Night Lights and Polyp Extension

[gtrider]

Hello fellow reefers!

I run a Radion xr30 pro over my 65g sps dominant DT. I noticed the other night when my night light moon-cycle had the lights completely off i was getting amazing polyp extension on my SPS. When i checked the past few nights where the night light was on, there was a lot less extension.

Has anyone had this experience? I would assume better polyp extension would equate to faster growth... no?

 

[C. Eymann]

Hello fellow reefers!

I run a Radion xr30 pro over my 65g sps dominant DT. I noticed the other night when my night light moon-cycle had the lights completely off i was getting amazing polyp extension on my SPS. When i checked the past few nights where the night light was on, there was a lot less extension.

Has anyone had this experience? I would assume better polyp extension would equate to faster growth... no?

Aside from growth nocturnal axial corallite polyp extension is one of the best indicators of Acropora health/stability.

As far as moonlights go, I am not a fan and studies have shown many of the moonlights or moonlight settings on the market are far too bright and show little if any benefit at all. Many can actually be disruptive to biological cycles of coral and other animals.

If you have ever been on a night dive, even on a full moon, its pitch black even at only 20ft or so, when you cover or turn off your dive lamp, you are surrounded by blackness.

Fossa and Nielsen did a study involving moonlights in captive reefs, I'll try to dig that up if I can.

 

[gtrider]

Aside from growth nocturnal axial corallite polyp extension is one of the best indicators of Acropora health/stability.

As far as moonlights go, I am not a fan and studies have shown many of the moonlights or moonlight settings on the market are far too bright and show little if any benefit at all. Many can actually be disruptive to biological cycles of coral and other animals.

If you have ever been on a night dive, even on a full moon, its pitch black even at only 20ft or so, when you cover or turn off your dive lamp, you are surrounded by blackness.

Fossa and Nielsen did a study involving moonlights in captive reefs, I'll try to dig that up if I can.

@C. Eymann Thanks for this response! I would love to see that study if you can dig it up!

 

[Softhammer]

I totally agree with Eymann above. Even a blue light at 1% power on the new fixtures is way way too bright. Night lights should be barely a shimmer. I have had acros spawn using the lunar cycles from a Tunze controller which uses a single white old school low power LED. The moonlight settings on high end fixtures, I think are perceived as almost daylight to the corals so they don’t totally open up. It is my humble opinion that it’s important to allow the corals the dark time to allow for full polyp extension. That’s when peak feeding occurs and just so happens all the nocturnal plankton is out and about. Live food, the best there is, and also not even remotely a coincidence timing wise.

 

[gtrider]

@Softhammer thank you for the response! I think it makes perfect sense and i would agree that might night light was way too bright during certain moon cycles. I've turn off my night lights completely. I do have a little blue flashlight which will allow me to check things out

 

[jda]

Polyp extension on SPS is mostly for gas exchange. They are out more at night because there is no photosynthesis to help them respirate. This has nothing to do with the lights directly, but indirectly it does because with lights out, the corals have to rely on gas exchange through the polyps.

Again, this is not a reaction to the light in a direct manner.

 

[SeaDweller]

I get the MOST PE when all lights are off in the DT. Whether or not it's because of whats said above, I don't know.

 

[C. Eymann]

Polyp extension on SPS is mostly for gas exchange. They are out more at night because there is no photosynthesis to help them respirate. This has nothing to do with the lights directly, but indirectly it does because with lights out, the corals have to rely on gas exchange through the polyps.

Again, this is not a reaction to the light in a direct manner.

While gas exchange may play a part in nocturnal PE, my understanding is Acropora primarily feed at night and that plays a large part of it,
As far the reasoning behind using nocturnal axial polyp extension to gauge acro health/stability is that stressed/unhappy acropora will not waste precious energy to capture and digest food particles if under stress, and I saw it in my experience working at a few LFS and one that can only be described as a chop shop that would import lots of WC acros for fragging.
Right after we would get these acro colonies in, there would be no nocturnal axial corallite tentacle extension for the first few nights, but after a few days when they became settled they would start presenting nocturnal axial PE.


