Saturday, February 07, 2009

A Possible State of Confusion

Silk worm moths are supposed to emerge from their cocoons frantic to mate, but all my silkmoths seem to do is occasionally twirl their sinister little faces or flutter their wings. Mainly they do nothing. I have come to the conclusion they are either (i) all male or (ii) hopelessly confused.

According to Pabran Baishya in the 'The Silk Industry of Assam' the Indian word for the adult silk moth, Punjapati, is the same word as for 'the divine creator' since, like the god, it lives not to eat, but to love and procreate. The silk moth does not have a fully formed mouth, and therefore cannot eat; it does, however, have some very sophisticated apparatus for seeking out a member of the opposite sex.

From glands in the abdomen the female silkworm emits a pheromone called bombykol. It is a fairly simple molecule - a chain of 14 carbon atoms with an alcohol group at the end, and two unsaturated carbon- carbon double bonds. It was the first pheromone ever to be discovered - by a Nobel-prize winning chemist called Adolf Butenandt in 1959 (he won the Nobel Prise in 1939 for his discovery of sex hormones). A male silk moth can detect the bombykol from a single female in the middle of an acre of field by means of his feathery antennae.

There are minute openings on the surface which allow the pheromone of the female through. A single molecule of bomykol is all that is required. It is transported to where it fits snugly into a chemical receptor molecule, which sets off a chain of reactions which eventually results in a signal to the male's brain to 'come hither'...and mate.

So, given it is such a sensitive detection system, why aren't my silkworms mating? Surely they can't all be males. I am beginning to come to the conclusion that they might be confused.

According to this paper from the 1988 edition of the Journal of Agricultural and Biological Chemistry, the level of female hormone peaks four hours after the light has come on - and my moths have been kept in semi-darkness. Perhaps the females aren't producing any pheromone as a result, and so the males are forced to sit and wait.

So tomorrow morning I am intending to expose them to the light in the hope that if there is a female there it will start to produce bombykol and secure a mate.

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