INFECTION WITH TROPHOZOITES OF Ichthyophthirius multifiliis (CILIOPHORA) IN Poecilia vivipara (POECILIIDAE) AS AN EXPERIMENTAL HOST

Abstract

This experiment studied the parasitic degree in Poecilia vivipara experimentally infected by Ichthyophthirius multifiliis trophozoites. In flasks with 400 mL of water, four fish were maintained with constant aeration in two replicates and added 0, 1, 2, 4, 8, 16 and 20 trophozoites/fish. Mean values of water temperature, pH and dissolved oxygen were 19.5±0.39ºC, 6.35±0.09 and 7.02±0.45mg/L, respectively. Before experimental infection the fish were treated with formalin solution 1:4000 for 1 hour in two consecutive days. The parasites were obtained from five infected Salminus brasiliensis that were maintained into Petri dishes with water for 30 minutes. Trophozoites were collected with pipette and the respective number of inoculums added. To avoid the parasite adherence, the plates were maintained into the respective flask. After seven days all fish were killed for exam, except for treatment 20 trophozoites/fish in which mortality occurred in two days. The mean value of treatment with 20 trophozoites/fish was significantly higher (P<0.05) than 0, 1, 2, 4, 8 and 16. It is suggested that 1 to 16 trophozoites/fish is practicable to the study of experimental infection, by the fact that these fish were maintained parasitized during whole period. KEY WORDS: Ichthyophthirius multifiliis, experimental infection, Poecilia vivipara.