Comparison of differential leukocyte counts in fish of economic and indicator importance

The aim of this study was to determine the percentage of individual types o f leukocytes in fish of economic (carp - Cyprinus carpio L., tench Tinca ti nca L., European catfish - Silurus glanis L., rainbow trout - Oncorhynchus mykiss Walb.,) and indicator importance (bream - Abramis brama L., perch - Perca fluviatilis L., chub - Leuciscus cephalus L., brown trout - Salmo tru tta m. fario L.). In all, we examined 191 fish specimens caught in non-cont aminated or insignificantly contaminated localities in good state of health during the vegetation season and not within the season of their reproducti on. Leukocytes stained according to Giemsa were classified as: lymphocytes, monocytes, myelocytes, metamyelocytes, neutrophilic granulocytes with band and segmented nuclei, eosinophils and basophils. Blood of all the fish spe cies examined was of lymphocytic character. The mean percentage of individu al lymphocytes varied from 84.2 +/- 5.08 to 99.1 +/- 0.99%. The lowest perc entage of lymphocytes was found in the rainbow and brown trout (84.2 +/- 5. 08 and 87.3 +/- 7.21%, respectively), while the highest values were in the perch (99.1 +/- 0.99 and 97.5 +/- 3.19%). Monocytes were sporadic in all th e fish species; with the highest mean value found in the female spawner Eur opean catfish (1.42 +/- 1.74%. The highest percentage of granulocytic serie s cells was found in rainbow (15.4 +/- 7.80%) and brown trout (11.6 +/- 7.2 3%); whereas the lowest values in the perch (0.8 +/- 1.01 and 2.4 +/- 3.15% ). As far as the granulocytic series cells are concerned, metamyelocytes we re most common with regards to their percentage in all the fish species exc epting salmonids. There were prevailing band and segmented neutrophils in t he rainbow and brown trout. Granulocytes were mostly represented by neutrop hils in all the fish species studied. Eosinophilic granulocytes were found sporadically in the tench (0.17 +/- 0.59%) and in 3-year old carp (0.10 +/- 0.19%). Basophilic granulocytes were not found in any of the fish species examined. We found practically equal percentage of individual types of leuk ocytes in the carp, bream and perch of various age categories caught under the same conditions and in the same season of the year. There were no signi ficant differences in the percentage of individual leukocytes in male and f emale spawners of 3-year-old carp, 3-year-old tench, and 2- to 3-year-old b rown trout. Our results contribute to the use and help in introducing the e xamination of differential leukocyte counts as a biological monitoring meth od to evaluate surface water contamination.