Salinity_Acclimation-JEZ-130712.doc-digital-csicDigitalCSIC.doc

Salinity Acclimation Enhances Salinity Tolerance in Tadpoles living in Brackish Water Through Increased Na+, K+-ATPase Expression Chi-Shiun Wu1, Wen-Kai Yang2, Tsung-Han Lee2, Ivan Gomez-Mestre3, and Yeong-Choy Kam4* 1. Department of Life Science, Chinese Culture University, Taipei, Taiwan 2. Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan 3. Do?ana Biological Station, CSIC, Seville, Spain 4. Department of Life Science, Tunghai University, Taichung, Taiwan Total number of text figures: 3 Running headline: Acclimation Enhances Salinity Tolerance in Tadpoles *Correspondence to: Yeong-Choy Kam, Department of Life Science, Tunghai University, Taichung, 40704, Taiwan Phone: 886-4#32416 Fax: 886-4E-mail: biyckam@thu.edu.tw Grant sponsor: National Science Council Grant (NSC 95-2311-B-029-006-MY3) to YCKABSTRACT Amphibians are highly susceptible to osmotic stress but, nonetheless, some species can adapt locally to withstand moderately high levels of salinity. Maintaining the homeostasis of body fluids by efficient osmoregulation is thus critical for larval survival in saline environments. We studied the role of acclimation in increased physiological tolerance to elevated water salinity in the Indian rice frog (Fejervarya limnocharis) tadpoles exposed to brackish water. We quantified the effects of salinity acclimation on tadpole survival, osmolality, water content, and gill Na+, K+-ATPase (NKA) expression. Tadpoles did not survive over 12 h if directly transferred to 11 ppt (parts per thousand) whereas tadpoles previously acclimated for 48 h in 7 ppt survived at least 48 h. We reared tadpoles in 3 ppt and then we transferred them to one of a) 3 ppt, b) 11 ppt, and c) 7 ppt for 48 h and then 11 ppt. In the first 6 h after transfer to 11 ppt, tadpole osmolality sharply increased and tadpole water content decreased. Tadpoles pre-acclimated for 48 h in 7 ppt were able to maintain lower and more stable osmolality within