Background. To assess stress levels in fishes, plasma cortisol levels are measured by radioimmuno assay and phagocytic activity is assessed using macrophages. However, the small size of some fishes makes it difficult to measure stress using these physiological and immunological indicators. In this study, we investigated the possibility of obtaining macrophages from zebrafish via whole body extractions by assessing the respiratory burst activity and phagocytic capacity of extracted cells and we studied the effects of temperature stress on zebrafish using the extracted macrophages. Materials and methods. One hundred and fifty genetically pure zebrafish, Danio rerio (Hamilton, 1822), were randomly divided into three groups and placed in three different environments: optimal (28°C), warm (32°C), and cool (23°C). Using the newly developed extraction method described in this article macrophages were extracted from whole fish bodies and the phagocytic activity of these cells were assessed. Results. The method yielded enough macrophages to examine their respiratory burst activity and phagocytic capacity. Values obtained for experimental replicates were similar and the assessment measures were sensitive enough to detect differences in these parameters among fish maintained at three different temperatures for 2, 4, 6, and 8 weeks. These results suggest that macrophages can be successfully extracted using the whole body method and the extracted macrophages are useful for studying stress. Conclusion. The method of macrophage extraction described in this article is simple and rapid, and will enable researchers to study the effects of any stressors, environmental or pathogenic, on the non-specific immune response of fish.

fish, zebrafish, Danio rerio, stress, macrophage functions