Lifespan of corals

[aninjaatemyshoe]

I'm not sure how many other people have thought much on this, but does anyone know how long corals actually live? Are they "immortal" like sponges, or do they reach senescence and die?

[mfp1016]

I'm pretty sure most will just keep growing and growing under perfect conditions. But even in the wild something can and will statistically happen. I know that there are several large Porites corals off the GBR that are thought to be well over 800 to 1000 years old. Just an example, I'm sure someone will chime in.

[IPT]

I guess it depends on the specices. I'm sure some of the big cloanies live forever in a sense. As it builds probably some of the lower polyps die but the higher newer polyps are probably thriving with new ones budding all the time. Without disease or catastrophy I see no reason they couldn't "grow" for ever.

[MCsaxmaster]

Some appear to be theoretically immortal. Some appear to senesce and supposedly the genes for senescense have been found in some corals.

Once they actuall reach a size where we can see them, most corals on Pacific reefs live a decade or two, though they can theoretically live much longer. On those same reefs it is not at all uncommon to find corals that are many decades or even a few centuries old. Rarely corals may survive to be several centuries old or even over 1000 years. Typically massive Porites and Diploastraea are the corals that will live to be very, very old.

In the Caribbean the corals tend to be a bit longer lived and the average age is likely a few decades. Montastraea spp., which are major reef-builders in the Caribbean, regularly get to be hundreds of years old. Some of the other major reef-builders like Diploria spp., Colpophyllia natans, etc. can get to be very old as well. Acropora in the Caribbean can likely live quite a long time as well, though most of them are dead nowadays.

On the other end of the spectrum, Favia fragum never gets that big. Most are the size of a golf ball or smaller--a size they can reach in a few years--and only rarely will you find one as big as a baseball. Why don't they live a long time and get very big like their relatives? I couldn't say, but nonetheless you'll never find big F. fragum in the field like you will with other Caribbean faviids.

[SuperNerd]

I've wondered about this too. But is it the life of the colony as a whole or each individual polyp?

[MCsaxmaster]

<a href=showthread.php?s=&postid=11637846#post11637846 target=_blank>Originally posted</a> by SuperNerd
I've wondered about this too. But is it the life of the colony as a whole or each individual polyp?

Well, I suppose the two are not necessarily mutually exclusive, if the primary polyp survives as long as the colony. In a colony all of the polyps are genetically the same as all the others and in most corals the polyps remain attached via tissue over the coenosarc. While an individual polyp could certainly be detached and grow into another colony, therefore allowing us to think of it as an individual, the entire colony is grown from a single planula, thus we could just as easily think of the colony as an individual.

For example, if we look at the age of a plant (e.g., a tree) we'd want to know how long ago it sprouted from a seed. While we can make cuttings of most plants and successfully grow a new plant we probably wouldn't consider a new branch from a tree, or a leaf from a plant a new individual. It can be made to grow into another entity, but it is most certainly a part of the original individual.

Thus, for corals that are colonial and maintain tissue connections, I'd think of the entire colony as an individual with many mouths, though any one of those pieces is in fact capable of producing a new colony.

So, when we talk about the age of a coral, usually we would mean how long ago it settled as a larva and started growing.

cj

[luke.varga]

Colonies of some Acropora and Pocillopora species when they reach their adult size do not live longer than 4-5 years.

[Carnavor180]

lots of corals collected should be left in the ocean, only ones that are proven good in captivity should be colected.

[aninjaatemyshoe]

Carnavor, how is that at all related to what we're talking about?

[zeusfc]

<a href=showthread.php?s=&postid=11640270#post11640270 target=_blank>Originally posted</a> by aninjaatemyshoe
Carnavor, how is that at all related to what we're talking about?

OF COURSE IT'S RELATED!

if something is going to live for a thousand years in the wild, or two weeks in your tank, what sort of selfish individual would want to take it?

the lifespan of corals is directly related to their environment... that's why global warming is such a big issue.

in 50 years this conversation coul go...

"what's the lifespan of corals in the wild"?

"corals live in the wild"?

see my point

[garygb]

On the anemone/clownfish forum, someone asked a question regarding whether an anemone would contribute to the bioload. Assuming an anemone is healthy and fully colonized with zooxanthellae, how much of a contribution would you expect an anemone to make to the bioload. Most aquarists direct feed their anemones, and I just wonder what percentage of the food biproduct (ammonia) is utilized by the zooxanthellae. I'm confident that some of the ammonia is released into the aquarium, but I also remember reading that the algae can also directly utilize some of the ammonia that is produced. Likewise, I understand that the zooxanthellae also use nitrates. Can anybody explain this a little better to me?

[garygb]

I'm sorry, I thought I was starting a new thread. Didn't mean to hijack.

[aninjaatemyshoe]

<a href=showthread.php?s=&postid=11642458#post11642458 target=_blank>Originally posted</a> by zeusfc
OF COURSE IT'S RELATED!

if something is going to live for a thousand years in the wild, or two weeks in your tank, what sort of selfish individual would want to take it?

the lifespan of corals is directly related to their environment... that's why global warming is such a big issue.

in 50 years this conversation coul go...

"what's the lifespan of corals in the wild"?

"corals live in the wild"?

see my point

This is just asinine. The point that was made was in no relation the question. Not only that, it was a generic one sentence response. I didn't ask the question to delve into an ethical discussion on reef keeping, I asked it because I was unsure of the biology. I'm sorry to the others that find this kind of discussion important (I do as well), but personally I see it as a hijack. Using the same logic, one could bring up this discussion in just about every thread on this entire site. Just because it is important doesn't mean that it is relevant.

[ahullsb]

It's an interesting subject to me as well. I'd like to hear more about this from you mairine biology majors so we don't get off topic.

[ahullsb]

It's an interesting subject to me as well. I'd like to hear more about this from you marine biology majors so we don't get off topic.

[greenbean36191]

Is there something in particular you would like to know more about?

[ahullsb]

<a href=showthread.php?s=&postid=11638006#post11638006 target=_blank>Originally posted</a> by MCsaxmaster
Well, I suppose the two are not necessarily mutually exclusive, if the primary polyp survives as long as the colony. In a colony all of the polyps are genetically the same as all the others and in most corals the polyps remain attached via tissue over the coenosarc. While an individual polyp could certainly be detached and grow into another colony, therefore allowing us to think of it as an individual, the entire colony is grown from a single planula, thus we could just as easily think of the colony as an individual.

