Salinity effects on osmoregulation and growth of the euryhaline flounder Paralichthys orbignyanus

1. Salinity effects on osmoregulation and growth of the euryhaline flounder Paralichthys orbignyanus 鹽度對廣鹽性比目魚Paralichthys orbignyanus之 滲透壓調節與成長影響

2. Introduction

4. Paralichthys orbignyanus • Family : Paralichthyidae • Order : Pleuronectiformes • Class : Actinopterygii • Max. size: 50.0 cm NG (male/unsexed; Ref. 36453); 38 cm TL (female) • Environment: demersal; oceanodromous (Ref. 51243); brackish; marine; depth range 1 – 45 m • Climate: subtropical; 23°S - 41°S

5. Distribution: Coastal and estuarine waters of Western South Atlantic Ocean (Brazil , Uruguay and Argentina) • High market price. • Wide tolerance to environmental factors such as salinity(0-40‰), pH , and nitrogenous compounds and acid stress. To evaluate the effect of hypo-(freshwater) and hyperosmotic (seawater) conditions on survival and growth.

6. Materials and methods • Osmo- and ionoregulatory studies • Growth studies

7. Isosmotic point(等滲點)： 血漿中滲透壓與外界滲透壓相等的點。 • Isoionic point(等離子點)： 血漿中離子濃度與外界離子濃度相同時的點。 如果魚生活在水中的鹽度，可以達到等滲點鹽度或是 等離子點鹽度，魚就不用在耗費太多的能量調節滲透 壓與離子濃度，也可以達到比較高的成長率。

8. Osmo- and ionoregulatory studies Cassino Beach(32∘S,52∘W)

9. 馴養5天 馴養3天適應鹽度分 別為0‰,10‰20‰, 30‰and 40‰ 實驗飼養15天 Average weight=176.0±19.5g 取出樣本 上升到50℃加速曝氣 自來水(0‰) 濃縮海水(50‰) 1000-l 鹽度維持在33‰ 22±1°C海水 12L/12D 餵食活的鯔科仔稚魚 300-l Six fish per tank 餵食活的鯔科仔稚魚 每天以虹吸的方 式抽出排泄物， 更換50%的水。

10. 在不同鹽度中馴養15天後的魚，以50ppm benzocain (苯坐卡因)麻醉，抽出1ml 的血，離心後，將血漿保存 在液態氮中。 Osmotic analysis Ionic analysis Anion (Cl-)利用 titration (滴定法) Cations(Na+,k+,Ca2+)

11. Growth studies 500-l 鹽度維持在30‰ 500-l 鹽度維持在30‰ 放置一星期使比目魚適應鹽度 定量餵食 X2 500-l 在一星期內逐漸適應 鹽度降到0‰ • 14 flounders per group. • Water temperature was kept within • 22±1°C. • 12L/12D • 一天餵食4次. • 排泄物以虹吸方式抽出，每日換水 • 30 %. X2

12. (天) 90 0 30 60 麻醉，測量 體長、重量， 取出腮及血 麻醉，測量 體長、重量 麻醉，測量 體長、重量 麻醉，測量 體長、重量 Specific growth rate (SGR) =[( ln wf - ln wi ) / t x 100] wf = final weight (g) wi = initial weight (g) t = time (days). EX ： wf = 38.85 (g) wi = 29.19 (g) t = 30 (天) SGR = [( ln38.85 - ln 29.19 ) / 30 x 100] = 0.953 %

13. 2 ml (250mM sucrose 20mM EDTA and pH 7.4 Tris- HCl buffer) • Blood：Osmolality and ionic composition (Na+ and Cl- ). • Gill：Na+,k+ ATPase Bianchini and Castilho (1999) Castilho et al. (2001) 腮絲 3°C 1000 x g for 20min Glass Teflon Potter homogenizer

14. Results • Osmo- and ionoregulatory studies • Growth studies

15. Osmo- and ionoregulatory studies 增加

17. Isosmotic point = 328.6 mOsm kg-1相當於10.9 ‰

18. Isoionic point =210.8 mEq l-1 相當於11.6 ‰

19. Isoionic point = 136.8 mEq l-1 相當於8.4 ‰

20. Isoionic point = 5.41 mEq l-1 相當於22.6 ‰

21. Isoionic point = 5.21 mEq l-1 相當於15.7 ‰

22. 可推估Paralichthys orbignyanus是廣鹽性的魚類。

23. Growth studies • No significant between replicates for both flounder survival and growth over 90-day test. • Survival was not significantly affected by salinity, since, at the end of the 90-day test, it was 92.9 % in both freshwater and seawater.

26. Discussion

28. Stenohaline freshwater teleosts Stenohaline marine teleosts • The isosmotic point of P. orbignyanus was estimated as 328.6 mOsm kg-1 H2O and corresponded to 10.9‰ salinity. 260 mOsm kg-1H2O 330 mOsm kg-1H2O 370 mOsm kg-1H2O 480 mOsm kg-1H2O P.orbignyanus 321 mOsm kg-1H2O ( 0 ‰ ) 370 mOsm kg-1H2O ( 40 ‰ )

30. It is described that environment stressors such as salinity can effect fish growth (Borski et al.,1994). 淡水中P.orbingnyanus的成長率比海水中P.orbingnyanus的成長率小。

32. Conclusions

33. P. orbignyanus can be characterized as a marine/estuarine euryhaline teleost capable of carrying hyper/hypo iono- and osmoregulation over the fluctuating salinity regime faced by this species in the environment. • Long-term exposure to freshwater induces a reduction in growth rate of P. orbignyanus, possibly due to an increase in energy expenditure associated to the osmo- and ionoregulation under this salinity condition.

34. ~The end~ Thank you for your attention