Seasonal patterns of infestation by monogenean parasites of fish and their relationship with water parameters in two rivers with different disturbance gradients in southeastern Brazil.

Here, we evaluate the relationships between the infestation rates of five monogenean parasites species with the dry and wet seasons, with the organic and inorganic parameters of the water of two rivers: the Jacaré-Pepira and Jacaré-Guaçú, and with the condition factors of its fish hosts: Serrasalmus maculatus and Astronotus crassipinnis, in the state of São Paulo, southeastern Brazil. Fish were collected between January and December 2017. Anacanthorus serrasalmi, Amphithecium speirocamarotum and Gussevia asota had higher abundance rates (Student's t test, p ≤ 0.05) in the wet season. Gussevia asota had its abundance negatively correlated to nitrate in the Jacaré-Pepira River and with total nitrogen and potassium in the Jacaré-Guaçú River. Regarding the fish hosts condition factors, was observed a positive correlation with the abundances of G. asota in the Jacaré-Guaçú River, and with A. serrasalmi in the Jacaré-Pepira River. In general, wet season favored an increasing in the infestation rates of the monogeneans parasites in their host species, mainly in the river considered as the most polluted, the Jacaré-Guaçú River. Of the five parasites species analyzed in this study, only Gussevia astronoti and Rhinoxenus piranhus had no interaction with seasonality, river water variables, or fish host condition factors. On the other hand, G. asota had interactions both with water parameters (nitrate and total nitrogen) and with the hosts condition factors, which reflected in the abundance and intensity rates, showing itself as a species sensitive to changes in the environment and, therefore, that can be considered as a bioindicator organism.

First record of Rhipidocotyle santanaensis (Digenea) parasitizing Acestrorhynchus lacustris from Batalha River, Brazil.

This paper describes the occurrence of digenetic Rhipidocotyle santanaensis Lunaschi, 2004 in Brazil. This parasite was found in the liver, heart, gonads, intestine, pyloric caeca, stomach, swim bladder and cavity of Acestrorhynchus lacustris (Lütken, 1875) from the Batalha River, São Paulo State, with higher incidence in gonads and digestive tract. The parasite specimens found in this study showed morphological characteristics very similar to specimens from Argentina, with differences only in relation to the ejaculatory duct and seminal vesicle. However, Brazilian specimens presented great morphometrical differences between specimens described in Argentina, with much higher measures. This is the first record of this metazoan parasite species in Brazil and in this host fish.

First record of Rhipidocotyle santanaensis (Digenea) parasitizing Acestrorhynchus lacustris from Batalha River, Brazil / Primeiro registro de Rhipidocotyle santanaensis (Digenea) parasitando Acestrorhynchus lacustris do rio Batalha, Brasil

Abstract This paper describes the occurrence of digenetic Rhipidocotyle santanaensis Lunaschi, 2004 in Brazil. This parasite was found in the liver, heart, gonads, intestine, pyloric caeca, stomach, swim bladder and cavity of Acestrorhynchus lacustris (Lütken, 1875) from the Batalha River, São Paulo State, with higher incidence in gonads and digestive tract. The parasite specimens found in this study showed morphological characteristics very similar to specimens from Argentina, with differences only in relation to the ejaculatory duct and seminal vesicle. However, Brazilian specimens presented great morphometrical differences between specimens described in Argentina, with much higher measures. This is the first record of this metazoan parasite species in Brazil and in this host fish.

Resumo O presente trabalho descreve a ocorrência do digenético Rhipidocotyle santanaensis Lunaschi, 2004 no Brasil. Estes parasitos foram encontrados no fígado, coração, gônadas, intestino, cecos pilóricos, estômago, bexiga natatória e cavidade do peixe Acestrorhynchus lacustris (Lütken, 1875) provenientes do rio Batalha, Estado de São Paulo, com maior abundância nas gônadas e trato digestório. Os espécimes dos parasitos encontrados neste trabalho apresentaram características morfológicas muito semelhantes aos espécimes provenientes da Argentina, com diferenças apenas em relação ao ducto ejaculatório e vesícula seminal. Porém, os exemplares brasileiros apresentaram grandes diferenças morfométricas entre os espécimes descritos na Argentina, com medidas muito superiores. Este é o primeiro registro desta espécie de parasito no Brasil e neste hospedeiro.