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On Tetraploidy or Parasitism
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Author:  Pedant [ Sun Mar 18, 2018 7:21 pm ]
Post subject:  On Tetraploidy or Parasitism

Greetings, all! Been working on a science-fiction world for a time now, and I seem to be stuck in a rut as regards the reproductive system of a species of mine, called (for the moment, anyway) the Conjugans. This less-than-subtle name is a reference to a proposed form of reproduction similar to bacterial conjugation:
1. That each individual starts life as a "larva".
2. That each larva can transfer its full complement of DNA to another larva of its own kind.
3. That the cells within do not have nuclei, but instead contain:
a) Thousands of encapsulated plasmids known as microteuchs, which serve the double function of genetic storage and organelle utility;
b) Sutri organelles, which coordinate the merger of genetic material from outside the cell with that inside it.
4. That the organism, with new genetic material, undergoes metamorphosis into a new being, an "imago".
5. That the imago parthenogenetically gives birth to new larvae who are genetically identical to it.
The effect is that individuals adapt as necessary to their surrounding environment somewhat more quickly, with the more adaptable traits spreading to individuals as they live before they give birth to their children.
Of course, this is highly speculative as of yet, and really not quite up to snuff as regards science. I should, however, like to give it a try. My starting query, therefore, is whether the organisms should simply remain diploid throughout, have haploid larvae and diploid imagos, or have diploid larvae and tetraploid imagos. Additionally, are there any methods that someone can think of that might make a little more sense? (If there is enough consensus that it's bonkers I'll drop it and try something else...)

Author:  mèþru [ Mon Mar 19, 2018 6:51 pm ]
Post subject:  Re: On Tetraploidy or Parasitism

Combining DNA most of the time will give random junk the the cell can't activate. There is a danger of the new DNA's information conflicting or impairing the processes read from other DNA.

Author:  Pedant [ Tue Mar 20, 2018 5:53 am ]
Post subject:  Re: On Tetraploidy or Parasitism

Bother. Maybe if it were just the "nuclear" DNA as opposed to the microteuchs, with the latter remaining haploid/diploid throughout?
I mean, I know with meiosis it's an entire living creature being created out of nothing as opposed to having an old creature being altered, but maybe if there were stem cells or something that remained basically untouched, then started reworking the biology of the individual from the inside? Leaving the nervous and circulatory systems haploid, of course.

Author:  Salmoneus [ Tue Mar 20, 2018 3:08 pm ]
Post subject:  Re: On Tetraploidy or Parasitism

The imago, it should be noted, is a different individual from the larva. So really you've just got a two-stage reproductive process:

- two A-people have sex
- one of the A-people has a baby, but dies in the process
- the baby is a B-person, who can't have sex, but who gives birth to lots of A-people anyway

This seems more complicated than the ordinary system, and has some downsides:
a) every time there's a child born in the A-generation, somebody has to die. That means that in A-generations there can be no population growth.
b) it may also have less direct consequences: like, sex becomes terrifying (if you get pregnant, you're going to die!) and the knowledge and experience accrued can't be passed on; more generally, it's harder to maintain cultural continuity

c) people in the B-generation can't have sex, so can't mix their genes. So in half the generations there's no population growth, and in the other half of generations there's no genetic mixing. This seems like it would get outcompeted by faster-breeders!


I think the potential in this system lies in reducing the significance of the A-generation - since they can't grow the population, you want to reduce the proportion of the social cycle spent in the A-state.

And it turns out, there is at least one species that reproduces like that! They're called... humans. What you call "larvae" are usually called "sperm" and "eggs", and what you call "imagos" are usually called "people", but it seems to be the same principle...

Anyway, i'm not saying this can't work. Just... maybe think a bit about the downsides, and what the upsides might be.

Author:  Pedant [ Tue Mar 20, 2018 7:06 pm ]
Post subject:  Re: On Tetraploidy or Parasitism

Ah...yeah, that could be problematic. I was actually hoping that I could find some justification for individuals being alive and then changing into something new, without dying, thanks to the addition of new DNA, as opposed to having a generation that can't breed. Everyone can fertilize, and everyone can breed. They just do it at different times of their life, was the thought that hovered around within my skull. Might be stretching the limits of probability or credibility, I admit...

Author:  LinguistCat [ Fri Mar 23, 2018 2:06 pm ]
Post subject:  Re: On Tetraploidy or Parasitism

In a sense, your "A generation" individuals are basically walking gametes (or swimming or flying, depending on how they get around), for a species that otherwise reproduces asexually. There are creatures on Earth that have a similar set up (normally reproducing asexually but reproducing sexually when there is a stress on population), however most of these are single celled, and those that aren't are still very small in scale.

This isn't to say you couldn't have multi cellular creatures that do this too. I'm sure it could be possible. Some thoughts though:

Why does the A generation only produce one offspring at a time? If anything, I'd assume they'd want to produce as many offspring as possible (since they would be reacting to stresses in the environment most likely, and want as much variation as possible). Even if the species started with A gens only producing one offspring and then dying, any mutation to produce more than one at a time, or to survive that first pregnancy and have a chance at a second, would be selected for as long as they weren't likelier to die during the pregnancy than their one-offspring competitors.

Could the A generation be non sentient, but understood as the source of the B generation and the B generation takes care of the young produced by the A generation? They'd basically have an instinct to take in young even remotely similar to them, but this would also allow for a lot of genetic mixing since the A generation a B gen person produced might travel far away before finding a mate.

Author:  svld [ Mon Mar 26, 2018 11:13 pm ]
Post subject:  Re: On Tetraploidy or Parasitism

Maybe This is the life cycle model you're looking for?

Author:  LinguistCat [ Tue Mar 27, 2018 6:30 pm ]
Post subject:  Re: On Tetraploidy or Parasitism

svld wrote:
Maybe This is the life cycle model you're looking for?


If this was directed at me absolutely. The name was evading me.

Author:  Torco [ Tue Mar 27, 2018 6:46 pm ]
Post subject:  Re: On Tetraploidy or Parasitism

Quote:
Could the A generation be non sentient, but understood as the source of the B generation and the B generation takes care of the young produced by the A generation? They'd basically have an instinct to take in young even remotely similar to them, but this would also allow for a lot of genetic mixing since the A generation a B gen person produced might travel far away before finding a mate.


i think there's no point, evolutionarily speaking, in both the varieties of the species being sentient: not having them be, however, sort of makes them more like gametes, which may kill the fun.

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