For example, if we look at the age of a plant (e.g., a tree) we'd want to know how long ago it sprouted from a seed. While we can make cuttings of most plants and successfully grow a new plant we probably wouldn't consider a new branch from a tree, or a leaf from a plant a new individual. It can be made to grow into another entity, but it is most certainly a part of the original individual.

Thus, for corals that are colonial and maintain tissue connections, I'd think of the entire colony as an individual with many mouths, though any one of those pieces is in fact capable of producing a new colony.

So, when we talk about the age of a coral, usually we would mean how long ago it settled as a larva and started growing.

cj

Posts such as this one. And in what location have they found coral that is 1000 years old?

[WarrenG]

I remember diving at either Belize or Cozumel where I swam next to a closed brain coral/colony that was about the size and shape of a VW bug (car), and I wondered how old it was.

I've also seen purple barrel sponges that were about the size and shape of a 60 gallon garbage can. And what's inside at the bottom of those big barrels? Often, it's a bristle star or two.

I saw some very large soft corals in Fiji. The largest that I saw was when we were on a dive site that was essentially undiscovered a month prior and it was hidden/protected within a small cave/swim-through. It was bright orange, it's trunk was about a foot in diameter, and it stood about 4 feet tall and almost as wide. I have video of it somewhere.

I also have video of my wife swimming next to two different gorgonian fans that are each near 7 feet wide and tall.

[BeanAnimal]

This is a very interesting thread. I suppose that there is actually very little research done on this subject? I too would like to hear more about what is known.

[MCsaxmaster]

<a href=showthread.php?s=&postid=11678194#post11678194 target=_blank>Originally posted</a> by ahullsb
Posts such as this one. And in what location have they found coral that is 1000 years old?

On most developed reefs you can find corals in excess of 400-500 years old. Really, really old corals can be found here and there in most any region.

I mean, consider the growth rates of a head coral and consider that you can often find massive corals the size of cars on many if not most reefs. If a colony of Montastraea faveolata (Mountainous Star coral, Caribbean) is a good 5 m across and has a linear extension rate of typically a few mm per year, assuming it is extending in all directions, it will take it at least 300 years to reach 5 m across, probably more like 500 years+. Branching corals normally grow much, much faster, but a single colony may occupy a huge space. You used to be able to find stands of Acropora cervicornis covering hundreds of square meters all over the Caribbean. There aren't many places that is still true, but nonetheless those stands may have been produced by corals that settled as planulae many centuries and even millenia hence.

If you go to really deep stretches on a coral reef (say 100 m down) some of the very large gorgonians and such will be on the order of thousands of years old. Some cold-water corals like Lophelia pertusa can live to be thousands of years old as well. Many of these animals do not senesce, and if nothing kills them they just keep on living and growing.

Chris

[KingDiamond]

<a href=showthread.php?s=&postid=11678960#post11678960 target=_blank>Originally posted</a> by MCsaxmaster
On most developed reefs you can find corals in excess of 400-500 years old. Really, really old corals can be found here and there in most any region.

I mean, consider the growth rates of a head coral and consider that you can often find massive corals the size of cars on many if not most reefs. If a colony of Montastraea faveolata (Mountainous Star coral, Caribbean) is a good 5 m across and has a linear extension rate of typically a few mm per year, assuming it is extending in all directions, it will take it at least 300 years to reach 5 m across, probably more like 500 years+. Branching corals normally grow much, much faster, but a single colony may occupy a huge space. You used to be able to find stands of Acropora cervicornis covering hundreds of square meters all over the Caribbean. There aren't many places that is still true, but nonetheless those stands may have been produced by corals that settled as planulae many centuries and even millenia hence.

If you go to really deep stretches on a coral reef (say 100 m down) some of the very large gorgonians and such will be on the order of thousands of years old. Some cold-water corals like Lophelia pertusa can live to be thousands of years old as well. Many of these animals do not senesce, and if nothing kills them they just keep on living and growing.

Chris

I think that your above example is a good reason to keep in mind that individual poylps are individual animals. When we talk about the age of a "coral" most are refering to the colony as a whole. Polyps on a colony probably die frequently (eaten by predators, killed by other corals ect..) but can be replaced by new members of the colony. When compaired to a social animal like ants you can see that individuals are not as important as the whole. If an individual ant dies in a colony (save the Queen) it really is not missed because of the constant reproduction and growth of the colony. Coals (individual polyps) probably don't live all that long, while the whole colony can live for many many year.

[BeanAnimal]

I understand the reasoning behind your comments, but am not sure I agree on par.

The details may vary by species, but I am not sure that you can define the individual polyps as individual animals in all cases. I could be VERY wrong though.

[KingDiamond]

<a href=showthread.php?s=&postid=11679633#post11679633 target=_blank>Originally posted</a> by BeanAnimal
I understand the reasoning behind your comments, but am not sure I agree on par.

The details may vary by species, but I am not sure that you can define the individual polyps as individual animals in all cases. I could be VERY wrong though.

Invertebrate Zoologists define each individual polyp as an individual animal.

[BeanAnimal]

Would it then follow that any single polyp from any coral could be cut away and used to form a new colony? I did not think that this was always the case.

[BeanAnimal]

Let me take that step further as well. Take a big soft sinularia for example. There is MUCH more there than just polyps isnt there? The whole "coral" acts as a whole retracting and expanding. What is the rest of the tissue? If we slice away all of the fuzzy polyps, more will grow. If we cube a section from the center of a stalk (with no exterior tissue) will the cube survive by growing polyps?

[MCsaxmaster]

<a href=showthread.php?s=&postid=11679586#post11679586 target=_blank>Originally posted</a> by KingDiamond
I think that your above example is a good reason to keep in mind that individual poylps are individual animals. When we talk about the age of a "coral" most are refering to the colony as a whole. Polyps on a colony probably die frequently (eaten by predators, killed by other corals ect..) but can be replaced by new members of the colony. When compaired to a social animal like ants you can see that individuals are not as important as the whole. If an individual ant dies in a colony (save the Queen) it really is not missed because of the constant reproduction and growth of the colony. Coals (individual polyps) probably don't live all that long, while the whole colony can live for many many year.

