When blokes discuss reproduction, many lapse into macho – or at least slightly hur-hur – innuendo. So it’s reassuring to discover that science now recognises the role of aerial combat technology in the whole process.
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Machismo and testosterone fuels at least 90 percent of every Hollywood movie. Basically, any title not mentioned in the same sentence as the words Merchant Ivory, Sundance, subtitles or French Art Film will feature some high-performance machinery, whether it’s a spacecraft, firearm or car, and often all three at once.
A good example was the visually arresting Top Gun, with umpteen scenes of Tom Cruise going “where’d he go, where’d he go”, while roaring around the sky in a jet fighter paid for by the US taxpayer.
Cruise’s character fired off as many gung-ho, inane one-liners as heat-seeking missiles. And as a result, US Air Force recruitment rates soared. It seemed (and still seems, given world events) that a good many US males fancied being strapped into a rocket that fires other rockets.
But even if you’re an avowed pacifist, the principle behind heat-seeking missiles has been found to have an application much closer to home. It seems that just as heat-seekers like the SAM-7 or Sidewinder can sense and follow the heat of a jet engine, sperm are guided to fertilisation by temperature.
What’s more, the new finding may on day make conception easier for couples undergoing in vitro fertilisation.
A new study conducted at the Weizmann Institute in Israel and published in the journal Nature says the site where the egg lies is a bit warmer than that of the surrounding body tissue.
Heat guides sperm to egg
But the difference in temperature seems to be what guides the little swimmers to their destination. Scientists knew the process existed in worms, but this new study proves it works for mammals too.
The sperm must swim up the uterus and make their wiggly way into the fallopian tubes. Once inside one of the tubes, they attach themselves to the tube wall for a bit. This pause seems to give them a chance to go through a maturation process, which helps prepare them for the final part of the journey, penetrating the egg.
They may also do a mirror check for spinach between their white teeth, and to freshen up with really tiny tins of GoldSpot. Once “mature” the sperm detach themselves from the tube wall and look for an egg.
But how? The question asked by scientists (And no doubt by incredulous, shocked teenagers) was how the sperm manage to find their way up the fallopian tubes?
Egg also releases scent
Then researchers discovered that the egg releases a chemical, a scent for the sperm to follow – call it Channel No. 2. This is useful, but it’s only effective over a short range. So the questions by the scientists and the teenagers had only partly been answered.
Then the researchers discovered that the “storage site” where the sperm did their maturing was about two degrees Celsius cooler than the egg itself. The heat played a role, they deduced, and named the process thermotaxis, which makes sense when you think about it.
Being scientists, they had to prove their deduction, so they set up and experiment with rabbit sperm (Don’t even ask) and very carefully controlled temperatures.
Two more points proved interesting. Firstly, the sperm could detect a temperature difference of as little as half as degree. Secondly, it was only the mature sperm – those that had stayed stuck to the wall of the fallopian tube for a while – that could behave like heat-seeking missiles on their way to the egg.
The mature sperm were able to follow the heat signal for most of their journey, then to detect the chemical signal once they got close to the egg. – (William Smook)
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