Calling all acro anatomy experts!

[lizzyann]

I've been curious about something for a while and can't find much info from Google. What affects the shape and growth of an acro's corallites? Several of my acros came to my tank with cute, fat, rounded corallites that have slowly become thinner, flared, and sometimes even pointy and long!

 

My supposed oregon tort barely even looks like a tort anymore:

 

Before

 

After

 

Side note, or possibly important related note, I know this coral looks awful, I actually just fragged it to save it, the downfall was a much more sudden change than the corallite growth, maybe related, maybe not, that issue is in a separate thread here 

 

Here's my slimer's change:

 

To:

 

Again, this one started really struggling too, I'm trying to frag to save it.

 

So about those pointy corallites! What's going on? Is it flow? Light? Some other parameters? Does corallite shape affect health of the coral? Is it normal? Or is it a sign of bad health? Could it have something to do with these corals' eventual crash?

 

I also have a spathulata whose corallite rims seem thinner, though not as drastically different as these two, though these two have been in the tank the longest. Another flaming unicorn and mad raver milli seem less affected.

 

[lizzyann]

Just for reference, this is a pic from just over a month ago. I've had the slimer and tort since March, and they've always done well until the past two weeks (turning brown/losing color pretty much overnight). It's hard to tell from this angle, but the corallites were definitely stretching then too.

 

[jservedio]

Just like your LPS corals, acros can puff themselves up. The underlying skeleton always looked the same, just the flesh that is over the skeleton has changed. If you've got a healthy stylo, they make it really easy to see just how much SPS corals can change in shape without their skeleton changing.

 

New skeletal growth that is incomplete can look very different. However, in a healthy coral with it's flesh all puffed up, they will look close to normal, but once it recedes or thins out, it looks really different.

[mitten_reef]

Interesting topic, following.   I did have some acros that changed their corallite shapes/forms slightly after being in my tank.  Nothing as drastic as the tort or slimer like the OP's.  

 

11 minutes ago, jservedio said:

New skeletal growth that is incomplete can look very different. However, in a healthy coral with it's flesh all puffed up, they will look close to normal, but once it recedes or thins out, it looks really different.

I think this is definitely one factor. The follow-up question would then be, what if the skeletal growth were just "never" complete, is that possible?  If so, what could cause it?     

[jservedio]

12 minutes ago, mitten_reef said:

The follow-up question would then be, what if the skeletal growth were just "never" complete, is that possible?  If so, what could cause it?     

If you buy an acro from a fellow reefer who has a spectacular tank and their acros grow like weeds and then transfer it to your tank that has very different conditions, for the first few weeks, you will get "carryover growth" from their tank and it'll keep exploding in growth and then basically hit a wall as it starts to adjust to your tank. If you get a ton of rapid growth, but your tank isn't as healthy, then all growth basically shuts off, you will have a lot of young, incomplete corallites for a while (or until it dies). Phosphates can play a role in this as well - they are absolutely required biologically, but when they get too high, they can directly inhibit skeletal growth.

 

This is why a lot of people with newer tanks get their first acro, it does incredibly well for a month or two, and then withers away and dies of STN over the next couple of months.

[jservedio]

Here's a perfect example of a healthy vs. unhealthy tort over time, but in the opposite direction. I got this very unhealthy tort frag about a year ago - it looks pretty similar to yours now (pardon the low res, it's a crop of an already-web-sized FTS):

 

I fragged the top 1/2" off that 1" frag as it was receding and bleaching. Here's the same exact coral today, one year later looks just like a tort should:

 

Other than showing how the same exact acro can look like it has wildly different corallites depending on it's health, you can absolutely save a dying tort from just a 1/2" frag or less if you have patience!

[mitten_reef]

1 hour ago, jservedio said:

If you buy an acro from a fellow reefer who has a spectacular tank and their acros grow like weeds and then transfer it to your tank that has very different conditions, for the first few weeks, you will get "carryover growth" from their tank and it'll keep exploding in growth and then basically hit a wall as it starts to adjust to your tank. If you get a ton of rapid growth, but your tank isn't as healthy, then all growth basically shuts off, you will have a lot of young, incomplete corallites for a while (or until it dies). Phosphates can play a role in this as well - they are absolutely required biologically, but when they get too high, they can directly inhibit skeletal growth.

 

This is why a lot of people with newer tanks get their first acro, it does incredibly well for a month or two, and then withers away and dies of STN over the next couple of months.

I, too, believe in the "carryover" effect.  I nearly use that term in @MrObscura tank journal about sps suddenly not doing well after being in his tank for a couple weeks.  To expand on that, his question was more; happy on frag rack vs not happy after mounting - but the time gap was roughly under 2 weeks since RAP-Chicago).  

 

I did read that high phosphate inhibits skeletal growth by preventing uptake(?) of calcium and carbonate into corals.  