An individual of a species is typically defined as a genetically unique member of that species.

A colony of ants (or other social animal) includes many individuals. They are all very close relatives (all sisters with ants/bees), but they are individuals nonetheless. They are produced by sexual reproduction and are genetically distinct. A coral colony is completely different. New polyps are produced as asexual buds and in most corals the polyps maintain tissue connections to all other polyps. This is all genetically the same tissue and the same individual.

If some polyps are killed--say the colony gets partially buried with sand--some of the tissue that makes up that colony will die but the individual remains. As the coral grows it may resheet over the skeleton, but it may just as easily sheet over rock, over coralline algae, or over other objects.

While it is true that a single polyp can be separated from the rest of the colony to produce a new colony, the same can be done with many other organisms without us considering each little piece a separate individual. We don't consider every leaf of a tree a new individual. We wouldn't say a 100 yr old deciduous tree growing back its leaves in spring is only a few weeks old, though that may be the age of its leaves.

And for that matter, consider that in living things the very atoms that make up our tissues are replaced regularly. If asked I'd say that I am 24 because I was born 24 years ago. If you examine the chemical makeup of my body, however, you'll find that most of the atoms in my body have been part of my body for only a few months. You'll also find that essentially none of the atoms I was born with remain in my body. Does this mean I'm only a few months old? Certainly not!

I will grant you that due to the colonial nature of corals and the propensity of some species to reproduce asexually due to fragmentation muddies the waters. However, in massive corals where fragmentation is uncommon the age of the coral is, by convention, typically thought of as the number of years before present the planula that produced that colony settled. In branching, foliaceous, etc. corals that are more easily fragmented we'd like to apply the same definition, but the practicality of things is such that it is sometimes difficult in the field to determine if adjacent colonies were produced by different sexual recruitment events (two different planulae) or if the colonies resulted from fragmentation of a single colony. Knowing the difference is very important, howver.

For example, we see that throughout its range the genetic diversity of Acropora cervicornis is not terribly high primarily because fragmentation and reattachment is usually more common than sexual reproduction. Thus, on an entire reef there may only be a few individuals (= genetically distinct) though there may be many colonies. This is similar for Acropora palmata in the West Caribbean/Atlantic whereas sexual reproduction is a more common source for new colonies of A. palmata in the East Caribbean.

We might be tempted to call clones of the same organism different individuals, but from a biologically relevant perspective we really shouldn't. We really should use different terms. In fact such terms are typically used. Genetically different individual of corals are called genets. Different colonies that are genetically the same (= the result of fragmentation) are called ramets.

Genetically distinct members of a species are what we usually mean when we say "individual" and probably what we should save this term for. To refer to genetically indistinct members we should probably talk about "ramets" or "clones" because, while separate and living separately, this are by many biologically relevant measures the same "individual."

Chris

[MCsaxmaster]

p.s. And just to be clear, particular polyps within a coral colony often will be as old as the entire colony. For many corals all the polyps remain as part of the colony, even if they are not in an actively growing part of the colony. Think foliaceous or massive Montipora spp. The polyps in the center may not be calcyfying very fast or growing that rapidly as compared to those near the periphery, but those same polyps (which will be among the first polyps formed) may live on as long as the colony is alive. The only reason they would not is if something kills them but not the rest of the colony.

[KingDiamond]

<a href=showthread.php?s=&postid=11680057#post11680057 target=_blank>Originally posted</a> by MCsaxmaster
p.s. And just to be clear, particular polyps within a coral colony often will be as old as the entire colony. For many corals all the polyps remain as part of the colony, even if they are not in an actively growing part of the colony. Think foliaceous or massive Montipora spp. The polyps in the center may not be calcyfying very fast or growing that rapidly as compared to those near the periphery, but those same polyps (which will be among the first polyps formed) may live on as long as the colony is alive. The only reason they would not is if something kills them but not the rest of the colony.

True some polyps could be as old as the entire colony. I don't think I said that was impossible. What would be very difficult to determine would be to find out if the polyps that occupied the intermost parts of the colony were actually the originial polyps that grew there. If a file fish ate them and they re-grew it would be very difficult to know if they were re-growth or original polyps. I think that the older the colony is the more unlikly the original polyps are alive. That is just probability. When you look at any form of asexual reprodution the term individual can be "fuzzy", especially if you look at genetics. Frankly, one could make an argument that any creature that reproduced by fission or sexual reproduction were one and the same.

Brad

[MCsaxmaster]

<a href=showthread.php?s=&postid=11680839#post11680839 target=_blank>Originally posted</a> by KingDiamond
True some polyps could be as old as the entire colony. I don't think I said that was impossible. What would be very difficult to determine would be to find out if the polyps that occupied the intermost parts of the colony were actually the originial polyps that grew there. If a file fish ate them and they re-grew it would be very difficult to know if they were re-growth or original polyps. I think that the older the colony is the more unlikly the original polyps are alive. That is just probability. When you look at any form of asexual reprodution the term individual can be "fuzzy", especially if you look at genetics. Frankly, one could make an argument that any creature that reproduced by fission or sexual reproduction were one and the same.

Brad

But by using that argument everytime there is a turnover of tissues you have a new individual. The proteins, fats, minerals, etc. in my body are turned over over the course of months. Am I a knew individual then? Skin cells and hair are constantly shed by we mammals. Should we determine our age by the age of our skin cells or hair? Tissue turnover is not a good basis upon which to determine the age of an organism by the usual meaning of age. We may be very interested in rates of tissue turnover, but for reasons entirely different from determining an organisms age.

Chris

[KingDiamond]

<a href=showthread.php?s=&postid=11679814#post11679814 target=_blank>Originally posted</a> by BeanAnimal
Let me take that step further as well. Take a big soft sinularia for example. There is MUCH more there than just polyps isnt there? The whole "coral" acts as a whole retracting and expanding. What is the rest of the tissue? If we slice away all of the fuzzy polyps, more will grow. If we cube a section from the center of a stalk (with no exterior tissue) will the cube survive by growing polyps?

If you cut your hair and set it on the floor will it form a new you? :) Some parts are more important to a colonial species than others. The polyps are individuals the other tissiues associated with the coral (stolon, sclerites ect...) are important but are the result of the colony of individuals growing.

