Specimens of Dekeiseria amazonica Rapp Py-Daniel, 1985 and Hypostomus oculeus (Fowler, 1943) captured from July 2015 to December 2016, in the Catalão Lake complex, Iranduba, Amazonas, were studied. The specimens of D. amazonica measured 12 – 16.5 (13.70 ± 1.33) and weight (g) 29 – 59 (40.85 ± 9.78) and H. oculeus 12 – 21 (15.80 ± 2.13) and weight (g) 75 - 125.40 (101.11 ± 14.28). Both species were parasitized by the acanthocephalan Gorytocephalus elongorchis Thatcher, 1979 (Neoechinorhynchidae), parasitizing the intestine, with a prevalence of 55% and abundance of 18.  The intensity ranged from 1 to 3 parasites and the average intensity was 1.63 parasites per fish for D. amazonica, and prevalence 59.25%, abundance 29. The intensity of 1 to 4, mean intensity 1.81 for H. oculeus. Two new hosts for G. elongorchis are recorded and their specificity for fish of the Loricariidae is...