A Special Sort of Swimmer
I have two of them producing them now (although you couldn't tell):
One sort of sperm has a nucleus, but the other does not. And what, you might ask, is the point of a sperm without a nucleus?
Well, things are tough for a silkworm moth sperm. Whereas the human sperm has to swim the sperm-equivalent of the English Channel (or something like that) and then puncture the egg cell wall, the silkworm moth sperm has a more interesting challenge: he must embark on a spermatazoa assault course. After his swimming session (into the female's oviduct) he will encounter a hard shelled egg. He must then find a secret twisting channel through this shell, and only then, if he's successful, will he be able to fuse with the egg and start making an embryo.
But that's not all. The 'sea' this silkworm moth sperm has to swim through before meeting the egg is as gloopy as treacle, and the silkworm moth sperm is inclined to be sluggish. In fact he has to be 'activated' in order to move at all - and this is where the sperm-without-a-nucleus comes in. Both sperm are activated by an enzyme but the sperm-without- a-nucleus is activated first. And once activated it goes a little wild. It stirs things up - which not only breaks down the gloopy liquid and makes it more runny, but helps the sperm-with-the-nucleus to quickly mature and become more mobile. So the sperm-without-a-nucleus acts a little like a trainer getting an athlete to speed.
I find all this incredibly interesting, but when I explained it to Hodmandod Minor he did not seem too enthralled at all. In fact he just looked at the two males in the box and said (in a voice I can only describe as faintly hopeful), 'When those die, that'll be it, won't it? No more silkworms?'
And looked quite disappointed when I said I that actually I was hoping to establish generation number three.