Brad

[KingDiamond]

<a href=showthread.php?s=&postid=11680862#post11680862 target=_blank>Originally posted</a> by MCsaxmaster
But by using that argument everytime there is a turnover of tissues you have a new individual. The proteins, fats, minerals, etc. in my body are turned over over the course of months. Am I a knew individual then? Skin cells and hair are constantly shed by we mammals. Should we determine our age by the age of our skin cells or hair? Tissue turnover is not a good basis upon which to determine the age of an organism by the usual meaning of age. We may be very interested in rates of tissue turnover, but for reasons entirely different from determining an organisms age.

Chris

So is it impossible to tell if any polyp in a colony are original? I don't claim to knew much about how the age of coral colonies is determined but wouldn't biologists/geologists look at the age of the skeleton?

Brad

[MCsaxmaster]

<a href=showthread.php?s=&postid=11680866#post11680866 target=_blank>Originally posted</a> by KingDiamond
If you cut your hair and set it on the floor will it form a new you? :) Some parts are more important to a colonial species than others. The polyps are individuals the other tissiues associated with the coral (stolon, sclerites ect...) are important but are the result of the colony of individuals growing.

Brad

Fair enough, but coral tissue tends toward totipotency much more often than the tissue of higher animals. If I cut myself in half I can't grow two of me. If I cut a coral polyp in half I can. If I cut off my arm, or a hand, or a finger I can't grow a new me. With corals it appears that as we hack them into smaller and smaller pieces (tissue explants) we continue to be able to produce viable tissue from the explants. There may be a cut-off on how little tissue is required to grow a new colony, but if so it seems smaller than the pieces into which we have cut corals so far. This is especially true when hacking up coral larvae. For instance, in humans twins cannot form after a certain period of development (I'm not sure exactly where that point is). If the embryo is too developed then the loss of cells will kill it. With coral larvae folks have cut them into smaller and smaller pieces at later and later stages of development and so far it seems as though they just keep on developing.

Chris

[KingDiamond]

By the way Chris I like your signature!

Brad

[KingDiamond]

<a href=showthread.php?s=&postid=11680932#post11680932 target=_blank>Originally posted</a> by MCsaxmaster
Fair enough, but coral tissue tends toward totipotency much more often than the tissue of higher animals. If I cut myself in half I can't grow two of me. If I cut a coral polyp in half I can. If I cut off my arm, or a hand, or a finger I can't grow a new me. With corals it appears that as we hack them into smaller and smaller pieces (tissue explants) we continue to be able to produce viable tissue from the explants. There may be a cut-off on how little tissue is required to grow a new colony, but if so it seems smaller than the pieces into which we have cut corals so far. This is especially true when hacking up coral larvae. For instance, in humans twins cannot form after a certain period of development (I'm not sure exactly where that point is). If the embryo is too developed then the loss of cells will kill it. With coral larvae folks have cut them into smaller and smaller pieces at later and later stages of development and so far it seems as though they just keep on developing.

It depends on what kind of coral polyp your cutting and where you cut it.

Brad

Chris

[MCsaxmaster]

<a href=showthread.php?s=&postid=11680941#post11680941 target=_blank>Originally posted</a> by KingDiamond
By the way Chris I like your signature!

Brad

RAmen to that :D

[MCsaxmaster]

<a href=showthread.php?s=&postid=11680910#post11680910 target=_blank>Originally posted</a> by KingDiamond
So is it impossible to tell if any polyp in a colony are original? I don't claim to knew much about how the age of coral colonies is determined but wouldn't biologists/geologists look at the age of the skeleton?

Brad

That's a toughy. It really depends on the species and coral in question. All corals start as planular larvae that metamorphoses into a single polyp upon settlement. That primary polyp can sometimes be identified in young corals, especially if they have relatively large polyps. For instance, with young Mycetophyllia (and sometimes even older one) you can often tell which was the primary polyp. For something like a big Montastraea faveolata colony that is a few hundred years old...well, good luck. Typically for these corals age is estimated from cores of the skeleton, though this likely gives underestimates since these guys are slow-growing and may take several years just to reach a few centimeters across. For something that is estimated to be 500 yrs old, the difference of 5 years is probably already within the error of the estimate. For something that is estimated to be 10 years old based on linear extension and size being off by 5 years is a pretty large error.

[greenbean36191]

If you cut your hair and set it on the floor will it form a new you? Some parts are more important to a colonial species than others. The polyps are individuals the other tissiues associated with the coral (stolon, sclerites ect...) are important but are the result of the colony of individuals growing.
Why is the polyp more important than the coenosarc? If you were to remove all of the polyps from it, it still has undifferentiated cells that could give rise to new polyps. If it's not an individual because it's not a polyp, but it can differentiate into one or many, then what is it? You could theoretically take patches of coenosarc and establish new colonies with them. Wouldn't each of those new corals be an individual?

[MCsaxmaster]

<a href=showthread.php?s=&postid=11683718#post11683718 target=_blank>Originally posted</a> by greenbean36191
You could theoretically take patches of coenosarc and establish new colonies with them.

Actually, not even theoretically--it's been done. Very cool new paper just out in PNAS that I'm waiting on.

[KingDiamond]

<a href=showthread.php?s=&postid=11683718#post11683718 target=_blank>Originally posted</a> by greenbean36191
Why is the polyp more important than the coenosarc? If you were to remove all of the polyps from it, it still has undifferentiated cells that could give rise to new polyps. If it's not an individual because it's not a polyp, but it can differentiate into one or many, then what is it? You could theoretically take patches of coenosarc and establish new colonies with them. Wouldn't each of those new corals be an individual?

I think what we have to remember is that the whole animal in question is a coral. Secondly, the regeneration abilities of Anthozoans is pretty amazing. I think that the polyp is more important just because it came first. When a planula lavae forms a coral it starts with a single polyp. You can cut flat worms just about anywhere and form a new flat worm but I guess you need a flat worm to cut to get a part of a flat worm. You need at least one polyp or an established colony of coral to get a cutting of coenosarc.

