Journal of Comparative Physiology B

, Volume 175, Issue 1, pp 37–44

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

  • Richard D. Pillans
  • Jonathan P. Good
  • W. Gary Anderson
  • Neil Hazon
  • Craig E. Franklin
Original Paper

DOI: 10.1007/s00360-004-0460-2

Cite this article as:
Pillans, R.D., Good, J.P., Anderson, W.G. et al. J Comp Physiol B (2005) 175: 37. doi:10.1007/s00360-004-0460-2

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 hypo-osmotic 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.

Keywords

Carcharhinus leucas Osmoregulation Na+/K+-ATPase Salinity Seawater Freshwater Acclimation 

Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • Richard D. Pillans
    • 1
    • 2
  • Jonathan P. Good
    • 3
  • W. Gary Anderson
    • 3
  • Neil Hazon
    • 3
  • Craig E. Franklin
    • 1
  1. 1.School of Life SciencesThe University of QueenslandBrisbaneAustralia
  2. 2.Co-operative Research Centre for Coastal Zone, Estuary and Waterway ManagementIndooroopillyAustralia
  3. 3.Department of Biology, Division of Environmental and Evolutionary Biology, Gatty Marine LaboratoryUniversity of St AndrewsSt. Andrews, FifeUK

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