African lungfish circulatory system

[Hrvoje]

Hi guys,

I am studying a schematic diagram given here:
https://biology.stackexchange.com/questions/34067/are-there-fishes-with-a-double-circulatory-system/34071
I don't know what book is this picture taken from, but I hope it accurately describes the african lungfish circulatory system.
If I understand that correctly, the main differences between a fish circulatory system and this, are following:

• lungs output directly into a separate atrium, instead of mixing output together with other organs that do not contribute to oxygenation into a single atrium
• lungs have separate input from gills through pulmonary artery, instead of through dorsal aorta that brings blood to other organs
• dorsal aorta receives input from gills through ductus, and from a gill bypass that receives input from the separate ventricle filled by lungs

Does anyone know why is that bypass presented double there, what does that mean?
 

... comparison may be in fact with a fish circulatory system that has a swimming bladder with a respiratory function developed to a certain extent, but not "replumbed" in this way to enable better efficiency.

[Hrvoje]

I understand that pulmonary artery vasomotor segment plays a key role in bimodal respiration and circulation, as it dilates or constricts that vessel depending on emersion, or immersion into water, while ductus is antagonistically regulated. Can anyone point me at a document that explains exactly that mechanism in detail?

Also, although the circulatory network topology is one key difference, the actual difference between lungs and a swimming bladder enabled for respiratory function is about the structure of the organ, for example the breathing surface area and such things, ie it is about how the organ is built, and not how it is connected to the system?

Edited November 30, 2017 by Hrvoje
error in the ordering of words

[Hrvoje]

In one of the first papers in topology, Leonhard Euler demonstrated that it was impossible to find a route through the town of Königsberg (now Kaliningrad) that would cross 
each of its seven bridges exactly once. This result did not depend on the lengths of the bridges, nor on their distance from one another, but only on connectivity 
properties: which bridges connect to which islands or riverbanks. This problem in introductory mathematics called Seven Bridges of Königsberg led to the branch of mathematics known as graph theory. Connectedness-related properties have discrete values, which can be expressed by this definition:
The incidence matrix of a directed graph is a n × m matrix B where n and m are the number of vertices and edges respectively, such that B_i,j = -1 if the edge e_j leaves vertex v_i, 1 if it enters vertex v_i and 0 otherwise (many authors use the opposite sign convention).
Conventional wisdom related with evolution theory is that every change in fenotype, regardless of how big and significant is, can be achieved
over a generation continuum by accumulating smaller, less significant changes, given enough time, that is adequately large number of generations.
However, since discrete values cannot be continuously changed, no topologically significant change can be achieved by accumulating topologically
insignificant changes, where network graph stays isomorphic through generations, ie where incidence matrix is unchanged.
Which means that if african lungfish circulatory system developed from the fish circulatory system, this must have happened in much
less stages (and generations!) than one might "conventionally" think. Right? Is this one of James A. Shapiro's arguments too? Is he considered mainstream biologist with highest possible reputation? I just "discovered" him, and I'm going to watch and read carefully every material I could from him.

Edited December 5, 2017 by Hrvoje
indentation

[Hrvoje]

OK, so this is a schematic diagram I am talking about, that depicts an african lungfish circulatory system. You can compare it with a fish single circulatory system given here:

So if we suppose that the upper evolved from the lower, than it must have been stages in that development when organisms had a swim bladder that had respiratory function, ie able to contribute to oxygenation, but due to the way it was connected to the circulatory system, as any other organ whose tissues are collectively depicted on upper picture as "Tissues", and on the lower as "Body", that wasn't sufficiently efficient. Then there had to be another stage when that organ was "replumbed", ie connected to the circulatory system as "Lung" is connected in the upper picture. As I said, the difference between a swim bladder and a lung is not only in how it is connected but also in how it is built, and these changes could have been developed in parallel to the replumbing. But, at the moment I am focused on replumbing. In how many generations could have this development occur?

