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When I say multicellular I mean it's made of more that one viruses. Basically it's a bunch of viruses that act like viruses but use the viruses made by infected cells to build a "multicellular" lifeform (which would break up into smaller copies of itself and the cycle repeats). My thoughts are it would be a parasite that would devolve reproduction and use other living things for it. It wouldn't be an advanced lifeform but complex enough to have a small brain-like structure (with not much more intelligence than a snail); it would also be large enough to be noticed and might have a slug-like shape. Essentially it's a normal life form but without reproduction, it has almost everything else.

Could this exist within reason? if it helps:

  • this is set in a alternate reality where Saturn's moon Titan is more Earth-like and has life (it's on Titan)
  • it is preferably a creature that mainly lives in the ocean

So could it happen?

Note: for lack of a better term I am calling it a virus when in reality is is an in-between kind of organism.

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    $\begingroup$ It's tricky, it wouldn't realy fit the definition of virus that we use, but that doesn't mean it couldn't exist - it would just be given a different name. $\endgroup$ – Tantalus' touch. Apr 16 at 3:44
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    $\begingroup$ yes it is called any obligate parasite. Once a virus makes a cell its not a virus anymore its just another organism. $\endgroup$ – John Apr 16 at 4:18
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    $\begingroup$ they lack ribosomes... $\endgroup$ – user6760 Apr 16 at 4:24
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    $\begingroup$ So in other words, you're looking for a multicellular organism that requires infecting a host to reproduce? That's much more possible than a virus doing this. Though a man-made virus could hijack a cell to do almost anything. $\endgroup$ – NomadMaker Apr 16 at 11:10
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    $\begingroup$ @John is right - once it's multicellular, it's a parasitic animal. ("Animal" in the sense that it would fit into the animal domain, although it might have to get its own phylum.) $\endgroup$ – tbrookside Apr 16 at 12:11
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Basically it's a bunch of viruses that act like viruses but use the viruses made by infected cells to build a "multicellular" lifeform (which would break up into smaller copies of itself and the cycle repeats).

There are two concepts that you might be interested in:

  1. Oncoviruses are viruses that cause cancer. A group of different oncoviruses might cooperate to provoke a cancer in a multicellular organism, therefore hijacking that organism's metabolism not only to make copies of themselves, but also to rapidly make new cells that are both good at evading the immune system of the host and making lots and lots of new viral particles.

  2. Virophages are viruses that can only infect a cell in the presence of another virus. In fact the virophage is a parasite for the other virus, as they need to hijack another virus's replication factory. This may be the reason why your viruses need to be together in the first place, but if you wish they may also have evolved past parasitism and into cooperation.

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  • $\begingroup$ hmm, these are interesting, i could maybe use the first one in some way $\endgroup$ – Topcode Apr 16 at 18:23
  • $\begingroup$ These oncoviruses remind me of plant gall bacteria. $\endgroup$ – XenoDwarf Apr 16 at 22:51
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The basic concept of a virus is a protein capsule (capsid) surrounding RNA or DNA. The virus hijacks (either by injection or entry) a cell's protein synthesis and genetic replication abilities to reproduce multiple versions of itself. Viruses (tens to a few hundred nanometers across) are very small compared to the cell (a few micrometers to hundreds of micrometers across) This is really simplified, of course, but generally true.

Viruses in and of themselves are not "alive", just like the individual organelles of cells are not alive. However, to form a living cell, you need more than DNA and proteins, which are the only things that viruses are composed of (yes, some viruses have lipid structures, but these are optimized for entry through cell membranes and are nowhere near the complexity of membrane-like structures). Even the simplest cells have highly complex and differentiated internal structures. Thus it is highly unlikely you could have an organism form from virus-like, non-cellular structures.

A similar concept which might work (I don't believe there are any IRL counterparts, but that doesn't mean its physically impossible), is for an organism which produces a series of viruses which infect cells and produces the components necessary to build new cells which come together to form this organism. Thus the viruses serve as gametes in a strange way. Of course, this is just to keep the bizarre form of reproduction, I'm not sure what evolutionary pressures would result in a multicellulared organism having this method of reproduction, but I see no ab initio reason why this would be impossible.

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  • $\begingroup$ im sorry if my wording was unclear but: I am not looking for an actual virus, more of a devolved cell that is in the middle of the two groups meaning it would do most cellular function except for some reason it cant do mitosis $\endgroup$ – Topcode Apr 16 at 4:22
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So as far as multicellular virus go, I’m not sure. These ideas are using a vector organism that creates and injects viruses. I don’t see a way that viruses can create multicellular organisms without at some point being one.

Tumour Babies

My first idea would be a creature that employs the host cells to create masses of stem cells which then differentiate much like a regular eukaryote embryo.

The first stage would need to involve creating a shell or ‘womb’ to encase the alien cells, most likely presenting the surface proteins of the host cells.

After this the embryo would form itself inside the ‘womb’, protected from antibodies by the shell. Multiple wombs would spring up in areas of the host with highly regenerative cells - for us unfortunately that’s the external membranes (tongue, mouth, gastrointestinal lining). If the ‘seeding’ virus bodies have a capsule to protect them from the stomach then they can reach the nutrient-filled and quickly dividing cell population of the gut, though there will be competition down there.

