THE MECHANISM OF ACID-BASE REGULATION IN SEAWATER-ACCLIMATED GREEN CRABS, CARCINUS MAENAS
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Date
2015
Authors
Fehsenfeld, Sandra
Weihrauch, Dirk
Journal Title
Journal ISSN
Volume Title
Publisher
Canadian Journal of Zoology
Abstract
The present study investigated acid-base regulatory mechanisms in seawater-acclimated green crabs Carcinus maenas. In seawater (32 ppt), this decapod crustacean is osmo-conforming and therefore the majority of the observed responses can be attributed to ion fluxes based on acid-base compensatory responses alone. Similar to what is observed in brackish-water acclimated C. maenas, seawater-acclimated green crabs exposed to environmental hypercapnia rapidly accumulated HCO3- in their hemolymph to compensate for the respiratory acidosis caused by excess hemolymph pCO2 after only 24 48 hours. A full recovery of the decreased hemolymph pH was not observed in this time frame. Isolated gill perfusion experiments on anterior gill 5 applying inhibitors for potential key-transporters located in the crabs’ gill epithelium supported the involvement of all investigated genes in ammonia excretion and the excretion of acid-base equivalents. The most significant effect was observed targeting basolateral applied Na+/HCO3--cotransporter and V-ATPase. Under the influence of these two inhibitors the excretion of H+ and partly for CO2 was reversed and an enrichment of these two molecules in the hemolymph was observed. A working model for acid-base regulatory mechanisms and their link to ammonia excretion in the gill epithelium of C. maenas has been hypothesized including basolateral Na+/HCO3--cotransporter, V-ATPase, Na+/H+-exchanger, Na+/K+-ATPase, carbonic anhydrase and K+-channels. The data of the present study suggests transport of CO2 and NH4+ in acidified and non-acidified vesicles.
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Keywords
Carcinus maenas, Acid-base regulation