Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 


Forgot your password?
Close
typodupeerror
×
Science

Mule Gives Birth 123

Posted by timothy from the new-twist-to-asimov-books dept.
!splut writes "Thumbing it's nose as science, a Moroccan mule has given birth. Mules, hybrids between horse and donkey, are normally infertile, due to differences between the number and structure of horse and donkey chromosomes. Nevertheless, for reasons not well understood, fertile mules do occur, infrequently, with some 60 documented live births since 1527."
This discussion has been archived. No new comments can be posted.

Mule Gives Birth More

Mule Gives Birth

Comments Filter:
  • Thumbing it's nose as science...

    Sheesh, the things they're calling "science" these days!
  • We always joke about how they make seedless watermelons - and this article made me think of it.

    (and no, I don't care what everything2 says - sexually-deviant horses and fertile watermelons do NOT make seedless ones.)
  • I've heard that fertile mules are generally destoyed. The breeders don't want to sell them and put themselves out of business.

    Or perhaps that's just a legend?
    • > Or perhaps that's just a legend?

      An urban legend, with emphasis on the urban.
    • Why would you want to destroy a fertile mule? Chances are that its offspring would be infertile anyway, and therefore there would be no risk of putting onesself out of business. Given also that there have only been around 60 live births from female mules since the 16th century, I hardly think that the sale of one such mule would do much to the hypothetical mule breeding industry...Which brings me to another point; if you really want a mule rather than a horse or donkey, all you have to do is cross the two. I seriously doubt that there are too many specialised mule breeders out there anyway. Plus, given that you would have to breed a mule with a horse or donkey anyway - male mules are also infertile due to an uneven number of chromosomes -a fertile mule would really be no threat, as there would be no telling what the offspring would be like. Which is better? A donkey+mule or horse+mule. Breeders would, I am sure, be more likely to continue to produce mules by crossing horses and donkeys rather than breeding form an animal which is a scientific anomaly anyway.
  • ...given in the article has to do with if the hybrid creature has an even number of chromosomes. I was under the impression that sterility of offspring was one of the determinations of speciation used by biologists. (And one of the frequent "disproofs" of evolution by creationists.) If a hybrid offspring had an even number of chromosomes, could it be fertile?

    Are there known hybrids/half-breeds can have normal fertility, as opposed to requiring a "miracle" to occur? This is a sincere question, even though I know full well the trolls that are going to be attracted to this post.

    • Liger/Tigon (Score:3, Interesting)

      by crow ( 16139 )
      A quick google search on Liger and Fertile tells me that male hybrids are rarely fertile. Another page states, "No fertile male ligers have yet been found and it is assuemd all are sterile." Though reading a bit more, there may be some fertile males, or males that are fertile for a brief period.
    • I am no biologist, but isn't downs syndrome caused by the "freak" addition of an extra chromosome? If this is the case couldn't something like this happen with great rarity in mules resulting in a 64-chromosome mule, which would be capable of breading?
      • 64-chromosome mule, which would be capable of breading

        I like breaded mule, especially the chicken-fried I had at Outback. Oh, you mean breeding!

        Sorry, corny joke. Had to do it. So sorry. :)

    • There are some birds that make fertile hybrids all the time - I think the finches do this a lot. But they are probably closely related species anyway. For what its worth.

    • Re:The reason for sterility == odd chromosomes? (Score:4, Interesting)

      by geoswan ( 316494 ) on Wednesday October 02, 2002 @04:12PM (#4376110) Journal
      The reason for sterility given in the article has to do with if the hybrid creature has an even number of chromosomes.

      The beeb and the British Mule org may have said mules are infertile because they have an odd number of chromosomes. But I am skeptical.

      Here is an excerpt from a page about the Przewalski Horse [okstate.edu]

      Some authorities feel strongly that the Przewalski horse is the ancestor of all modern breeds. Others point out that it is a different species from the domesticated horse, having 66 chromosomes as compared to the 64 of the domestic horse. They further point out that while crosses between the Przewalski and domestic horses result in a fertile hybrid, the offspring has 65 chromosomes. Subsequent crosses result in 64 chromosomes and bear little resemblance to the Przewalski. The Foundation for the preservation and protection of the Przewalski's Horse, in Rotterdam, the Netherlands, report that only a few Przewalski horses are tamable, in proportions similar to a Zebra.

      So, even if this site is mistaken to say that the 65 chromosome hybrid is fertile, what if you crossed a 62 chromosome Ass with a 66 chromosome Przewalski's Horse? That hybrid would have 64 chromosomes. Would that make it fertile?

