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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Lui's Andre´ Sampaioa , Adalto

Bianchinib,*

Journal of Experimental Marine Biology and Ecology269(2002) 187-196

Reporter:Hui-ting Zhuang

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Introduction

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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

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• 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.

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Materials and methods

• Osmo- and ionoregulatory studies

• Growth studies

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• 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。

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Osmo- and ionoregulatory studies

Cassino Beach(32 S,∘52 W)∘

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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

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-lSix fish per tank餵食活的鯔科仔稚魚

自來水 (0‰) 濃縮海水 (50‰)

每天以虹吸的方式抽出排泄物，更換 50%的水。

取出樣本

上升到 50℃ 加速曝氣

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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+)

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Growth studies

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

500-l鹽度維持在 30‰

500-l在一星期內逐漸適應

鹽度降到 0‰

X2

X2

•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 %.

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Specific growth rate (SGR) =[( ln wf - ln wi ) / t x 100]wf = final weight (g)wi = initial weight (g)t = time (days).

0 30 60 90

麻醉，測量體長、重量

麻醉，測量體長、重量

麻醉，測量體長、重量

麻醉，測量體長、重量，取出腮及血

EX ：wf = 38.85 (g)wi = 29.19 (g) t = 30 ( 天 )SGR = [( ln 38.85 - ln 29.19 ) / 30 x 100] = 0.953 %

( 天 )

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• Blood ： Osmolality and ionic composition (Na+ and Cl- ).

• Gill ： Na+,k+ ATPase

Glass Teflon Potter homogenizer

2 ml (250mM sucrose 20mMEDTA and pH7.4 Tris- HCl

buffer)

3°C 1000 x g for 20min腮絲

Bianchiniand Castilho (1999)Castilho et al.(2001)

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Results• Osmo- and ionoregulatory

studies

• Growth studies

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Osmo- and ionoregulatory studies

增加

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

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Isoionic point =210.8 mEq l-1

相當於 11.6 ‰

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Isoionic point = 136.8 mEq l-1

相當於 8.4 ‰

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Isoionic point = 5.41 mEq l-1

相當於 22.6 ‰

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Isoionic point = 5.21 mEq l-1

相當於 15.7 ‰

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等離子點鹽度

Na+ 11.6 ‰

Cl- 8.4 ‰

K+ 22.6 ‰

Ca2+ 15.7 ‰

可推估Paralichthys orbignyanus 是廣鹽性的魚類。

等滲點鹽度滲透壓 10.9 ‰

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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.

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Discussion

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• The isosmotic point of P. orbignyanus was estimated as 328.6 mOsm kg-1 H2O and corresponded to 10.9‰ salinity.

Stenohaline freshwater teleosts Stenohaline marine teleosts

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 ‰ )

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• 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

。

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學名；俗名 可以忍受的鹽度Paralichthys.

orbignyanus 0 – 40 ‰

Paralichthys. lethostigmaSouthern flounder

對鹽度耐受力隨年齡成長而增加，在完全變態後，可以生活在鹽度 0‰中。

Paralichthys.dentatusSummer flounder

5 – 50 ‰在仔稚魚階段對鹽分的耐受力達到最高。

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Conclusions

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• 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.

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~The end~

Thank you for your attention