Open thread: parthenogenesis in Komodo dragons

A baby Komodo dragon born by parthenogenesis, photographed at Chester Zoo (CC BY-SA 3.0, Wikipedia user Neil)

A baby Komodo dragon born by parthenogenesis, photographed at Chester Zoo (CC BY-SA 3.0, Wikipedia user Neil)

What the hell. It’s geeky. And this is a fairly new (published 2006) finding about komodo dragons. To quote from Wikipedia:

On December 20, 2006, it was reported that Flora, a captive Komodo dragon living in the Chester Zoo in England, was the second known Komodo dragon to have laid unfertilized eggs: she laid 11 eggs, and 7 of them hatched, all of them male. Scientists at Liverpool University in England performed genetic tests on three eggs that collapsed after being moved to an incubator, and verified that Flora had never been in physical contact with a male dragon. After Flora’s eggs’ condition had been discovered, testing showed that [London Zoo dragon] Sungai’s eggs were also produced without outside fertilization…

Komodo dragons have the ZW chromosomal sex-determination system, as opposed to the mammalian XY system. Male progeny prove that Flora’s unfertilized eggs were haploid (n) and doubled their chromosomes later to become diploid (2n) (by being fertilized by a polar body, or by chromosome duplication without cell division), rather than by her laying diploid eggs by one of the meiosis reduction-divisions in her ovaries failing. When a female Komodo dragon (with ZW sex chromosomes) reproduces in this manner, she provides her progeny with only one chromosome from each of her pairs of chromosomes, including only one of her two sex chromosomes. This single set of chromosomes is duplicated in the egg, which develops parthenogenetically. Eggs receiving a Z chromosome become ZZ (male); those receiving a W chromosome become WW and fail to develop.

The Nature article is Phillip C. Watts et al (2006) Parthenogenesis in Komodo dragons, Nature 444, 1021–1022 (21 December 2006), doi:10.1038/4441021a.

This is an open thread, for a discussion of biology geeking, great nerdy events and, of course, anything else you want to discuss!

11 thoughts on “Open thread: parthenogenesis in Komodo dragons

  1. Tony Mechelynck

    I read somewhere (but it was years ago) about a (different, I think) reptile “dragon” species who have done away with males altogether: all individuals are female, and they still need to couple in order to reproduce, but their coupling exchanges no genetic material, it just triggers ovulation. I think these females are all haploid but I could be mistaken.

    This said, I’ve long known that chickens also use the ZW system, but I’ve yet to see (or hear about) a chick hatching out of an egg laid by a hen living away from any rooster.

    An earlier “open thread” (now closed to comments) was about reproducing human females parthogenetically, doing away with the (what is the opposite of “fair”?) the “foul” sex (as I suppose it would be named here ;-) ). You know what, gals? I don’t feel particularly menaced. Making babies the old-fashioned way, when it’s done right, is more fun for everyone involved, and (IIUC) it also shuffles genes more efficiently, which is part of a species’s resistance against hardships. Oh, so humans are disconnected from Darwin’s “struggle for life”, probably since the “agricultural revolution” which happened at some point between (IIUC) the Neolithic and Bronze Ages. However, in the face of overpopulation, global warming and what-not, our very success could quite possibly hit us back in the face, not in our own lifetimes perhaps, but at some predictable future time.

    Oh well. Let us end on a more humorous note with a quote from Robert Heinlein (a male writer) who put it into the mouth of (IIRC) Lazarus Long (a male character, but often expressing the author’s views): To women who want to be the equals of men, I say they lack ambition.

    1. Mary Post author

      Uh… so, first thing, that thread was intended to be humorous. Entirely displacing sexual reproduction in humans, either the fertilisation process or the most common (but not only) mechanical process of bringing sperm near ova, certainly shouldn’t be assumed to be genuinely a goal of this blog or of its readers and writers.

