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Comment by christudor | Hacker News Reader

Hesiod in his Works and Days (c. 700 BC) talks about the behaviour of octopuses, saying that when octopuses get hungry they will eat their own tentacles. Amazingly, Hesiod was right about this behaviour (octopuses do sometimes eat their own tentacles) but it's not because they're hungry, but because they're stressed.

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Apparently this was a matter of much debate, with further takes by (at least) Aristotle, Athenaeus, Oppian, Pliny and Plutarch:

https://books.google.com/books?id=Tun_DwAAQBAJ&lpg=PA61&dq=O...

A bit like how we bite our fingernails perhaps :)

How does the octopus persuade the tentacles to allow themselves to get eaten? :)

Why is eating your tentacle useful when "stressed"?

Eating your tentacle is a net negative in "calories" long term, and there is probably the opportunity cost of not having said tentacle (for some time?)

I guess maybe they want a quick snack for the high energy jet propulsion predator escape that they are preparing for when stressed.

But then Hesoid is kid of right, they do eat it because they need more energy.

It's a misunderstanding that evolution leads to only positive behaviours remaining. Eating your own tentacles might be similar to humans cutting themselves, or the stress response behaviours spillover by zoo animals: a spillover réaction that turns adaptive behavioural patterns (eating) into maladaptive (eating yourself)

Very few humans cut themselves and it has very limited health consequences for those who do.

Evolution predicts that self-harming behaviour will be observed less frequently compared to self benefitting behaviours.

So whenever an apparently self-harming behaviour is observed it is quite useful to ask: "is it really self-harm or secretly useful somehow?". And also: "how often does that really happen?"

You also need to ask yourself "is there a way to do a useful thing without this". Like, evolution can't jump, if the same gene expression gives you better pattern matching and improved chances of hallucinations, depending on the selection drift, you might go for this, and then you are stuck with hallucinations long after the benefit of pattern matching might be lost.

A simple answer might be that octopuses get stressed when there are to many other octopuses around which limits resources. Some octopuses eating their own tentacles and dying might give them an evolutionary advantage.

Net negative in calories but that tentacle is stored energy, so maybe it's like burning fat?

> Amazingly, Hesiod was right about this behaviour

I don't see why this is a surprise.

I'd be pretty surprised if I saw a guy eating his hands.

I mean, I do it. (Less now than I used to.) The amount of flesh I take off is unnoticeable visually or as a percentage of my hand.

But more to the point, if somebody from a coastal, extensively seafaring culture 2700 years ago says octopi sometimes eat their own tentacles, there is every reason to believe he's saying it because it's true. The options are (I) octopi sometimes eat their own tentacles, as advertised; (II) octopi sometimes engage in a behavior that looks very similar to eating their own tentacles, but is subtly different; or (III) someone made it up and nobody in a culture with extensive exposure to octopi ever noticed that it never happened.

Incidents of type III are far from unheard of -- I have a dictionary with the Tongue Map printed in it -- but they're not the way to bet.

Ancient Greek observations of nature have a spotty record of accuracy, as far as I know.

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