Effect of Short-term Elevation Temperature and Salinity Stress on Caspian Roach, Rutilus caspicus

proliferation and development of mitochondrion-rich cells (MRCs) presumably hormonally regulated allowing for increased transport capacity [8], increasing net Na + and Cl -efflux and restoring plasma ions balance [9,10].Na + /K + -ATPase, primary driving force for flux of intra and extra cellular NaCl which is specifically present in high concentrations on the basolateral side of MRCs, plays important roles in maintaining the cell membrane potential by pumping Na + out and K + in through active transport [9].Changes in gill NKA activity are observed 2-3 days after transfer from a hypoosmotic to hyperosmotic environment in euryhaline teleosts [11].In anadromous species [12,13], activation of gill NKA takes place 3-7 days after transfer to SW and also in mullet and killifish, gill NKA activity elevated rapidly within 3 h after transfer from FW to BW or SW [14].In both of FW and seawater (SW), the regulation of the ion levels and osmolality of body fluids of fishes are doing actively [2].The plasma osmolalities of euryhaline teleost species of FW and SW origin vary [15] and in a number of euryhaline teleosts showed the effects of changing salinity on plasma osmolality and circulating electrolytes [16][17][18][19][20][21].Since the most organisms on Earth are ectotherms, such as fish, surviving and adaptation to temperature fluctuations are crucial for AbstractCaspian roach, Rutilus caspicus must have adaptive mechanisms to control internal homeostasis over a broad range of ambient various such as the heat shock (HS) and salinity changes.This experiment was carried out in two stages.In first stage, thirty juveniles fish (3.2 ± 0.34 g) transferred to 20 L circular tanks, containing three different salinity (5, 10, 15 ppt).Initially, half of the treatments exposed to a HS (26°C for 2 h) while the range of normal temperature was 16.5-17.5°C.At 96 h after transferring, survival rate, hematocrit, plasma Na + , K + and Cl -and osmolality and gill NKA activity were determined.In the second stage (second 96 h), all of the first treatments were transferred to 15 ppt and similar sampling was done.In first stage, no mortality in 5 and 10 ppt of both non heat shock (NHS) and HS treatments and higher plasma osmolality, ions (except K + ), and hematocrit were observed.Mortality was observed in 15 ppt of NHS and in second stage, both treatments of 15 ppt showed mortality (15-20%).In NHS, significant increase of gill NKA found at in 10 ppt of second stage while in HS treatment was in 10 ppt of first stage.Changes in plasma osmolality and electrolytes in HS treatment were more less similar to NHS treatment.Together, it seems HS and salinity changes resulted to disturbances from an internal fluid shift thus a stress situation and Caspian roach juveniles need to complete ion-osmo regulation systems for adaptation with brackish water.

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