Reason for Polyp Extension?

[diverbh4]

I was wondering why we strive to have polyp extension for our sps when in the ocean, most corals do not have any? Also, many zoas are flat against the rock they are on versus being able to see the "stalk".

 

[jazzsam]

Very good question but I don't have the answer for you. I will see who does and watch this thread though.

 

[jarrodsanborn]

This is just my un educated guess.....
The amount of usable light(par) we have in our tanks is often dismally low compared to the ocean being slammed with light from the sun. In an attempt to adapt to the lower light levels the corals will stretch, and extend polyps to increase surface area.

In out tanks we have either on or off for the light(not counting actinic)
The sun however is a varying light source and increases and decreases brightness daily. The corals can ride the line of photo inhibition easier in the ocean than in our tanks thus not needing to stretch for light. If the corals have been in captive conditions for thousands of generations....with un changing light source, i would imagine the coral would adjust to the situation and reduce polyp extension.

 

[DoctaQ]

also fish can affect it. i saw a tank where the acros were growing crazy but didnt extend thier polyps because of the fish in the tank

in the wild corals open up at night too

 

[diverbh4]

I have seen this same thing (minimal to no PE) at 80+ depth though...maybe it is a nutrient thing?

DoctaQ- Do you think it was a fish touching the corals issue or nutrient issue? I am trying to find some of my pics of night dives to see if there is PE then as well, I know LPS will put out their feeders but they also do that during the day.

Maybe I am curious as to why there is PE in the first place...light, food, they wanna show off to their coral neighbors...

 

[DoctaQ]

it was fish touching the coral, also there were fish that are known to pick on the coral too..i imagine it wasnt much of a nutrient issue

polyps catch food mostly..and sting

 

[diverbh4]

it was fish touching the coral, also there were fish that are known to pick on the coral too..i imagine it wasnt much of a nutrient issue

polyps catch food mostly..and sting

The issue I have with this is that in our tanks when a fish touches a coral, the polyps go away but come back...in the wild I saw that every colony had no extension.
Also if polyps catch food then would minimal polyp extension mean there is enough food for it to not need to expend the energy to extend their polyps?

 

[Jocko]

Just totally making stuff up off the top of my head, my first guess would be something along those lines of them not needing to extend their polyps all of the time because there is so much plankton in the water for them to feed off, they are probably more "full." Whereas in our tanks the plankton levels are pathetic at best so they always have empty bellies. Then again maybe they are hiding from the intense sunlight. Who knows. Those would be some fun experiments to conduct. Anybody got a small fusion reaction they could mount over a tank?