Inside the cocoon

What's inside? I knew there was something. I could hear it rattle, and peering through the moth's escape hole I could see something dark. So I cut one open. It was satisfying, like breaking into a tomb, and the compacted layers of silk just the right thickness and resistance to my sharp, thin-bladed knife. It revealed this


the discarded outer casing of the pupa like darkly polished breast plates of some ancient hardwood, and something less discernible, maybe excreta of a sort...

Cocoons! (part 1)

Just took a look a few minutes ago and have discovered that a couple of silkworms have settled down to work...



Already they have eaten their last meal. Soon, whatever they were, will be changed into something else: pupae, and then into mouthless moths. Are they still the same individuals? If we could change from one thing to another - would we still be the same being?

Then, after they become moths, they will live only enough days to mate and for the female to lay eggs. Why are they programmed to self-destruct in this way? What if we knew exactly how long we were to live - to the day?

As usual, the more I find out, the more I need to find out.

Why my father's brain is like a silkworm pupa

Last February, my father went into a coma for several hours as the result of a stroke. He was not expected to survive and I had to say good-bye to him over the phone. Then, the next morning, as we were on our way to see him, my brother rang me on my mobile. 'He's a little better.' he said.

When we arrived at the hospital we were surprised to be shown into the main ward, and even more surprised when a voice called out to us. My father was sitting up in bed - a bit confused but perfectly lucid. Over the next few days he recovered completely. In fact he seemed to me to have more than recovered, he seemed to be more alert and more fluent than he had been before. 'Better than ever.' I'd tell people, but not really believe it, but it really did seem that my father's brain had somehow been rejuvenated by the stroke.

Recently I read that this could be true. When the brain is damaged by a stroke there is evidence that stem cells are produced and these differentiate into the types of cells required to repair the damage. The way this might happen is for 'mature' cells (which have long been differentiated into specialised brain cells like neurons) revert back to unspecialised stem cells that can change into anything that is required.

A similar discovery was found in insect pupa which was reported in this paper in Nature in August last year. When a larva (like a silkworm) changes into a pupa most of its cells die and inside the shell of the pupa is a sort of 'gloop' with islands of special sorts of cells called imaginal cells.

Until last year it was thought that the adult insect (in this case, the moth) is formed from clumps of imaginal cells, which like stem cells can turn into anything that is required. These imaginal cells are inactive in the grub but become activated when the larva is turning into a pupa, and then again when the pupa is turning into the adult insect. However this paper reports that scientists in Stanford (Molly Weaver and Mark Krasnow) have found that it is not just the imaginal cells which turn into the components of the adult insect. In fact other cells - old specialised cells that had survived from the larva - also form part of the adult. They do this by reverting back to a less specialised state and then turn into differently specialised cells in the developing adult.

So, by looking at what happens in something as lowly as a silkworm scientists have discovered why exactly my father's brain may have recovered from his stroke. It always amazes me how the most disparate things often turn out to be connected.