[Endy0816]

Looks like it may have been a case of increasing specialization of the pre-lung/swimbladder. Rather than one directly evolving into the other.

https://evolution.berkeley.edu/evolibrary/article/fishtree_09

[Hrvoje]

In wikipedia article it says that Darwin believed that swim bladder evolved into lungs, and that scientists now believe it is the other way around, as is also written on the site you posted. While here it says that:

>>Fishes having respiratory swim bladder (Polypterus, Protopterus and Lepidosiren) cannot be regarded as the pro­genitors of the teleosts possessing the swim bladder of hydrostatic type. So it is logical to think that fishes having the hydrostatic type of swim-bladder evolved independently.<<

Looks like scientists are confused what actually happened, but it may have been a case that organisms in which lungs evolved while gills were retained, evolved from those in which only gills were present. How did it happen? How long does it take to connect a brand new organ to circulatory system in a way fundamentally different compared to the way all other organs are connected? Besides that, a tree is an object that features both continuous lines that may present thousands or millions of generations of continuous development, as well as discrete splitting points that present what exactly? In how many generations occurs splitting actually?

Edited December 19, 2017 by Hrvoje

[Moontanman]

3 hours ago, Hrvoje said:

In wikipedia article it says that Darwin believed that swim bladder evolved into lungs, and that scientists now believe it is the other way around, as is also written on the site you posted. While here it says that:

>>Fishes having respiratory swim bladder (Polypterus, Protopterus and Lepidosiren) cannot be regarded as the pro­genitors of the teleosts possessing the swim bladder of hydrostatic type. So it is logical to think that fishes having the hydrostatic type of swim-bladder evolved independently.<<

Looks like scientists are confused what actually happened, but it may have been a case that organisms in which lungs evolved while gills were retained, evolved from those in which only gills were present. How did it happen? How long does it take to connect a brand new organ to circulatory system in a way fundamentally different compared to the way all other organs are connected? Besides that, a tree is an object that features both continuous lines that may present thousands or millions of generations of continuous development, as well as discrete splitting points that present what exactly? In how many generations occurs splitting actually?

 

You do understand that what Darwin said is meaningless in of itself... right? Hydrostatic swim bladders evolved into swim bladders that were used to breathe air. It's quite possible the lungfish is not in the evolutionary lineage that includes animals with lungs. I see no reason to assume this, can you tell us why you would assume this? 

Edited December 20, 2017 by Moontanman

[Hrvoje]

If you ask me do I need you to explain me that authority has no place in science, then the answer is no, and I resent that question of yours. I did neither try to appeal to his authority nor to undermine it, since authority is irrelevant in science, I simply mentioned what he wrote in "On the Origin of Species". I see no sense in the other question too, as I only assumed that african lungfish circulatory system (described as "the beginnings of a double circulatory system" in that question on biology.stackexchange.com) evolved from a single circulatory system, which is characteristic for fishes. That seems like a reasonable assumption to me, if you think is not, then what do you propose it evolved from?

[Moontanman]

1 hour ago, Hrvoje said:

If you ask me do I need you to explain me that authority has no place in science, then the answer is no, and I resent that question of yours. I did neither try to appeal to his authority nor to undermine it, since authority is irrelevant in science, I simply mentioned what he wrote in "On the Origin of Species". I see no sense in the other question too, as I only assumed that african lungfish circulatory system (described as "the beginnings of a double circulatory system" in that question on biology.stackexchange.com) evolved from a single circulatory system, which is characteristic for fishes. That seems like a reasonable assumption to me, if you think is not, then what do you propose it evolved from?

 Well first of all if it wasn't an appeal to authority I read it that way and I apologise. How ever assuming that a living species is anything but vaguely relative to today's organisms needs some citation. I offer you modern amphibians, many think they are ancestral to modern reptiles but they branched off well before reptiles and are not ancestral to them so using them as a model to explain adaptations in modern animals is not a good idea. 

Lungfishes are unique and may or may not have branched off well before the evolution of modern animals. In fact they very may have evolved after modern circulatory systems evolved... I know some fish able to breath air are recent as are some fish that walk on a solid surface. I wouldn't claim they are ancestral to modern land animals...  