      • Przewalski's Horse [okstate.edu] is pretty interesting. Something like 150 of these equids survive. All in zoos. There are people dedicated to trying to re-introduce them to the wild.

        There are three different species of Zebra, including the Quagga [museums.org.za], which genetic analysis shows to be a subspecies of the Plains zebra.

      • I can't help but reinforce what was said earlier about depending on various species. All species are to have an even set of chromosomes, but you can't count on playboy bunny taking it from Black Beauty and expect to get a centaur. Nor can you expect a ass with 62 chromosomes and a Przewalski horse with 66 chromosomes to produce the offspring. If the Hybrid was possible, and had 64 chromosomes, the odds are that two of the chromosomes would have not have pairs. Pairing of the chromosomes being the most important part of genetic structure.
        • I am not suggesting that the hybrid of an Ass with 62 chromosomes and a Przewalski's Horse with 66 would breed true just because it would have 64 chromosomes. I was just giving an example of a possible cross where the infertility would not be due to having an odd number of chromosomes.

          Pairing of the chromosomes being the most important part of genetic structure.

          Is it? Can you explain this to me?

          First, let me restate this, so I am sure we mean the same thing. You are saying that paired chromosomes are necessary for an animal to breed true with its peers, is this correct? You are not saying that having paired chromosomes are necessary for an offspring to be born, because mules obviously don't fulfill this condition.

          So, how did the proto-equid, that was the ancestor of both Asses and the Horse split into two species with different numbers of chromosomes?

          So, what about Down's syndrome individuals, who have an extra copy of chromosome 21? They don't fulfill your requirement for an even number of chromosomes. Yet I don't believe they are sterile.

          Like MS-Windows programs, [ncl.ac.uk] our chromosomes contain a lot of code bloat.

          I heard a lecture about this, when I was in high school. So this info may be incorrect, and I would welcome correction. That lecture included slides of individuals born with chromosome abnormalities. Our chromosomes vary in size. And they are numbered in order of size. The lecturer showed some individuals with an abnormality on a larger chromosome. She said that these individuals were more profoundly affected and had more health problems and more profound cognitive challenges than Down's Syndrome individuals. She said that abnormalities on the larger chromosomes result in problemso profound that the children are spontaneously aborted before they come to term.

          Then there are chromosome abnormality of the X and Y. Turner's syndrome women lack a sex chromosome. They have a single X and no Y. They are of normal intelligence. But they never go through puberty, so they can't have children. There are people who have XXY and XYY. I don't believe they are sterile either. Another slashdotter said something about XXX women - women with three X chromosomes.

          Since that lecture I have heard that some Down's symdrome individuals have only a fraction of the extra 21, and that there are less profoundly affected than individuals with a full extra chromosome 21.

          Genes slip around. They slip from chromosome to chromosome. I saw a science documentary about how genes were slipping from the Y to the X. I am not a molecular biologist, but I imagine that 61 of the 62 chromomosomes of Horses and Asses correspond, and that sometime after they split into different species one of the chromosomes split in two. If this was the case, there would be genes for the same traits in the chromosomes from both parents, even though they had them on different chromosomes.

          There was an article in Scientific American, on mule fertility about 45 years ago. It advanced a theory about Mule fertility, that Mules produce gametes, eggs and sperm, but that almost all of them contain a mixture of Ass and Horse chromosomes. And those would be no good. But occasionally a gamete is produced that has all the gametes from a single parent. IIRC the theory was that that gamete could be fertilized and brought to term. That offspring would be pure Horse or pure Ass. "One in million" is the estimate of how often a mule brings an offspring to term. Check my math. If this theory is correct

          Here is something I don't understand. That documentary said that some of the genes on the Y are duplicated dozens of times. So, why does the mere single extra copy of genes in chromosome 21 cause the profound manifestations of Down's? Does each gene contain the molecular equivalent of an instruction pointer, or a map of bad sectors?

          • I must have been half asleep when I posted this, there is stuff missing.

            There was an article in Scientific American, on mule fertility about 45 years ago. It advanced a theory about Mule fertility, that Mules produce gametes, eggs and sperm, but that almost all of them contain a mixture of Ass and Horse chromosomes. And those would be no good. But occasionally a gamete is produced that has all the chromosomes from a single parent. IIRC the theory was that this gamete could be fertilized and brought to term. That offspring would be pure Horse or pure Ass. "One in million" is the estimate of how often a mule brings an offspring to term. Check my math. If this theory is correct then the chance is more like one in 2^61.
    • That definition of a species is problematic because there ARE many exceptions. For example, finches in the galapagos come in many different distinct species identified by their distinctive beaks and the foods they are adapted to eat. However the species can and do interbreed often and share the same habitat. The offspring are fertile, however they are not terribly successfull since their beaks are not specialized enough to open any nuts at all, so the species remain distinct. Also that definintion of a species does not account for organisms that reproduce asexually - for instance bacteria exist in species even though they reproduce by simply cloning themselves. Really all you can say about a species is that it is and remains a more or less genetically distinct pool of dna, evolving without genes being introduced into the species gene pool.

