en Histopathology Histopathology پژوهشي Original research papers <p>Gill chloride cells and prolactin hormone are of high importance in the adaptation of euryhaline fish. Guldenstati (<em>Chalcalburnus chalcoides, </em>1772), an adromous fish, migrates from the Caspian Sea to rivers to have a more successful reproduction. The present study was aimed to evaluate the changes in the number and size of <em>C. chalcoides</em> gill chloride cells as well as to determine the relationship of its plasma prolactin with water salinity. Eighty-four individual <em>C. chalcoides</em> were collected from river (Lale Roud; 0.4 ppt), Lale Roud estuary (3.75 ppt), and Caspian Sea (9.71 ppt). The sampling was lasted for a-12 month period in 2014. The highest (1349&plusmn;152) and lowest (881&plusmn;37) number of gill chloride cells were observed in the animals collected from the Caspian Sea and in the river (Lale Roud), respectively. However, plasma prolactin demonstrated the highest level in <em>C. chalcoides </em>caught from the river (0.89&plusmn;0.02 ng ml^-1), but the lowest amount (0.70&plusmn;0.03 ng ml^-1) in the ones collected from the Caspian Sea. Overall, these results suggest that&nbsp;<em>C. chalcoides</em> migration across its habitats is an energy consuming ecological behavior, and the fish consumes high energy just after breeding and while returning to the Caspian Sea.<br> &nbsp;</p> Salinity, Chloride cells, Prolactin, Chalcalburnus chalcoides. 11 21 http://ijaah.ir/browse.php?a_code=A-10-176-2&slc_lang=en&sid=1 N Neurasteh نگار نورسته neurasteh@yahoo.com 10031947532846001550 10031947532846001550 No islamic azad u دانشگاه ازاد m Setorki محبوبه سترکی doctor.setorgi@gmail.com 10031947532846001551 10031947532846001551 No islamic azad u دانشگاه ازاد A Tehranifard اکرم تهرانی فرد tehrani@yahoo.com 10031947532846001552 10031947532846001552 No islamic azad u دانشگاه ازاد A Moshfegh اعظم مشفق moshfeghazam@gmail.Com 10031947532846001553 10031947532846001553 Yes islamic azad u دانشگاه ازاد