E. S. S.
BBC NEWS | Science & Environment | Bacteria selectively kill males: "Males cannot transmit infection to their offspring because, while egg cells are large and have lots of cytoplasm, sperm cells are comparatively tiny and have very little cytoplasm, she explained. Dr Zeh continued: 'Males are an evolutionary dead end for the bacteria. So they engage in gender manipulation to bias sex ratio in favour of females.' But this selective killing is very damaging for the host. 'Infected hosts give birth to only 62% as many nymphs (or offspring) as tetracycline-cured females,' said Dr Zeh."
The simple math says that a bacteria that only propagates through females would want the highest number of females to be put into the next generation, but Mother Nature has figured out that 62% is a better outcome. I wonder if this means that there is a gestational aspect to the infection that would be hampered if male larvae were to consume more of the mother's incubational resources.
2 comments:
Well, evolution isn't survival of the fittest, it's survival of the just-good-enough... so 62% is probably just good enough.
What he said, plus: if the bacteria are killing all the males, the fact that we're getting any more than 50% of the expected number of nymphs suggests there is some compensation going on. That extra 12% is probably all embryos that form anyway, but would normally die off because large brood species often lose a lot of embryos at very early stages, in turn because the mother can only provide for so many.
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