Are Butterflies Two Different Animals in One? | Hacker News Reader

Are Butterflies Two Different Animals in One?

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64 pointsnreece33 comments

This was submitted a few month ago (4 points, 3 comments): http://news.ycombinator.com/item?id=4334906

I will quote a comment that I made that time (beacuse I don't want to write the same thing again):

This article doesn't have any scientific base.

Insect have exoskeleton so they can't grow like ducks or bats. They have to make a series of metamorphosis to grow. Usually the form for change from one stage to the next step, because they are adapted to different lifestyle. See: http://en.wikipedia.org/wiki/Metamorphosis#Insect_metamorpho.... .

Butterflies are one of the most well known and extremes cases of changes. The caterpillar shape is adapted to eat a lot and be camouflaged, the butterfly shape is adapted to travel and mate. (Both shapes share the same general blueprint. For example, if you see a caterpillar carefully, it has only 6 small real legs in the front, and some prolegs in the back.)

It's an intriguing idea though if nothing else. A question here (I don't know your background if it's biology mind you): what actually happens in the metamorphosis between caterpillar and butterfly/moth or any larval animal for that matter?

It does seem rather radical to switch off a massive amount of genes and switch on a bunch of others in adulthood, drastically changing your physical form.

I don't know exactly what happens but apparently they mostly turn to mush then reassemble. Interestingly their nervous system/memories have been shown to survive between the different stages.

Re genes turned off: as another poster mentioned huge numbers Of genes are switched off and on at different stages in our life cycle. It's kind of the same as saying 'but neurone don't need the same genes as skin cells so isn't it wasteful having all those extra genes doing nothing?' DNA is relatively cheap so while some 'skin' genes may never Be used in 'neuron' cells the cost is not prohibitive To the organism.

Http://bit.ly/VNYxx2 (a link to livescience.com - apologies am moving between different devices, blocked HN on my mac!)

A lot of insects have a fully intact, if immature, nervous system during their adolescence. For example, fruit flies (drosophilla) have brain features called "mushroom bodies". These grow during larval development then hit a state of hibernation until the larva changes into an adult fly, at which point growth continues and the mushroom body fully develops.

I'm not familiar with a lot of other insects, but I believe it is fairly common for the bulk of structures to form, hibernate, and then finish growing during metamorphosis.

Nah, you can consider puberty to be a less extreme form of metamorphasis. Hundreds of genes are switched on and off to accomplish rather drastic sexual and physical changes.

Switching genes is cheap and easy. You have dozens of genes that switch on/off acting as pacemakers and timers. You have other genes that switch on when there is a boost of insulin, and then turn back off once the insulin is gone. There are genes that are only turned on when stressed, hypoxic, over-temperature, under-temperature, over-fed, underfed, growing, not growing, genes that turn on when neurons are excited or inhibited. The list is endless.

If you think of your body as one giant state machine, it makes sense that you need thousands of flags to control the exact state that it is in.

It's actually much more complicated, since genes really aren't binary. Each gene is also a scalar, producing varying quantities of protein, or causing various kinks in the DNA which affects nearby genes (called "enhancers"). So really, you have a bunch of binary states which are then modulated by the amount of protein that is being created.

Then you have different parts of a gene that can be individually turned on/off, producing different isoforms of a single protein. Each isoform has different capabilities, especially when paired with regulatory proteins that modulate it's behavior (which also have their own regulation at the genetic and proteomic level). And each of these proteins in turn effects an numerable array of other proteins and genes, cascading throughout the entire system.

The body is a remarkably vast state machine.

Edit: This is totally ignoring all the microRNA and shRNA which modulates the state between DNA translation and transcription. Basically, add a few more million states to the state machine.

Sorry, I don't enough about what happens during the metamorphosis. I hope that someone can answer that. (Another question: If the caterpillar lost a leg, the butterfly has a missing leg?)

Changing the form is very popular between insects. (Almost?) All of them do it. For example:

* Grasshoppers: http://commons.wikimedia.org/wiki/File:Snodgrass_Melanoplus_...

* The young grasshoppers look like small wingless grasshoppers, so it is not a surprising transformation (if you ignore the wings and some internal details)

* Ants: http://askabiologist.asu.edu/individual-life-cycle

* Bees: http://www.magicpest.com/the-life-cycle-of-an-arizona-bee/

* The young ants / bees look like eggs, because they live safely inside the hive, and get the food from their sisters. So we don't have a special name for them.