Edited December 21, 2017 by Moontanman

[Hrvoje]

I'm not talking about modern circulatory systems, and what (if anything) evolved from the lungfish circulatory system, I'm just asking you what do you think the ancient circulatory system looked like, the one from which the african lungfish circulatory system evolved? Do you think it wasn't single circulatory system?

[Moontanman]

5 hours ago, Hrvoje said:

I'm not talking about modern circulatory systems, and what (if anything) evolved from the lungfish circulatory system, I'm just asking you what do you think the ancient circulatory system looked like, the one from which the african lungfish circulatory system evolved? Do you think it wasn't single circulatory system?

 

Ultimately everything evolved from single celled ancestor, I would have to say it did indeed evolve from a single circulatory system at some point. I don't see how that can be disputed... 

But I think you are making too much of the diagram or maybe too little. You seem to think that the "lung" is separate from tissue in some manor but all that would be required is increased blood flow to the swim bladder. That would seem to favor, at some point, a more differentiated blood system to the swim bladder/lung. 

The state that is being skipped in the diagram is the transition from a swim bladder connected to the gut to a vascularised swim bladder/gut to a partitioned swim bladder and gut to a swim bladder/lung to increased blood flow via pulsating blood vessels to the swim bladder/gut...  Lots more steps no doubt I've left out...

[Hrvoje]

If you think I'm making too much of the diagram here, then you think I have no business here discussing things with you, as I don't see how an informed conversation on this topic can be led without posting at least these two diagrams, and I would resent that thought of yours.
If you think there is too little diagrams posted here that show all the stages in between, in the development of the african lungfish circulatory network from the single circulatory network of its ancestor, then fine, please post them. I'm struggling to find them, but in the process of searching for it, I think I maybe answered one of my questions by my self. The reason for showing a double bypass in the first picture is to present the bypass arterioles of the third and fourth gill arches (which do not actually have gills), as explained here in "Perfusion of water" chapter: 
https://en.wikipedia.org/wiki/Lungfish
These bypasses also get open and closed with a system of valves, ie not only ductus arteriosus and the pulmonary artery although I mentioned only them previously when talking about bimodal respiration and circulation.
If you actually read what I wrote, instead of constructing what you think I think, you would understand that I'm interested in how many stages of development there are exactly, and what they look like. I asked that here:

https://biology.stackexchange.com/questions/68470/replumbing-of-a-swim-bladder

"In how many stages could have such change occur? In one of the first papers in topology, ..."

But the feedback there is equally insightful and informative as the one I received here so far. And yes, I think that the "lung" is separate from "tissues" in a very precise manner in the first picture, and that is how it is connected to the circulatory system, and how it actually contributes to blood oxygenation, which other "tissues" don't.

[Endy0816]

I think he's talking about how you are not looking at the gastrointestinal tract too. At work now, but saw a reference earlier mention the lungs started as an offshoot of that.

[Moontanman]

Endy is correct, you are leaving out the gut and the stages in between. You ask how a modern animal is connected with ancestors from around a quarter billion years ago and expect it be explained in one step.  As for how many stages there were, as many as there are generations of fish between now and the last common ancestor of that fish and all other fishes... 

No one is saying you have no right to discuss this but it has to be discussed accurately, not some idealised or simplified version. 

And BTW, there are fishes alive today that demonstrate the various gross stages between a gut only fish and a lung only fish. Arapaima are a good example, they will drown if held under water but they do have functioning gills, as do Bowfin, Bichirs, some Catfish and so on. Some fish can walk on land but have no lungs, some fish can walk on land and don't even have a swim bladder. Some fish walk around on perfectly functional legs and can't go on land and in fact live at great depths in the ocean. It's really a very complex subject... 

