No abstract

The life cycle of the digenetic trematode Clinostomum complanatum was studied on the floodplain of the high Parana´river, Brazil. Sampling was done between June 1999 and June 2000. The mollusc Biomphalaria peregrina was the first intermediate host with a prevalence of infection of 0.75%. The fish Loricariichthys platymetopon, Hoplosternum littorale, Parauchenipterus galeatus, Hoplias malabaricus and Loricaria sp. were second intermediate hosts, with the prevalence varying from 2.45% (H. malabaricus) to 60.8% (L. platymetopon). The birds Ardea cocoi, Phalacrocorax brasilianus, Egretta alba and Egretta thula were definitive hosts, with the prevalence ranging between 5.5% (E. thula) and 95% (A. cocoi). The high prevalences in birds, especially in A. cocoi, suggest some kind of mechanism facilitating the predation of infected fish. The importance of the various hosts is discussed, and it is concluded that the floodplain of the high Parana´river has suitable conditions for the maintenance of the life cycle of C. complanatum.

The prevalence of Clinostomum complanatum Rudolphi, 1814 (Digenea, Clinostomidae) in fishes Loricariichthys platymetopon, Parauchenipterus galeatus and Hoplosternum littorale, which are second intermediate hosts, was studied at the floodplain of the high Paraná River, Brazil. Season (alternation flood-drought), habitat (lentic and semi-lotic), and sex were not related to its prevalence. For L. platymetopon, the immature and smaller fish had the lowest prevalence, whilst the opposite was observed for P. galeatus and H. littorale. This suggests that the probability of being predated is unchanged by parasitism for L. platymetopon; thus, a cumulative effect of repeated infections is observed; for the two other species, the highest parasitised fish may have higher predation mortality rates. While H. littorale is the preferred item in birds' diet, L. platymetopon is the most abundant fish species and has the highest C. complanatum prevalence, which makes it the most likely path of transmission to the bird, the definitive hosts of C. complanatum.

Parasites are important components of communities and constitute great part of the biological diversity found in ecosystems, providing valuable information about their hosts and the environment in which they live. However, despite its importance, parasitic diversity is still not well known in some regions of Brazil, especially with respect to fish parasites in the Northeast Region. The present study aims to perform the survey of gill parasites of fish from two tropical estuaries located in northeastern Brazil: Paraíba and Mamanguape rivers. Two collections were made in each estuary, one during the dry period (November / 2013) and the other during the rainy season (July / 2014). The fish were caught using a beach seine net, dragged along the main channel margin. After the identification, biometry and necropsy of the fish, their parasites were collected, stored and identified. For each species of parasite, the values of prevalence, mean intensity and mean abundance were calculated. Of the 882 examined fish, belonging to four species, 145 were parasitized by at least one species of parasite. In total, 18 taxa of parasites of the groups Monogenea, Digenea, Nematoda, Copepoda and Isopoda were recorded, being the copepod Acusicola brasiliensis the most abundant species of parasite.