Brad

[greenbean36191]

Obviously I'm playing devil's advocate a little bit, and I do understand the argument and agree with your answer. However, I don't really subscribe to the polyp-as-an-individual school of thought mostly because it's not very practical in the real world. When we work with corals, people are almost always looking at the effects on colonies as a whole rather than at individual polyps within colonies. The polyps of a colony are identical genetically, have a common skeleton, nerve net, tissue layers, share nutrients and sometimes have interconnected guts. In many species there's no clear demarcation between polyps, so any dividing line you make between them is pretty much arbitrary. Besides as a teaching tool in invert textbooks IMO there's little reason to think of polyps as individuals rather than units of a larger individual.

[BeanAnimal]

I am being twisted both ways here.... I suppose it comes down to a matter of perspective AND context.

[MCsaxmaster]

If it were not for the high regenerative capabilities of corals we would have no reason to call an single polyp from a colonial species where tissue connections are maintained an individual. Coenosarc tissue can also produce a new colony if it is explanted: who would argue that tiny divisions of the coenosarc are also individuals?

While corals can reproduce asexually due to fragmentation, as can many other organisms, the only practical and biologically sensible system to me is to think about genets and ramets. A coral colony, if never fragmented, is a single individual. Many colonies produced due to fragmentation and reattachment are separate colonies, but are functionally the same individual by every other conceivable standard. In this case we really have to discuss genets vs. ramets to maintain any sort of clarity at all I think.

Consider a non-settled planula. You can hack them into pretty small bits and even at fairly late stages of development--far beyond where you'd think you could do so without killing the larva--and get the pieces to develop into competent larvae. Coral tissue is nearly totipotent. It wouldn't be reasonable to consider every cell an individual organism though ;)

[Mishri]

this reminds me of tape worms.. you have 1 6ft long tape worm, but if you segment it at all the new segment can operate and become a new worm.. but nobody thinks of it as 1,000 worms if you extract one from your digestive tract ;)

[greenbean36191]

It's a problem with a lot of the invert groups (and plants) because we try to apply concepts that originated with "higher" animal groups where they work well, but they really don't work with simpler groups. Asexual reproduction throws us a huge curveball, hence the need for ideas like ramets and genets like Chris has pointed out.

There are all sorts of similar problems within biology. Probably the biggest one being the definition of a species, but the definitions are blurry for just about every level from the individual all the way to kingdoms or domains. Ultimately, the root of the problem is that biology makes arbitrary distinctions that don't necessarily reflect the real world. We try to categorize things discreetly, when there's really a continuum.

[KingDiamond]

"There are all sorts of similar problems within biology. Probably the biggest one being the definition of a species, but the definitions are blurry for just about every level from the individual all the way to kingdoms or domains. Ultimately, the root of the problem is that biology makes arbitrary distinctions that don't necessarily reflect the real world. We try to categorize things discreetly, when there's really a continuum."

A clone of something is still an individual. If anything, biology is usually specific about the distinctions it makes. Coral polyps may be connected by living tissue but the digestive system, nervous system, sexual reproductive capabilites and radial symmetry are contained within an individual polyp.

Brad

[KingDiamond]

<a href=showthread.php?s=&postid=11698945#post11698945 target=_blank>Originally posted</a> by Mishri
this reminds me of tape worms.. you have 1 6ft long tape worm, but if you segment it at all the new segment can operate and become a new worm.. but nobody thinks of it as 1,000 worms if you extract one from your digestive tract ;)

The segments (proglottids) themselves do not become a new worm, the eggs held inside of them do.

Brad

[BeanAnimal]

Very persuasive information from both perspectives. I feel somewhat enlightened now and am waiting for the whack on the skull to push me fully into enlightenment...

Thanks guys.

[MCsaxmaster]

<a href=showthread.php?s=&postid=11701888#post11701888 target=_blank>Originally posted</a> by BeanAnimal
Very persuasive information from both perspectives. I feel somewhat enlightened now and am waiting for the whack on the skull to push me fully into enlightenment...

Thanks guys.

hahaha, very good ;)

[MCsaxmaster]

<a href=showthread.php?s=&postid=11701842#post11701842 target=_blank>Originally posted</a> by KingDiamond
"There are all sorts of similar problems within biology. Probably the biggest one being the definition of a species, but the definitions are blurry for just about every level from the individual all the way to kingdoms or domains. Ultimately, the root of the problem is that biology makes arbitrary distinctions that don't necessarily reflect the real world. We try to categorize things discreetly, when there's really a continuum."

A clone of something is still an individual. If anything, biology is usually specific about the distinctions it makes. Coral polyps may be connected by living tissue but the digestive system, nervous system, sexual reproductive capabilites and radial symmetry are contained within an individual polyp.

Brad

But for those corals that maintain tissue connections, by and large the tissue connections are anything but superficial. The nervous and digestive systems, not to mention other systems, are fully integrated throughout the entire colony. I don't see any more reason to think of different polyps as different individuals than I do to think of the various body parts of higher organisms as individual oganisms.

Also, if we really want to look to highly undifferentiated tissue, consider poriferans. Should we consider every cell in a sponge a separate individual? That makes absolutely no practical or biological sense to me. Since corals have more differentiated tissue than sponges (but less than higher organisms) I still see little practical or biological basis to talk about each separate polyp as an individual.

As Mike points out, the problem really stems from trying to apply a system that we developed to work with higher organisms that only reproduce sexually to lower organisms that reproduce both sexually and through various asexual means. Applying the term "individual" that we use for mammals or birds to corals is very much trying to shoe-horn a square peg into a round hole. It simply doesn't come close to adequately describing the system.

A coral colony wherein the polyps remain connected behaves as a single mass of tissue. Separate colonies produced through sexual reproduction act as seperate individuals by every measure. Separate colonies produced through asexual reproduction act as separate individuals behaviorally (e.g., in response to stimuli) but as the same individual physiologically (e.g., reproduction, physical tolerance, etc.).

We simply cannot apply the same standard to corals that we do to birds or mammals.

Chris

[KingDiamond]

We simply cannot apply the same standard to corals that we do to birds or mammals.


It has worked for the passed 100 or so years.
:) Now all you have to do is right a paper and convince the Biological community and reprint every invertebrate zoology text written to date. :D

Brad

[BeanAnimal]

Hey they took Pluto away...

Anything is possible.

[greenbean36191]

If anything, biology is usually specific about the distinctions it makes.
Hardly. What's the definition of a species and how do you tell what is and isn't one?