    • Are there known hybrids/half-breeds can have normal fertility, as opposed to requiring a "miracle" to occur?

      Short answer: YES. There are very many recorded cases of animals and plants of different species hybridizing and the descendants being fertile. Depends on the species involved, some hybrids are sterile, some are not. They often are. But that hybrids are sterile is a myth.

      • Are there known hybrids/half-breeds can have normal fertility, as opposed to requiring a "miracle" to occur?

        Here is an example [orst.edu]. Most of the most widely used cereals are hybrids that breed true. However, from memory, I think that the number of chromosomes of triticale and similar hybrids is the sum of the number of chromosomes in the parent stock, not the average.

        If the name triticale rings a bell it may be because Captain Kirk had to make an emergency delivery of QuadroTriticale in an old Star Trek episode.

        • >However, from memory, I think that the number of chromosomes of triticale and similar hybrids is the sum of the number of chromosomes in the parent stock, not the average.

          Yes, it's called hybrids stabilized by polyploidy. Common in plants. The new number is (obviously) even, so there in no problem during segregation of chromosome pairs (this is what screws up gametes of some hybrids).

          But this is not alwasy neccesary; many related species have the same chromosome number, so there is no problem to begin with.

  • Offspring fertile? (Score:4, Interesting)

    by crow ( 16139 ) on Wednesday October 02, 2002 @01:12PM (#4374511) Homepage Journal
    So what is really interesting is whether the offspring are fertile. If so, then we can start breeding mules from mules, and we have a new species.

    And where does the infertility in mules normally lie? Is it a male thing or a female thing? Or both?
    • If so, then we can start breeding mules from mules, and we have a new species.

      How do you know that these fertile mules are not able to breed with horses and/ or donkeys? If they could, it would rather be an example of our 'species' definition breaking apart.

      Tor

    • Re:Offspring fertile? (Score:4, Interesting)

      by geoswan ( 316494 ) on Wednesday October 02, 2002 @02:30PM (#4375267) Journal
      So what is really interesting is whether the offspring are fertile. If so, then we can start breeding mules from mules, and we have a new species.

      And where does the infertility in mules normally lie? Is it a male thing or a female thing? Or both?

      I looked into this when we discussed cloning Mammoths, [slashdot.org] or harvesting frozen Siberian Mammoth sperm a few months ago.

      It was my impression that the very rare offspring of a mule mare and a horse sire, or a mule mare and a donkey sire, are the same species as the father. The mule has a mixture of donkey and horse chromosomes. Sperm and ovum are haploid cells -- they have one chromosome, not a pair. That is how sexual reproduction works. It was my impression that most ovum will have a mixture of horse and donkey chromosomes. But very occasionally, by chance, an ovum will have entirely horse chromosomes or donkey chromosomes.

      Male mules are almost always gelded, to curb their agressiveness.

      Hobbyists cross donkeys with zebras. They call the offspring "golden zebras". Hobbyists cross lions and tigers. These crosses are, apparently, a bit nuts. Lions are, of course, social. And tigers are, of course, solitary. The hybrid is drawn both ways.

      The Moroccan foal looks a bit like a baby donkey and a bit like a baby mule - but not exactly like either.

      The site I found about crossing cats talked about the differences between lion tiger crosses where the lion was the mother and when the tiger was the mother. When the tiger was the mother the hybrid is larger than a tiger. The maternal influence on the foal's embryonic environment has an influence on how the genotype is expressed.

      Another anecdote. You can tell whether a mule's mother was a horse or a donkey by putting it in a corral that contained both donkeys and horses. The mule will go hang out with the kind of animals it was raised with.

      • Re:Offspring fertile? (Score:4, Funny)

        by Tackhead ( 54550 ) on Wednesday October 02, 2002 @04:03PM (#4376046)
        > Hobbyists cross donkeys with zebras. They call the offspring "golden zebras". Hobbyists cross lions and tigers. These crosses are, apparently, a bit nuts.

