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I've been creating a world where most-to-all of its life resides in the deep ocean. For story purposes, I would like said creature to have lungs, but it is not necessary.

Description of the Creature in Mind The creature in question is something along the lines of a massive sea serpent. Ideally, it would be able to either surface into an area that has air in it and be able to move on land, through legs or just by slithering along in a similar fashion to a snake. It lives around 2000 meters down, give or take ~500 meters.

Ecosystem of the Planet The planet is a large oceanic planet, which is slightly larger than Earth, and only has some small archipelagos for land. The plants of the planet primarily exist at the surface, as to the much smaller prey animals. small predators eat these smaller prey animals, but most animals who are purely "prey" don't exist very far down. Predators prey on smaller predators in a hierarchical type system, with the largest predators also bien the deepest. The creature would be in the mid-size range, but they have the advantage of being omnivores: there are massive underwater caverns that are filled with air. Very large plants, in some ways similar to those on Earth, grow in these caverns, and are adapted to using chemosynthesis to create energy, along with some small to mid size mammals and reptiles. This is really the only sizable prey besides smaller oceanic predators down this low, so the creature profits greatly from this resource. Due to much larger predators from below, they are forced to move around, and as these caverns, while common, are not common enough to allow for consistent breathing. These creatures do have large enough lungs to get to the surface, but this is impractical for them, as it would include long diving and surfacing sessions that may make to creature more vulnerable to predators.

By my understanding, there are many types of bacteria that could create oxygen as a waste resource, not through photosynthesis, but by some form of chemosynthesis, but I'm not certain. It is possible for a reasonably large creature (whale sized or larger) be able to host some form of bacteria in its body in a symbiotic relationship as a way of generating the oxygen that it needs to live? I'm presuming that the bacteria simply consumes some of the food that the creature eats, and then the oxygen created is somehow sent to the lungs.

If there are any other ideas as to how a creature of this size could get air, besides gills, as they collapse in while in regular air conditions, they would be helpful.

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    $\begingroup$ One can always imagine an almost arbitrarily thin jellyfish type of animal that can become as big as you wish with almost no oxygen requirements that is able to contain an entire ecosystem. Could you give us details on what your creature is supposed to be? $\endgroup$ – Raditz_35 Oct 27 '17 at 16:59
  • $\begingroup$ What's the ecosystem look like? Does the creature you're designing live its entire life in the deep ocean, or does it just go down there to feed? Why is most life on the world there? $\endgroup$ – Rob Watts Oct 27 '17 at 17:01
  • $\begingroup$ @Raditz_35 Ideally, the creature would be something similar to a gigantic sea serpent, or the like. I need it to be able to surface, but most of its life is going to be spent in the deeper parts of the ocean. $\endgroup$ – Dawnfire Oct 27 '17 at 17:06
  • $\begingroup$ @RobWatts The ecosystem of the planet is organized to have increasingly larger predators in the deeper depths, with the small prey up at the surface. The planet only has a few small archipelagos, but it does have massive air-filled underwater caverns, similar to some underwater air filled caves, only much larger. The creature needs to be able to get into these caverns, but hey are too far apart to really be practical breathing sources, and they often suffer cave ins due to the massive pressure of the ocean. The creature would never normally surface, but it could, if necessary. $\endgroup$ – Dawnfire Oct 27 '17 at 17:12
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    $\begingroup$ Why would evolution come up with such a creature ? If it needs oxygen to survive then there's simpler and more effective ways to harvest it from the ocean, gills are a pretty good idea :) $\endgroup$ – Jack Judge Oct 27 '17 at 17:19
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I like very much the premise: sort of the opposite of sperm whales who live shallow and feed deep. And I am always loving the combination of giant sea monsters, gianter deeper sea monsters, and exotic bacterial metabolism!

from Bacterial oxygen production in the dark. Ettwig KF et al Frontiers of Microbiol. 2012 Aug 7;3:273

For a long time, photosynthesis was the only biological process known to produce oxygen. Cyanobacteria, green plants, and algae use light energy to split water(E0′ = + 0.82⁢V) via photosystem II. The electrons obtained serve NADPH and ATP generation for carbon dioxide fixation; oxygen is a mere by-product of this metabolism...

