such as snappers are scarce in the literature, which already emphasizes the need for an update in this regard. The presente study found, morphologically characterized and mapped the geographic distribution and in known hosts the species Microcotyloides incisa and Microcotyloides impudicus, describing the first occurrence of these monogeneans for South America and in new hosts. The survey of hosts in the literature shows that M. incisa seems to have a greater Affinity with congener species of Lutjanidae and fish from other families, which may indicate a preference or specificity for fish of this family because they are congeners of their host type. The introduction of these parasites into South American waters may have occurred due to the migratory behavior of snappers, which are well distributed along the Mexican coast, where the parasites are usually reported. Here, we also bring the first occurrence of M. incisa for Lutjanus analis and Lutjanus jocu and M. impudicus for Ocyurus chrysurus and Lutjanus synagris, helping in the mapping and distribution of these monogenetic species in the Americas. flatworms variety regard found M families type coast reported Here synagris Americas

It was studied the monogenean communities on the gills of a Pimelodus albicans Valenciennes, 1840 juvenile, in the Northern Salado River, tributary of the Middle Paraná River (Argentina). Monogenea taxa were found: Demidospermus armostus, Demidospermus bidiverticulatum, Demidospermus idolus, Demidospermus majusculus, Scleroductus yuncensi, Demidospermus sp and Ancyrocephalinae sp. The results allow us to conclude that: D. majusculus, D. armostus, D. idolus and Ancyrocephalinae sp were secondary species and there is no a dominant one. The local diversity of parasites is moderate and there is no correlation between the size of the hosts and the intensity of parasitism. In this article, the infrapopulations and infracommunities of monogenean of P. albicans, were analyzed. These reports show a new geographical distribution register ofneotropical monogenean species.

Se estudió la comunidad de Monogenea de las branquias de juveniles de Pimelodus albicans Valenciennes 1840, en el río Salado del Norte, tributario del río Paraná Medio (Argentina). Se hallaron los siguientes taxa: Demidospermus armostus, Demidospermus bidiverticulatum, Demidospermus idolus, Demidospermus majusculus, Scleroductus yuncensi, Demidospermus sp y Ancyrocephalinae sp. Los resultados permiten concluir que no existe una especie dominante, aunque D. majusculus, D. armostus, D. idolus y Ancyrocephalinae sp se destacan por ser secundarias. La diversidad parasitaria local es moderada y no existe correlación entre la talla de los hospedadores y la intensidad de infestación de todos los taxa. En este artículo se analizan las infrapoblaciones e infracomunidades de Monogenea de P. albicans, y se presenta un nuevo registro de distribución geográfica de estos ictioparásitos neotropicales.

A new species of Kritskyia inhabits the urinary bladder of the "curimba", Prochilodus lineatus in the floodplain of the high Paraná river. The new species resembles others members of Kritskyia in the following features: haptor lacking anchors and with 14 hooks marginal, posterior male copulatory organ non articulated with the accessory piece and vagina a sclerotized tube. However, it differs from the known species mainly by the shape of the copulatory complex. This is the third endoparasitic monogenean species reported from freshwater Neotropical fish.

Spasskyellina mandi n. sp. (Proteocephalidea: Monticelliidae) is described from the Siluriform fish Pimelodus ornatus Kner, 1857, caught in the Paraná River, Paraná, Brazil. The new species differs from other species of the same genus mainly by a fewer number of testes and by a larger osmoregulatory canal. This is the second species of proteocephalidean cestode collected in P. ornatus.

Metacamopia oligoplites n. sp., a gill filament parasite of carangid fishes of three species of Oligoplites Gill, O. palometa (Cuvier), O. saurus (Bloch & Schneider), and O. saliens (Bloch), from the coast of the State of Rio de Janeiro, Brazil, is described and illustrated. Metacamopia oligoplites n. sp. differs from M. indica by: the shape of the body; the pre-, para-, and post-germarial testes; vaginas lacking sclerotized structures; well-developed seminal receptacles; muscular sleeves around the constriction between the vaginas and the seminal receptacles; and the haptor highly asymmetric, with a large, heel-like area; and differs from M. chorinemi by: the esophagus lacking diverticles; a larger number of testes (26-55) and not just, approximately 10; and the vaginas lacking sclerotized structures of any kind. This is the first record of Metacamopia in the South Atlantic Ocean. The generic diagnosis of Metacamopia is emended. Hargicola oligoplites is reported for the first time in the South Atlantic Ocean. Oligoplites palometa and O. saliens are new host records for Hargicola oligoplites.

One hundred and ten specimens of Pseudoplatystoma corruscans (Agassiz, 1829) (Pimelodidae), "pintado", and 582 specimens of Schizodon borelli (Boulenger, 1900) (Anostomidae), "piava", collected in the floodplain of the high Paraná River were analyzed. P. corruscans presented 74.54% of parasitism while S. borelli presented 19.42%. Results of the present research show that in the case of P. corruscans, two species of proteocephalideans presented a significant relationship with the type of environment with regard to prevalence. Spasskyelina spinulifera (Woodland, 1935) was the only species that presented a relationship between the intensity of infection and the environment. In S. borelli only Cucullanus pinnai Travassos. Artigas & Pereira, 1928 presented a relationship with the environment. In this case the mean intensity was greater in lentic environments. The high values of the similarity index in the three environments studied indicate a considerable homogeneity of the endohelminths' species with regard to P. corruscans and S. borelli. This is probably due to what occurs with environments during the high water period when they are interlinked. The hydrological level was a less influential variable in endoparasitic infrapopulations of the hosts studied. In P. corruscans only three species, S. spinulifera, Nomimoscolex sudobim Woodland, 1934 and Megatnylacus travassosi Pavanelli & Rego, 1992 presented higher mean intensities in the high water period. This fact was also observed in the case of C. pinnai in S. borelli.

In the present paper the authors describe and illustrate a new species of proteocephalidean cestode, Monticellia belavistensis, sp.n., parasite of a freshwater siluriform fish (thorny catfish). Pterodoras granulosus (Valenciennes, 1833), from the Itaipu Reservoir and Paraná River, in the region of Porto Rico. This is the first reference of a proteocephalid in this host. The values of prevalence and mean intensity of infection are given and the life cycle is discussed.