the combined effects of gradual changes in salinity and temperature on gill tissue of common carp (cyprinus carpio)

abstract environmental factors including salinity and temperature can affect the physiology and performance of the growth of fish, so many of internal organs such as gill may be showed wide range of morphological and functional changes. fingerling common carp were exposed for 21 days in groups at 20, 25 and 30°c and three salinity levels 0, 5 and 10ppt. histological changes of gills tissue of common carp with average weight and length 38.28 ± 0.58 g and 14.04 ± 0.10 cm respectively is studied. after biometry, sampling was performed on 7 and 21 and transferred to the laboratory. the gill arc was fixed in bouin's solution for 24-48 hours. to evaluate the chloride cells in the gill tissue of the fish, pas-hematoxylin were used. the results showed that the size and number of chloride cells increased by increasing the temperature and salinity. the maximum number and size of chloride cells was observed at treatment with temperature 30 °c and salinity 10ppt. in conclusion, it could be stated that the number and size of chloride cells in the gill were affected by combined environmental factors, salinity and temperature.