 

you know who might also have some good insight to this discussion?  @markalot. Mark, if you're around, maybe you can chime in on this?  

[mitten_reef]

tagging a few more acroholics that I can think of to see if they have some thoughts on the OP's topic: @xM3THODx, @Asureef, @pokerdobe

[pokerdobe]

I see I have been summoned from my lair. 

42 minutes ago, mitten_reef said:

tagging a few more acroholics that I can think of to see if they have some thoughts on the OP's topic: @xM3THODx, @Asureef, @pokerdobe

 

As for your particular questions - I find that the biggest contributors to my acro's structure is flow and placement of lighting. Too much uni-directional flow will cause my acros to grow in the direction of that flow. If my lighting is insufficient, my acros will grow "towards" the light. 

 

I am however concerned as your tort is showing tissue necrosis and recession from the base. I haven't quite seen it anywhere, but what are your current parameters and has there been any recent swings? A history of the basic 5 parameters would be helpful. 

[mcarroll]

On 10/31/2019 at 11:11 AM, jservedio said:

Phosphates can play a role in this as well - they are absolutely required biologically, but when they get too high, they can directly inhibit skeletal growth.

While there is factual truth in there, I think there are several problems with that theory. 

 

Mostly related to conclusions drawn (decades ago in some cases) from too little data and too much theory.

 

Maybe the main one is that "slower growth" is being used as a marker for "unhealthy". 

 

That's a huge assumption that seems to have little or no basis of support.

 

I know this is mostly just old information.  (Even older than that 2006 posting, which references a defunct 2002 article this link from advanced aquarist.)

 

I think old enough that it was composed before it was realized that skeletal secretion is biologically controlled, not abiogenic as was previoiusly thought.

Biological control of aragonite formation in stony corals

 

I think that info was also based on experiments where only phosphates were elevated, and only on a staccato/intermittent schedule....almost like they were trying to tweak the corals.  Slowed growth (at least) would be expected, IMO.

 

In any event, they were not testing the relative health of corals under natural (or even naturalistic) "high nutrient" scenarios that just happened to include high phosphates.

 

IMO Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates gives a much better (more realistic) view on the effect of "high nutrients" vs "low nutrients". 

 

One (low) is clearly bad, and one (high) is clearly not bad.  (There is middle ground as well, of course.)

 

The best part of that article IMO is the visual evidence where you get side-by-side photos of the coral, a tissue sample of the coral and a photo of the dino-symbiont from that coral:

H=high

L=low

N=nitrates

P=phosphates

(click to the main article for more details)

 

I also don't think anyone then would have been aware of the evidence that faster growing corals seem to be more susceptible to stress and to heal less quickly from damage than slower growing corals:

Fast Growth May Impair Regeneration Capacity in the Branching Coral Acropora muricata

 

IMO at least...

...slow growth is either totally coincidental, or it's actually a sign of good health. 

...under relatively stable circumstances, dissolved phosphates seem to be nothing but good as well.

 

I haven't seen this next one before...

"Crystal growth of aragonite in the presence of phosphate" by Tadier, Solène and Rokidi, Stamatia and Rey, Christian and Combes, Christèle and Koutsoukos, Petros G.

(PDF)

...but it gives a survey of more recent scientific inquiry into the study of phosphates' interaction with calcium carbonate crystals like aragonite. 

 

That aspect of the topic is simply more complicated than we thought.  Yes, there is a set of conditions where phosphates slow crystal growth....but (surprise!!) there's also a phase at even higher phosphate levels where growth is increased. 

 

It's not simply "phosphates = bad", which is pretty much the impression you'd be left with after most of the hobby's phosphate-oriented articles.

 

 

On 10/31/2019 at 11:11 AM, jservedio said:

This is why a lot of people with newer tanks get their first acro, it does incredibly well for a month or two, and then withers away and dies of STN over the next couple of months.

It seems like almost all new tanks these days seem to be systematically starved of phosphates and nitrates (if they aren't also being subjected to a generally unstable tank environment as well). 

 

Dead rock plus filtration (plus massive fear of pests) seems to be "the way" to start a new tank these days.

 

So the equation seems to be:

([new tank syndrome ^ 2] + starvation) = trouble.  

 

Many corals have foundered in that circumstance.  No question that most Acro's would too.

 

 

I think the contrary is true as well though.

 

Even new tanks "can be" suitable even for sensitive corals like Acros, if the proper needs are met (and common problems avoided). 

 

That is a BIG "if" though! 

 

It hinges heavily on the reefkeeper's skill since a dead rock tank isn't capable of much on its own at this point.  (Vs a live rock-founded tank which can be quite forgiving by comparison, even at the beginning.)

 

I've saved references to quite a few good articles on the topic if anyone wants leads to more info like this:

https://reefsuccess.com/tag/nutrients/

https://reefsuccess.com/tag/coral/