Changes in Chloride Cell Abundance, Na+,K+-ATPase Immunolocalization and Activity in the Gills of Golden Grey Mullet, Liza Aurata, Fry During Adaptation to Differend Salinities

Objective: Changes in chloride cell abundance, Na+, K+-ATPase immunolocalization and activity were investigated in the gills of the golden grey mullet, Liza aurata, fry acclimated to freshwater (FW) and different salinities (12‰, 36‰ and 46‰). Materials and Methods: Na+, K+-ATPase localization was performed through immunofluorescence light microscopy using a mouse monoclonal antibody IgG?5. Quantitive analysis of Na+, K+-ATPase intensity was analyzed using Optima’s version 6.51 image analysis software (Media Cybernetics, Silver Spring, MD, USA). Results: In FW, the fluorescent cells (chloride cells) were observed on the epithelia of filaments (mainly in inter-lamellar regions) and on the lamellae. Following transfer to 12‰ salinity, the abundance of Na+, K+-ATPase immunofluorescence cells on the filaments decreased 1.7-fold, and no immunofluorescence cells were detected on the lamellae. Samples from 36‰ and 46‰ salinity showed a high density of chloride cells on the epithelia of filaments, and a few cells on the lamellae. Na+, K+-ATPase intensity did not change significantly with an increase in salinity from 36‰ to 46‰ but it was significantly higher (p > 0.05) in the FW compared to 12‰ salinity. There was no significant difference between gill Na+, K+-ATPase activity in FW and 12‰ salinity, but it was significantly higher (p > 0.05) in the fish acclimated to 36‰ and 46‰ salinity (3.3- and 5.1-fold) compared to 12‰. Conclusion: The capability of L. aurata fry to change the number and size of gill chloride cells, as well as their activities indicate the high degree of adaptability of this fish to a wide range of salinity.