Three hearts; blue blood; no skeleton; arms like tongues. These are just some of the alien features of octopuses, squid and cuttlefish ' members of the cephalopod family. The outlandish list continues. Cephalopod skin can taste chemicals, sense light and change colour and texture rapidly. In many species, the sucker-covered arms can even regenerate. These invertebrates have evolved independently from the vertebrate lineage for more than 600 million years. Their last common ancestor was probably a worm-like creature with a rudimentary nervous system and eye-like patches of light-sensitive cells. Despite this evolutionary gulf, vertebrates and these highly specialized molluscs share strange similarities. Their eyes, for example. 'It's eerie how similar they ended up,' says Cristopher Niell, a neuroscientist at the University of Oregon in Eugene. 'The convergent evolution of the eye still blows my mind.' Now, one similarity is spurring a boom in cephalopod neuroscience. Around 400...
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