acid-base and ammonia regulation in cephalopods

Cephalopods have probably evolved the highest physiological complexity among all invertebrate taxa to compete with fish for similar resources in the marine environment. As a trade off to their less efficient swimming mode and active lifestyle they have the highest metabolic rates among marine animals and strong metabolic CO2 induced temporal acid-base disturbances during jetting and fast swimming. To accommodate CO2 induced acid-base challenges cephalopods have evolved moderate to strong acid-base regulatory abilities to stabilize blood pH. Accordingly cephalopods are highly suitable organisms to study the acid-base physiology of invertebrates.

My work identified the cephalopod gill as an important site for acid-base regulation and characterized key transporters in gill epithelia including Na+/H+ exchangers, Na+/HCO3- cotransporters, carbonic anhydrases Vacuolar-H+-ATPase and the Na+/K+-ATPase. Interestingly, in convergence to teleosts already during their oviparous development cephalopod embryos use their skin and yolk epithelium to regulate internal pH homeostasis. Furthermore, based on my findings there is strong evidence that acid-base regulation is highly coupled to ammonia transport in regulatory epithelia. This is of particular importance since little information is available regarding the mechanistic basis for NH3/NH4+ homeostasis in invertebrate phyla like the mollusca.

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