De novo oxygen production can be driven by either light or chemical energy. The second, “dark” way takes advantage of oxidants with a more positive redox potential than the O2/H2O couple. Only a few redox couples are biologically relevant in this respect: hypochlorite(ClO-)/Cl-;E0′ = + 1.31⁢V, chlorite (ClO − 2 )/ClO − (E 0 ′ =+1.28V),ClO − 2 /Cl − (E 0 ′ =+1.08V), nitrous oxide (N2O)/N2(E0′ = + 1.36V), ⁢ nitric oxide (NO)/N2O(E0′ = + 1.18V), ⁢ and NO/N2(E0′ = + 1.27V). Most of these compounds are intermediates in the respiration of (per)chlorate and nitrate/nitrite, respectively. In this perspective, we review what is known and still to be learned about oxygenic pathways from chloro-oxo species and nitrogen oxides, with a focus on a hypothetical enzymatic mechanism for the hitherto elusive nitrite-driven oxygen production.

To make it work you need a (presumably mineral) source of strong oxidizers as listed that the bacterial symbionts could use; I think in these creatures the production of oxygen is tied to the energy they get back from oxidizing the substrate with it. It is pretty clear in the text that these metabolic paths are not making bubbles of oxygen like plants do. Whatever oxygen is produced is in small amounts.


But here is another idea for your creature as regards oxygen: it minimizes its use of oxygen by using anaerobic metabolism. When humans do this it is https://en.wikipedia.org/wiki/Anaerobic_glycolysis Energy can be derived from glucose without oxygen in short bursts. Lactate is the end product and builds up - this is the burn you feel when you feel the burn. Ultimately the liver has to oxidize the lactate when there is oxygen around again. It is an inefficient use of sugar compared to aerobic metabolism but we can do it.

But what about a creature that did anaerobic glycolysis and then ignored the end product? Yeast do exactly this - the end product is ethanol and it just builds up until they cant stand it any more. Or it evaporates away. A sea monster with lots of food and little oxygen could just let the lactate waste product ooze out of its pores into the water. It would need a lot more food (I think three times as much?) than a comparably sized creature using oxidative glycolysis, which extracts more energy from the sugar. But it could get by with much less oxygen.


I could imagine such a creature storing huge amounts of oxygen in myoglobin. Whales store oxygen in myoglobin and this is why some can hold their breath under conditions of exertion for over an hour. If you had a creature which did only anaerobic metabolism and jettisoned the waste it would have much lower oxygen requirements. Maybe you could have only the brain require oxidative metabolism with the rest of the body using anaerobic. One whale sized breath could last the creature weeks.

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  • $\begingroup$ @Will it you seems you might have an answer to my question ;-) $\endgroup$ – anon Oct 30 '17 at 14:40
  • $\begingroup$ @anon - I looked hard at your question as you might imagine. But to do it right I wanted to calculate the enthalpies and I am sad to say that was beyond my abilities. I am still ruminating on it... $\endgroup$ – Willk Nov 1 '17 at 13:35
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Here on Earth, deep sea bacteria do power entire ecosystems, but not through photosynthesis or the creation of oxygen. Rather, they harvest the heat energy and chemicals pouring out of oceanic vents and use chemosynthesis to both provide food and energy for themselves, as well as creating the bottom rung of a food chain particular to that environment.

enter image description here

Hydrothermal vent

Any creatures that live in the environment will not be using oxygen for their life processes in the way fish or whales do, so their consumption of chemosynthetic bacteria is more analogous to food rather than oxygen.

Indeed, something like this might explain the strange life forms from the Ediacaran Period.. If they were living by capturing and digesting chemosynthetic bacteria, this might explain their rapid spread during a period when the Earth's atmosphere was not fully oxygenated yet, and possibly their mysterious structure (they don't seem to have a body plan the way Cambrian creatures do, and may have been simply filtering out bacteria from the water).

enter image description here

Possible reconstruction of Ediacaran life

This combination of factors suggests that whatever life forms are evolving in the depths of your ocean may not even be remotely analogous to what exists on Earth. On the other hand, the life forms which do live around hydrothermal vents on Earth today are clearly related to worms and other creatures which evolved in the Cambrian period, so they obviously were more competitive in that environment than Ediacaran life forms were.

enter image description here

Tube worms living near hydrothermal vents

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  • $\begingroup$ This is a horrible misrepresentation of both hydrothermal vent fauna and the ediacaran fauna. There is no obvious ling between vent fauna and the ediacaran other than the same link thant joints the ediacaran with everything alive today. There is no evidence for bacteria symbiosis in ediacaran fauna, If you want to know why they look the way they do consider that they basically evolved from something like Trichoplax, in which the entire animal is the stomach. $\endgroup$ – John Mar 24 '18 at 3:40
  • $\begingroup$ Since no one knows how Ediacaran life forms or the Ediacaran ecosystem worked, it is rather silly to suggest that this is "mischaracterized". The paragraph clearly states that this is a possible reconstruction, if you have a different interpretation, write an answer. $\endgroup$ – Thucydides Mar 25 '18 at 2:45
  • $\begingroup$ no it really doesn't the placement makes it look like the title of the image not a statement about the write up. $\endgroup$ – John Mar 25 '18 at 15:21
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The answer is sure, but I'm going to say no because of your lack of understanding on how the chemistry works here

