Androgenetic species of clam utilizes rare gene capture

May 24, 2011 by Deborah Braconnier report
Corbicula fluminea. Image credit: USGS

(PhysOrg.com) -- In a new study published in the Proceedings of the National Academy of Sciences, biologist David Hillis from the University of Texas shows how the freshwater Corbicula clam utilizes rare gene capture to avoid the accumulation of mutations in their androgenetic lines.

The Corbicula clam is a freshwater species of clams that originated in China and Taiwan but can now be found all over the world. The clams utilize asexual reproduction known as androgensis where the offspring are essentially clones of the male parent. Asexual reproduction lacks and can eventually lead to mutations and possible lineage . This new study reveals that the Corbicula clam may have just found a way to avoid this mutation issue.

Hillis and his team looked at the genomes of 19 Corbicula species found throughout the world (both sexual and asexual) and found groups of genes which belonged to one species would show up in another one. This would not occur if the asexual species were strict with their cloning. Hillis found that these clams were essentially using the eggs of other species and occasionally capturing the maternal nuclear DNA in order to replenish the clone’s lineage and avoid lineage mutations.

The Corbicula clam is also known for its sudden population increases and has become a pest in many areas of the world. Hillis now plans to look at if there is a connection between the population booms and this rare gene capture event.

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More information: Rare gene capture in predominantly androgenetic species, PNAS, Published online before print May 23, 2011, doi: 10.1073/pnas.1106742108

Abstract
The long-term persistence of completely asexual species is unexpected. Although asexuality has short-term evolutionary advantages, a lack of genetic recombination leads to the accumulation over time of deleterious mutations. The loss of individual fitness as a result of accumulated deleterious mutations is expected to lead to reduced population fitness and possible lineage extinction. Persistent lineages of asexual, all-female clones (parthenogenetic and gynogenetic species) avoid the negative effects of asexual reproduction through the production of rare males, or otherwise exhibit some degree of genetic recombination. Another form of asexuality, known as androgenesis, results in offspring that are clones of the male parent. Several species of the Asian clam genus Corbicula reproduce via androgenesis. We compared gene trees of mitochondrial and nuclear loci from multiple sexual and androgenetic species across the global distribution of Corbicula to test the hypothesis of long-term clonality of the androgenetic species. Our results indicate that low levels of genetic capture of maternal nuclear DNA from other species occur within otherwise androgenetic lineages of Corbicula. The rare capture of genetic material from other species may allow androgenetic lineages of Corbicula to mitigate the effects of deleterious mutation accumulation and increase potentially adaptive variation. Models comparing the relative advantages and disadvantages of sexual and asexual reproduction should consider the possibility of rare genetic recombination, because such events seem to be nearly ubiquitous among otherwise asexual species.

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User comments : 8

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210
1.2 / 5 (6) May 24, 2011
Well, well, well - In fact, mother nature has been the master of DNA/gene recombination without peer waiting for the human race to grow up and learn about it.
From a previous post I submitted, "Random mutation, cannot account for all the varieties of life and form seen in our world nor in the cone snail:Natural DNA recombination meets the definition of a very precise instrument for change as well as normal reproduction. Cancer/death unless it wipes out a species, does not prevent change, nor make it"
From the above abstract,"The rare capture of genetic material from other species may allow androgenetic lineages of Corbicula to mitigate the effects of deleterious mutation accumulation and increase potentially adaptive variation...Models comparing the relative advantages and disadvantages of sexual and asexual reproduction should consider the possibility of rare genetic recombination" Now, to find the adaptive messaging method:The who, when, where to get stuff from
WORD TO YA MUTHAS
Phideaux
5 / 5 (2) May 24, 2011
The article should say more about how these clams are "using the eggs of other species". Perhaps there is some form of lateral DNA transfer involving virus.
Dug
not rated yet May 24, 2011
Wow, two responses out of two that are on topic and offer significant insights on the subject. Now that's why I read Physorg instead of the Fluffington Post.
frajo
not rated yet May 25, 2011
The article should say more about how these clams are "using the eggs of other species". Perhaps there is some form of lateral DNA transfer involving virus.
Exactly. Just telling us that
these clams were essentially using the eggs of other species and occasionally capturing the maternal nuclear DNA
hides the most interesting information. What "other species"? How do they acquire the eggs?

Sidenote:
It's "androgenesis", of course. (Not "androgensis".)
But using the maternal DNA is not really asexual reproduction.

Na_Reth
1 / 5 (1) May 25, 2011
Most logical thing would be fish eggs or frog eggs...
Ethelred
3 / 5 (2) May 25, 2011
From a previous post I submitted, "Random mutation, cannot account for all the varieties of life and form seen in our world nor in the cone snail:
A post that was about cancer in an individual and not evolution of a species, as was pointed out to you.

Cancer/death unless it wipes out a species, does not prevent change
It CONTROLS the surviving changes to fit the environment. Though cancer is not involved except as one more way to die and that only when it significantly effects the rate of reproduction.

Now, to find the adaptive messaging method:The who, when, where to get stuff from
Usually from the opposite sex so there is no reason to claim this as support of your religion based desire for an Intelligent Designer.
Ethelred
4 / 5 (4) May 25, 2011
In mollusks that can be the ANY other member of the species as they can be of both sexes at once. Or switch. In this case the authors were making some guesses as to how the genes were crossing lines of decent. MY first thought is that they occasionally change sexes and produce eggs.

On second thought they could have sexual reproduction with organisms that are so closely related that they really should be considered the same species. Mollusks just spray germ cells into the water and those combine or don't willy nilly with whatever is around. Mostly it gets eaten by filter feeders.

Monty Python on Mollusks
http://www.youtub...zvE615dM

I see this group of organisms as a single species with a set of subspecies that have a trick of reproducing on their own when the sperm fail to meet with compatible eggs. Keep in mind that the eggs and sperm in this case are more a matter of point of view than a strong genetic component.

Ethelred
DavidMcC
not rated yet May 26, 2011
Frajo, if "using the maternal DNA is not really asexual reproduction" then what is? In asexual reproduction, maternal DNA is all you have, there being no father.