I haven't been able to find the article on the study Fossa and Nielsen did on moonlighting , I may have read it in their 3 volume series.

Either way, that is my experience/understanding.

 

[jda]

They have to extend to exchange gas, at least some. They do not have to extend as much if they are stressed and not growing - this is likely what happened after shipment. This is why PE is a sign of nothing... it can be a false positive as well as a sign of real trouble. The best that I can tell people is to look for color and growth as about 99% of your indicators and just look for "different" PE than you normally have.

No acropora needs fed. Feeding acropora is a used too much as an excuse, red herring or other in our tanks where there is absolutely no evidence that anything that we feed can be caught (outside of some poci species) nor that what we feed is worth the energy used to catch and digest. There is plenty of evidence that corals do not need to catch anything at all.

PE can really come out a LOT if excess ammonia or other organics that inhibit respiration and photosynthesis are present in the water and the coral is having trouble exchanging gas - this is not a good thing, so I don't want people to think that lots of PE is always good.

 

[C. Eymann]

They have to extend to exchange gas, at least some. They do not have to extend as much if they are stressed and not growing - this is likely what happened after shipment. This is why PE is a sign of nothing... it can be a false positive as well as a sign of real trouble. The best that I can tell people is to look for color and growth as about 99% of your indicators and just look for "different" PE than you normally have.

No acropora needs fed. Feeding acropora is a used too much as an excuse, red herring or other in our tanks where there is absolutely no evidence that anything that we feed can be caught (outside of some poci species) nor that what we feed is worth the energy used to catch and digest. There is plenty of evidence that corals do not need to catch anything at all.

PE can really come out a LOT if excess ammonia or other organics that inhibit respiration and photosynthesis are present in the water and the coral is having trouble exchanging gas - this is not a good thing, so I don't want people to think that lots of PE is always good.

I was referring to nocturnal axial corallite polyp extension only, not just PE in general and I never said anything about Acropora needing to be fed additional foodstuffs in our reefs to survive. However I do believe feeding certain food suspensions can be beneficial to them.
I simply just said that they actively feed at nighttime, both in our aquarium and in the wild.

I'm interested in your ideas of the gas exchange "theory" do you have source or an article where you read that? sounds really interesting.

 

[Charlie’s Frags]

It’s hard to see in the pic but the axial corallite polyp caught a morsel of meat and has been slowly working on it for the last 4 hours. I see this all the time with my polyps. Everything I’ve ever read or watched about corals is that polyps are used to catch food particles, and polyp retraction was the first phase of any coral demise. Every time. So to me, PE is a very good indicator of coral health.

 

[jda]

It is coral anatomy 101, not a theory. There are probably thousands of volumes on it that you can find if you want to read up. There are probably lots of archives from Fenner on WWM if you can stand all of the < and > and layout.

 

[jda]

If you are going to research "polyps," be sure and not confuse the many different types of the word. Polyps of Z&P are colonial anemones, star polyps are different than polyps on LPS which are different than on montis or on birdsnest or on acropora.

...or polyps on a NPS which do need to exchange gas even more since there is not photosynthesis but also need to catch a lot of food.

 

[Charlie’s Frags]

I can’t find anything about gas exchange. Everything I’ve read states the polyp has 2 functions, a mouth for capturing phytoplankton and an anus to expel waste.

 

[C. Eymann]

If you are going to research "polyps," be sure and not confuse the many different types of the word. Polyps of Z&P are colonial anemones, star polyps are different than polyps on LPS which are different than on montis or on birdsnest or on acropora.

...or polyps on a NPS which do need to exchange gas even more since there is not photosynthesis but also need to catch a lot of food.

