Investigation of changes in goblet cells in the digestive tract of Van fish during reproductive migration

Lake Van is among the largest soda lakes in the world. The Van fish is an endemic species of the carp family living in Lake Van. In order to breed, they migrate in flocks to the streams flowing into the lake between April and July, depending on the water temperature. After the fish lay their eggs in the fresh water, they return to Lake Van. In this study, goblet cells in the digestive tract of Van fish during reproductive migration were labeled with periodic acid–Schiff, Alcian Blue pH 2.5, Alcian Blue pH 1.0, Alcian Blue pH 0.5, and aldehyde fuchsin dyes. Changes in cell localization, density, and area were determined in different parts of the digestive tract in goblet cells containing neu- tral, acidic, O-sulfate ester, strongly sulfated, and sulfated acidic glycoconjugate. In the esophagus, goblet cells were only observed in the fish from Lake Van. Although goblet cell size and density varied in other parts of the digestive tract, all glycoconjugates were labeled. In the digestive tract of fish from the lake, the goblet cell areas were large, but the cell density was low, whereas the situation in the digestive tract of fish sampled from the streams was the opposite. It was concluded that the main reason for the goblet cell change in the digestive tract of Van fish is related to its feeding behavior and habitat.