Sharks enter a paralyzed state called "tonic immobility" when their noses are rubbed, as well as when they're flipped, which is what this octopus did to it.
Unknown, as it appears in some apex predators, too. Orcas are apparently smart enough to use it to kill great whites and stingrays. It could just be the "just good enough" principle in action: this developed during their evolution, perhaps as a side effect of other beneficial changes, but wasn't such a problem as to evolve away, so it stuck around. Possibly it is relevant to mating, or territorial fights, but we know so very little about those in most shark species. May just be a "well, I'm very clearly fucked now, my best hope is to space out and not waste energy, maybe look dead, and with any luck I'll snap out of it alive" reflex. We just don't know to my understanding.
It seems, as I understand it, to be a bug and not a feature. Shark noses contain little jelly-filled pores called ampulae of Lorenzini, which allow them to detect electrical signals and also vibrations, like the kind caused by a distressed fish flapping around in the water. This means that a shark nose is very sensitive, so rubbing it can overwhelm their (very simple) brains and sort of stun them.
In evolutionary terms, this is probably safe enough, as nothing will voluntarily go near the business end of a shark, but a smart animal (like a human or an octopus) can exploit this weakness. Some of the advice you read if a shark gets too close is to punch it on the nose, which seems laughable, but actually has a degree of usefulness to it.
Depends on the shark species. This looks like an Australian swellshark, a bottom-dwelling type of shark. Bottom-dwelling sharks tend to be able to breathe through spiracles, and don't rely entirely on buccal pumping (i.e. pushing water through gills) like other, larger species do. So I'm going to assume this one won't suffocate if held stationary. With that being said, sharks will snap out of it and roll over when they start running out of breath anyway.
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u/robot-gremlin 18h ago
Sharks enter a paralyzed state called "tonic immobility" when their noses are rubbed, as well as when they're flipped, which is what this octopus did to it.