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.
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.
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?"
“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.
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.
> 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
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.
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.
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.
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.
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.