Author's personal copy

Author's personal copy48 W.-K. Yang et al. / Journal of Experimental Marine Biology and Ecology 375 (2009) 41–50days (Mancera et al., 1993; Claireaux and Audet, 2000; Hsieh et al.,2003; Frisch and Anderson, 2005; Sangiao-Alvarellos et al., 2005)after shocks. Higher plasma glucose levels can be maintained over20 days after salinity shocks (Fig. 7; Woo and Chung, 1995; Morganand Iwama, 1998; Kelly et al., 1999; Claireaux and Audet, 2000; DeBoeck et al., 2000; Fiess et al., 2007). Consistently higher glucoselevels after transfer illustrated a higher energy demand for acclimatationto the new environment (Soengas et al., 1995; Arjona et al.,2007).Increased expression of HSPs including HSP90 of fish upon transfer toa hyperosmotic environment, suggests a role for HSPs in maintaining thenormal functions of proteins and cells (Iwama et al.,1999). Upon salinitychallenge, HSP90 expression varied differentially among species. HSP90expression in livers (protein amount; Deane et al., 2002) and gills(mRNA abundance; Choi and An, 2008) of black porgy was found to behigher in hypoosmotic environments (BW or FW) than in SW. However,no change in HSP90 mRNA expression was found in the livers and gills ofchinook salmon at one day after transfer from FW to SW (Oncorhynchustshawytscha; Palmisano et al., 2000). On the other hand, the branchialHSP90 mRNA expression in the gills of Atlantic salmon was raised andthen returned to baseline levels within two days after transfer from FWto SW (Pan et al., 2000). HSP90 is abundantly expressed in mosteukaryotes and it performs its role by forming a multiple proteincomplex with ATPase activity as well as cooperating with other HSPs(Wegele et al., 2004). Elevated hepatic and branchial HSP90 expressionin SW-acclimated sailfin molly might play important roles for reachinghomeostasis upon salinity challenge. More evidence such as plasmacortisol levels will be necessary to illustrate the stress response of sailfinmolly upon salinity challenge in future work.5. ConclusionEuryhaline sailfin molly is able to survive in FW, BW, and SW.Moreover, elevated plasma glucose concentrations, as well as branchialand hepatic HSP90 protein abundance, revealed that SW was stressfulthan FW to the sailfin molly. To maintain homeostasis, higher NKAactivity was necessary for ion secretion in gills of the sailfinmollyinSW(the stressful environment). Although the plasma osmolality of sailfinmolly increased with environmental salinities within a tolerated range,the MWC were constant among different salinity groups. These resultsillustrated that the sailfin molly was proved to be an efficientosmoregulator with gill NKA expression altering in response to salinitychallenge to maintain ion and water homeostasis in environments ofdifferent salinities.AcknowledgementsThe monoclonal antibody of Na + /K + -ATPase α-subunit (α5) werepurchased from the Developmental Studies Hybridoma Bank maintainedby the Department of Pharmacology and Molecular Sciences, JohnHopkins University School of Medicine, Baltimore, MD 21205, and theDepartment of Biological Sciences, University of Iowa, Iowa City, IA 52242,under Contract N01-HD-6-2915, NICHD, USA. This study was supportedby a grant from the National Science Council of Taiwan to T.H.L. (NSC 94-2311-B-005-009). [SS]ReferencesArends, R.J., Mancera, J.M., Muñoz, J.L., Wendelaar Bonga, S.E., Flik, G., 1999. The stressresponse of the gilthead sea bream (Sparus aurata L.) to air exposure and confinement.J. 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