毋須交配 雌蟲繁衍1億年【明報專訊】英國科學家在顯微鏡下，意外發現一個小蟲女兒國！小蟲族群中只有雌性，繁衍1億年從沒性生活，卻能世世代代「玉女添丁」，自行誕下未受精卵，孵化出基因與母體相同的翻版後代。
這種無性繁殖的小蟲(bdelloid rotifer)在水中生活，身長僅人類精子的四分一。科學家指出，一般無性繁殖動物在進化過程中很易絕種，但這種小蟲卻能長期繁衍演化，這是前所未見的，「推翻過往認為，兩性繁殖是促進物種進化多樣性必要條件」。無性繁殖常見於蚜蟲等無脊椎動物，也有少數魚類或蛙類可用此方式繁殖。泰晤士報
The bdelloid genome shows an odd pattern of differences between versions of the same genes, report David Mark Welch and Matthew Meselson. This pattern most likely arose during eons without sex, they argue in the May 19 Science. [what kind of odd pattern?]
Of the planet's 2 million named species, only about 2,000 appear totally asexual, Meselson notes. Hardly any of these lineages seem old, and fossil evidence has suggested that asexuality is a dead end. "It's not because asexual species don't appear," Meselson says. "It's because they don't last."[if scientists think asexual is a dead end and sexual can lead the diversity of lives which is more adaptable to the changing environment, so what makes this ancient organism has been surviving such a long time and what contributes to the more than 300 species? ]
One asserts that sex speeds the process of dumping bad mutations, and the other focuses on spreading benefits. The Red Queen hypothesis, for instance, finds the main benefit of sex in shuffling the genome quickly, making it difficult for parasites to lock onto weaknesses. [sex is so important. It almost a driving force or essential aim to survive. But sex and propagation are equally cored. Asexual can't last too long but this kind of asexual form has been exisiting everywhere. People think only female human survives on the earth one day because of asexual reproduction.]
This is very interesting of life form.
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