Ionocyte changes in the skin of Sander lucioperca larvae exposed to different salinities

The aim of the present study was to evaluate the osmoregulation ability of zander (Sander lucioperca) at two larval stages including before (group “a”) and after (group “b”) yolk sac absorption. Both groups were exposed to freshwater (less than 0.5‰ salinity), estuarine conditions (7‰) and Caspian Sea water (12‰) for 96h. Larva survival rate and chloride cell number, size and the its surface percentage were examined by classical histology using H & E staining and immunolocalization of Na+,K+-ATPase. Survival rate was 97% for both groups in freshwater and was 86% and 97%, respectively for group “a” and “b” at 7‰ salinity. At 12‰ salinity, all larvae in group “a” died while 20% of group “b” survived. The size of skin chloride cells did not change in the face of different salinity. At the end of the experiment, the number and the surface percentage of chloride cells significantly increased in the group “a” at 7‰ salinity and in group “b” at 12‰ salinity (P<0.05). The results showed that in the Caspian Sea zander larvae, the function of skin chloride cells in osmoregulation improved with development of body and it could act in such a way that the survival rate in the post-yolk sac uptake stage was more than the pre-yolk sac uptake stage exposed to salinity.