Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8318578 | Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology | 2015 | 8 Pages |
Abstract
While there is a considerable body of work describing osmoregulation by elasmobranchs in brackish and saltwater, far fewer studies have investigated osmoregulation in hypersaline waters. We examined osmo- and ionoregulatory function and plasticity in juvenile brown-banded bamboo sharks, Chiloscyllium punctatum, exposed to three experimental salinities (25, 34 and 40â°) for two weeks. C. punctatum inhabits sheltered coastal areas and bays which can naturally become hypersaline as a consequence of evaporation of water but can also become hyposaline during flood events. We hypothesised that C. punctatum would demonstrate a phenotypically plastic osmoregulatory physiology. Plasma osmolality, urea, Na+ and Clâ levels increased significantly with increasing environmental salinity. Rectal gland and branchial sodium-potassium ATPase (NKA) activities were unaffected by salinity. Using immunohistochemistry and Western Blotting we found evidence for the presence of the key ion-regulatory proteins vacuolar H+-ATPase (VHA), pendrin (Clâ/HCO3â co-transporter) and the Na+-H+ exchanger isoform 3 (NHE3) in discrete cells within the branchial epithelia. These results indicate that C. punctatum is a partially euryhaline elasmobranch able to maintain osmo- and ionoregulatory function between environmental salinities of 25â° and 40â°. As suggested for other elasmobranchs, the gills of C. punctatum likely play a limited role in maintaining Na+ homeostasis over the salinity range studied, but may play an important role in acid-base balance.
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Authors
R.L. Cramp, M.J. Hansen, C.E. Franklin,