Wire Black Coral helix ?

[Genady]

Some years ago while diving around the island where I live I've noticed that this coral always makes a right-handed helix. I wonder if it might be an adaptive feature or, more generally, what could cause it. I mean, I saw dozens of them and never one turning left...

 

[joigus]

Look up the words "chirality in Nature" and you'll find more wonderful examples of this.

Chirality is the property of being distinguishable from your mirror image.

https://en.wikipedia.org/wiki/Chirality

I don't know whether it's related, but for most proteins, only one chiral version is present in Nature, at least in this part of the galaxy. The left-handed version is here, but the right-handed version is not, or is biologically irrelevant.

[Genady]

Thank you. I know about chirality - in the Standard Model, in chemistry, in biochemistry (e.g. DNA), in biology, too. Most examples in biology I know of have explanations, e.g. chirality of snails. Those are not applicable to corals. Looking for new ideas ...

[StringJunky]

Could it be a response to the direction of the local current? How big that locale might be, I have no idea.

[Doogles31731]

I liked Joigus' reference. Joigus, just to get my own thinking straight, does this chirality apply to dextro- and laevo- isomers of chemicals such as tartaric acid (Pasteur's discovery) and glucose?

I'm interested in an answer to String-Junky's question, and also whether anyone has checked whether the spiral in corals is the same in the northern and southern hemispheres.

[Genady]

Happy to answer all specific questions:

The size of the locale is a couple of dozens mi/km. Depth about 100+ft /30+m. No strong currents, mostly no currents at all, certainly no prevailing currents. Orientation varies - around the island and along a curved shoreline. The location is practically on equator, about 12N, between the hemispheres

[Doogles31731]

Thanks Genady. Does this particular coral grow in only one locality on the planet?

[TheVat]

Between the hemispheres is a description sometimes applied to Kiribati.  Is that the general location?  Chirality in some species, like molluscs, relates to members of a species tending to all spiral one way to ease reproduction.  The adaptive advantage for coral is harder to discern.  Would be interested to see larger sample than a few dozen.   

[Genady]

Here is a description including its distribution. Not in Kiribati. Correct, the reproduction is not an issue for corals. A few dozens of them are all I could find where I dive.

Marine Species Identification Portal : Wire coral - Cirrhipathes leutkeni (species-identification.org)

 

[joigus]

1 hour ago, Doogles31731 said:

I liked Joigus' reference. Joigus, just to get my own thinking straight, does this chirality apply to dextro- and laevo- isomers of chemicals such as tartaric acid (Pasteur's discovery) and glucose?

I'm interested in an answer to String-Junky's question, and also whether anyone has checked whether the spiral in corals is the same in the northern and southern hemispheres.

Thank you. Yes it does apply to tartaric acid and a bunch of sugars, including glucose. Google for "stereoisomers of" and whatever compound you're interested in and you'll get the physico-chemical information.

As to the relevance in biology, I don't know. I hope some experts can illuminate aspects of it at least. I'm not one.

Whether it's an effect due to the currents, it could be for all I know, if eddies tend to form with a particular chirality, which they do. A Coriolis effect, as you suggest, is possible. Maybe @Genady is also a traveller, and can provide more information.

I somehow find it hard to believe that the calcium carbonate scheletons of corals could be shaped by local eddies, but let's see what others think.

Interestingly enough, I've googled for "chirality and corals" and I've found that some calcium carbonate coral scheletons are affected by chirality: 

https://www.nature.com/articles/ncomms15066

Corals and chirality seems to be an active field of research, judging by Google Scholar's search results. Most of what I've seen is targeted at a molecular level.

[Doogles31731]

Once again Joigus, I found that to be a very interesting reference. I found this sentence in the Introduction -- "A remarkable example of change in chirality can be seen in the helical shell of the marine foraminifer Globigerina pachyderma, where in the Arctic and Antarctic oceans the mineralized CaCO₃ shells grow in a right-handed (dextral, counterclockwise) direction; however, for unknown reasons, in temperate and tropical waters, left-handed (sinistral, clockwise) shells predominate^4,5."

