Natures wonders: the brilliant octopus (Introduction)

by David Turell , Monday, September 17, 2018, 20:21 (2257 days ago) @ David Turell

A new descriptive article:

https://cosmosmagazine.com/biology/how-the-octopus-got-its-smarts

"Some researchers who study the octopus and its smart cousins, the cuttlefish and squid, talk about a ‘second genesis of intelligence’ – a truly alien one that has little in common with the mammalian design.

"While the octopus has a large central brain in its head, it also has a unique network of smaller ‘brains’ within each of its arms. It’s just what these creatures need to coordinate the mind-boggling complexity of eight prehensile arms and hundreds of sensitive suckers, which provide the octopus with the equivalent of opposable thumbs (roboticists have been taking note). Not to mention their ability to camouflage instantly on any of the diverse backgrounds they encounter on coral reefs or kelp forests. Using pixelated colours, texture and arm contortions, these body artists instantly melt into the seascape, only to reappear in a dazzling display to attract a mate or threaten a rival.

***

"It turns out the octopus has a profusion of brain-forming genes previously seen only in back-boned animals. But its secret weapon may not be genes as we know them.

"A complex brain needs a way to store complex information. Startlingly, the octopus may have achieved this complexity by playing fast and free with its genetic code.

"To build a living organism, the decoding of the DNA blueprint normally proceeds with extreme fidelity. Indeed it’s known as ‘the central dogma’. A tiny section of the vast blueprint is copied, rather like photocopying a single page from a tome. That copy, called messenger RNA (mRNA), then instructs the production of a particular protein. The process is as precise as a three-hat chef following her prized recipe for apple pie down to the letter.

"But in a spectacular example of dogma-breaking, the octopus chef takes her red pen and modifies copies of the recipe on the fly. Sometimes the result is the traditional golden crusted variety; other times it’s the deconstructed version – apple mush with crumbs on the side.

"This recipe tweaking is known as ‘RNA editing’. In humans only a handful of brain protein recipes are edited. In the octopus, the majority get this treatment.

“'It introduces a level of sophistication and complexity we never thought of. Perhaps it’s related to their memory,” says Eli Eisenberg, a computational biologist at the University of Tel Aviv. Though he quickly adds, “I must stress this is complete speculation”.

***

"But those limber bodies were a tasty treat to fish predators, so the octopus evolved ‘thinking skin’ that could melt into the background in a fifth of a second. These quick-change artists not only use a palette of skin pigments to paint with, they also have a repertoire of smooth to spiky skin textures, as well as body and arm contortions to complete their performance – perhaps an imitation of a patch of algae, as they stealthily perambulate on two of their eight arms.

“'It’s not orchestrated by simple reflexes,” says Roger Hanlon, who researches camouflage behaviour at the Marine Biological Laboratory in Woods Hole, Massachusetts. “It’s a context-specific, fast computation of decisions carried out in multiple levels of the brain.” And it depends critically on a pair of camera eyes with keen capabilities.

"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.

"Indeed, until an experiment by Kuba and colleagues in 2011, some suspected the arms’ movements were independent of their central brain. They aren’t. Rather it appears that the brain gives a high-level command that a staff of eight arms execute autonomously.

“'The arm has some fascinating reflexes, but it doesn’t learn,” says Kuba, who studied these reflexes between 2009 and 2013 as part of a European Union project to design bio-inspired robots.

"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."

Comment: The article is much longer, in greater detail, and i suggest reading it in full. an amazing branch of evolution.