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So, there are numerous species of animals who use parthenogenesis, but to my knowledge the reproduction is clonal. That is, the offspring are identical to the mother. Are there any documented cases where a female goes through meiosis one to produce varied cells that are now diploid and these cells do not go through meiosis two, but rather develop in to a diploid organism? It would seem an effective reproductive strategy in that it generates genetic variation without a mate (at least more-so than strict asexual reproduction). Is my logic flawed in some way?

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In automixy the meiotic cells give rise to diploid offsprings. This can happen by diploidization of the haploid cell (1n->2n), which will produce homozygotes or endomitosis prior to meiosis (4n->2n) which produces heterozygotes. Examples:

  1. Cnemidophorus uniparens : 4n->2n

  2. Sphyrna tiburo: 1n->2n

I don't know of any case where there is fusion of similar gametes to form a diploid cell. It is difficult for two ova to fuse in natural conditions because the vitelline membrane has to be dissolved. Experimentally a haploid ES-cell can be fused to ovum to form a progeny. Haploid ES cells undergo diploidization and when injected in blastocyst, can develop properly (Ref). In fact haploid androgenic-ES cell line had been made in this study by injecting sperm into an enucleated oocyte. These androgenic-haploid cell lines can be fused to ovum to give rise to viable offsprings.

Also see this question. Similar topic

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  • $\begingroup$ Good to know! However, I was under the impression that Cnemidophorus lizards gave rise to clones. If I understand you (and the article) then this gives rise to varied offspring. Obviously there is no infusion of new genetic information from other individuals, but it would still seem farm more advantageous (especially in vertebrates) to produce offspring in this way, than by a mitotic mechanism. I find it odd that there don't seem to versions of automixy (that I can discern) that simply forgo meiosis II. Wouldn't this be the simplest way to generate variation and maintain chromosome number? $\endgroup$
    – single_digit
    Commented May 8, 2013 at 14:23
  • $\begingroup$ It is indeed surprising.. Usually the metphase-II spindle starts assembling before meiosis-I ends.. Slight delay in this process can cause nucleus to assemble¹ ² ³ and perhaps the dihaploid cell can convert to diploid. $\endgroup$
    – WYSIWYG
    Commented May 8, 2013 at 16:21

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