* Mosquitoes: http://www.mosquito-misting.com/life%20cycle.htm

* Flies: http://www.flycontrol.novartis.com/species/housefly/en/life_...

* The young mosquitoes / flies are very different from the adult forms, they have a very different lifestyle and food. But they are nasty so it's better to just ignore them.

* Butterflies: http://questgarden.com/120/22/8/110228062006/process.htm

* Young butterflies live in the wild without protection like the ants/bees equivalent. So they are easy to spot and they are more difficult to relate to the adult forms. They are colorful to hide or as a bad taste signal, so they are nice and many of them have a special name that is unrelated to the name of the adult form. Butterflies in general are colorful and nice too, so we know a lot of names of the species of caterpillars and butterflies.

(You can find more examples in Google, searching for: life cycle <insect> )

So the changes are very common insects, but the case of the caterpillars / butterflies is more surprising because both forms are popular.

(Changes are also common in other kinds of animals / plants /fungus / etc., but this is getting too long, so lets analyze only.)

Here's another counterpoint:

Moths can remember experiences they made as caterpillars. http://www.newscientist.com/article/dn13412-butterflies-reme...

These findings suggest that they are not two different species - I can't remember the experiences of my dinner, either.

DNA transfer in higher life forms occurs far more frequently than the geneticists of 60 years ago could have suspected.

Astonishingly, only 1.5% of the genetic material in our cells codes for human life. Half of the rest is sometimes described as "junk DNA" with no known function, and the other half consist of genes introduced by viruses and other parasites.

[http://www.bbc.co.uk/news/science-environment-17809503]

My guess is that organisms are so susceptible to viruses, because in the long term viruses benefit their hosting organisms a lot -- by transferring potentially useful DNA.

The term "junk DNA" is not used in science anymore, much of it is repetitive regions that serve regulatory functions, or other unknown reasons. "Junk" DNA has been renamed to "noncoding DNA", the recent ENCODE-project stated that 80% of human DNA has some purpose. See: https://www.sciencemag.org/content/337/6099/1159

P.S.: That article reads like the ENCODE-project killed the term "junk DNA", however, that term wasn't in use before the release of ENCODE, either.

This is eerily similar to the biology on the planet of Lusitania in the Ender's Game series book 'Xenocide' in which every remaining species has a two part life cycle which is the result of an virus's effect on two previously separate species. They start as one form, die and are reborn into another form.

Bit of a spoiler for the previous novel in the series, that.

Ah, I'm sorry, I completely forgot about spoiling it given it being so old. Too bad HN doesn't have spoiler tags :(

Ha, this was all I could think about while reading.

This is extremely silly. Genes that act in larval, pupal, and adult development are all mixed up together in the same chromosomes; there's no plausible way for them to have integrated in the manner suggested. Moreover, the same genes and used and reused again and again in different contexts in insect development. Again, this is absurdly unlikely under the scenario he proposes.

I agree that it is extremely silly, however what you suggest about the genes being all mixed up in the same chromosomes as disproving it I don't buy..

I'm not sure if you've ever seen chromosome maps showing gene locations on chromosomes between different species but this is instructive in this matter: between species and thus, as numbers of chromosomes flux up and downwards, the genes which may have started in one chromosome end up spread throughout many-

I am sure you will find the following links interesting

Background: on chromosome rearrangement: http://scienceblogs.com/pharyngula/2008/04/21/basics-how-can...

Synteny map - cool explination http://scienceblogs.com/pharyngula/2006/06/08/pufferfish-and...

mouse human synteny map http://www.mun.ca/biology/scarr/MGA2-11-33smc.html

Yes, to some extent genes are mobile and do get shuffled around, but if this hypothesis were true, it would be obvious. Whole genomes don't just merge on the time scales we're talking here. If this hypothesis were true, there would be clear genomic anomalies indicating it (e.g. biases of genes used at the same developmental stage tending to cluster in similar genomic regions); no such anomalies have been found.

One way I've heard it described is that the caterpillar effectively develops an organ that is analagous to an egg from which the butterfly hatches. Then the rest of the caterpillar's body becomes food for the newly-hatched bufferfly. This all occurs inside the chrysalis so that we are spared from witnessing the carnage.

