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First published online October 5, 2006
Journal of Experimental Biology 209, 4040-4050 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02462
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Plasticity of osmoregulatory function in the killifish intestine: drinking rates, salt and water transport, and gene expression after freshwater transfer

Graham R. Scott1,*, Patricia M. Schulte1 and Chris M. Wood2

1 Department of Zoology, University of British Columbia, Vancouver BC, V6T 1Z4, Canada
2 Department of Biology, McMaster University, Hamilton ON, L8S 4K1, Canada


Figure 1
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  		Fig. 1. Drinking rate of killifish decreases after transfer from brackish water (BW, 10% sea water; grey bars) to fresh water (FW; black bars). Values are means ± s.e.m. (N≥6). *Significant difference from pre-transfer (Pre) brackish water control (P<0.05).

 

Figure 2
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  		Fig. 2. (A) Plasma concentrations of Na+ (solid bars) and Cl– (hatched bars) in killifish decrease after transfer from brackish water (BW, 10% seawater; grey bars) to fresh water (FW; black bars) and recover slowly thereafter. (B) Plasma cortisol concentrations increase transiently as a result of transfer to freshwater, compared to both pre-transfer and time-matched BW controls. Values are means ± s.e.m. (N≥6). *Significant difference from pre-transfer (Pre) brackish water control (P<0.05). {dagger}Significant difference between time-matched FW and BW groups.

 

Figure 3
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  		Fig. 3. Bulk water transport rate across the isolated intestine increases transiently in killifish, after transfer to fresh water (FW; black bars) from brackish water (BW, 10% seawater; grey bars). Net absorption occurs in the positive direction. Values are means ± s.e.m. (N≥6). *Significant difference from pre-transfer (Pre) brackish water control (P<0.05).

 

Figure 4
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  		Fig. 4. (A) Net Na+ (solid bars) and Cl– (hatched bars) flux across the isolated intestine increases transiently in killifish, after transfer to fresh water (FW; black bars) from brackish water (BW, 10% seawater; grey bars). (B) Unidirectional Na+ influx across the isolated intestine does not change significantly after fresh water transfer, but the small non-significant increase is enough to account for the change of net Na+ flux shown in A. Net absorption occurs in the positive direction. Values are means ± s.e.m. (N≥6). *Significant difference from pre-transfer (Pre) brackish water control (P<0.05). Net Cl– flux was found to be greater than net Na+ flux by two-way ANOVA.

 

Figure 5
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  		Fig. 5. Bulk water absorption rate correlated to net strong ion absorption rate (sum of net Na+ and Cl– flux rate) across killifish intestine, in brackish water (BW, 10% seawater; grey squares) and at several time intervals after transfer to fresh water (FW; black triangles and diamonds). Bulk water transport was extremely well correlated to net ion transport (r2=0.960, P<0.0001), with a slope of 0.00342±0.00010 ml water per µmol strong ion. Grey broken curves represent 95% confidence limits of the regression.

 

Figure 6
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  		Fig. 6. Na+/K+-ATPase activity in the anterior segment of the intestine increases transiently in killifish, after transfer to fresh water (FW; black) from brackish water (BW, 10% seawater; grey). Values are means ± s.e.m. (N≥8). *Significant difference from pre-transfer (`pre') brackish water control (P<0.05). {dagger}Significant difference between time-matched FW and BW groups.

 




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