        Okay. That's it. That's the last time anybody on Slashdot ever gets away with saying "Building a watercooled PC rig out of Kraft Dinner and installing cold cathode lights in their hard drives? Those silly PC hobbyists have too much time on their hands!" :)

    • Re:Offspring fertile? (Score:4, Informative)

      by !splut ( 512711 ) <sputNO@SPAMalum.rpi.edu> on Wednesday October 02, 2002 @04:48PM (#4376437) Journal
      So what is really interesting is whether the offspring are fertile. If so, then we can start breeding mules from mules, and we have a new species.

      And where does the infertility in mules normally lie? Is it a male thing or a female thing? Or both?

      The infertility arises from the fact that normally, during meiosis (the production of sex cells), like chromosomes in the diploid compliment of chromosomes (one chromosome from each parent) pair up, separate, and produce haploid daughter cells. Mules are in the awkward position of having 31 chromosomes from the donkey parent and 32 from the horse parent, giving them an odd number of chromosomes total, even though they are in a diploid state.

      On the one hand this gives the mule "hybrid vigour" - it exhibits many of the desirable characteristics of each parent. On the other hand, this odd number of chromosomes poses problems for meiosis - the normal meiotic process just doesn't produce viable sex cells. (So, in answer to your question, the infertility is a male and female thing.)

      The fact that the foal was born at all suggests that the mother, the father, the foal, or some combination has some manner of chromosomal aberration - an extra chromosome from one parent, or something along those lines - resulting ultimately in a viable diploid zygote.

      Chromosomal aberrations often result in infertility to begin with... but lets pretend that the foal is fertile, and is able to breed with horses, donkeys, or future siblings. It's offspring will not exhibit the hybrid vigour that is observed in the mule, because the offspring will not have the characteristic compliment of horse and donkey chromosomes. And since that vigour is the reason why people breed mules in the first place, a new breed of fertile mule would not be that useful.

  • I guess that will be next headline.
  • I didnt even know her nime months ago.

  • Not again (Score:5, Funny)

    by Boglin ( 517490 ) on Wednesday October 02, 2002 @01:17PM (#4374558) Journal
    The Second Foundation barely saved the Seldon plan from the Mule the last time. This kid could ruin everything!
    • Yeah, I wonder if a certain robot is behind all this...

      BTW: If mules are infertile, where do they come from? Do we have to deal with a bunch of sex-fixated donkeys out there, trying to mate with horses whenever they can? On the other hand: most mules are used in rough terrain, like moutains. If I were a horse, I'd probably agree to this as well, rather then living in total celibate. Hell, even as a human... NO! This thought goes to far... =:*)

  • Bat baby (Score:1, Offtopic)

    by Vodak ( 119225 )

    "hybrids between horse and donkey, are normally infertile, due to differences between the number and structure of horse and donkey chromosomes"

    Oh boy, more proof that the bat baby exists

  • Fertility (Score:4, Interesting)

    by ktulus cry ( 607800 ) on Wednesday October 02, 2002 @01:40PM (#4374810)
    One possible explantion for this rare occurance, one that I can see, anyway - Horses have 64 chromosomes in their normal diploid state, with haploid gametes having 32. Donkeys have 62 chromosomes in normal diploid state, with haploid gametes having 31. This gives a mule 63 chromosomes. If one gamete had experienced non-disjunction during meiosis (that is, one pair of homologues did not split correctly, giving one daughter cell 2 copies of a chromosome, and one none), a mule could have 62 or 64 chromosomes (depending on which gamete it received). This is not a very rare occurance, Down Syndrome or Kleinfelter's Syndromes in humans (trisomy 21 and XXY respectively). While most cases of non-disjunction produce abnormal offspring, in humans, for example, an XXX female is completely normal, except for a usually smaller stature. A case like this, where the offspring IS normal, is relatively rare, and a similar situation could be occuring in these fertile mules.
    • Has anyone ever mated mules? can you get male mules? what about a mule and a donkey, anybody care to explain the different combos?

      • Re:Anyone mated mules? (Score:4, Informative)

        by geoswan ( 316494 ) on Thursday October 03, 2002 @02:00AM (#4379067) Journal
        Yes, mules come in both male and female. Male mules are almost always gelded, prior to puberty. There is no advantage to keeping them intact. And, if they are not gelded they get very aggressive.

        Horse mother, donkey sire - offspring is a mule. Donkey mother, horse sire - offspring is a hinny. Genetically indistinguishable from a mule. I presume the two different names predate modern genetics.

        Mules are stronger, and more intelligent than horses.