Coral polyps may be connected by living tissue but the digestive system, nervous system, sexual reproductive capabilites and radial symmetry are contained within an individual polyp.
Like Chris pointed out the gut and nerve nets are usually highly connected among polyps. Also, while the gonads are contained within the polyps, the ability to reproduce sexually depends on the colony as a whole. In many species, there is a minimum colony size for sexual reproduction. Small colonies won't spawn even if they were started from fragments of old corals that had spawned previously.

It has worked for the passed 100 or so years.
Now all you have to do is right a paper and convince the Biological community and reprint every invertebrate zoology text written to date.
It wouldn't take a whole lot of convincing. Most of the community already realizes that it hasn't worked for the past 200 years. Pretty much all of my books already address the issue and there has been a lot of discussion about the need for new systems. The problem is that so far no one has come up with something better.

[Mishri]

I'll never be convinced that my acropora is really 200 different individuals for each polyp... the whole thing is 1 individual.. and if i fraged it and made a 2nd one.. that other one is a new individual.. even if genetically the same...

they act a little like animals and a little like plants.. so corals really need to be in a group all by themselves with different standards.. you cant put everything in the world in one big group and try to organize them according to shape/color/skeleton... its impossible.. even if they try to it doesn't work.

[SquidHC]

Im no scientist, not even that smart, but if I can toss in my two cents here Id have to agree that a colony in my mind is a single individual. If a piece breaks off and grows a new colony, its a new colony and not part of the colony it broke off of. If I frag a piece of coral and give it to a buddy, he has a coral and I have a coral. Even though they are geneticaly identicle we have two seperate animals.

Now, in the case of some LPS like say a frogspawn or torch, are the heads connected or are they self supporting? In this case if they are completely seperate I would say that each head would be its own individual.

By saying that if you cut a single polyp embryo in half and it creates two seperate colonies that are the same individual. Well that would be like saying that a human having twins, being geneticaly the same, and even comming from the same egg splitting in two, was the same person. No, its to seperate people.

[KingDiamond]

<a href=showthread.php?s=&postid=11703029#post11703029 target=_blank>Originally posted</a> by greenbean36191
Hardly. What's the definition of a species and how do you tell what is and isn't one?


Like Chris pointed out the gut and nerve nets are usually highly connected among polyps. Also, while the gonads are contained within the polyps, the ability to reproduce sexually depends on the colony as a whole. In many species, there is a minimum colony size for sexual reproduction. Small colonies won't spawn even if they were started from fragments of old corals that had spawned previously.


It wouldn't take a whole lot of convincing. Most of the community already realizes that it hasn't worked for the past 200 years. Pretty much all of my books already address the issue and there has been a lot of discussion about the need for new systems. The problem is that so far no one has come up with something better.

I always thought that the simple nerve net of Athozoa surrounded the mouth and extended into the tentacles. When did biologists discover that individual polyps were connected by the nerve net? I guess I am dating myself a little bit. I thought the gut terminated and "channels" took neutrents to surrounding tissue but did not connect with other polyps "channels"?

Brad



Brad

[greenbean36191]

I'm not sure how long the architecture of the nerve nets has been known, but it's been known for at least 40 years that the nerves run throughout the polyp and between polyps as well.

The gut connection within colonies varies a lot. It can be anything from multiple mouths with a common gastrovascular cavity all the way to no connection. In most cases there is a series of gastrovascular tubes that not only runs within polyps, but also forms direct connections between the GV cavities of nearby polyps. I'm not sure to what extent particulate food is shared within the GV tubes, but it's clear that they're used for transport of dissolved material, including nutrients from food.

[KingDiamond]

<a href=showthread.php?s=&postid=11729308#post11729308 target=_blank>Originally posted</a> by greenbean36191
I'm not sure how long the architecture of the nerve nets has been known, but it's been known for at least 40 years that the nerves run throughout the polyp and between polyps as well.

The gut connection within colonies varies a lot. It can be anything from multiple mouths with a common gastrovascular cavity all the way to no connection. In most cases there is a series of gastrovascular tubes that not only runs within polyps, but also forms direct connections between the GV cavities of nearby polyps. I'm not sure to what extent particulate food is shared within the GV tubes, but it's clear that they're used for transport of dissolved material, including nutrients from food.

Thanks for the information! That clears things up a bit....I guess...

Brad

[hammmerhead]

Here is an old one. It was flawless as well.

http://i55.photobucket.com/albums/g152/JMC_711/P8290649.jpg

[BeanAnimal]

I cant really get a good look at her, the photo is a bit dark... you say flawless?

[rexdenton]

I am certain that on larger reefs, coral colonies comprising a large coral have lived thousands of years. So long as the niche is stable, and conditions appropriate for coral growth, there is really nothing that would prevent coral from being virtually immortal. The current decay of reef colonies is testimony to some impact of global warming on the niche. Whether the water is changing, the fish, food web, the inverts, whatever, coral will disappear when the niche that they are accusomed to, changes in a way that growth is no longer an efficient process.

[BeanAnimal]

"Global Warming" and "Global Cooling" have occured numerous times. I would suspect that a "niche" is more like a passing moment in time.

Coral colonies that are thousands of years old would not shcok me. However, coral colonies that are tens of thousands or hundreds of thousands of years old would be another story. Climate change is certainly a part of our planet and niche environments simply do not last very long in scheme of things.

[MCsaxmaster]

<a href=showthread.php?s=&postid=11737889#post11737889 target=_blank>Originally posted</a> by BeanAnimal
"Global Warming" and "Global Cooling" have occured numerous times. I would suspect that a "niche" is more like a passing moment in time.

Coral colonies that are thousands of years old would not shcok me. However, coral colonies that are tens of thousands or hundreds of thousands of years old would be another story. Climate change is certainly a part of our planet and niche environments simply do not last very long in scheme of things.

Let's not confuse "niche" with a particular location. An organism's niche are those conditions in which it can survive (fundamental niche) or does survive (realized niche) and those functions it performs within an ecosystem. Without evolution a species fundamental niche does not change (though its realized niche may), even if the environment changes. For example, Acropora palmata as a species has been around ~3 million years. During ice ages it had a somewhat more restricted range than it does today. In particular, there are obvious refuges for the species in the Southern and Eastern Caribbean. During interglacial periods it spreads to higher latitudes. Six thousand years ago there was a huge, fast-growing reef of A. palmata and A. cervicornis off of Ft. Lauderdale. A palmata is limited to about 50 km south of that nowadays. A. cervicornis used to be, but it has recently spread back to these areas due to ocean warming.

