polyps at night

[Detritivore]

hey all,

i have noticed that during the day, i get pretty good polyp extension on my acros, but at night, the tentacles on the polyps get even longer (almost 1cm on a certain coral), especially on the axial corallite. (i am pretty sure these are polyps and not mesentaries) then, the next day, i see a little bit of growth. anyone else notice that?

[Aged Salt]

I seen studies showing growth occurs greater at photosynthesis & others demonstrating increased skeletonogenesis during dark periods. This would be a good question to pose to our "Advanced-Forum" experts, Jake[coralite] & Gary[mesocosm]. Bob

[mesocosm]

Greetings All !

I seen studies showing growth occurs greater at photosynthesis & others demonstrating increased skeletonogenesis during dark periods. This would be a good question to pose to our "Advanced-Forum" experts, Jake[coralite] & Gary[mesocosm]. Bob

Bob ... it's like a scene from Ghostbusters, "... we're close ... we're very close ... ."

...


In terms of "growth", we're probably talking about at least three major processes: Colony Formation, Calcification & Skeletogenesis. Three fundamentally different processes that are very interconnected, and which occur during both day and night.

"At various rates and times of the day and night, and through possibly different processes, sections of the coral tissue are lifted up from the skeleton in small areas called lappets" (Borneman, 2001).

Lappets are the space where calcium and carbonate are precipitated on the external surface of the calicoblastic epithelial cells as aragonite. I doubt that this "swelling" is readily visible, let alone directly correlated to polyp extension.

"Night calcification does not seem to result in skeletogenesis. To quote Barnes and Crossland (1980):"It seems possible that the symbiotic association permits rapid growth because the coral can invest in flimsy scaffolding at night with the certainty that bricks and mortar will be available in the morning" (Borneman, 2001).

If we're using "trans calcification" as the model for calcification during skeletogenesis, then we're talking about a process that is primarily driven by photosynthesis.

... i get pretty good polyp extension on my acros, but at night, the tentacles on the polyps get even longer ...

Since we're talking about a photosynthetic coral, this doesn't surprise me a bit. While polyp expansion is sometimes argued to be nothing more than a coral behavior which alters its surface-to-volume ratio (a behavior fundamentally associated with making chemical exchange processes more efficient), it seems to me that night polyp expansion may turn out to be more intimately associated with feeding behavior. Energetically, it makes too much sense. At night, a coral's energy budget isn't centered around photosynthesis ... it's the perfect opportunity for a coral to direct its energy resources towards nitrogen acquisition in a very efficient way. Remember, in Nature, during the nighttime there is rich planktonic nutrient availability in the water column. While you are seeing a correlation between polyp extension and growth, I suspect that it's not a directly causal relationship.

HTH ...