Protective effect of Terminalia catappa leaf extracts against Saprolegniosis on angelfish eggs

Abstract

The Saprolegniosis causes major reduction egg hatching rate by angelfish (Pterophyllum scalare); therefore, we investigated the effectiveness of two Terminalia catappa extracts (27 ℃ and 80 ℃) against S. parasitica on fish eggs. Mycelium growth was evaluated in vitro at 0, 2.5, 5.0 and 10 g/L for 96 h, in solid and liquid medium culture. In an in vivo assay, we tested lower concentrations of hot extract (25, 50 and 100 mg/L) to prevent infection by zoospores. The hot aqueous extract was the most effective, and the concentrations of 5 and 10 g/L demonstrated great efficiency in liquid medium. In vivo conditions, 50 and 100 mg/L of hot extract provided more viable eggs, greater percentage of total larvae and lower percentage of infected eggs. Thus, the hot extract should be used instead of the room-temperature extract as a prophylactic measure, to prevent saprolegniosis in P. scalare eggs and improving the hatching rate.