parthanogenesis

Doug Eernisse Doug_Ee at um.cc.umich.edu
Sun Oct 10 22:08:35 EST 1993


In article <293nbg$3il at zikzak.apana.org.au>
Lynne Shandley, bunny at zikzak.apana.org.au writes:
>Well, I'd say one of the reasons why males of any species are not capable of
>parthenogenesis (as far as I know) is because of the different forms of
>gametogenesis that occur in male and female.  The gametes produced by
>males tend to be little sacs of DNA with not much in the way of cell
>cytoplasm, whilst females tend to produce what could be considered a whole
>cell that is lacking half its chromosome complement - probably an easier start
>point for parthenogenesis to occur.  Anyway, aren't the products of
>parthenogenesis clones of the parent?

That is one kind of parthenogenesis, termed apomixis. That is when unreduced
eggs complete development without fertilization, sometimes involving 
pseudogamy. Examples include digenean trematodes, bdelloid rotifers, some
nematodes, tardigrades, coccids, cladocerans, aphids, cynipid wasps,
telid lizards, the clam Lasaea (all but the last example from Bell, G. 1982:
The Masterpiece of Nature..., p. 36). 

Another kind of parthenogenesis is automictic thelytoky, in which syngamy
occurs between nuclei of the same (female) gender, sometimes involving
pseudogamy. An example is when a polar body fuses with the oocyte haploid
nucleus. This is very much like self-fertilization in its genetic consequences.
It is a form of severe inbreeding, which will lead to very low (if any)
heterozygosity, in contrast to apomixis which preserves heterozygosity.

I recommend Bell's book for a review of parthenogenesis, although you will
have to catch up on examples published in the last decade. I would assume
that you won't find examples of parthenogenetic "males," for reasons
others have mentioned.

Doug



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