Histological Changes in the Gill Epithelium of Endemic Lake Van Fish (Chalcalburnus Tarichi) During Migration From Alkaline Water To Freshwater Tarichi

Abstract

The gill histology of the endemic Lake Van Fish (Chalcalburnus tarichi, Pallas 1811) was compared in two different water systems during the reproductive migration from alkaline water to freshwater. The histological examination of gill samples showed that freshwater samples had a thinner primary lamella. While the cells that secrete mucous into the gills showed no volumetric change, a significant increase in their number was observed. In fish acclimated to freshwater, a small number of mucous cells was identified in the secondary lamella. Epithelial lifting was observed in both types of aquatic environments. Gill anomalies were mostly observed in the freshwater samples. Hyperplasia, lamellar fusion, vasodilation, and necrosis were observed in the gills of most fish that migrated to freshwater. The observed changes to the primary lamella, mucus cell distribution, and increase in mucous cell number in the gills may be functional in fish osmoregulation. Lesions may be related to the effects of different pollutants in a certain period, physicochemical differences, or stress caused by the two different aquatic environments. In addition, the present study is the first to demonstrate that the gills of the Lake Van fish are infected by Myxobolus parasites.