Why are corals colorful?

[Formulator]

I understand the physiology and physics of it, but why did corals evolve to be so aesthetically pleasing? There must be some kind of evolutionary advantage to drive such colors right? I know many of the crazier variations were created by the hobby’s own artificial selection, but there are still some vibrant colors that occur naturally.

 

[WalkerLovesTheOcean]

I believe it was to attract prey? Almost like flowers are colorful to attract pollinators.

 

[Formulator]

I believe it was to attract prey? Almost like flowers are colorful to attract pollinators.

What prey though? With flowers there is a mutual benefit since the insects/birds get nectar, so those animals know to look for the bright colors for a meal.

 

[WalkerLovesTheOcean]

What prey though? With flowers there is a mutual benefit since the insects/birds get nectar, so those animals know to look for the bright colors for a meal.

Yeah, good point. I just read that the pigments are there to filter out harmful UV rays. Makes alot more sense.

 

[Cichlid Dad]

There's been studies I've heard about that coral can reflect out the color spectrum they are lacking for photosynthesis and absorb it back into themselves.


“rainbow of colors” from the deep sea
Joerg Wiedenmann, the lead author on the study, discovered corals could glow by mistake.

According to Newsweek, Wiedenmann placed corals under ultraviolet light while researching sea anemones, and was “blown away by a rainbow of colors.”

Interestingly, the color seemed to correspond to where the coral lived. The deeper the coral lived, the more likely it was to glow red and orange.

This is no coincidence. Little light reaches coral in the deep sea. It soaks up what it gets, but it needs more. So it reflects sun rays back as red-orange light, which is a special type of light that infiltrates the coral’s tissue, where the algae can turn it into food.

Essentially, the coral is doubling the amount of light it gets by creating its own. Double the mileage for the same amount
of gas.

 

[encrustingacro]

In shallower waters, corals develop bright colors to shield themselves from the intensity or UV rays of the sun. In deeper waters, fluorescent colors are developed to alter the wavelength of light absorbed by their zooxanthellae.

 

[encrustingacro]

I believe it was to attract prey? Almost like flowers are colorful to attract pollinators.

Corals are filter-feeders, so I don't think it would be that.

 

[Formulator]

There's been studies I've heard about that coral can reflect out the color spectrum they are lacking for photosynthesis and absorb it back into themselves.


“rainbow of colors” from the deep sea
Joerg Wiedenmann, the lead author on the study, discovered corals could glow by mistake.

According to Newsweek, Wiedenmann placed corals under ultraviolet light while researching sea anemones, and was “blown away by a rainbow of colors.”

Interestingly, the color seemed to correspond to where the coral lived. The deeper the coral lived, the more likely it was to glow red and orange.

This is no coincidence. Little light reaches coral in the deep sea. It soaks up what it gets, but it needs more. So it reflects sun rays back as red-orange light, which is a special type of light that infiltrates the coral’s tissue, where the algae can turn it into food.

Essentially, the coral is doubling the amount of light it gets by creating its own. Double the mileage for the same amount
of gas.

Very interesting! Thank you for the detailed info!

 

[VintageReefer]

I thought it was like the animal / insect world and the bright colors were to DETER attacks. Almost like a warning saying - I’m poisonous / not tasty

 

[Naekuh]

I believe it was to attract prey? Almost like flowers are colorful to attract pollinators.

But wait.. wouldnt color attract more preditors into thinking it taste good? or does Mushroom logic apply here?
Meaning the more pretty the mushroom looks, the faster it will kill you.

 

[VintageReefer]

Look at poison dart frogs and black widow spiders. Those colors are a warning to others

 

[Formulator]

But wait.. wouldnt color attract more preditors into thinking it taste good? or does Mushroom logic apply here?
Meaning the more pretty the mushroom looks, the faster it will kill you.

I could see this. In the animal kingdom, brightly colored reptiles and frogs are often poisonous or venomous.

 

[VintageReefer]

These creatures have no real defense except their poison. And frequently they need to be in the mouth of something else to pass it on….Killing the attacker but putting the victim at risk of death also. The colors are a warning because they would rather avoid the situation entirely

 

[encrustingacro]

But wait.. wouldnt color attract more predators into thinking it taste good? or does Mushroom logic apply here?
Meaning the more pretty the mushroom looks, the faster it will kill you.

Coral colors don't really have much to do with warding off predators; that's more of a terrestrial organism thing.

 

[VintageReefer]

Coral colors don't really have much to do with warding off predators; that's more of a terrestrial organism thing.

Ghosts of the Ocean: Explaining Marine Life Devoid of Color

ocean.si.edu

It could go either way. With nudibranches it’s plausible the ones closer to the surface evolved to have brighter colors to deter predators and those deeper evolved to be clear to blend in and hide better

But as the article also mentions, it’s a logical theory but not known fact.

 

[encrustingacro]

Ghosts of the Ocean: Explaining Marine Life Devoid of Color

ocean.si.edu

It could go either way. With nudibranches it’s plausible the ones closer to the surface evolved to have brighter colors to deter predators and those deeper evolved to be clear to blend in and hide better

But as the article also mentions, it’s a logical theory but not known fact.

I stand corrected, but nonetheless, coral coloration is not to ward off prey. As far as I know, Scleractinians don't have any poisonous substances in them that would make a corallivore sick. The closest I can think of is Palytoxin in Zoantharians, but they still have predators.

 

[encrustingacro]

Remember that most corals in the wild are also not very colorful, so these theories would also have to take into account the drab grey/brown corals within a species. How would the drab specimens attract prey? Do gray/brown corals contain toxins too, or do only the colorful variants of a species contain toxins?

Corals can change color depending on the environment they are in. If coral coloration were for attracting prey or warning predators, one would think they would keep their color in all environments. Corals tend to be the most colorful in shallow, high-turbidity reef crests, where the sun's intensity is very high, or in deeper areas, where the sunlight is filtered out by the seawater. Colorful corals can also occur in areas with a lot of available suspended food; more food means more energy gained, which means less energy needs to be produced by the zooxanthellae, so the coral reduces the amount of zoox in its tissue, revealing the coral's pigments more.

 

[Spare time]

Ghosts of the Ocean: Explaining Marine Life Devoid of Color

ocean.si.edu

It could go either way. With nudibranches it’s plausible the ones closer to the surface evolved to have brighter colors to deter predators and those deeper evolved to be clear to blend in and hide better

But as the article also mentions, it’s a logical theory but not known fact.

Use the word hypothesis and not theory. Sorry it's a pet peeve of mine haha

 

[Spare time]

Most corals aren't "colorful." It's important to keep in mind that the corals in the hobby are not representative of average corals found in the wild. However, the color from my understanding is, as someone else states previously, sunscreen for the corals except for deep water corals who use it for another purpose. I've never heard of corals using color to ward off predators and I doubt it because they are mostly not filled with toxins as another person mentioned. Also keep in mind nothing "evolves to do x." It's not a goal driven process but there are pressures that push organisms in one direction as well as random drifts.

 

[VintageReefer]

There are fish who have spots to look like an extra pair of eyes by the rear fin. Just because it’s “non functional” doesn’t mean it’s purpose is not to deter predators.

Whose to say that some corals use bright colors as a means to appear toxic

And I do understand the pigment is a means for if sunscreen and has other purposes as well.

This is all open conversation and I enjoy throwing another viewpoint out there. I could be wrong it’s all theor…err…hypothesis