Abstract
While uptake of Na + from the water is well-characterized in fish, little is known about the uptake of Na + from the diet. A method involving radiolabeling of the diet with [ 22Na +] and [ 3H] PEG-4000 has been developed to study this process, and to separate the systemic efflux of absorbed [ 22Na +] via gills and kidney from the potential efflux of [ 22Na +] into the water via defecation. Killifish were acclimated to 10% sea water, a typical salinity for this estuarine fish where they are hyperosmotic to the environment. The fish were fed a single meal (0.81% ration, containing 5.09μmol total Na +gbody weight -1) of re-pelleted food labeled with both radiotracers. Effluxes into the water were monitored for 48h. Sharp increases in [ 3H] PEG-4000 appearance provided a clear definition of defecation events, which started at about 7h post-feeding and finished by 16h, with the midpoint at 11.5h. In contrast, the evolution of [ 22Na +]-radioactivity in the water showed a smooth curvilinear relationship starting at 3h, with a gradually declining slope through 48h. There was no efflux of [ 22Na +] associated with defecation events, showing that all [ 22Na +] was quickly absorbed from the meal. By 48h, about 50% of the consumed [ 22Na +] had been excreted to the external water by systemic efflux. The efflux relationship was best described by a two-phase exponential relationship, with a breakpoint at about 13h post-feeding. The first phase (rate constant 0.0309h -1) corresponded to branchial efflux of dietary [ 22Na +] equilibrated with the exchangeable whole body Na + pool, while the second phase was much slower (0.0114h -1). These results emphasize the importance of dietary Na + when the killifish is hyper-regulating, and provide a method applicable to a wide range of conditions, ions, and species.
| Original language | English |
|---|---|
| Pages (from-to) | 53-57 |
| Number of pages | 5 |
| Journal | Journal of Experimental Marine Biology and Ecology |
| Volume | 434-435 |
| DOIs | |
| State | Published - Dec 1 2012 |
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Keywords
- [ Na ]
- [ H] PEG-4000
- Feeding
- Gills
- Intestine
- Ionoregulation
ASJC Scopus subject areas
- Aquatic Science
- Ecology, Evolution, Behavior and Systematics
Cite this
Defecation and the fate of dietary sodium in the common killifish (Fundulus heteroclitus macrolepidotus Walbaum, 1792). / Wood, Chris M.; Bucking, Carol.
In: Journal of Experimental Marine Biology and Ecology, Vol. 434-435, 01.12.2012, p. 53-57.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Defecation and the fate of dietary sodium in the common killifish (Fundulus heteroclitus macrolepidotus Walbaum, 1792)
AU - Wood, Chris M.
AU - Bucking, Carol
PY - 2012/12/1
Y1 - 2012/12/1
N2 - While uptake of Na + from the water is well-characterized in fish, little is known about the uptake of Na + from the diet. A method involving radiolabeling of the diet with [ 22Na +] and [ 3H] PEG-4000 has been developed to study this process, and to separate the systemic efflux of absorbed [ 22Na +] via gills and kidney from the potential efflux of [ 22Na +] into the water via defecation. Killifish were acclimated to 10% sea water, a typical salinity for this estuarine fish where they are hyperosmotic to the environment. The fish were fed a single meal (0.81% ration, containing 5.09μmol total Na +gbody weight -1) of re-pelleted food labeled with both radiotracers. Effluxes into the water were monitored for 48h. Sharp increases in [ 3H] PEG-4000 appearance provided a clear definition of defecation events, which started at about 7h post-feeding and finished by 16h, with the midpoint at 11.5h. In contrast, the evolution of [ 22Na +]-radioactivity in the water showed a smooth curvilinear relationship starting at 3h, with a gradually declining slope through 48h. There was no efflux of [ 22Na +] associated with defecation events, showing that all [ 22Na +] was quickly absorbed from the meal. By 48h, about 50% of the consumed [ 22Na +] had been excreted to the external water by systemic efflux. The efflux relationship was best described by a two-phase exponential relationship, with a breakpoint at about 13h post-feeding. The first phase (rate constant 0.0309h -1) corresponded to branchial efflux of dietary [ 22Na +] equilibrated with the exchangeable whole body Na + pool, while the second phase was much slower (0.0114h -1). These results emphasize the importance of dietary Na + when the killifish is hyper-regulating, and provide a method applicable to a wide range of conditions, ions, and species.
AB - While uptake of Na + from the water is well-characterized in fish, little is known about the uptake of Na + from the diet. A method involving radiolabeling of the diet with [ 22Na +] and [ 3H] PEG-4000 has been developed to study this process, and to separate the systemic efflux of absorbed [ 22Na +] via gills and kidney from the potential efflux of [ 22Na +] into the water via defecation. Killifish were acclimated to 10% sea water, a typical salinity for this estuarine fish where they are hyperosmotic to the environment. The fish were fed a single meal (0.81% ration, containing 5.09μmol total Na +gbody weight -1) of re-pelleted food labeled with both radiotracers. Effluxes into the water were monitored for 48h. Sharp increases in [ 3H] PEG-4000 appearance provided a clear definition of defecation events, which started at about 7h post-feeding and finished by 16h, with the midpoint at 11.5h. In contrast, the evolution of [ 22Na +]-radioactivity in the water showed a smooth curvilinear relationship starting at 3h, with a gradually declining slope through 48h. There was no efflux of [ 22Na +] associated with defecation events, showing that all [ 22Na +] was quickly absorbed from the meal. By 48h, about 50% of the consumed [ 22Na +] had been excreted to the external water by systemic efflux. The efflux relationship was best described by a two-phase exponential relationship, with a breakpoint at about 13h post-feeding. The first phase (rate constant 0.0309h -1) corresponded to branchial efflux of dietary [ 22Na +] equilibrated with the exchangeable whole body Na + pool, while the second phase was much slower (0.0114h -1). These results emphasize the importance of dietary Na + when the killifish is hyper-regulating, and provide a method applicable to a wide range of conditions, ions, and species.
KW - [ Na ]
KW - [ H] PEG-4000
KW - Feeding
KW - Gills
KW - Intestine
KW - Ionoregulation
UR - http://www.scopus.com/inward/record.url?scp=84865574219&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84865574219&partnerID=8YFLogxK
U2 - 10.1016/j.jembe.2012.08.002
DO - 10.1016/j.jembe.2012.08.002
M3 - Article
AN - SCOPUS:84865574219
VL - 434-435
SP - 53
EP - 57
JO - Journal of Experimental Marine Biology and Ecology
JF - Journal of Experimental Marine Biology and Ecology
SN - 0022-0981
ER -