Functional evidence for the presence of a carbonic anhydrase repressor in the eyestalk of the euryhaline green crabCarcinus maenas

Eyestalk ablation in green crabs resulted in a 23% increase in carbonic anhydrase activity in response to low salinity.

• Eyestalk ablation alone increased carbonic anhydrase activity and mRNA expression in the posterior gills of crabs acclimated to 32 p.p.t. salinity.
• Injections of eyestalk extract from crabs at 32 p.p.t. salinity abolished the increase in carbonic anhydrase activity due to eyestalk ablation.
• Transfer to 10 p.p.t. salinity for 7 days caused an eightfold increase in carbonic anhydrase activity and a sixfold increase in mRNA expression in posterior gills.
• Daily injections of eyestalk extract reduced low salinity-induced carbonic anhydrase induction by nearly 50% in intact crabs and by almost 75% in eyestalk-ablated crabs.
• A 4-day transfer to 10 p.p.t. salinity led to significant increases in carbonic anhydrase activity and mRNA expression, further enhanced by eyestalk ablation.
• Reduction of carbonic anhydrase induction by 66% was associated with disrupted hemolymph osmotic regulation.

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