On the octopus and why it is extra-specially weird. Via Joe Carter.
Otto, a six-month-old octopus, had crawled out of his tank and, using his siphon like a fire hose, aimed it at the overhead light. Apparently it annoyed him or maybe he was just bored. As director Elfriede Kummer told The Telegraph, “Otto is constantly craving for attention and always comes up with new stunts... Once we saw him juggling hermit crabs in his tank”.
It takes serious computing power to control eight arms, hundreds of suckers, ‘thinking skin’ and camera eyes. Hence the oversized brain of the octopus. With its 500 million neurons, that’s two and a half times that of a rat. But their brain anatomy is very different.
A mammalian brain is a centralised processor that sends and receives signals via the spinal cord. But for the octopus, only 10% of its brain is centralised in a highly folded, 30-lobed donut-shaped structure arranged around its oesophagus (really). Two optic lobes account for another 30%, and 60% lies in the arms. “It’s a weird way to construct a complex brain,” says Hanlon. “Everything about this animal is goofy and weird.”
Take the arms: they’re considered to have their own ‘mini-brain’ not just because they are so packed with neurons but because they also have independent processing power. For instance, an octopus escaping a predator can detach an arm that will happily continue crawling around for up to 10 minutes.
And then there’s their ‘thinking’ skin. Again the brain, primarily the optic lobes, controls the processing power here. The evidence comes from a 1988 study by Hanlon and John Messenger from the University of Sheffield. They showed that blinded newly hatched cuttlefish could no longer match their surroundings. They were still able to change colour and body patterns but in a seemingly random fashion. Anatomical evidence also shows that nerves in the lower brain connect directly to muscles surrounding the pigment sacs or chromatophores.
https://cosmosmagazine.com/biology/how-the-octopus-got-its-smarts
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