Evolution of Metamorphosis

[Edella]

Seeing all the butterflies in my garden this summer got me thinking about the process of insect metamorphosis, and more specifically the evolution of this process. What is the advantage for the insect? Why would natural selection produce this adaptation?

Although I have a basic understanding of the processes of evolution, my searches have led me to pages that are, quite frankly, over my head, require subscriptions or simply describe the process without offering any theory on its evolution.

Can anyone suggest books or web sites that describe the current theory or hypothesises regarding general evolution of insect metamorphosis, or offer his/her own thoughts?

Disclaimer: I know this is a hot topic for some creationists, I have no desire to start a creation - evolution debate.

[MortenS]

You may want to request a copy of the following article at your library:
The origins of insect metamorphosis. [Nature. 1999] - PubMed Result

Managed to find a copy of this available as pdf online:

http://www.biology.usu.edu/courses/b...0/Truman99.pdf

A good read...

[Thunderbird]

Since my postal episode I cannot start my own thread I am reviving an old thread that was a question that was never properly answered .



I have a challenge for anyone that can think in evolutionary way, now keep in mind I am an evolutionist so the answer follows adaptation. How did the insect metamorphosis phases of pupa larva to flying winged insects evolve. It is still a bit of a puzzle. Now you will read about all the genetics involved, but what I would like to explore is the actual evolutionary adaptations that lead to the ability to encapsulate second stage of the cocooned pupa stage to the butterfly or winged stage. Any scenarios?

[Moontanman]

Originally Posted by Thunderbird

Since my postal episode I cannot start my own thread I am reviving an old thread that was a question that was never properly answered .



I have a challenge for anyone that can think in evolutionary way, now keep in mind I am an evolutionist so the answer follows adaptation. How did the insect metamorphosis phases of pupa larva to flying winged insects evolve. It is still a bit of a puzzle. Now you will read about all the genetics involved, but what I would like to explore is the actual evolutionary adaptations that lead to the ability to encapsulate second stage of the cocooned pupa stage to the butterfly or winged stage. Any scenarios?

Uh Oh I answered this and it disapeared!

[Moontanman]

Originally Posted by Thunderbird

Since my postal episode I cannot start my own thread I am reviving an old thread that was a question that was never properly answered .



I have a challenge for anyone that can think in evolutionary way, now keep in mind I am an evolutionist so the answer follows adaptation. How did the insect metamorphosis phases of pupa larva to flying winged insects evolve. It is still a bit of a puzzle. Now you will read about all the genetics involved, but what I would like to explore is the actual evolutionary adaptations that lead to the ability to encapsulate second stage of the cocooned pupa stage to the butterfly or winged stage. Any scenarios?

This is my take on it, if you remember that lots of invertebrates have alternating life cycles then this doesn't look all that strange.

Not sure about the basics but it is something I've thought about. "Maybe" It comes from a short lived reproductive phase being lengthened into the main phase with what was the major phase becoming a larval phase. something like this.

aquatic
1. egg
2. larvae/eating
3. main phase, also eating
4. quick skin shedding stage
5. short lived non eating/reproductive phase.

to land and water

water
1. egg
2. larvae/eating growing phase
3. quick skin shed (crystalis)
4. main nymph phase eating/swimming
land
5. quick skin shed (crystalis)
5. short lived nymph/reproductive phase non eating

to

land
1. egg
2. larvae/eating phase
3. skin shed becomes crystalis or cocoon for surviving dry or over wintering
4. to longer lived reproductive/eating phase

all the different phases are shuffled around to adapt to different environments. this could probably use some cleaning up of the stages. since some insects use more or less of these stages. neotiny plays a big part

[Thunderbird]

Originally Posted by Moontanman

Uh Oh I answered this and it disapeared!

No.. you just described the stages.. you did not explain the way in which the pupa could emerge from a cocoon to a flying creature in the adaptive process of evolution. How did it evolve the ability to go into this state in come out in another?

[Moontanman]

Originally Posted by Thunderbird

No.. you just described the stages.. you did not explain the way in which the pupa could emerge from a cocoon to a flying creature in the adaptive process of evolution. How did it evolve the ability to go into this state in come out in another?