Edited December 21, 2017 by Moontanman

[Hrvoje]

You are right, I'm focused on respiratory and circulatory system now, and I'm not sure what is your objection, I'm not interested in gastrointestinal tract at the moment, except to observe that all its organs are mere oxygen consumers. Therefore I will ignore this excerpt from the article that I already linked, because it's of no relevance for the discussion:

>>The swim-bladder in fishes and the lungs of tetrapods are closely similar in structure and development. Both these structures are inti­mately associated with the gut. The lungs of higher vertebrates arise exactly the same way as that of the swim-bladder in fishes. Both develop as outgrowths from the gullet and the glottis occupies exactly the same position.<<

African lungfish is a modern animal, that however may not significantly evolved for a long time, certainly did not significantly evolve in each generation, in fact, changes that were relevant for circulatory network topology may have occured in very few generations. The point is that such changes must be developed in concert with each other. For example, for these two bypasses to develop at the time of appearance of the lung, gill capillaries should disappear from the third and fourth gill arches, and be replaced with arterioles with a valve, and this should be synchronized with the development of ductus arteriosus, pulmonary artery and its vasomotor segment, separation of atrium, separation of ventricle. This development simply cannot be performed gradually over a million of generations so that in the first generation only one millionth part of that change is performed, then in the second generation another millionth part and so on. That simply has no logic whatsoever. I mean, how would you divide that change in such a manner, and more importantly, why? There may be certain stages in that development, but certainly not millions of them. And most importantly, how would you attribute such changes to random mutations?

[Moontanman]

28 minutes ago, Hrvoje said:

You are right, I'm focused on respiratory and circulatory system now, and I'm not sure what is your objection, I'm not interested in gastrointestinal tract at the moment, except to observe that all its organs are mere oxygen consumers. Therefore I will ignore this excerpt from the article that I already linked, because it's of no relevance for the discussion:

>>The swim-bladder in fishes and the lungs of tetrapods are closely similar in structure and development. Both these structures are inti­mately associated with the gut. The lungs of higher vertebrates arise exactly the same way as that of the swim-bladder in fishes. Both develop as outgrowths from the gullet and the glottis occupies exactly the same position.<<

 

The swim bladder arose from the gut in fishes, it gave rise to lungs in fishes, the lungs of higher vertebrates is not a seperate evolution but evolved from the gut/swim bladder in fishes. You cannot ask how the circulatory system/respiratory evolved without taking into account the gut to swim bladder to primitive lungs. 

 

28 minutes ago, Hrvoje said:

African lungfish is a modern animal, that however may not significantly evolved for a long time, certainly did not significantly evolve in each generation, in fact, changes that were relevant for circulatory network topology may have occured in very few generations.

Citation please. 

 

28 minutes ago, Hrvoje said:

The point is that such changes must be developed in concert with each other. For example, for these two bypasses to develop at the time of appearance of the lung, gill capillaries should disappear from the third and fourth gill arches, and be replaced with arterioles with a valve, and this should be synchronized with the development of ductus arteriosus, pulmonary artery and its vasomotor segment, separation of atrium, separation of ventricle. This development simply cannot be performed gradually over a million of generations so that in the first generation only one millionth part of that change is performed, then in the second generation another millionth part and so on. That simply has no logic whatsoever. I mean, how would you divide that change in such a manner, and more importantly, why? There may be certain stages in that development, but certainly not millions of them. And most importantly, how would you attribute such changes to random mutations?

You are incorrect, the scientific consensus says these things did evolve in small stages, if you claim otherwise a citation is required...  

Quote

And most importantly, how would you attribute such changes to random mutations?

This is a strawman argument, no one would say random mutations resulted in these changes apart from another factor. The other factor is natural selection and every individual is a transitional species. yes millions of generations and each is transitional to the next. 

[Hrvoje]

In order to discuss accurately, one should focus on not so many things. So, in fact, instead of taking into account some more things, let's talk about a topic of discussion, and that is only circulatory system (not respiratory), and how it continously evolved. We still need diagrams that present intermediary stages of its development.

If I say that something may have happened, then it must be speculation, so why would you need some citation for that? 

If I, on the other hand, say that there is no logic whatsoever for something to have happened, then again citation seems like appealing to someones authority, and that is something we don't want here. We need those diagrams that I asked you to post, that will convince us that there can be millions of stages in development of that circulatory system, because I'm struggling to find them by myself. Appealing to scientific consensus (which might be non existent anyway, we cannot interview all nowadays authorities) is not a step in right direction, it is not a scientific method.

Let me rephrase my last question: How would you attribute such changes to random mutations and natural selection? And let us not jumping to answer that question first, let us answer the previous question first.

