Journal article
Salt-water acclimation of the estuarine crocodile Crocodylus porosus involves enhanced ion transport properties of the urodaeum and rectum
Journal of Experimental Biology, Vol.223(4), pp.1-10
2020
PMID: 31953364
Abstract
Estuarine crocodiles, Crocodylus porosus, inhabit freshwater, estuarine and marine environments. Despite being known to undertake extensive movements throughout and between hypo-osmotic and hyperosmotic environments, little is known about the role of the cloaca in coping with changes in salinity. We report here that, in addition to the well-documented functional plasticity of the lingual salt glands, the middle of the three cloacal segments (i.e. the urodaeum) responds to increased ambient salinity to enhance solute-coupled water absorption. This post-renal modification of urine serves to conserve water when exposed to hyperosmotic environments and, in conjunction with lingual salt gland secretions, enables C. porosus to maintain salt and water balance and thereby thrive in hyperosmotic environments. Isolated epithelia from the urodaeum of 70% seawater-acclimated C. porosus had a strongly enhanced short-circuit current (an indicator of active ion transport) compared with freshwater-acclimated crocodiles. This enhanced active ion absorption was driven by increased Na + /K +-ATPase activity, and possibly enhanced proton pump activity, and was facilitated by the apical epithelial Na + channel (ENaC) and/or the apical Na + /H + exchanger (NHE2), both of which are expressed in the urodaeum. NHE3 was expressed at very low levels in the urodaeum and probably does not contribute to solute-coupled water absorption in this cloacal segment. As C. porosus does not appear to drink water of salinities above 18 ppt, observations of elevated short-circuit current in the rectum as well as a trend for increased NHE2 expression in the oesophagus, the anterior intestine and the rectum suggest that dietary salt intake may stimulate salt and possibly water absorption by the gastrointestinal tract of C. porosus living in hyperosmotic environments.
Details
- Title
- Salt-water acclimation of the estuarine crocodile Crocodylus porosus involves enhanced ion transport properties of the urodaeum and rectum
- Authors
- Martin Grosell (Author) - University of MiamiRachael M Heuer (Author) - University of MiamiN. C Wu (Author) - University of QueenslandRebecca L Cramp (Author) - University of QueenslandYadong Wang (Author) - University of MiamiEdward M Mager (Author) - University of MiamiRoss G Dwyer (Author) - University of QueenslandCraig E Franklin (Author) - University of Queensland
- Publication details
- Journal of Experimental Biology, Vol.223(4), pp.1-10
- Publisher
- Company of Biologists Ltd.
- DOI
- 10.1242/jeb.210732
- ISSN
- 1477-9145
- PMID
- 31953364
- Organisation Unit
- University of the Sunshine Coast, Queensland; School of Science and Engineering - Legacy; School of Science, Technology and Engineering
- Language
- English
- Record Identifier
- 99498405002621
- Output Type
- Journal article
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