Insect larvae co-evolution question - probably nonsense

[PsychoSerenity]

I heard somewhere (or perhaps I dreamed it, because it sounds a bit ridiculous ) a theory that insects that have larvae, originally co-evolved together from two separate species - the larvae, as some sort of worm creature, and the flying insect.

The flying insect would originally lay it's eggs in the worm, (like some wasps do today I think), but when the new insect hatched out of the worm, it somehow helped the reproduction of the worm (taking the worms eggs with it or something?) - and eventually the flying insect's eggs were simply laid inside the worms eggs, and they became completely dependant on one another.

So the worm hatches from it's egg (which was laid by the insect), with the insect egg already inside it, the worm goes around eating and growing and starts to produce eggs of it's own - at which point the insect egg hatches, eats the worm from the inside out (pupal stage), and flies away taking the worm's eggs with it - the insect then puts it's own eggs inside the worms eggs, and lays them, so it all starts again.

Anyway if someone can say with some authority that it's absolute bollocks, then I'll be able to put it out of my mind. Otherwise it might make for an interesting discussion about co-evolution.

[GenesForLife]

[Feck]

[PsychoSerenity]

Well I don't know, do I? Nature has produced some pretty bizarre things - and I have no specific knowledge of insect evolution or genetics, with which to rule it out.

I just wish I could remember where the hell I heard it..

[Berthold]

See here.

[Dory]

Not that far-fetched, but probably not the case.

[PsychoSerenity]

See here.

Thanks.

Well I assume that's the one that I vaguely heard, but I seem to have added in the co-evolution bit myself.

Not that far-fetched, but probably not the case.

Hehe, I'm interested now to know which you think is least far-fetched, my co-evolution version, or the original with hybridization through accidental mating.

Of course there should be some way to actually test this. The only real reason I can't rule it out as a possibility, is my very limited knowledge on the subjects! What's the currently accepted explanation of insect metamorphosis?

I was always led to believe that the metamorphosis/pupal stage involved a 'complete transformation', but I don't know how accurate that is. If it's not true i.e. vital organs (or something, what organs do insects have?) are kept, that pretty much rules out separate species thing, I think?

Also, as far as I know, genes don't move about much on, or in between, different chromosomes throughout evolution (or do they? and I don't know how much that would be distorted by 300 million years of evolution anyway). But assuming they don't, then after the egg cells combined, the genes for the development and life of the worm would be mostly separated from the genes for the development and life of the adult insect. If all the genes are muddled up together then again, that pretty much rules it out (assuming genes wouldn't be expected to have moved). If they are separated, there could of course still be other explanations.

I know it's probably all nonsense but I'm curious now. I want details people, details! Is there any definite way to rule it out?

[Dory]

Hehe, I'm interested now to know which you think is least far-fetched, my co-evolution version, or the original with hybridization through accidental mating.

I thought you're presenting the same theory here, not? It's kinda like the eukaryotic evolution via endosymbiosis theory, whereas now the mitochondria and chloroplasts can't live independently of them, and neither does the eukayote.

But there's a very simple way to test it. DNA. If they indeed evolved from 2 separate organisms it will show in the DNA. The DNA of the insect larva will contain a segments of DNA very similar to that "some sort of worm creature", and segments of DNA very similar to that flying insect. These two organisms that co-evolved to create one organisms in different stages of life probably don't exist anymore, but they surely have very close relatives who do. You just compare their DNA with the DNA of those relative organisms, run the stats machine and see if the likelihood of the theory based on the matches.

[PsychoSerenity]

Hehe, I'm interested now to know which you think is least far-fetched, my co-evolution version, or the original with hybridization through accidental mating.

I thought you're presenting the same theory here, not? It's kinda like the eukaryotic evolution via endosymbiosis theory, whereas now the mitochondria and chloroplasts can't live independently of them, and neither does the eukayote.

Well I was intending to present the same theory, but I either heard it from a different place, or I was a bit creative when trying to remember it for the OP.

But there's a very simple way to test it. DNA. If they indeed evolved from 2 separate organisms it will show in the DNA. The DNA of the insect larva will contain a segments of DNA very similar to that "some sort of worm creature", and segments of DNA very similar to that flying insect. These two organisms that co-evolved to create one organisms in different stages of life probably don't exist anymore, but they surely have very close relatives who do. You just compare their DNA with the DNA of those relative organisms, run the stats machine and see if the likelihood of the theory based on the matches.

Is anyone likely to run the necessary tests, as a result of the paper? I imagine DNA experts are fairly busy already without spending time on things like this.

[Dory]

Is anyone likely to run the necessary tests, as a result of the paper? I imagine DNA experts are fairly busy already without spending time on things like this.

Good question. And actually, so much DNA has been tested and added to bioinformation databases to be compared that it may already be there-- in this case any bioinformatician ought to haven noticed such obvious genetic correlation. Otherwise it might need some proactiveness. The paper might be a start, but it needs support from other scientists. Since the theory is rather radical and contradicts the way nature usually works in a typically gradual Darwinian fashion, I can imagine there's an outright dismissal.

But these scientists might have a point. Nature doesn't tend to play high-level genetic engineering. Horizontal gene transfer in animalia is unheard of. It did occur between fungi->plants and plants->plants on a few rare occasions that scientists found evidence for, but even so it was probably just among the chloroplasts/mitochondria and didn't have a phenotypical effect.

[JimC]

Anyone want to raise the ante and include frogs and tadpoles in the debate?

A few thoughts...

There are always a sequence of changes in body form in embryonic development from fertilised eggs to adults in all animals. Insects show a wide range of developmental forms, from larval stages (usually termed instars) that are relatively similar to the adults (for example Hemipterans), all the way through to the more dramatic metamorphosis of the Lepidoptera. In some insects, for example many of the ants and bees, the larval stage is a helpless thing, carried around by adults, with no need to have the equipment to live a separate life.

Horizontal gene transfer may well occur in a few minor examples in higher plants and animals, but is only an accidental shift of a small genetic fragment, not a large scale, wildly improbable fusion of unrelated genotypes.

In any case, no unlikely fusion of genetic material from vastly different organisms is required to explain metamorphosis, just a neatly programmed and well timed sequence of switching sets of genes on and off, stemming from the selective advantages of separting the food gathering and reproductive stages. The existence of developmental stages such as instars in primitive insects means that selection has something to work with, and extend further in lineages where it pays to do so.

[Dory]

Bah! You just said what I said JimC! Just sounded kinda more intelligent

[Psi Wavefunction]

Oh THAT paper. Utter bollocks. Written by a senile guy who's lost all his marbles, and pushed by an aggressive batshit insane lady overly obsessed with symbiosis, Lynn Margulis. We don't like her. We, as in, the colleagues in her field. People outside her field love her, however, and seem to think she represents the rest of us. Grrr.