This suggests that temperature can have an effect on chirality at the whole organism level.

The paper itself was surprising in that the authors were able to reproduce chirality at will in calcium carbonate crystals by adding either dextro-rotatory or laevo-rotatory acidic amino acids to their solutions - aspartic acid and glutamic acid, I assume. They could not produce chirality with glycine, alanine and lysine additions to their solutions. 

I don't know whether members are familiar with the work of Louis Pasteur or not, but as far as I know he was the first to discover that some crystals were mirror images of one another. As a young chemist (He could have even been a post-grad), he was challenged to solve the mysteries of the chemistry of tartaric acid. Apparently nobody could get consistent chemical reactions with it. He had to go  to the wineries to get tartaric acid crystals. In my younger days, every bottle of claret had a sediment of tartaric acid crystals in it. He spent hours using a microscope studying the crystals and was the first to observe that there was a mixture of mirror-imaged crystals. He grew larger specimens in solutions and observed that one type bent polarised light to the left (laevo-rotatory) and the other to the right (dextro-rotatory). He had discovered enantiomeres.

It's interesting that only laevo-enantiomeres of amino acids are used in the building of proteins.

The  fact that he had to go to the wineries of course subsequently led to the discoveries that micro-organisms are in the air, that they can change the nature of fermentation reactions (vinegar or alcohol); and the standardisation of fermented food products of all kinds, and that micro-organisms could also multiply in the tissues of living organisms as causes of disease.

Almost every time I see a reference to  L- or R- enantiomeres, I tend  to recall that story about Louis Pasteur, and how it serendipitously led to huge advances in the standardisation of fermentable food products and awareness of microbiological processes and diseases.  

[Genady]

It is hard for me to see a chain of causal connections between chirality on molecular level and chirality of a large scale morphology not even of organism but of a colony of organisms.

The water here and specifically on that depth is practically still - the movement of about 1 cm/s or less.

"Black corals" belong to so-called soft corals. They don't have calcium carbonate skeletons. Their "housing" is made of hardened mix of minerals and proteins.

Coriolis effect doesn't appear on such a small scale. Here I have a story to tell. Six years ago I was in Ecuador and visited the Middle of the World, where they have equator line marked on the ground. The guides there gave a bunch of various presentations including the famous one with a water rotating opposite ways while being flashed. They had a tab with a hole, put it on one side of the equator, poured water from a backet and it rotated clockwise. They then relocated the tab to the other side of the equator, poured water - and it rotated counterclockwise. 'Coriolis,' they said. After the presentation I took one of the guides aside and tell her that I know that Coriolis has nothing to do with this and asked her to tell me the secret. She did. The sense of rotation is determined by which side of the hole they pour water to.

  

[joigus]

9 hours ago, Genady said:

It is hard for me to see a chain of causal connections between chirality on molecular level and chirality of a large scale morphology not even of organism but of a colony of organisms.

Take some time to read about homeobox genes and your difficulties will ease considerably. As I said, I'm not an expert, but I do remember development of organism spatial patterns is heavily monitored by homeobox genes and decides what's up, and down, left, or right, where your liver is, and such. Symmetry is also determined by this package of genes, AFAIR.

 

[Genady]

One more piece of information. I've tried to compare my local findings with a global "data" by googling "wire black coral" images. As far as I could identify Cirrhipathes leutkeni in random pictures, I've found all of them right-handed as well.

2 minutes ago, joigus said:

Take some time to read about homeobox genes and your difficulties will ease considerably. As I said, I'm not an expert, but I do remember development of organism spatial patterns is heavily monitored by homeobox genes and decides what's up, and down, left, or right, where your liver is, and such. Symmetry is also determined by this package of genes, AFAIR.

 

Thank you. I took time to read about them about 10 years ago. Yes, building up of an organism is programmed by genes and their is a strange correspondence between the linear order of these genes on DNA and linear order of body parts of bilateral organisms.

