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The ocean is a strange place after dark (bbc.com)
141 points by happy-go-lucky on Aug 28, 2017 | hide | past | web | favorite | 33 comments

Here's another story/fact that should be included.

There's a species of octopi that live in groups. On nights with bright moon, predators can identify them because they cast a shadow. They have evolved an organ to intake particular bacteria that use what's called quorum sensing to detect when there's enough of them around. When the organ is full of these bacteria, the bacteria glow and therefore stop the shadow of the octopi. It's a great example of symbiosis, more specifically mutualism of two species. The octopi get saved and the bacteria get a safe place to live.

The squid symbiosis is mentioned in the article. Oh and btw, it's octopuses or octopodes (greek not latin, fyi).

Both forms are correct and are used as synonyms although referring to different things. Octopoda is an order, Octopus is the common name of animals in this order. On the other hand, octopuses normally are solitary and bottom attached; squids like the jewel squids do that countershading by light. Octopuses do not need this kind of defense normally. On the other hand squid countershading will not work with its smartest predators.

Merriam-Webster dictionary disagrees:


Oxford Dictionary disagrees with Merriam-Webster:


This whole discussion is somewhat moot as a real biologist would almost always write "species of octopus", singular.

or, Latin 5th declension plural, also "species (plural) of octopus"

What's popular isn't always correct and dictionaries by definition reflect usage.

That is unless it doesn't literally kill you that literally now actually means figuratively too.

I was walking across campus with a friend and we came upon half a dozen theoretical linguists committing unprovoked physical assault on a defenseless prescriptivist. My friend was shocked. She said: "Aren't you going to help?"

I said, "No; six should be enough."

(copypasted from http://itre.cis.upenn.edu/~myl/languagelog/archives/002938.h...)

“Literally” doesn't actually mean figuratively, even in use; it's used (figuratively itself) as an intensifier applied to some other figurative expression. This actually has the opposite effect to “figuratively”, which by explicitly stating that a use is figurative acts as a qualifier, rather than an intensifier, of the figurative expression it modifies.

> What's popular isn't always correct and dictionaries by definition reflect usage.

What's popular is correct by definition, that's why dictionaries reflect usage, they don't prescribe it. Language is about communication, not syntax, people do use "literally" when they mean figuratively and you know it, I know it, so they are communicating, the word has obtained new meaning. Words are not static things.

Some cultures put more emphasis on the top down approach than others. France[1] tends to be more into top down control of its language than the English.

[1] https://en.wikipedia.org/wiki/Dictionnaire_de_l%27Acad%C3%A9...

Adam Ruins Everything had a episode that covered this: https://www.youtube.com/watch?v=fu5XDrdD7KM

In short: The dictionary isn't the "law", it lags behind the language as it is actually used. Once the "reverse" definition of "literally" became common in usage it became the new definition - not what a dictionary used to define it as.

What's the point of being "correct" if nobody understands you?

Oh you are right. I only quickly read the first paragraph or two of that section about the light in the eyes.

Actually it's English, where octopi is a perfectly acceptable and widely-understood plural.

> When the organ is full of these bacteria, the bacteria glow and therefore stop the shadow of the octopi.

It seems weird because the animal itself would be a lot more visible.

This wikipedia article [1] about firefly squid says that the animal uses it's ability to match the brightness and colour of its underside to the light coming from the surface, making it difficult for predators to detect it from below

Is that it?

[1] https://en.wikipedia.org/wiki/Firefly_squid

Here is the species that I learned about. [1] As I mentioned in another comment, I learned about this in a microbiology course so the focus was on the Vibrio species of bacteria, not as much about the octopus.

1. https://en.wikipedia.org/wiki/Euprymna_scolopes

Social Octopuses? GTFO? Really? I must know more (as I am an avid octopus junky) and I thought that octopus were not social .. Got any more specifics?

I could be wrong about that. I learned this in a microbiology course 10 years ago. So the focus was on the bacteria and the quorum sensing rather than the ecology of the octopus.

Here's the wiki on the octopus species though. https://en.wikipedia.org/wiki/Euprymna_scolopes

I see. This is a sepiolidae. In a different superorder than octopuses then. Neither a squid nor a octopus; a close relative to cuttlefishes.

it's called the glowing squid.

If you're interested in this, you might like http://www.nautiluslive.org. It says they're planning to do another dive tonight.

The ocean is a fantastic place. We've recently crossed the Bay of Biscay under sail and have seen many pods of dolphins, bio-luminescence in our wake at night and the stars in a way you can only see far away from any source of light.

Here's some dolphins for you (daytime though): https://www.youtube.com/watch?v=6lWmOhS83kU

A nice pod of common short-beaked dolphins (Delphinus delphis) :-)

Saw a document once about red octopuses called red devils that attack in pack during night. Definitely not a fun thought to have.

Turns out the 'red devils' you are referring to are squid not octopuses: https://en.wikipedia.org/wiki/Humboldt_squid

It's OK -- I didn't know either, until right now. Thanks for the tip!

Thank you too, i will correct myself for the future XD

Most all waves glow at night. But to see it with the naked eye you need proper darkness. Ocean + waves + darkness = bad idea. So i cannot suggest anyone go looking for this.

There are significantly different levels of bioluminescence. You see some regularly. Occasionally it's truly glowing. Once I saw it at incredible levels. I was fortunate to be with friends and a spot we could swim. We were diving from about 3m above the water and watching our bodies go through the water leaving these tunnels of glow. If you were the diver and looked back your skin was glowing. Very cool and I can suggest everyone getting this experience assuming usual safety is covered.

Where was that and at what time in the year?

Sydney and not sure time of year. I dont remember it being cold so probably around summer.

Reminds me of this scene from apollo 13 https://youtu.be/N91ogCGpYl0

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