[BeanAnimal]

Thank you for putting the word in the proper context for the subject matter.

So the species has adapted to different environments to survive. It may be traced back ~3 million years but today's specimen is not the same coral as that which was growing 3 million years ago. I.E. there is not a 3 million year old head of coral out there. Instead there are descendents that have of that coral that have adapted to the ever changing planet. Is my understanding correct?

[hammmerhead]

<a href=showthread.php?s=&postid=11732696#post11732696 target=_blank>Originally posted</a> by hammmerhead
Here is an old one. It was flawless as well.

http://i55.photobucket.com/albums/g152/JMC_711/P8290649.jpg



Anyone have an idea how old this one is? I figured it was a pretty good find.

[timrandlerv10]

My BTA split. Again. And again. All of which were shortly after it split before I got it.

How old is the smallest one in my tank today?

(does that sound like a NetFlix commerical?)

seriously...lets assume it was created by fertilized eggs, God snaps his fingers, anything. Then a year later it split, and I bought one. Over the next year, it split then one of the splits split again. Are those three one individual? No. They're ramets? (is that ray or rah? meets or mets?) One of them has to be the oldest...but I feel funny applying my concept of 'birth' and age to the two new clones. As long as one BTA is alive, is he the first BTA created/evolved (lipservice paid to being PC for the month...)? Is he a bajillion years old?

[aninjaatemyshoe]

I'm definitely no geneticist but I know that in vertebrates there is a genetic age. The genetic age determines the point at which the body's cells will stop dividing. When you clone a vertebrate, the clone starts that the genetic age of the cloned animal. So, if you cloned an old animal, you would end up with a clone that wouldn't live very long.

For cnidarians that can propagate through asexual splitting, I would imagine that the presence of the genes for senility would prevent the animal from propagating in such a manner indefinitely. The clones of the coral or anemone would carry the same genetic age as the "original." For us, that would mean the captive propagation methods of such animals (which is only through asexual means) could not be sustained.

[MCsaxmaster]

<a href=showthread.php?s=&postid=11743858#post11743858 target=_blank>Originally posted</a> by BeanAnimal
Thank you for putting the word in the proper context for the subject matter.

So the species has adapted to different environments to survive. It may be traced back ~3 million years but today's specimen is not the same coral as that which was growing 3 million years ago. I.E. there is not a 3 million year old head of coral out there. Instead there are descendents that have of that coral that have adapted to the ever changing planet. Is my understanding correct?

There may have been some adaptation of the species over this time, but by and large the species has simply been able to grow in locations that provide the proper conditions. From this perspective, the fundamental niche has remained the same but the physical locations where that niche can be realized have changed.

Corals, like most organisms, reproduce sexually. Corals also reproduce asexually. While you can get patches of a given coral due to fragmentation and asexual reproduction, all genetically distinct individuals originated through sexual reproduction. A. palmata probably doesn't live to be more than a century or two most places, and most probably don't live more than a few decades, eventually getting trashed by a hurricane or something else. More is probably possible, but unlikely.

When I say the species has existed for ~3 million years I don't mean to imply that individual corals have existed that long. Our species (H. sapiens) has existed for ~100,000 years. As individuals die they are replaced by sexual reproduction, and the same is true in A. palmata; the only twist is they can be fragmented and reproduce asexually as well, whereas we can't.

[MCsaxmaster]

<a href=showthread.php?s=&postid=11744967#post11744967 target=_blank>Originally posted</a> by timrandlerv10
My BTA split. Again. And again. All of which were shortly after it split before I got it.

How old is the smallest one in my tank today?

(does that sound like a NetFlix commerical?)

seriously...lets assume it was created by fertilized eggs, God snaps his fingers, anything. Then a year later it split, and I bought one. Over the next year, it split then one of the splits split again. Are those three one individual? No. They're ramets? (is that ray or rah? meets or mets?) One of them has to be the oldest...but I feel funny applying my concept of 'birth' and age to the two new clones. As long as one BTA is alive, is he the first BTA created/evolved (lipservice paid to being PC for the month...)? Is he a bajillion years old?

Given that the anemone is splitting in half, why would you say one half is "original" whereas the other half is "new?" ;)

In a case like this I think the only sensible thing is to say very clearly that the genotype of this anemone resulted from sexual reproduction X years ago but that these two clones were produced through asexual reproduction X months ago.

The reality is that, even if the anemone is very old the tissue it is made of is relatively young. The tissues in living organisms are constantly replaced. Thus, there is absolutely no way nor any practical meaning in trying to decide which of the two anemones was "original": both were and neither were.

[MCsaxmaster]

<a href=showthread.php?s=&postid=11745909#post11745909 target=_blank>Originally posted</a> by aninjaatemyshoe
I'm definitely no geneticist but I know that in vertebrates there is a genetic age. The genetic age determines the point at which the body's cells will stop dividing. When you clone a vertebrate, the clone starts that the genetic age of the cloned animal. So, if you cloned an old animal, you would end up with a clone that wouldn't live very long.

For cnidarians that can propagate through asexual splitting, I would imagine that the presence of the genes for senility would prevent the animal from propagating in such a manner indefinitely. The clones of the coral or anemone would carry the same genetic age as the "original." For us, that would mean the captive propagation methods of such animals (which is only through asexual means) could not be sustained.

That is true of senescent organisms, but not for those that don't senese. It appears some corals become senescent while others do not, thus one coral will eventually die of old age, no matter when it was fragmented, while another will never die of old age regardless of fragmentation.

[MCsaxmaster]

<a href=showthread.php?s=&postid=11744057#post11744057 target=_blank>Originally posted</a> by hammmerhead
Anyone have an idea how old this one is? I figured it was a pretty good find.

Hard to say precisely without a real good sense of scale, but I'll estimate it's about 1.5 m high. Typically this coral has a linear extension rate of 2-4 mm/yr which depends heavily on local conditions (e.g., they grow slower in the north where winter-time temps and light are low and faster in the south where winter is more similar to summer).

So, given a linear extension rate of 2-4 mm/yr and a colony 1.5 m high I'd estimate it is maybe 500 years old.

