Acclimation of brackish water pearl spot (Etroplussuratensis) to various salinities: relative changes in osmoregulatory parameters and in abundance of branchial Na+/K+-ATPase and Na+/K+/2Cl- co-transporter.

Chandrasekar, S and Nich, T and Tripathi, G and Sahu, N P and Pal, A K and Dasgupta, S (2014) Acclimation of brackish water pearl spot (Etroplussuratensis) to various salinities: relative changes in osmoregulatory parameters and in abundance of branchial Na+/K+-ATPase and Na+/K+/2Cl- co-transporter. Fish Physiology and Biochemistry, 40 (3). pp. 983-996.

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    Abstract

    The present study was conducted to elucidate the osmoregulatory ability of the fish pearl spot (Etroplussuratensis) to know the scope of this species for aquaculture under various salinities. Juvenile pearl spot were divided into three groups and acclimated to freshwater (FW), brackish water (BW) or seawater (SW) for 15 days. The fish exhibited effective salinity tolerance under osmotic challenges. Although the plasma osmolality and Na+, K+ and Cl− levels increased with the increasing salinities, the parameters remained within the physiological range. The muscle water contents were constant among FW-, BW- and SW-acclimated fish. Two Na+/K+-ATPase α-isoforms (NKA α) were expressed in gills during acclimation in FW, BW and SW. Abundance of one isoform was up-regulated in response to seawater acclimation, suggesting its role in ion secretion similar to NKA α1b, while expression of another isoform was simultaneously up-regulated in response to both FW and SW acclimation, suggesting the presence of isoforms switching phenomenon during acclimation to different salinities. Nevertheless, NKA enzyme activities in the gills of the SW and FW individuals were higher (p < 0.05) than in BW counterparts. Immunohistochemistry revealed that Na+/K+-ATPase immunoreactive (NKA-IR) cells were mainly distributed in the interlamellar region of the gill filaments in FW groups and in the apical portion of the filaments in BW and SW groups. The number of NKA-IR cells in the gills of the FW-acclimated fish was almost similar to that of SW individuals, which exceeded that of the BW individuals. The NKA-IR cells of BW and SW were bigger in size than their FW counterparts. Besides, the relative abundance of branchial Na+/K+/2Cl− co-transporter showed stronger evidence in favor of involvement of this protein in hypo-osmoregulation, requiring ion secretion by the chloride cells. To the best of our knowledge, this is the first study reporting the wide salinity tolerance of E. suratensis involving differential activation of ion transporters and thereby suggesting its potential as candidate for fish farming under different external salinities.

    Item Type: Article
    Subjects: Fish and Fisheries > Biochemical Study
    Freshwater Fisheries
    Divisions: CMFRI-Mandapam
    Depositing User: Dr. V Mohan
    Date Deposited: 17 May 2018 08:56
    Last Modified: 29 May 2018 08:29
    URI: http://eprints.cmfri.org.in/id/eprint/12741

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