I have no idea if this is a valid way of looking at it or not, but it's one explanation that I've heard. The appealing part about this is when you realize that some wasps lay their eggs inside other insects, which then become food for the wasp larvae in the same way that the caterpillar's body is supposed to become food for the butterfly.

Mating between two different speciecs? Rather carying over significant dna of the host inside the parasite that grew out of it.

There are a lot of the winged insects that lay egs inside other insects. Maybe some freakish viral infection long time ago carried over lots of dna of the host into the parasite egg.

It's still insane but at least it's imaginable.

IIRC, from an article long ago in New Scientist, there are precedents for this in small marine animals. i.e. plankton or hydras. The "adult" form grows inside of the "larval" form. And then breaks out, fully formed. The "larval" form continues as a separate individual for a few days, before dying.

The eggs are then produced by the "adult" form, and the process continues.

It's easier to do with smaller animals. The process is also simpler (grow new "adult" as a parasite of the "larva"). The caterpillar to butterfly change is much more complex.

I suppose you could look at it as a parasitic relationship. But it's actually much simpler than that. (Hydra are super cool, so allow me to geek out for a sec)

Basically, every cell in the hydra knows how to become a new hydra. What prevents a single hydra organism from trying to become a thousand hydras is a dual chemical gradient. The head emits one chemical, the tail emits another. Cells respond to this gradient depending on how concentrated it is in one particular direction

At the "head" end, the "head" chemical is very strong. Those cells respond by being the "head". At the other end, the "head" chemical is very weak (and the "tail" very strong). Those cells respond by becoming the appendages.

If you chop a hydra in half, the gradient becomes altered. On one half of the hydra, there is only "head" chemical diffusing. The other half only has "tail" chemical. These changes in chemical gradients signal the cells to start producing the parts of the body that were just lost. Eventually, you end up with two identical, smaller hydra.

Theoretically, you could keep chopping hydra in half and keep getting identical, smaller hydra. Obviously you hit a point where you are just going to kill the poor thing, but in theory it doesn't matter...the hydra will always be capable of regenerating.

Cool, right!

I have a hypothesis of equal scientific merit: Caterpillars are turned into butterflies by an invisible wizard in the sky.

According to this theory, long, long ago, two very different animals, one destined to be wormy, the other destined to take wing, accidently mated, and somehow their genes learned to live side-by-side in their descendants.

This is simply rubbish, and demonstrates a fundamental misunderstanding of genetics.

No, it is entirely possible. Entire chromosomes could modified, as by methylation, and the transcription machinery could switch between the two at the appropriate developmental stage.

What it is is (1) extremely unlikely, and (2) easily checked by looking at the DNA sequence of any insect that metamorphoses.

The only somewhat similar thing I can think of would be mitochondria, but even mitochondria retain their own unique DNA outside of the nucleus.

True, mitochondria contain functional DNA, but the majority of mitochondrial genes have migrated to the eukaryotic nucleus. The transcripts are transcribed in the nucleous, translated in the cytosol, and the protein products are translocated into the mitochondria. There's not necessarily anything preventing the remainder of the mitochondrial genome from making the same transition, although perhaps the mitochondrion would still require a "placeholder" chromosome because its cycle of reproduction is tied in with replication of that chromosome as it is in bacteria.

Betteridge's Law of... oh, whatever. Is the fetal human form a different animal from the adult human form? Different genes are switched on, but this doesn't mean that the baby growing inside of you is some alien that you're nurturing that just happens to become an adult human.

Anyway, genetic analysis should make the actual question–if it were a serious scientific question–answerable: are butterflies the result of some prehistoric mating between different species? Is the genetic architecture vastly different between the two sets of genes? Is there evidence of what one or both of these two progenitor species were, and if so, can we identify the direction of gene flow and relative contributions?

Dissolving into the liquid oblivion of sleep, we are caterpillars to the butterflies of our next morning's waking selves.

Brrr, reminds me of http://en.wikipedia.org/wiki/The_Metamorphosis

(A novel by Franz Kafka, in which a traveling salesman, Gregor Samsa, wakes to find himself transformed into a monstrous vermin.)

Is there any actual evidence that supports this hypothesis?

Biological Ship of Theseus.

If the headline is a yes/no question, the answer is always no.

I once smashed two clocks together and a butterfly came out.

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