Differences between rainbow trout and perch in opsonin recognition by blood phagocytes suggest that the living habits of perch, which prefers approximately a 10 degrees C higher temperature than rainbow trout, may be reflected in immune cell functions. Results of the present examination suggest that also in fish phagocytes pattern recognition is the prevailing system at low temperatures, and specific recognition is more effective at high temperatures. (C) 2015 Elsevier Ltd. All rights reserved.