Tuesday, March 10, 2009

Silkworms at 15 days old

Still my silkworms grow. They shed their skin leaving an image of themselves impressed there like the shroud of an icon or a holy relic. Then they eat again and grow.


Silk worms at 15 days old. The scale is in centimetres.

According to the book I received yesterday, which I am going to have to go through carefully since it is translated from the Japanese in the style usually reserved for instruction manuals, it says that moulting depends on a hormone secreted from a pair of small organs called Corpus allutum. These protrude backwards from the insect's brain like a pair of internal antennae inside its head. I have drawn a crude little sketch here:

Sketch of silkworm's head showing the location of the brain and Corpus allutum.

The fact that they are not integral to the brain was of interest to a Frenchman called Bouhniol. In 1937 he managed to excise the Corpus allutum from some silkworms in their fourth instar (that is caterpillars before their fourth and final moult) and found that they then changed into pupae without moutling. Similarly, if he removed the Corpus allutum from silkworms in their third instar they missed out two of their moultings.

This experiment was extended by a Japanese scientist called Kin. He removed the Corpus allutum from a silkworm early on in its fourth instar and then replaced it. He found that if he did this quickly enough all was well and the silkworm moulted as usual. However, if he delayed the transplant a few days the moulting didn't occur and the silkworm went straight to pupa. Clearly enough time had elapsed for the hormone that initiated the pupation process to come into play. Futhermore this pupation hormone was not secreted by the Corpus allutum but by something somewhere else.

This result obviously piqued the interest of the entomological world because they then performed some more interesting experiments, but I am still trying to understand these and shall write another post when I do.

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5 Comments:

Blogger Jud said...

I saw a bit of a program last night: What the Ancients Knew - The Japanese, and they had a segment on silk worms and silk production. I immediately thought of you and your experiments.

Tue Mar 10, 02:55:00 pm  
Blogger Jud said...

This may be very simplistic compared to your depth of experience and personal research, but I found a link to the segment:

http://videos.howstuffworks.com/science-channel/29205-what-the-ancients-knew-japanese-silk-video.htm

Tue Mar 10, 03:06:00 pm  
Blogger Clare Dudman said...

That video is really interesting and useful, Jud! Thank you so much. It shows silk being reeled in a different way from how I've seen it being reeled before. The Japanese process looks like something close to spinning.

Tue Mar 10, 05:13:00 pm  
Blogger BarbaraS said...

The more you show, the more I learn. Wow. And the silk reeling too...

Tue Mar 10, 09:40:00 pm  
Blogger Clare Dudman said...

Thanks, Barbara. That video link of Jud's is really good, Makes me want to go there.

Tue Mar 10, 09:44:00 pm  

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