BeanAnimal
Premium Member
I am being twisted both ways here.... I suppose it comes down to a matter of perspective AND context.
Lifespan of corals
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MCsaxmaster
New member
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
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
greenbean36191
Premium Member
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.
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
New member
"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
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
New member
<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
Premium Member
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.
Thanks guys.
MCsaxmaster
New member
hahaha, very good
MCsaxmaster
New member
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
New member
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. 
Brad
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. Brad
BeanAnimal
Premium Member
Hey they took Pluto away...
Anything is possible.
Anything is possible.
greenbean36191
Premium Member
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.
Mishri
Active member
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.
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.
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.
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
New member
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
Premium Member
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.
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
New member
Thanks for the information! That clears things up a bit....I guess...
Brad
hammmerhead
New member
Here is an old one. It was flawless as well.
BeanAnimal
Premium Member
I cant really get a good look at her, the photo is a bit dark... you say flawless?
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.