[Hrvoje]

And you don't have to post a million of diagrams, because that would be impossible. Post at least 5 of them that would let us see how there is a room for further extrapolation of an arbitrarily large number of stages between each of them.

Edited December 22, 2017 by Hrvoje

[Moontanman]

6 hours ago, Hrvoje said:

And you don't have to post a million of diagrams, because that would be impossible. Post at least 5 of them that would let us see how there is a room for further extrapolation of an arbitrarily large number of stages between each of them.

I'm not going to post any diagrams, you are erecting a strawman, google is your friend... but stay away from AIG and all the other creationist sites... 

You talk as if you assume the lung just appeared. Originally, as an many modern fish there was just a gut. This "stomach" was already heavily vascularized so as to make absorption of nutrients more efficient that fish who did not have "type" the stomach evolved because some fish who lived oxygen poor water started gulping air at the surface. 

This can been seen in modern fish trapped in a body of water with low oxygen levels. The connection to the gut disappeared in fish that didn't live in anoxic water.   

Fish that did live in anoxic water retained that trait because it allowed them to live in areas where they didn't have to compete with other fish. more vascularization allowed them even more of an advantage. Your diagram omits that fact that the bladder had to have a connection to the gut for it to obtain air. Gulping air at the surface into a gut and then transferring  bladder wasn't as efficient as drawing air directly into the bladder and evolutionary pressure favored those animals in which the opening the bladder/lung was closer to the head. Over thousands if not millions of generations the opening to the bladder became a separate tube that muscles could draw air in separately from the gut. Some totally unrelated fishes are in the various stages of this process while some land vertebrates when the other way and lost lungs completely. Opting for breathing through their skins, some actually breath through their anus...  

[Hrvoje]

This is not "my" diagram, and it omits no such thing, as it doesn't deal with air circulation, it only presents schematically blood circulation. Since organisms that had only gills evolved to those that had both gills and lung, then lung must have appeared in the process, you can call it development, formation, shaping, whatever you like. In concert with that morphological change, that no doubt could have happened continuously over a long period of generations, occured a change in a cardiovascular network that supports functioning of a new organ in profoundly new and different way. The question is when and how did it happen, it could have happened very early on, but it also could have start only after the new organ was completely shaped, equipped for respiration with alveoli and bronchioli (which is actually a separate detail from mere shaping of the organ) and in fact may have contributed to blood oxigenation for some generations but still working in the old single circulatory system mode. For example extant hydrostatic swim bladders that have no respiratory function, are they not connected that way to cardiovascular system?
So formation of the organ has nothing to do with remodelling its connection to the circulatory system, it is just another thing that has to be done symultaneously for the whole thing to make sense. The only thing that makes no sense is the idea that this remodelling may have occured continuously over a million of generations, because making a connection or disconnection is a binary discrete change, not a continuous one.
Since google is apparently only my friend here, I have found some further science articles:

http://circres.ahajournals.org/content/circresaha/25/1/23.full.pdf
http://biologylabs.utah.edu/farmer/manuscripts/1999 AnnuRevPhysiol61.pdf
http://biologylabs.utah.edu/farmer/manuscripts/1997 Paleobiology23.pdf

What do they tell you about the subject and my question?
And finally, I resent your mentioning of creationist sites, stick to the subject if you can and stay away from insinuations.

[Moontanman]

4 hours ago, Hrvoje said:

This is not "my" diagram, and it omits no such thing, as it doesn't deal with air circulation, it only presents schematically blood circulation. Since organisms that had only gills evolved to those that had both gills and lung, then lung must have appeared in the process, you can call it development, formation, shaping, whatever you like. In concert with that morphological change, that no doubt could have happened continuously over a long period of generations, occured a change in a cardiovascular network that supports functioning of a new organ in profoundly new and different way. The question is when and how did it happen, it could have happened very early on, but it also could have start only after the new organ was completely shaped, equipped for respiration with alveoli and bronchioli (which is actually a separate detail from mere shaping of the organ) and in fact may have contributed to blood oxigenation for some generations but still working in the old single circulatory system mode. For example extant hydrostatic swim bladders that have no respiratory function, are they not connected that way to cardiovascular system?
So formation of the organ has nothing to do with remodelling its connection to the circulatory system, it is just another thing that has to be done symultaneously for the whole thing to make sense. The only thing that makes no sense is the idea that this remodelling may have occured continuously over a million of generations, because making a connection or disconnection is a binary discrete change, not a continuous one.
Since google is apparently only my friend here, I have found some further science articles:

