RNA editing, a post-transcriptional process, allows the diversification of 
proteomes beyond the genomic blueprint; however it is infrequently used among 
animals for this purpose. Recent reports suggesting increased levels of RNA 
editing in squids thus raise the question of the nature and effects of these 
events. We here show that RNA editing is particularly common in behaviorally 
sophisticated coleoid cephalopods, with tens of thousands of evolutionarily 
conserved sites. Editing is enriched in the nervous system, affecting molecules 
pertinent for excitability and neuronal morphology. The genomic sequence 
flanking editing sites is highly conserved, suggesting that the process confers 
a selective advantage. Due to the large number of sites, the surrounding 
conservation greatly reduces the number of mutations and genomic polymorphisms 
in protein-coding regions. This trade-off between genome evolution and 
transcriptome plasticity highlights the importance of RNA recoding as a strategy 
for diversifying proteins, particularly those associated with neural function. 
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