Well, we are talking about the genus Acropora specifically when it comes to nocturnal axial corallite extension so -


"As sessile organisms, coral behavioral changes include polyp and tentacle extension and
retraction, which often display diel patterns (Levy et al. 2006). Tentacle behaviors, which may help
the animal avoid predation while maximizing photosynthesis, heterotrophic feeding and gas
exchange (Levy et al. 2006), appear to be light-responsive, but may also have a circadian
component of regulation (Tsang et al. 1997; Levy 2003). In some corals, such as the Caribbean
Acropora corals, tentacle behavior varies between different parts of the colony (E. Hemond & S.
Vollmer, personal observation), suggesting complex regulation beyond uniform light-response.
Tentacles of Symbiodinium-rich radial polyps throughout most of the colony are extended during
the day to capture light and remain extended at night, while axial polyps at the tip of the branch,
which contain few Symbiodinium, are retracted during the day and only extended at night for
feeding on active zooplankton."


I have yet to see anything regarding gas exchange and noctural axial corallite extension specifically in Acropora in my searches, I have only read of the axial corallite polyp extension being associated with feeding.

 

[jda]

Do you mean except for the part of that quoted paragraph that says that all tentacles are for photosynthesis, feedings and "gas exchange?" Levy et al. 2006 would be upset that you missed it.

If you don't want to believe me, then don't. If you want to test it out, get a water/viewing box, put a frag in it under the light and let the coral sit in the stagnant water for a while and watch the polyps really, really extend. This is not a good thing since the coral is struggling to exchange gas. This is how some vendors get the really good PE that you see in some of their photos. ...or just turn all of the pumps off in your tank for 30-60 minutes... leave the lights on so that you can eliminate that variable.

There are three pages about this in Veron book. Maybe BRS needs to do a video about it so that the newer generation can understand.

 

[C. Eymann]

Do you mean except for the part of that quoted paragraph that says that all tentacles are for photosynthesis, feedings and "gas exchange?" Levy et al. 2006 would be upset that you missed it.

If you don't want to believe me, then don't. If you want to test it out, get a water/viewing box, put a frag in it under the light and let the coral sit in the stagnant water for a while and watch the polyps really, really extend. This is not a good thing since the coral is struggling to exchange gas. This is how some vendors get the really good PE that you see in some of their photos. ...or just turn all of the pumps off in your tank for 30-60 minutes... leave the lights on so that you can eliminate that variable.

There are three pages about this in Veron book. Maybe BRS needs to do a video about it so that the newer generation can understand.

Yes I saw that part, but again that applied to PE in general, daytime or nighttime, but here we are discussing nocturnal axial corallite polyp extension specifically, not PE in general.


newer generation reefer? Are you referring to me? because I think you are mistaken there.
;-)

 

[jda]

...so take the next step...

What happens at night when the zoox is not producing gases and sugars and the coral still needs to expel and grab certain gasses? More gas exchange... more polyp extension.

 

[C. Eymann]

...so take the next step...

What happens at night when the zoox is not producing gases and sugars and the coral still needs to expel and grab certain gasses? More gas exchange... more polyp extension.

I still think you are missing the point here and are applying this to polyp extension in acropora in general, nocturnal or not, AGAIN we are specifically only talking about nocturnal AXIAL corallite polyp behavior/extension.


and I am not saying you are wrong when it comes to gas exchange and PE in general, nocturnal or not.

But we are specifically discussing axial corallite polyp extension only !

 

[jda]

I know, and I am telling you that nearly all of the difference that you are seeing between night and day is because of gas exchange. The polyps are out more at night because the corals need them to extend more to respire since photosynthesis is not providing this benefit to the coral during the night hours. It is that simple.

Levy et al., mentions this behavior being circadian, which sparked an interesting debate that I watched at a show about two decades ago, or so, in St. Louis. They were trying to figure out if this was physiological or if it was environment. Unfortunately, no conclusions were reached.