Saturday, January 1, 2011

What is Life? Evolution from invertebrates to vertebrates 4(無脊椎動物から脊椎動物への進化その4)

Good morning and a happy new year everyone. Are you still in your laboratory now? If you are so busy, you should call to your mother or father living in your country. It's called as Love. OK?


Here we go! This is the 4th of the special course about the story of evolution from invertebrates to vertebrates. In the last year, Sammy showed about the classification of animals, the importance of sea urchin, and the Metamorphosis. For explaining a hypothesis about the mechanism of the evolution resolved from our results in the study, Sammy has to show you the life style of sea urchin in below.


(6) Late development of sea urchin larvae
The sea urchin's fertilized egg divides into 2, 4, 8…… cells. And finally, the embryo takes a very beautiful shape called as 4-arms pluteus larvae. After long period of feeding, the pluteus larvae grows at 8-arms pluteus.


In the left of the larval body, the adult structure (adult rudiment) is appered. Such structure is originated from specific cells stocked inside the larval body at early period, and thought as a kind of stem cells, described later. Anyway, the structure grows rapidly in the larval body with the degeneration (resorption) of the larval body. In most cases, the metamorphosis comprises the resorption of larval body and growth of adult structure occurs at the bottom of the sea.


(7) Construction of the experimental model
In amphibia, the degeneration of tail and the growth of the legs are controlled by same endogenous hormones. For amphibia, we do not need sea water for their experiments. Most important thing is that there was few data about inducing factors for such drastic changes in the sea urchin larvae.


But we knew only the protocol for rearing the larvae and foods for them. When the larvae were kept with foods (algae) and gentle rotation, the growth and the metamorphosis can be observed easily. However, when the feeding was terminated at a period, such changes were stopped at the point. From these observation, we could identified the assay point to elucidate the inducing factors of the metamorphosis. This was just a start point to reveal the question for us.


Today's class is over. Have a nice day. Click the button at the bottom of this "What is Life?", if you are a student of this class. Mind you? If you have any question about life, please send an e-mail for me.


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  1. 明けましておめでとうございます!

  2. Thank you Aya.

    About 6 months have passed from the start of "What is Life?". While sustaining this class, Sammy has met many students having interesting blog, like you.

    So please attend this class for various categories of life science inside the back number.

    At this year, Sammy will start the real course of biology at the small company. Such class "What is Life?" is for children of weekend farmers.

    This is my final goal with a partner.

    Best regards.


Thank you!