I see what you mean, I was attempting to show the stages it went through to get to the larvae-flying stages but i also think insects lost this at first and then got it back as they moved to land. I'm not explaining this very well but think of the way a jelly fish grows from an egg to a larvae to a sessile animal to a jelly to an egg and so forth. All inverts carry this life style in their genes. In some the reproductive part is dominant in others the non reproductive part is dominant and in some both are significant and have separate parts of each. In coral you start with an egg and sperm then to a larvae to a sessile coral to a egg and so forth. In arthropods there was an egg then a larvae then a free swimming form and egg and so on. some stages disappear others are magnified. make any sense at all?

[Thunderbird]

Sure , and think you well get what I am proposing , What I am focusing on is an adaptive trait, {or more precisely a preexisting stage of development } that the arthropod utilized as a means to not only develop wings but also prior to that event of insect flight, allowed the arthropods of the burgess Cambrian event to develop diverse complex body plans in a short period of time. Think about life cycles of arthropods on land and in fresh water swamps prior to flight and the demands. Try to visualize how it could achieve winged flight. I think you have all the info in your first post. look at the stages its right in there.

[Moontanman]

Originally Posted by Thunderbird

Sure , and think you well get what I am proposing , What I am focusing on is an adaptive trait, {or more precisely a preexisting stage of development } that the arthropod utilized as a means to not only develop wings but also prior to that event of insect flight, allowed the arthropods of the burgess Cambrian event to develop diverse complex body plans in a short period of time. Think about life cycles of arthropods on land and in fresh water swamps prior to flight and the demands. Try to visualize how it could achieve winged flight. I think you have all the info in your first post. look at the stages its right in there.

I think flying probably developed from swimming by flapping gills, some of the gills developed into wings as the insects tried to swim faster and escape predators they might have developed the ability to skim the waters surface like flying fish do. Or there may have been an intermediate step of using the waters surface to respire in anoxic water and this may have led to the skimming. Couple that with the idea that the air was denser then with more oxygen and you just might have the mechanism of developing flight in insects.

[Thunderbird]

Originally Posted by Moontanman

I think flying probably developed from swimming by flapping gills, some of the gills developed into wings as the insects tried to swim faster and escape predators they might have developed the ability to skim the waters surface like flying fish do. Or there may have been an intermediate step of using the waters surface to respire in anoxic water and this may have led to the skimming. Couple that with the idea that the air was denser then with more oxygen and you just might have the mechanism of developing flight in insects.

I’m sure the wing attachments were originally gills and appendages, but the advent of the wings themselves for flight, and the boom of complex body forms of the burgess record can be explained quite neatly though the lens of a complex adaptive molting process.

IMHO the scenario would have happened something like this.

During the early days of arthropod evolution {preflight} they faced certain challenges. During this period the insect would have developed from the egg to the nymph , or in the case of the land insect something like a caterpillar, but they remained that way though their entire life span. They would have to molt just as any arthropod with an exoskeleton, but in the beginning they just would emerge with a better suit of armor but no wings.

The molting process would be an opportunity in the beginning not for full fledge flight but for the much more simple precursor of wings. A device that could meet the immediate needs of the time simply, which is to disperse outward from the group of hatch mates to find other food sources and a breeding partner. the ability to disperse from the original hatch site would have great advantages in the competitive environment.

During the molting stage the nymph or pupa would climb high in to the vegetation shed the exoskeleton completely except for the certain appendages that molted last. The light weight exoskeleton could then be held up into the passing air currents and carry the bug away, just as newly hatched spiders utilize streamers of silk to carry them away in the current of air.

The complex adaptive molt would start as a simple dispersal mechanism as the “paraglideres” land they would finish the molting process and remain a non flier. Over time however the exoskeleton would adapt to becoming more of something they could use over and over. climbing sailing, climbing sailing, until finally it developed the appendages and muscles and all associated linkages for powered flight.

Utilizing this same simple scenario for the arthropods of the burgess event of the complex adaptive molt it can be seen quiet clearly it could follow the same scenario. The vast array of appendages of pincers, antenna, spines, complex armor all could have developed by utilizing a partially molted retention of the exoskeleton of varying geometric useful shapes. In the case of the caterpillar cocoon to butterflies the cocoon is just a complex molt within a molt.