טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentSarit Uzzan
SubjectThe Effect of Salinity Acclimation on Gill Chloride Cells:
Morphology and Enzymes Binding in the Fish
Poecilia latipinna.
DepartmentDepartment of Biology
Supervisor Professor Katz Uri


Abstract

The localization and density of chloride cells in freshwater (FW)  and seawater (SW) acclimated Poecillia Latipinna (sailfin molly) which is an euryhaline teleost fish, were compared. Chloride cells play an important role in maintaining the ionic balance in bony fish. Localization of the following enzymes: Na+/ K+-ATPase, CA, H+- ATPase, and Cl-/HCO3- ion exchanger in gill cells of  freshwater and seawater acclimated fish, was achived by using immuno-cytological methods. Chloride cells were indentified and localized using silver and Hematoxiline-Eosin methods. Chloride cells were found in FW gills along the first and  the secondary lamella. Chloride cells found in the first lamella are bigger than those in the secondary lamella. In SW gills chloride cells were found exclusively in the first lamella. The number of chloride cells along the first lamella of SW gills was significantly higher than in FW gills and seawater acclimation caused a structural modification of their apical membrane (apical crypt) that was indentified by Scanning Electron Microscopy

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In FW gills the enzymes, Na+/K+-ATPase Carbonic Anhydrase and Cl-/ HCO3- ion exchanger were found in chloride cells, localized both in the first and the secondary lamella. The enzyme H+-ATPase was found only in the first lamella. On the other hand, the enzymes found in chloride cells of SW fish gills were in much larger quantities. One exception was the enzyme Cl-/HCO3- Anion exchanger that was not found at all in SW gills. Carbonic Anhydrase was identified in FW gills using Hansson’s histochemical method, corroborating with the antibody method. It is suggested that the gills of molly fish contain two types of chloride cells with different roles in the osmoregulatory mechanism. One type of chloride cells, probably b chloride cells, is located in the secondary lamella of the gills and seems to participate in the uptake of Cl- and Na+ ions in a dilute environment.  Another type of larger cells, believed to be a chloride cells, are located in the first lamella of the gills. They participate in the excretion of Na+ and Cl- ions to the plasma in SW, using the above enzymes which are found in higher quantities in these cells.