http://circres.ahajournals.org/content/circresaha/25/1/23.full.pdf
http://biologylabs.utah.edu/farmer/manuscripts/1999 AnnuRevPhysiol61.pdf
http://biologylabs.utah.edu/farmer/manuscripts/1997 Paleobiology23.pdf

What do they tell you about the subject and my question?
And finally, I resent your mentioning of creationist sites, stick to the subject if you can and stay away from insinuations.

Ahh, so your real agenda rears it's ugly head. No one thinks that lungs simply appeared ex nihilo, lungs developed from the gut which developed into a swim bladder because fish would swallow air for buoyancy, this developed in the ability to extract oxygen from this air. This gut/swim bladder connection survives to this day in many fishes. I have no idea why the lungfish developed that way but you cannot simply ignore where the air comes from. Your diagram does this and as such is incomplete. The binary system you tout is an artifact of your own misunderstanding... 

[Hrvoje]

But everyone knows that the air comes to lung from the outside. Why would you present such a thing on the diagram that shows circulatory system, how would that help its clarity, or answering my question?

Everyone understands that must be so for the respiratory swim bladder too, and for hydrostatic one, only if pneumatic duct disappears, then the gas gland has to introduce gas (usually oxygen) into it. What does it have to do with the evolution of african lungfish circulatory system?

[Endy0816]

Lung is good at gas exchange now, it wasn't originally.

If we imagine there are hard divisions between systems, then we might say as it evolved it later fell under the circulatory system.

[Moontanman]

11 hours ago, Hrvoje said:

But everyone knows that the air comes to lung from the outside. Why would you present such a thing on the diagram that shows circulatory system, how would that help its clarity, or answering my question?

Everyone understands that must be so for the respiratory swim bladder too, and for hydrostatic one, only if pneumatic duct disappears, then the gas gland has to introduce gas (usually oxygen) into it. What does it have to do with the evolution of african lungfish circulatory system?

You need to show it because it's part of the circulatory/lung system. And your question is a strawman

Never assume everyone understands anything and the gas contain in swim bladder is not oxygen. Air is not oxygen, it is a mixture of gases. 

Quote

lungs output directly into a separate atrium, instead of mixing output together with other organs that do not contribute to oxygenation into a single atrium

I don't know what you are on about here, please elaborate 

Quote

lungs have separate input from gills through pulmonary artery, instead of through dorsal aorta that brings blood to other organs

It evolved like that, is that a problem for some reason? Evolution doesn't make things perfect, it makes things just good enough. 

Quote

dorsal aorta receives input from gills through ductus, and from a gill bypass that receives input from the separate ventricle filled by lungs

Evolution works by adapting one thing to do another job. It doesn't create new things unrelated to every thing else. I can speculate that when the swim bladder started to become important larger arteries to the swim bladder became a positive trait. Blood vessels that pusate would be another step forward in fitness. As you can see in the diagram a fishes heart is not much more than pulsating blood vessels. It's not a long stretch to see that a pulsating blood vessel to the swim bladder would be a positive trait.  

Edited December 25, 2017 by Moontanman

[Hrvoje]

The gas contained in swim bladder can be air, if it is inhaled from the outside, which can be done only if pneumatic duct is present. Otherwise, it is whatever is produced by a gas gland, and that mixture of gases is not air. For instance, the eel Synaphobranchus has been observed to have 75.1% oxygen, 20.5% nitrogen, 3.1% carbon dioxide, and 0.4% argon in its swim bladder. 

This is not "my" diagram, it was obviously created by people who are seriously engaged in science, unlike you, and it would be silly to take into account your objections about that diagram.

Besides that, if you think that my question is a "strawman", whatever that means, stop posting here.