The main problems I see with this is mutation and evolution. Viruses are simple and quick at reproducing, so mutations are fast and so is adaption. They create so many ‘offspring’ so quickly that even if most mutations are unviable then the number of null and positive mutations still produces a net positive increase. With larger organisms this is harder. Still talking about mutation, creating mutation-prone masses of stem cells very quickly is just asking for a tumour.

Crustacean Carnage

Obviously this concept doesn’t exist in nature, but you can bet Earth is weird enough to get close. Read this sh** and tell me it isn’t terrifying.

I know it’s an article so even though I recommend the read here’s the gist: Stem crustaceans (basically a barnacle but not really) called Sacculina float around in a planktonic larval form, looking decently plankton-like until they land on a gap in a crab’s armour. They then insert a barb into the crab and inject the head-mass of cells called a vermigon into the blood stream and then to the intestine in which it then takes root - literally - and grows throughout the entirety of the internal tissue of the crab.

Once it’s got a hold, it gives the crab (regardless of sex) the ‘I’m pregnant protect the eggs’ hormones and forms a tumour-looking body that bursts through the crabs gonads (destroying them) and starts cooking up babies. The crab will clean, nurse and protect this sac as of it were it’s own eggsac. Once a free-swimming male comes in to fertilise the crab climbs to a high place and releases ‘their babies’.

This is obviously only highjacking the reproduction of an animal in a physical way, as they still need a male parasite, but the lifecycle can be used as a basis. The virus slug injects their microscopic vermigon into the host, taking root and multiplying, but specifically using the host cells to do the cell production.

The problem with this example is that the single source and single eggsac means this is basically mass cloning, and for complex life this is usually not sustainable for a viable gene pool.

The Worst of Both Worlds

The slug infects either sex, and the virus injection quickly travels to the gonads, completely replacing the germ cells’ DNA. Once mating happens between an infected and a healthy individual (perhaps the virus promotes sexual drives) both will become infected. This first mating will be unsuccessful as the germ cells will not merge. Once a second mating occurs (this parasite may rely on second chances) both germ cell populations will have virus DNA and will successfully germinate. The female will then nurture the parasitic offspring (maybe multiple) and give birth to them. This one is not fun.

The advantage: technically sexual reproduction without ever creating their own germ cells. Complex life-viable gene diversity is sustained.

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  • $\begingroup$ this is the closest answer yet, and also the most terrifying. I might use something like the first part $\endgroup$ – Topcode Apr 16 at 14:41
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A multicellular life form needs reactions that take place inside cells. It needs to metabolize a lot of energy (remember: mitochondria is the cell's powerhouse).

A virus does not have all this complexity and that is the reason it needs to parasitize cells.

Viruses are also small, about 10% the size of a mitochondria, and mitochondria are about 1% the size of an ordinary cell.

So, the quick answer is no.

However, perhaps, some kind of prokaryotic-like life form can fulfill what you want in your story.

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  • $\begingroup$ im sorry if my wording was unclear but: I am not looking for an actual virus, more of a devolved cell that is in the middle of the two groups meaning it would do most cellular function except for some reason it cant do mitosis $\endgroup$ – Topcode Apr 16 at 4:22
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    $\begingroup$ If it can't do mitosis there is no way it can hijack another cells mitosis to get a different cell structure. Your biggest problem is the sheer volume of DNA it needs which is not going to fit in a virus. $\endgroup$ – John Apr 16 at 15:17
  • $\begingroup$ @John please read the comment and think about what you just commented "I am not looking for an actual virus," how can i clarify that for you? $\endgroup$ – Topcode Apr 16 at 15:49
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There are some creatures on this planet that have elements of what you want:

Dictyostelids (https://en.m.wikipedia.org/wiki/Dictyostelid) are unicellular eukaryotes that does undergo mitosis, but they can "decide" to group together and form a multicellular creature.

Microsporidia ( https://en.m.wikipedia.org/wiki/Microsporidia) are unicellular eukaryotes that live inside other eukaryotic cells. They cannot reproduce outside of these host cells. They do spread out and infect other hosts.

You could think of a eukaryotic creature that starts off living inside cells of another being, and then at some point they come out and aggregate. Maybe this exists already on earth, though i dont know. But considering the two creatures i mentioned it seems possible. They could synchronize their departure via hormones that the host produces.

If you want more dependence, you could think of the mitochondria in our bodies. They only have about 13 genes, not enough to perform all of their functions. In the course of evolution there was horizontal gene transfer to the host. The mitochondrion was once an independent bacterium, but it has evolved dependence to the host, as well as the host to it.

I know this does not include really a virus, but some parasitic unicellular organisms can be very dependent on their host for reproduction, and assembling from unicellular to simple multicellular is possible.

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A multicellular virus could start as a membrane-bound virus, that infects a cell that can survive the infection. The virus would be able to reproduce easily, and could eventually bind together into a multicellular creature, with the true cell intermixed with its tissues

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