Review
Summary
The diversity of mechanisms of ammonia and urea excretion by the gills and other epithelia of aquatic organisms, especially fish
and crustaceans, has been studied for decades. Although the decades-old dogma of ‘aquatic species excrete ammonia’ still
explains nitrogenous waste excretion for many species, it is clear that there are many mechanistic variations on this theme. Even
within species that are ammonoteles, the process is not purely ‘passive’, often relying on the energizing effects of proton and
sodium–potassium ATPases. Within the ammonoteles, Rh (Rhesus) proteins are beginning to emerge as vital ammonia conduits.
Many fishes are also known to be capable of substantial synthesis and excretion of urea as a nitrogenous waste. In such species,
members of the UT family of urea transporters have been identified as important players in urea transport across the gills. This
review attempts to draw together recent information to update the mechanisms of ammonia and urea transport by the gills of
aquatic species. Furthermore, we point out several potentially fruitful avenues for further research.
ReviewSummaryThe diversity of mechanisms of ammonia and urea excretion by the gills and other epithelia of aquatic organisms, especially fishand crustaceans, has been studied for decades. Although the decades-old dogma of ‘aquatic species excrete ammonia’ stillexplains nitrogenous waste excretion for many species, it is clear that there are many mechanistic variations on this theme. Evenwithin species that are ammonoteles, the process is not purely ‘passive’, often relying on the energizing effects of proton andsodium–potassium ATPases. Within the ammonoteles, Rh (Rhesus) proteins are beginning to emerge as vital ammonia conduits.Many fishes are also known to be capable of substantial synthesis and excretion of urea as a nitrogenous waste. In such species,members of the UT family of urea transporters have been identified as important players in urea transport across the gills. Thisreview attempts to draw together recent information to update the mechanisms of ammonia and urea transport by the gills ofaquatic species. Furthermore, we point out several potentially fruitful avenues for further research.
การแปล กรุณารอสักครู่..
