How Removing Eyestalks Affects an Enzyme Controlled by the Nervous and Hormone Systems in Blue Crabs

Eyestalk ablation resulted in an approximate doubling of carbonic anhydrase activity in the gills of blue crabs acclimated to 35 ppt.

• Transfer of intact crabs to 28 ppt did not affect carbonic anhydrase activity, but prior eyestalk ablation led to a 5-fold increase in activity.
• There was a 7-fold increase in carbonic anhydrase activity in the gills of crabs transferred from 35 to 15 ppt, which was enhanced by eyestalk ablation.
• Hemolymph osmolality remained unaffected by eyestalk ablation, but slightly elevated in treated crabs.
• Methyl farnesoate concentrations were undetectable in intact crabs, while eyestalk ablation increased these levels, though they were still low and not related to salinity.
• These findings suggest that a regulatory substance in the eyestalk may repress carbonic anhydrase expression in high salinity conditions.

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