Effect of salinity and ration size on macrophage phagocytosis in juvenile black sea bream (Mylio macrocephalus)

The effects of salinity adaptation and ration size on macrophage phagocytos is were assessed in black sea bream (Mylio macrocephalus) juveniles. Salini ty had no effect on phagocytosis in fish that were fed a 10% ration size. R educing ration size from 10 to 5% resulted in a significant reduction in sp lenic and pronephric macrophage phagocytosis of fish adapted to hyper(33 p. p.t.) and hypo-osmotic (6 p.p.t.) salinities. The fish that were adapted to an iso-osmotic salinity (12 p.p.t.) and fed a 5% ration size were able to maintain macrophage phagocytic activity at levels comparable to those of fi sh that were fed a 10% ration size. It is proposed that the adaptation of s ea bream to an iso-osmotic medium is beneficial in that it stimulates the i mmune response through activation of macrophage phagocytosis.