Characterization of macrophage phagocytosis of the tropical fish Prochilodus scrofa (Steindachner, 1881)

Measurements of in vivo and in vitro macrophage phagocytosis, using vital fluorescent dyes, were determined for Prochilodus scrofa in order to evaluate the effect of different stimuli on the health condition of this tropical fish. The Phagocytic Capacity (PC), Phagocytic Index (PI) and Germicide Capacity (GC) using Saccharomyces cerevisiae were estimated using intraperitoneal (i.p.) macrophages. In vivo macrophages (MØ) were stimulated following i.p. injections of the yeast, while in vitro measurements were made by harvesting i.p. phagocytes on coverslips and placing a yeast suspension over them. In vitro results show differences over time, with PC, PI and GC being highest at 7–14 days. In vivo results reveal few differences over time, and the highest PC, PI and GC being observed after 7 days. This work shows that in vitro MØ activation period and the in vivo yeast incubation period influence the macrophage phagocytic activity. For the first time, MØ phagocytosis of P. scrofa was characterised under light microscopy, transmission electron microscopy and scanning electron microscopy.