      Secondly, don’t put words in our mouth (“the foul sex”?) or call us “gals”.

      1. Tony Mechelynck

        I didn’t assume that it was their goal: that was (in part) why I din’t feel “menaced”. Also, maybe my tongue-in-cheek humour wasn’t made obvious enough, also for what follows:

        That “foul sex” phrase was intended to be humorous, and I even put a smiley there to mean it wasn’t serious. English isn’t my mother language: French is, and in French we speak of le beau sexe and le sexe fort. Somehow “the stronger sex” didn’t feel right here, so I was at a loss for the right expression.

        About using the word “gals”: maybe I don’t understand all its connotations. English is (I repeat) not my mother language, and I call people of my own sex “guys” without anyone objecting. I thought that the feminine of “guy” was “gal” but maybe I was mistaken, outdated (I’m 60 years old) or using a different “national variant” of English than you do (and I don’t know myself which “national variant” is closest to the English I use: I was schooled in en_GB but most of my English reading has been from US authors). When I wrote “gals”, I didn’t mean any slur or otherwise disparaging undertone: if I had been talking to male people, I would have called them “guys” in this context, not “boys” and not “men”, and I used
        what I thought was the equivalent idiom at the same level of language for talking to female people felt to be on an equal footing with me and on a friendly and casual level of language. Please pardon me if I was mistaken.

        1. Jayn

          I think it has a bit to do with feminine pronouns and such being used as diminutives or insults. “Guys” implies you are treating the other person as an equal. “Gal”, on the other hand, can be seen as a form of talking-down-to. (I don’t know if it’s the same in French, though I do find it interesting that a group of mixed genders is referred to with ‘ils’ rather than ‘elles’.)

          And personally, I thought the ‘foul sex’ joke was funny. English doesn’t really have an equivalent phrase for men, and since women are generally assumed for be weak, passive, and air-headed (as opposed to strong, assertive and thoughtful, as men are), I thought it turned the usual discourse around nicely. I mean, if we’re fair, and men are the opposite of women, they must be foul, right? :P (Except for male chickens–they’re just fowl). You got into a little trouble by saying that’s what they’d be called ‘here’–we get accused of hating men enough as is–but I thought the phrase itself was good.

          On topic–It interesting that a non-fertilised egg from a komodo dragon can only create male offspring, while for mammalian species the equivalent would produce only females

    2. spz

      I would like to add the remark that making babies the old fashioned way will probably not survive the advent of a viable and affordable “uterine replicator” ((C) Lois McMaster Bujold, I think) very long, since neither morning sickness, nor pregnancy as such, nor birthing tend to be -that- enjoyable.

  2. Mary Post author

    So, as a generality, because of the hostility women in general and feminists in particular face on the Internet generally, it’s not a great start to the conversation to begin by telling jokes that require us to know or assume that you’re a friendly type playing along. Sometimes you can get away with really broad satire, but several serious comments here first would have got you a long way.

    Re “foul sex”, the joke seems to be assuming a premise that this site is woman-supremacist. Maybe that was part of the joke. But I can assure you that it’s also seriously assumed by many people on feminist websites in almost identical language. (Most often the rhetorical strategy is that “I’m only a man which means you must despise me hahaha” is trying to attract “no no we aren’t those kinds of feminists, we are caring women, we love you and would like to listen to all your problems” responses.)

    Re “gals” there are (almost?) no diminutives or slang for “women” that is neutral or friendly in enough dialects of English to really be a good idea in a space like this. This site (and I think most feminist blogs) therefore tend to use “women” to refer to adult women and “girls” to refer to female children. For what it is worth, “gals” reads to me (an Australian English native speaker) as either a belittling diminutive from an outsider (similar to “girls” “chicks” etc) or else possibly a term of affection from a woman friend.

  3. spz

    completely different topic:

    Google Summer of Code:
    is my impression mistaken that a more-than-representative number of women is involved in their projects GSoC activities?

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