Chris

[rbursek]

Very interesting thread!! I respect all here, not like some threads, example, to put foam under tank, where some of the egos got way out of wack!!!!! Nice to read one without that, stayed on topic, and just use good questions to bring out more info. Thank you all for an interesting read!!!!!!!!!!!!
Bob

[chrisalmand]

It's not like one organism is living forever, it's a family. Each polyp on a coral is an INDIVIDUAL, independent animal.

[capn_hylinur]

<a href=showthread.php?s=&postid=11762431#post11762431 target=_blank>Originally posted</a> by rbursek
Very interesting thread!! I respect all here, not like some threads, example, to put foam under tank, where some of the egos got way out of wack!!!!! Nice to read one without that, stayed on topic, and just use good questions to bring out more info. Thank you all for an interesting read!!!!!!!!!!!!
Bob

I agree with you Bob, I have been silently following this thread, in awe of the technical information that has been presented.
Scott

[greenbean36191]

Each polyp on a coral is an INDIVIDUAL, independent animal.
They aren't independent. That's what most of this discussion is about. They are genetically identical, in most cases their tissue is continuous between polyps, they share nutrients via an interconnected gut, they have interconnected nerves, etc. There's no discrete dividing line separating one polyp from another except in phaceloid species. Where we say one polyp starts and another begins is fairly arbitrary.

[JPMagyar]

<a href=showthread.php?s=&postid=11749981#post11749981 target=_blank>Originally posted</a> by MCsaxmaster
That is true of senescent organisms, but not for those that don't senese. It appears some corals become senescent while others do not, thus one coral will eventually die of old age, no matter when it was fragmented, while another will never die of old age regardless of fragmentation.

I am genuinely fascinated by this topic as its' not one that I have previously given any thought to, but one in which I am most interested now since I have an Heteractis Maginifica anemone that has split twice and one that I would love to continue to see splitting in the future.


Can you or anyone else on this thread recommend some reading that represents the latest research on coral and/or other invertebrate senescence?

Thanks a bunch,

joe

[MCsaxmaster]

<a href=showthread.php?s=&postid=11963169#post11963169 target=_blank>Originally posted</a> by chrisalmand
It's not like one organism is living forever, it's a family. Each polyp on a coral is an INDIVIDUAL, independent animal.

Just to add onto what Mike said, and the thread in general, if that were true then you would need to agree with these statements:

It's not like some sponges (poriferans) can live for hundreds of years, they're a family. Each cell is an INDIVIDUAL, independent animal.

It's not like some trees can live for thousands of years, they're a family. Each leaf, each branch, each root, etc. is an INDIVIDUAL, independent plant.

It's not like a nervous cell in my body can live for dozens of years, it's made of a family of atoms. Particular sets of atoms, which are replenished entirely about every 6 months, create and INDIVIDUAL, independent organism. A person 5 years old or 50 years old are really only about 6 months old--the average residence time of atoms that make up their tissues.

In corals that maintain tissue connections among polyps, which is almost all of them, the suggestion that each individual polyp is a seperate organism makes very little sense at all. For example, in these corals only larger colonies can reproduce, and only the polyps toward the center of the colony become competent to reproduce. Solitary polyps cannot and do not reproduce sexually. In fact, small colonies don't reproduce either, regardless of their age. The colony is the animal, the polyps are it's parts.

[MCsaxmaster]

<a href=showthread.php?s=&postid=11964832#post11964832 target=_blank>Originally posted</a> by JPMagyar
I am genuinely fascinated by this topic as its' not one that I have previously given any thought to, but one in which I am most interested now since I have an Heteractis Maginifica anemone that has split twice and one that I would love to continue to see splitting in the future.


Can you or anyone else on this thread recommend some reading that represents the latest research on coral and/or other invertebrate senescence?

Thanks a bunch,

joe

Good question. I don't have the studies handy, and I'm blanking on who did them now, but they are relatively recent (within the last decade). If I recall, genes for senscense were found in Acropora, but not Porites(???). I'd try to track these down with google scholar if you're interested.

From what I've heard from Daphne Fautin, reef anemones like H. magnifica or E. quadricolor can live quite a long time--a couple hundred years was normal if I recall. They also have pretty low rates of sexual recruitment, so those anemones that do establish themselves are normally there for a very long time, and are very slow to be replaced. For that reason, encouraging captive propagation of asexual clones of these species in captivity is the way to go. In areas where host anemones were collected for aquaria (e.g., Philippines) there are no more anemones nor any clownfish. Once they are removed, they are gone, at least for the foreseeable future.

So since you've got an H. magnifica splitting, take good care of it. We need more of that kind of thing :D

[SuperNerd]

Okay so then if a coral can live 100 years does that mean that each individual polyp theoretically will also live 100 years starting from its "birth?"

[MCsaxmaster]

<a href=showthread.php?s=&postid=12036595#post12036595 target=_blank>Originally posted</a> by SuperNerd
Okay so then if a coral can live 100 years does that mean that each individual polyp theoretically will also live 100 years starting from its "birth?"

If the primary polyp, the first polyp produced when the coral settled, survives 100 years then yes, it has survived 100 years. However, if it doesn't there's still no legitimate reason to claim that the coral is less than 100 yrs old. How old do you think many of the cells in your body are? How old do you think your tissues are? Corals replace tissues/polyps as they senesce, just as we replace cells/tissues in our body.

[SuperNerd]

<a href=showthread.php?s=&postid=12036865#post12036865 target=_blank>Originally posted</a> by MCsaxmaster
If the primary polyp, the first polyp produced when the coral settled, survives 100 years then yes, it has survived 100 years. However, if it doesn't there's still no legitimate reason to claim that the coral is less than 100 yrs old. How old do you think many of the cells in your body are? How old do you think your tissues are? Corals replace tissues/polyps as they senesce, just as we replace cells/tissues in our body.

Does this mean that each cloned/replaced polyp will live out the predetermined lifespan of the original mother colony polyp?

I read Xenia can live for 7 years. Does what you say theoretically mean each new xenia frag will live for an additional 7 years?

[MCsaxmaster]

If the corals have the genes for senesence (= aging) then any of the cuttings from it will have the same biological age as the original. It appears that not all corals have these genes, and in fact most may not.

I'm not so sure about Xenia spp. having a natural lifespan of 7 years...