However, as far as I remember, in didn't have anything to do with chirality. Plus, coral we discussing is not an organism but a colony of organisms. Plus, it is not bilateral.

[joigus]

Whether something is a colony or not is not a clearcut biologycal category in my opinion. Endosymbiosis* changed that picture, and while we still talk about "organisms", the distinction is blurry at best. Kelp is a multicellular protist. Eukaryotes have plastids (genetically-independent inclusions). I consider myself a colony that includes intestinal bacteria, my mom's mitocondria, etc. Yet my liver is on the right because my homeobox genes ordered developmental hormones that made my stem cells put it there.

*Among other things.

'My liver is on the right' is chirality, not of such sublime beauty as an helical coral. But chirality it is, and monitored by homeobox genes.

 

Edited December 27, 2021 by joigus

[Genady]

I think, my main point of curiosity in this phenomenon is, how these small organisms, each a few mm across and apparently radially symmetrical, genetic clones of each other, determine uniquely a global morphology of the structure 1000 times larger than themselves. Perhaps, it is an emergent feature, but how?

[Genady]

I got an idea. Firstly, we can assume that the polyps can chemically sense their neighbors. This thing is quite common and I think such an assumption is safe. Let's call it, Assumption 1.0.

Secondly, let's assume that they are programmed by their genes to grow in such a way as to minimize interference with their neighbors in a given neighborhood. This is good for filter feeding. Let's call this, Assumption 2.0.

Such a program will lead them to make a linearly arranged colony. This seems like a promising beginning. Now, how do we modify these assumption and add to them to get eventually to the right-handed helix?

[joigus]

Your assumption No. 1 is a must; otherwise there's no way you can correlate internal chirality with overall growth pattern that displays chirality. It stands to reason.

Your assumption No. 2 I don't see as necessary. If you can tell your head from your feet, and your liver-side from your non-liver-side, it's child's play to write an instruction (internal) in your memory that says: If your neighbour is to your left, hold hands and bend this way.

Minimize interference is not necessary. In fact, you must interact and correlate. The important thing is to correlate how you bend, how your neighbour bends, and what side you face to them --I think. You can 'amplify' chirality any way you want with these prescriptions --I think.

Edited December 27, 2021 by joigus

[TheVat]

Perhaps the common helical orientation relates to crowding effects?  Where these helical strings cluster more thickly, a transient event like a storm would generate some currents even in this placid zone and the strings would bump into each other - when they have common chirality, they are less likely to get tangled in each other, and so each colony thrives more.  (where they stay tangled, perhaps it's more likely some large swimming creature will run into the tangle and tear it up or uproot) This might (I know this is a stretch) exert a small selective pressure over time for a single chirality.   

[Genady]

17 minutes ago, joigus said:

If you can tell your head from your feet, and your liver-side from your non-liver-side...

That is what they can't do. They are radially symmetrical miniature upside-down jellyfish.  

[joigus]

 

22 minutes ago, TheVat said:

Perhaps the common helical orientation relates to crowding effects?  Where these helical strings cluster more thickly, a transient event like a storm would generate some currents even in this placid zone and the strings would bump into each other - when they have common chirality, they are less likely to get tangled in each other, and so each colony thrives more.  (where they stay tangled, perhaps it's more likely some large swimming creature will run into the tangle and tear it up or uproot) This might (I know this is a stretch) exert a small selective pressure over time for a single chirality.   

The problem I see with crowding effects is that one way or the other (one chirality or the other) makes no difference to the effects of getting tangled, as long as all the individuals (colonies or whatever) become helical in the same way. If that were the case, we would see left-handed colonies as often as right-handed ones. Also with eddies and currents playing a role, I would expect to see regional differences. All this, of course, taking at face value:

2 hours ago, Genady said:

One more piece of information. I've tried to compare my local findings with a global "data" by googling "wire black coral" images. As far as I could identify Cirrhipathes leutkeni in random pictures, I've found all of them right-handed as well.

