Monday, 19 February 2018

All-female Fish Makes Creationism Look Stupid

Amazon molly (Poecilia formosa)
Photo credit: Manfred Schartl
Universität Würzburg: No sex for all-female fish species

No wonder American creationists all seem to be uncritical fawns of Donald Trump, hoping he'll build a wall to shut Mexico out. Right on the Mexican border with Texas, that centre of Christian fundamentalism and creationism, is a little fish that could cause the whole thing to come down - creationism that is, not the wall which hasn't even been started yet, the truculent Mexicans not agreeing to pay for a Trump foible.

The little fish, the Amazon molly, Poecilia formosa, like the newly emerged new species of crayfish I wrote about earlier, is all-female and reproduces asexually. The daughters are all clones of their mother.

But that's not the only embarrassment for creationists. In order to reproduce, and unlike the all-female crayfish, these fish do actually mate - with males of a closely-related species. The sperm even penetrates the egg! Then the egg promptly destroys any DNA from the male.

If a creationist could explain the intelligence behind that system, I'd be ever so grateful.

But the problem for creationism doesn't end there. An even more difficult to explain feature of this all-female, self-cloning species, their genome contains genes for spermatogenesis, the development of males and the meiosis of egg and sperm cells, none of which are needed.

We found little evidence of genetic degeneration in the Amazon molly, but rather a unique genetic variability and clear signs of an ongoing evolutionary process.

Manfred Schartl, co-author
Department of Physiological Chemistry, Biocenter,
University of Würzburg, Würzburg, Germany
Genetic analysis shows that, like all asexually reproducing vertebrates, arose as a hybrid; in this case between P. latipinna and P. mexicana probably about 100,000 years ago. Although this is short on a human evolutionary scale, With a generation time of three to four months, this represents some 500,000 generations. This is far longer than would normally be expected of a clonal species.

The species was studied to discover why it appears not to be conforming to the theory that says cloned species should die out eventually because they lack genetic diversity and so lack the ability to respond to environmental changes, new pathogens, etc. The results of the study by an international team were published a few days ago, open access in Nature Ecology & Evolution:

Abstract
The extreme rarity of asexual vertebrates in nature is generally explained by genomic decay due to absence of meiotic recombination, thus leading to extinction of such lineages. We explore features of a vertebrate asexual genome, the Amazon molly, Poecilia formosa, and find few signs of genetic degeneration but unique genetic variability and ongoing evolution. We uncovered a substantial clonal polymorphism and, as a conserved feature from its interspecific hybrid origin, a 10-fold higher heterozygosity than in the sexual parental species. These characteristics seem to be a principal reason for the unpredicted fitness of this asexual vertebrate. Our data suggest that asexual vertebrate lineages are scarce not because they are at a disadvantage, but because the genomic combinations required to bypass meiosis and to make up a functioning hybrid genome are rarely met in nature.

Wesley C. Warren, Raquel García-Pérez, Sen Xu, Kathrin P. Lampert, Domitille Chalopin, Matthias Stöck, Laurence Loewe, Yuan Lu, Lukas Kuderna, Patrick Minx, Michael J. Montague, Chad Tomlinson, LaDeana W. Hillier, Daniel N. Murphy, John Wang, Zhongwei Wang, Constantino Macias Garcia, Gregg C. W. Thomas, Jean-Nicolas Volff, Fabiana Farias, Bronwen Aken, Ronald B. Walter, Kim D. Pruitt, Tomas Marques-Bonet, Matthew W. Hahn, Susanne Kneitz, Michael Lynch & Manfred Schartl
Clonal polymorphism and high heterozygosity in the celibate genome of the Amazon molly
Nature Ecology & Evolution
(2018) doi:10.1038/s41559-018-0473-y

Copyright: © 2018 The authors
Published open access
Reprinted under the terms of a Creative Commons Attribution 4.0 International (CC BY 4.0) License.

The answer is that, despite the cloning process, the genes associated with immunity appear to be subject to a high degree of variability. This means that the hybrid, asexual species has some ten times the rate of heterozygosity of the parent species. This seems to give them a unique ability to resist pathogens.

A very simple explanation for something that is totally inexplicable as the result of any sort of intelligence.

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3 comments :

  1. Very interesting, Rosa! Here is another example of speciation and evolution for creationists to consider, explain and, hopefully, refute: http://www.sciencemag.org/news/2015/08/crayfish-create-new-species-female-superclones .

    ReplyDelete
    Replies
    1. Oh, I should have known better, Rosa. It doesn't surprise me at all that you already noticed that same paper a fortnight ago.

      I suspect you have written blog posts about parthenogenesis as well. Or else, here's an interesting article about that phenomenon: https://www.sciencealert.com/watch-we-were-once-all-female .

      Geneticists have discovered that all human embryos start life as females, as do all embryos of mammals. During the first 5-6 weeks of embryonic development it's the X chromosome that works, i. e. the Y chromosome is still (more or less) "sleeping"/inactive.

      Not until the second month the fetus elaborates enough androgens to offset the maternal estrogens. Then maleness can at last begin to develop in fetuses containing the Y chromosome.

      AFAIK it's a gene called the SRY gene that activates the Y chromosome,thereby actively inhibiting certain features of the X chromosome.

      Genuine parthenogenesis per defintion lacks the Y chromosome, so that process always must result in a female offspring. Because of that I've often wondered why Jesus wasn't born a girl.

      Maybe you know the answer, Rosa? Or we should, both of us, turn to the creationists in order to get this interesting question answered and the process explained in detail why Jesus, a baby boy, is an exception and anomaly?

      On the other hand, I don't trust creationists or other liars for Jesus. So I'd rather listen to your answer, Rosa.

      Delete

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