Freshwater to seawater acclimation of juvenile bull sharks ( Carcharhinus leucas): plasma osmolytes and Na +/K +-ATPase activity in gill, rectal gland, kidney and intestine

Pillans, R. D., Good, J. P., Anderson, W. G., Hazon, N. and Franklin, C. E. (2005) Freshwater to seawater acclimation of juvenile bull sharks ( Carcharhinus leucas): plasma osmolytes and Na +/K +-ATPase activity in gill, rectal gland, kidney and intestine. Journal of Comparative Physiology B. Biochemical, Systematic and Environmental Physiology, 175 1: 37-44. doi:10.1007/s00360-004-0460-2


Author Pillans, R. D.
Good, J. P.
Anderson, W. G.
Hazon, N.
Franklin, C. E.
Title Freshwater to seawater acclimation of juvenile bull sharks ( Carcharhinus leucas): plasma osmolytes and Na +/K +-ATPase activity in gill, rectal gland, kidney and intestine
Journal name Journal of Comparative Physiology B. Biochemical, Systematic and Environmental Physiology   Check publisher's open access policy
ISSN 0174-1578
1432-136X
Publication date 2005-01-01
Sub-type Article (original research)
DOI 10.1007/s00360-004-0460-2
Volume 175
Issue 1
Start page 37
End page 44
Total pages 8
Editor G. Heldmaier
Place of publication Berlin
Publisher Springer-Verlag
Language eng
Subject C1
270599 Zoology not elsewhere classified
780105 Biological sciences
0606 Physiology
Abstract This study examined the osmoregulatory status of the euryhaline elasmobranch Carcharhinus leucas acclimated to freshwater (FW) and seawater ( SW). Juvenile C. leucas captured in FW ( 3 mOsm l(-1) kg(-1)) were acclimated to SW ( 980 - 1,000 mOsm l(-1) kg(-1)) over 16 days. A FW group was maintained in captivity over a similar time period. In FW, bull sharks were hyper-osmotic regulators, having a plasma osmolarity of 595 mOsm l(-1) kg(-1). In SW, bull sharks had significantly higher plasma osmolarities ( 940 mOsm l(-1) kg(-1)) than FW-acclimated animals and were slightly hypoosmotic to the environment. Plasma Na+, Cl-, K+, Mg2+, Ca2+, urea and trimethylamine oxide (TMAO) concentrations were all significantly higher in bull sharks acclimated to SW, with urea and TMAO showing the greatest increase. Gill, rectal gland, kidney and intestinal tissue were taken from animals acclimated to FW and SW and analysed for maximal Na+/ K+-ATPase activity. Na+/ K+-ATPase activity in the gills and intestine was less than 1 mmol Pi mg(-1) protein h(-1) and there was no difference in activity between FW- and SW-acclimated animals. In contrast Na+/ K+-ATPase activity in the rectal gland and kidney were significantly higher than gill and intestine and showed significant differences between the FW- and SW-acclimated groups. In FW and SW, rectal gland Na+/ K+-ATPase activity was 5.6 +/- 0.8 and 9.2 +/- 0.6 mmol Pi mg(-1) protein h(-1), respectively. Na+/ K+-ATPase activity in the kidney of FW and SW acclimated animals was 8.4 +/- 1.1 and 3.3 +/- 1.1 Pi mg(-1) protein h(-1), respectively. Thus juvenile bull sharks have the osmoregulatory plasticity to acclimate to SW; their preference for the upper reaches of rivers where salinity is low is therefore likely to be for predator avoidance and/or increased food abundance rather than because of a physiological constraint.
Keyword Physiology
Zoology
Carcharhinus Leucas
Osmoregulation
Na+k+-atpase
Salinity
Seawater
Freshwater
Acclimation
Bass Dicentrarchus-labrax
Stingray Dasyatis-sabina
St Johns River
Oxygen-consumption
Atlantic Stingray
Chloride Cells
Sea-water
Euryhaline Elasmobranch
Osmotic Regulation
Squalus-acanthias
Q-Index Code C1

 
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Created: Wed, 15 Aug 2007, 15:18:20 EST