The effect you propose is not to be ignored in many cases. There are mossy plants in New Zealand that grow to exactly the same height, so as to form a collaborative pad that's useful to protect the whole community against frost. Any plant that grows above that is penalised, because it losses protection. With chirality though, it's either this way or the other, --a binary menu of possibilities, shall we say-- which suggests to me a developmental mechanism based on molecular grounds.

I'm not sure though, and I wish this OP gets the contribution of experts ASAP.

x-posted with @Genady

11 minutes ago, Genady said:

That is what they can't do. They are radially symmetrical miniature upside-down jellyfish.  

That's interesting. I can't find this information on the web. Can you give me a pointer to that, please?

Edited December 27, 2021 by joigus

[Genady]

A bit OT here:

@joigus I also wish experts would contribute, but I didn't have a good experience with them. I emailed a few when this was fresh. Two replied. One just said, they never noticed such a pattern. The other said, they think I am wrong and the corals turn either way. They even attached a few pictures. Guess what? On all the pictures the corals were right-handed! This expert perhaps is a good biologist, but there is some issue with 3D geometry there

52 minutes ago, TheVat said:

Where these helical strings cluster more thickly...

In fact, they don't cluster thickly - there is half-meter or more between the loops and they don't bend easily. When there is some current, the entire thing just bends the other way, like a windsock.

Edited December 27, 2021 by Genady

[TheVat]

Thanks.  I was tossing out bad ideas, in hopes a good one would appear.  And, it occurred to me after posting, that the direction of coiling could simply be what Gould and Lewontin called a spandrel.  It is just a byproduct of some other feature that is adaptive.  (like, say, mooring consistency) Somewhere in the instructions for polyps attaching, as they evolved, it was simpler to have one instruction, like "extend a knot of cells for mooring the next fellow there on the upper right."  If you had a binary choice of instructions, you would just get a less stable mess, so at that evolutionary fork in the road, selective pressure was strong for one path to be taken.  It didn't really matter if it was left or right coiling, just that it was consistent all through the genome. 

BTW, I liked your Coriolis anecdote. 

Postscript on spandrels, for those who may be new to the concept:

Gould and Lewontin defined a biological spandrel as a byproduct of evolutionary adaptation. Simply put, they’re like ‘leftovers’ of some other trait that evolved. This means that the spandrel isn’t an adaptation to anything in the environment. Instead, it is a secondary trait that arose from the development of another primary trait.

The easiest spandrel to visualize is the human chin. One hypothesis about why humans are the only animals that have a chin is that it is merely a byproduct of the growth of different parts of the jaw.

The word spandrel comes from the architectural feature that Gould happened to notice in St. Mark's Basilica.  He wanted to distinguish between the way it was presently used and its actual architectural reason for being there. 

Edited December 27, 2021 by TheVat
pyto

[Genady]

@TheVat I was thinking in the same direction and got an idea of where the chirality leading to that byproduct could start. Although the body of polyp is radially symmetrical, the budding process is not. See illustration below. This provides an opportunity to make a "one-sided liver", like in the @joigusexample above. If the genetic instructions of this coral cause a baby polyp to be a bit tilted say to the right, the next clone will be tilted again to the right, and so on, and voila, we get a helix with the specific chirality.

Thanks a lot for the contributions!

 

Edited December 27, 2021 by Genady

[joigus]

1 hour ago, Genady said:

@TheVat I was thinking in the same direction and got an idea of where the chirality leading to that byproduct could start. Although the body of polyp is radially symmetrical, the budding process is not. See illustration below. This provides an opportunity to make a "one-sided liver", like in the @joigusexample above. If the genetic instructions of this coral cause a baby polyp to be a bit tilted say to the right, the next clone will be tilted again to the right, and so on, and voila, we get a helix with the specific chirality.

Thanks a lot for the contributions!

 

The problem is:

 

 

In other words, you said the polyps are cilindrically-symmetric. In that case, whatever you call the left, turn around 180 degrees and, voila, it's the right.

 

Edited December 27, 2021 by joigus
wrong image