        Like mules, a hybrid of a zebra and a horse, or a zebra and a donkey, is infertile. Or a hybrid between any of the three species of zebra.

        Fans of breeding exotic hybrids have dreamed up all kinds of "cute" names for the different crosses. Seems annoying to me.

        Breeding exotic hybrids of endangered species seems very irresponsible to me. But there are people who do it. It seems to me that breeding a Liger or Tigon means you are wasting the reproductive potential of the parents. The Quagga is a recently extinct subspecies of Plains Zebra. There is a project to find Plains Zebras with the most Quagga like characteristics, and breed them, to try to restore them.

        This seems like a bad idea to me too. It seems to me that it makes more sense to husband the remaing genetic heritage of the Plains Zebra.

        The sixth surviving equid is the very rare Przewalskis' Horse. Extinct in the wild. 150 survive in zoos. Originally found in Mongolia. It is not too late to try to preserve this animal's genetic heritage.

  • Speciation (Score:4, Interesting)

    by f97tosc ( 578893 ) on Wednesday October 02, 2002 @02:06PM (#4375058)
    The truth is that speciation is not very well understood. In many ways 'species' is a convenient abstraction - we humans like to put horses and donkeys into two discrete buckets and not think much about anything in between. In reality there is no law of nature that says that all living entities must belong to exactly one of our convenient buckets.

    The 'infertile children' definition works pretty well, but it is not perfect. Another problematic example is that of a species of birds that live in different territories around the globe. The birds can mate with other birds in their own or in adjacent territories. In other words, the birds in the first territory can mate with those in the second territory, and those in the second with those in the third, and so on all the way around the globe - and finally the birds of the last territory can again mate with those in the first. However, it turns out that the birds cannot mate with birds several territories away. Our convenient species definition breaks apart.

    Tor
  • about my former school's mascot [cmsu.edu]?
  • According to the British Mule Society [hamill.co.uk],

    "The donkey has 62 chromosomes (31 pairs), the horse 64 (32 pairs) and the mule and hinny each have 63 chromosomes - of which many pairs are unevenly matched. It is not just the number of chromosomes which is different in donkeys and horses, but their structure: they have developed slightly differently over evolutionary time....The donkey and horse chromosomes are almost completely unable to pair up."

    It's amazing that mules turn out as well as they do. If carrying heavy packs all day and being beaten daily by a bowlegged man with whiskey breath is your idea of turning out well.

  • A Mule giving birth (Score:5, Funny)

    by kcavness ( 63547 ) on Wednesday October 02, 2002 @02:42PM (#4375375) Homepage
    Now that's some half-assed science.
  • i'm not surprised.
    it's happened before [the-underdogs.org]with some decent [the-underdogs.org] results.
    though i haven't checked it on wine...

    i think we need to encourage this sort of thing, get back to the roots, you know?

  • A fertile M.U.L.E. [classicgaming.com] - we could have used one of those on planet Irata. ... wonder if I can genetically engineer them to be born already outfitted for Smithore?

  • Normally a mule has 63 chromosomes according to the article (presumably 62 paired donkey/horse and one paired horse/horse).

    However, this mule suffers a form of "mule Down's syndrome" - she only has 62 pairs. The father is a donkey. There is a match in the number of chromosomes.

    So, what is considered a genetic disability in humans could possibly be considered a genetic advantage in mules.

    Note: no science whatsoever backs this theory as far as I know ... but then again, there wasn't much in the article either.
  • Ooh! Ahh! That's how it always starts. Then later there's running and screaming...

    Nature will find a way.
  • Could it be possible that that mules don't reproduce very often due to the fact that no one tries to reproduce them due to the fact that its "common knowledge" that mules can't reproduce?
    • Could be, but keep in mind that because it's 'common knowledge' that mules can't reproduce, they are often kept in pens with horses/donkeys of the opposite sex.
      Farmers don't have to watch where they put an infertile animal, so they'll often just stick it in the pen with the most room available.
      If sex happens - hey, no problem. It's infertile, so no offspring.
  • A horse has 64 chromosomes and a donkey has 62, so a mule is left with 63, an uneven number which cannot divide into chromosome pairs. This should make a mule unable to reproduce.

    So how many does this baby mule have? Did it manage to end up with an odd number, or did it end up with an even number due to one of its mule parents having the mule equivilent of downs syndrome?
  • (a) freak birth by a mule

    or

    (b) sex with a mare

Slashdot Top Deals

I tell them to turn to the study of mathematics, for it is only there that they might escape the lusts of the flesh. -- Thomas Mann, "The Magic Mountain"

Close