[going to ignore nitrogen in this for simplicity] In photosynthesis plants take in water H2O, energy in the form of sunlight, and CO2 to form sugar compounds, basically hydrocarbon chains. A hydrocarbon chain is a molecule of carbon atoms connected to each other in a chain of any length and 2 hydrogen atoms connected to each carbon atom. When reacted with oxygen this releases energy. So the production of sugar is a means of storing energy. So going back the H20 and CO2 you can see there is a lot of O2 (oxygen) leftover from taking all those H's and C's. That is why O2 is byproduct.

Without providing your organism an energy source and the oxygen containing chemicals to make its own hydrocarbon chain you will never be able to produce oxygen.

In the circumstances you provide, I see the chances of this occurring to be very slim. There could be some potential radical ways to achieve this but it would take some radical changes to your concept.

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  • $\begingroup$ What kind of radical changes are you talking about here? I'm wondering how to potentially make them work. $\endgroup$ – Dawnfire Oct 27 '17 at 18:08
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    $\begingroup$ The reason I didn't mention them is because you need to change both how this creature works, its environment, as well as the ecosystem it lives in. Which is an incredibly lengthy topic with multiple cascading factors. A better way to begin to approach this is if you would ask about other theoretically possible ways an organism could produce oxygen other than through photosynthesis. Then pick one and build an ecosystem that supports it $\endgroup$ – anon Oct 27 '17 at 18:58
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The thermodynamics are probably wrong for a whale - sized creature. And, chemosynthesis does not create oxygen.

Chemosynthesis is a corollary to photosynthesis. It is the synthesis of complex carbon from chemicals (instead of light.)

The production of oxygen is most commonly a result of photosynthesis. The oxygen derives from water. (CO2 + H2O + light -> Sugar and O2)

Chemosynthesis (CO2 (actually probably bicarbonate) + H2S + H2O + O2 -> Sugar and sulfuric acid.)

In both cases CO2 is converted to sugar. One uses light, the other uses H2S. In only the first case is oxygen made. (Oxygenic photosynthesis. There is also something called anoxygenic photosynthesis.)

Secondarily: Although non-photosynthetic O2 production is hypothesized for some methane - oxidizing bacteria, it has not been demonstrated and it is not hypothesized to be excreted. Oxygen is incredibly reactive. It accepts electrons better than almost anything out there. It is only a waste product of photosynthesis because photons are that much more impressive. A large animal that uses oxygen as an electron acceptor (as we do) will require a great deal of it.

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More germane to your goal: The deep ocean has more oxygen than mid-depths in much of the ocean, because of mixing events, upwelling, and other physical processes.

Another possibility is to have your organism use nitrate as its electron acceptor instead of oxygen. Although this raises other problems, it might help you here.

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EDIT: Huh, cool! Sometimes AFAIK isn't far enough. Thanks to @P Chapman for enlightening me that there are in fact bacteria that are able to create their own oxygen. It doesn't solve the oxygen problem for the whale-like deep ocean creature because it'd all be metabolized within the cell, but it's incredible nonetheless.


Not with the biology we know of. The only way oxygen is produced via biological reaction is through photosynthesis, which requires sunlight. In the deep ocean, there’s no sunlight, so biology can’t make oxygen.

I suppose it’s imaginable that an organism could somehow use the thermal energy found at mid-ocean ridges (cold seeps and hydrothermal vents), but AFAIK one doesn’t exist- there are easier ways to get food, like via chemosynthesis, which doesn’t produce oxygen at all.

As the comments have pointed out, there’s also not a huge evolutionary pressure to develop such a skill. There’s enough oxygen in the deep sea for most gilled creatures, and their bigger problem is finding ways to use up the oxygen- that is, finding food to oxidize for energy.

