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The aim of the present study was to detect changes in the structure of the helminth parasite infracommunities in Salminus brasiliensis (Cuvier 1816) from the floodplain of the upper Paraná River after construction of the Porto Primavera Hydroelectric Plant. A total of 126 fish in the period before the dam's construction and 56 specimens 10 years after this event were analysed. Three species of parasites were collected before the construction of the dam: Prosthenhystera obesa Diesing, 1850 (Digenea), Cladocystis intestinalis Vaz, 1932 (Digenea) and Monticellia coryphicephala Monticelli, 1892 (Cestoda), and one nematode species in the larval stage, whose identification was not possible. After dam construction, the following helminth parasites were found: C. intestinalis, M. coryphicephala, Octospiniferoides incognita, Contracaecum spp. larvae and Contracaecum sp. type 2 larvae Moravec, Kohn & Fernandes 1993. The diversity of helminth parasites measured by the Brillouin diversity index (HB) differed significantly between the pre- and post-dam periods (mean HB = 0.069 and HB = 0.2, respectively; P= 0.0479; Mann-Whitney U test). The parasite community of S. brasiliensis before the construction of the dam showed concentration of dominance (C) of P. obesa (C = 0.38), while there was no concentration of dominance of any species of parasite (C = 0.22) after the dam's construction. Before the Porto Primavera dam the relative condition factor of fish was 1.0; after the dam's construction it was 0.93 (P < 0.0001; Mann-Whitney U test). This study records the disappearance of the species P. obesa and suggests that there has been local extinction of this parasite. The results show that the anthropic influence on natural systems is interfering with the welfare and health of S. brasiliensis, reflected by its fauna of helminth parasites.

This paper presents a science metric study of parasites of fish farming in Brazil, including a significant review of the literature. The methodology used was based on researching articles in three different databases, carried out on May 2012: ISI (Institute for Scientific Information), SciELO (Scientific Electronic Library Online), and Google Academic. The number of articles on fish parasites is mounting (currently over 110), having much increased since 1995. However, the quantity is still low compared with the amount of papers on parasites of fish from natural environments. In Brazil, the farmed fish that have been studied the most are pacu, tilapia and tambaqui. Monogeneans represent the most prevalent group, followed by protozoa and crustaceans. The regions most researched were the southeast and south, making up 84% of the total literature. The main issue addressed in articles was pathology, followed by treatment and record. In conclusion, the treatment of parasitic diseases of farmed fish in Brazil is still incipient, highlighting the importance and usefulness of management practices to prevent the occurrence of health problems.

The objective of the present study was to discover the hematological indices of Hoplias malabaricus infected by larvae of Contracaecum sp. A total of 105 fish were collected from two lakes located in the municipal district of Pirassununga, São Paulo, Brazil, of which 95.2% were infested by L3 larvae of Contracaecum sp., with an average intensity of 348.7 ± 231.55 helminths/fish. A total of 76 fish were analyzed to establish hematological parameters. Following analysis, it was found that there was a significant difference between hematological parameters Hct, erythrocytes (Er), thrombocytopenia (p = 0.01), and Hb (p = 0.02) in lakes A and B, while there was no significant difference for leukocyte (p = 0.68), mean corpuscular volume, mean corpuscular hemoglobin (p = 0.06), and mean corpuscular hemoglobin concentration (p = 0.47). The intensity of infection correlated negatively with Er (r(s) = -0.42; p < 0.01) and positively for (r(s) = 0.48; p < 0.01). The high intensity of infection by Contracaecum sp. in H. malabaricus did not affect the health of the fish despite causing alterations in hematological variables.

A new species of Jainus (Monogenea), gill parasite of Schizodon borellii (Characiformes, Anostomidae) Maringá, Av. Colombo, 5790, Maringá, Paraná, ABSTRACT. Jainus piava n. sp. is described from the gills of Schizodon borellii (Boulenger, 1900) (Characiform), commonly named as piava from the upper Paraná River floodplain, Brazil. The new species differs from the other members of Jainus in the following features: ventral bar thin broadly V-shaped and male copulatory organ (MCO) a coil of about 1.5 rings. Jainus piava n. sp. is similar to species of Jainus by having a ventral anchor base with flattened superficial root and elongate rodlike deep root.

Hematology is an important pathological and diagnostic tool. This paper describes the hematological parameters of 76 specimens of Hoplias malabaricus infested with monogenean parasites, which were collected from two lagoons. The hematological parameters included: erythrocyte count (Er), microhematocrit (Hct), hemoglobin (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC). The blood parameters showed no significant changes associated with the infestation. Water temperature was found to be negatively correlated with MCV and Hct, with values of r s = -0.52, p<0.0001 and r s = -0.48, p<0.0001, respectively. The mean Relative Condition Factor was Kn=1.01, indicating good health conditions of the fish in these lagoons. No correlation was found between the monogenean infestation and the blood parameters, or between the environmental factors and the monogeneans.Keywords: Parasites, blood cells, freshwater fish. ResumoA hematologia é uma importante ferramenta para patologia e diagnóstico. O presente estudo teve como objetivo descrever os parâmetros hematológicos de 76 espécimes de Hoplias malabaricus, coletados em duas lagoas, associados ao parasitismo por monogenético. Os parâmetros hematológicos foram: contagem de eritrócitos (Er), micro hematócrito (Hct), hemoglobina (Hb), volume corpuscular médio (VCM), hemoglobina corpuscular (HCM) e a concentração da hemoglobina cospuscular média (CHCM). Observou-se que não ocorreram mudanças significativas nos parâmetros sanguíneos relacionados com o parasitismo. Houve uma correlação negativa entre a temperatura da água o VCM e Hct, com valores de r s = -0,52, p<0,0001 e r s = -0,48, p<0,0001, respectivamente. O valor médio entre o fator de condição relativo foi de Kn = 1,01, indicando boas condições e os peixes estavam saudáveis nas lagoas estudadas. Não houve relação entre a infestação de monogeneas e os parâmetros sanguíneos, ou entre os fatores ambientais e as monogeneas.Palavras-chave: Parasitas, células sanguíneas, peixes de água doce.

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ABSTRACT. Tereancistrum paranaensis sp. n. is described from the gills of Schizodon borellii (Boulenger 1900) (Characiformes) from the upper Paraná river floodplain, Brazil. The new species is mainly characterized by morphology of copulatory complex, dorsal anchor with shaft recurved and pointed and arc-shaped dorsal bar. Tereancistrum parvus was described based on only one specimen and some characteristics were not observed. Now we provide an emendation to the diagnosis of this species.