EFFECTS OF TEMPERATURE ON LEUKOCYTES OF COLOSSOMA-MACROPOMUM AND HOPLOSTERNUM-LITTORALE (PISCES)

1. The effects of different thermal regimens on qualitative and quanti tative characteristics of leucocytes were evaluated in two fish specie s of the Amazon region. 2. The proportion of circulating types of leuc ocytes changed significantly in Colossoma macropomum (tambaqui) but no t in Hoplosternum littorale (tamoata) exposed for four-week terms to 2 0, 25, 30, 35, and 40-degrees-C. 3. The proportion of circulating lymp hocytes decreased significantly in tambaquis exposed to 30, 35, and 40 -degrees-C. No changes in lymphocyte proportions were observed in tamo atas. 4. Neutrophils were almost absent in tambaquis, except in animal s exposed to 40-degrees-C. No significant changes in circulating neutr ophils were observed in tamoatas. 5. The circulating leucocytes of Col ossoma macropomum and Hoplosternum littorale are affected in different ways by temperature changes, suggesting species-specific adjustments to this parameter.