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    $\begingroup$ I do not like contraditing people but you might be interested to know a bacteria that consumes methain and produces oxygen was found several years ago. mpg.de/621120/pressRelease201003241 I find this subject intesting and I am being over enthusiastic but trying not to be agumentative. $\endgroup$ – P Chapman Oct 27 '17 at 17:46
  • $\begingroup$ @PChapman Thank you! I will look in to this, as it could work quite well. $\endgroup$ – Dawnfire Oct 27 '17 at 18:06
  • $\begingroup$ The hypothesized oxygen in that case is kept within the bacterium to drive methanootrophy. It is not understood to be released to the environment. But it is still the correct example here, and remarkable. $\endgroup$ – DPT Oct 27 '17 at 18:27
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What you are describing is not dissimilar from the symbiosis between certain plants and nitrogen fixing bacteria. (https://en.wikipedia.org/wiki/Nitrogen_fixation#Root_nodule_symbioses) .

Further the conversion of water, carbon dioxide, and energy to oxygen is fairly common. (yes I know photosynthesis is not exactly what you are looking for). Your limitation is that this requires quite a bit of energy to do. So you reasonably large creature would need to have a fairly big appetite to make this work. This could be offset somewhat if you were using some other compound besides carbon dioxide which give you a bit of hand-wavy if you want. I would have to go review the chemistry to really give you a good answer and it would probably be boring. An example of alternate chemsitry is here (https://www.mpg.de/621120/pressRelease201003241)

Short Answer: Yes but a good energy source or a somewhat alien ocean will make it more realistic.

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  • $\begingroup$ A bit of hand-wavery is fine. I'll look into the actual chemistry of this. $\endgroup$ – Dawnfire Oct 27 '17 at 18:26
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Someone mentioned using Nitrate as a TEA (terminal electron acceptor). MnOx, after Fe3 (ferric iron) is the third or fourth best TEA after O2, then nitrate.

Im finding in my bioreactor research that facultative fungi (chemo-autotrophs just like you and me) can use stored MnOx (from coal mine drainage) as a back up TEA. (check out www.biominingproducts.com to learn about our self selecting bioreactors).

A creature that scavenges Mn nodules from the ocean floor and then rises to the surface every so often to breath O2 might be able to "replenish" their O2 tanks by switching back and forth from O2 to MnOx. The MnOx provides about 1/5th the energetic exchange compared to O2, but is also a solid, so its density is much higher. 1/5th the energy exchanged, but many times the density of dissolved O2 (0-12mg/l in water at best saturation based on temp)

Perhaps the creature has a special organ "MnOx Lungs" that take the accumulated Mn2 (dissolved Mn) in solution and convert it back and forth between the oxidized and reduced states. Essentially, it would function like a spare O2 tank. The organ would have maintain concentrations of Mn2 in solution until it is time to be replenished by producing a Mn peroxidase. You could say that the fungi which produce the Mn peroxidase (Santelli et al.) inhabit the organ (like our guts) and help in oxidizing the Mn2 for the creature.

Cheers and keep writing!

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This answer doesn't refer directly to bacteria but it might still help. There are some insects that no possess gills and yet are perfectly capable of breathing underwater. Through using microscopic hydrophobic hairs, the insect is able to create a barrier around itself where the danger of water with its nasty surface tension becomes negligible.

But it goes a step further, both carbon dioxide and oxygen are able to diffuse across this barrier allowing the insect to breathe easy. Hope this helps! www.youtube.com/watch?v=f7KSfjv4Oq0&t=4m35s

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YES! Algae, as a matter of fact, most of OUR oxygen is made by algae, not trees and, because algae grows in water, this would be perfect.perhaps you'd have it grow within or next to the lungs.

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    $\begingroup$ Algae cant live 2000 meters down let alone inside a giant leviathan $\endgroup$ – anon Oct 27 '17 at 19:51
  • $\begingroup$ Anon, again! u some sorta critic or something? Suppose however, that the creature emitted a bioioluminesent light, this would sustain the algae, and, depending on the clarity, and reflationary qualities of this "water" light could fall further. Not to mention the fact that a creature like that could probably extend one breath worth of that oxygen for Hours $\endgroup$ – Romell T-J Oct 27 '17 at 19:55
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    $\begingroup$ Then that needs to be part of your answer, simply saying algae completely ignores the needs of algae to the point that this broaches being a non answer. Yes im a critic, I enjoy the problem solving of this site, Im simply trying to help you better solve these problems. $\endgroup$ – anon Oct 27 '17 at 20:01
  • $\begingroup$ @RomellT-J How powerful would this bioluminescence need to be? At this point, it would essentially be carrying around an oxygen generator- I like the idea. $\endgroup$ – Dawnfire Oct 27 '17 at 22:27

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