Trichodina heterodentata (Ciliophora: Trichodinidae) Parasitizing Piaractus brachypomus Cultivated in Ecuadorian Amazon

Abstract

Ectoparasitic protozoa of the genus Trichodina are considered one of the main pathogens affecting cultured fishes, mainly in small organisms or early ages. However, its incidence and effects on Amazon traditional aquaculture species such as Piaractus brachypomus has been little studied. The objective of the present investigation was to establish the presence of Trichodina heterodentata, its parameters of infection, and associated damages in three aquaculture farms of P. brachypomus located in Puyo, El Coca and in Joya de los Sachas, Ecuadorian Amazon. In each farm, 15 fish were collected randomly. The size and weight of fishes were recorded, and smears were made from the surface of the skin, gills and fins for the detection of trichodinid parasites. Gill fragments of parasitized fish were fixed in 10% buffered formalin and processed by the paraffin inclusion technique, to evaluate the damages associated with parasites. Trichodina heterodentata was detected in specimens of P. brachypomus from the farm located in El Coca, with prevalence of 100%, and mean intensity of 0.21 ± 4.7 parasites per host. Histopathological analysis showed the presence of slight hyperplasia and thickening of the lamellae of parasitized fish. The fish from El Coca farm showed significantly lower average sizes and weights than the fish from the other two farms, confirming the susceptibility of the smaller fish to these parasites. This is the first record of T. heterodentata for P. brachypomus in its entire range of distribution, and the first report of Trichodina in aquaculture systems of Ecuador.