The present study describes Trypanosoma spp. infection and blood parameters in Pterygoplichthys pardalis from the Tapajós River basin in eastern Amazon (Brazil). Of 32 fi sh examined, 40.6% were infected by Trypanosoma spp., while a total of 112 trypomastigotes were found. Two Trypanosoma morphotypes were characterized and compared with species described in literature infecting other Loricariidae, and a similarity of 94% was found with one species described for another host. The plasma glucose and aspartate aminotransferase levels, hematocrit, number of total erythrocytes, mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC) in the infected and uninfected fi sh were similar, but hemoglobin was lower in fi sh infected with Trypanosoma spp. Hemoglobin levels declined with the abundance of the hemoparasites, but the condition factor was similar among fi sh infected and uninfected by Trypanosoma spp. This is the fi rst study on the hemoparasitism by Trypanosoma spp. and blood parameters in P. pardalis.

The aim of this paper was to report the occurrence of Austrodiplostomum spp. in the eyes and brain of Acaronia nassa, Caquetaia spectabilis, Satanoperca acuticeps, Curimatella sp. and Crenicichla marmorata in a lake of the Amazon River system in the state of Pará (Brazil). Of 49 fish examined, 10.2% were parasitized by Austrodiplostomum spp. metacercariae, and A. nassa was the host with higher number of metacercariae. In five examined fish species, a total of 51 metacercariae were collected, with 45 found in the eyes and 6 in the cranial vault. In the eyes, the metacercariae were free and active in the vitreous humor, but no opacification was observed. In the brain, the metacercariae were also free and active, and located mainly below the encephalon, on the cranial floor, at the height of the ophthalmic lobes and near the optic nerve. In laboratory observations, however, the infected fish did not exhibit any behavioral disorders, and this may be related to the low level of parasitism. This was the first report of this digenean for C. spectabilis, S. acuticeps, Curimatella sp., C. marmorata and A. nassa.