TY - JOUR
T1 - Assimilation of water and dietary ions by the gastrointestinal tract during digestion in seawater-acclimated rainbow trout
AU - Bucking, Carol
AU - Fitzpatrick, John L.
AU - Nadella, Sunita R.
AU - McGaw, Iain J.
AU - Wood, Chris M.
N1 - Funding Information:
Acknowledgments We are grateful to the staff of the Robertson Creek Hatchery for the supply of steelhead trout, and to the staff of the Bamfield Marine Sciences Centre for their assistance, particularly the Research Coordinator, Dr. Bruce Cameron. Two anonymous reviewers provided constructive comments. Funded by an NSERC Discovery Grant to C.M.W., who is supported by the Canada Research Chair Program, and an NSF grant (IBN #0313765) to I.J.M., C.B and J.L.F. were supported by NSERC Canada Graduate Scholarships.
PY - 2011/7
Y1 - 2011/7
N2 - Recent studies focusing on the consequences of feeding for ion and water balance in freshwater fish have revealed the need for similar comparative studies in seawater fish. A detailed time course sampling of gastrointestinal (GI) tract contents following the ingestion of a single meal of a commercial diet revealed the assimilation of both water and dietary ions (Na+, Cl-, K+, Ca2+, Mg2+) along the GI tract of seawater-acclimated rainbow trout (Oncorhynchus mykiss) which had been fasted for 1 week. Consumption of the meal did not change the drinking rate. There was a large secretion of fluid into the anterior intestine and caecae (presumably bile and/or pancreatic secretions). As a result, net assimilation (63%) of the ingested water along the GI tract was lower than generally reported for fasted trout. Mg2+ was neither secreted into nor absorbed from the GI tract on a net basis. Only K+ (93% assimilated) and Ca2+ (43% assimilated) were absorbed in amounts in excess of those provided by ingested seawater, suggesting that dietary sources of K+ and Ca2+ may be important to seawater teleosts. The oesophagus-stomach served as a major site of absorption for Na+, Cl-, K+, Ca2+, and Mg2+, and the anterior intestine and caecae as a major site of net secretion for all of these ions, except Cl-. Despite large absorptive fluxes of these ions, the ionic composition of the plasma was maintained during the digestion of the meal. The results of the present study were compared with previous work on freshwater-acclimated rainbow trout, highlighting some important differences, but also several similarities on the assimilation of water and ions along the gastrointestinal tract during digestion. This study highlights the complicated array of ion and water transport that occurs in the intestine during digestion while revealing the importance of dietary K+ and Ca2+ to seawater-acclimated rainbow trout. Additionally, this study reveals that digestion in seawater-acclimated rainbow trout appears to compromise intestinal water absorption.
AB - Recent studies focusing on the consequences of feeding for ion and water balance in freshwater fish have revealed the need for similar comparative studies in seawater fish. A detailed time course sampling of gastrointestinal (GI) tract contents following the ingestion of a single meal of a commercial diet revealed the assimilation of both water and dietary ions (Na+, Cl-, K+, Ca2+, Mg2+) along the GI tract of seawater-acclimated rainbow trout (Oncorhynchus mykiss) which had been fasted for 1 week. Consumption of the meal did not change the drinking rate. There was a large secretion of fluid into the anterior intestine and caecae (presumably bile and/or pancreatic secretions). As a result, net assimilation (63%) of the ingested water along the GI tract was lower than generally reported for fasted trout. Mg2+ was neither secreted into nor absorbed from the GI tract on a net basis. Only K+ (93% assimilated) and Ca2+ (43% assimilated) were absorbed in amounts in excess of those provided by ingested seawater, suggesting that dietary sources of K+ and Ca2+ may be important to seawater teleosts. The oesophagus-stomach served as a major site of absorption for Na+, Cl-, K+, Ca2+, and Mg2+, and the anterior intestine and caecae as a major site of net secretion for all of these ions, except Cl-. Despite large absorptive fluxes of these ions, the ionic composition of the plasma was maintained during the digestion of the meal. The results of the present study were compared with previous work on freshwater-acclimated rainbow trout, highlighting some important differences, but also several similarities on the assimilation of water and ions along the gastrointestinal tract during digestion. This study highlights the complicated array of ion and water transport that occurs in the intestine during digestion while revealing the importance of dietary K+ and Ca2+ to seawater-acclimated rainbow trout. Additionally, this study reveals that digestion in seawater-acclimated rainbow trout appears to compromise intestinal water absorption.
KW - Ionoregulation
KW - Marine
KW - Osmoregulation
KW - Prandial
KW - Teleost
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U2 - 10.1007/s00360-011-0550-x
DO - 10.1007/s00360-011-0550-x
M3 - Article
C2 - 21274542
AN - SCOPUS:79959207506
VL - 181
SP - 615
EP - 630
JO - Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology
JF - Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology
SN - 0174-1578
IS - 5
ER -
