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Tuesday, May 12, 2009

Sex, Sex, Sex, part 3

So, here's part three of a still growing series on sex

Researchers have recently identified an ant species that reproduces without sex.

There are farming ants. Apparently some species have been at it for about 80 million years, which makes our own agricultural revolution seem like a tweet in comparison to a novel. These ants would collect plant detritus, dead insects etc, and instead of eating it themselves, would use it to grow mushrooms.

When the researchers started examining the ant colony to find out how they organized their little farm, they noticed that they never came across any males. Upon genetic testing, they found that the population was all females, and in addition, they were all clones of the queen.

They also found upon dissection that all the females had lost an essential part of their reproductive organ in evolutionary time.

As you all have probably heard, there are some advantages to sexual reproduction, including creating greater genetic variation in recombination. There are some animals that have the ability to reproduce asexually, but this is rarely the main form, and especially not the only form, of reproduction. THe problem with a population of clones is that if one individual can get sick, all of them can get sick.

In spite of this, this species has evolved away the capability for sexual reproduction, and thereby the need for men! Ha-ha!

And since we're talking about ants, there is another "freak of nature" which happens to be an ant. The organism with fewest chromosomes is an ant.

For most eusocial insects, reproduction is quite different than our own. The females are diploid, and the males are haploid, meaning they only have half of the chromosomes of females. That is, the females have chromosome pairs (such as having XX for sex in humans), while the males only have one half of the pair(only one X). This means that if a female lays an unfertilized egg, it turns into a male drone, and if it is fertilized, it turns into a new female.

When the human genome project was being completed, the researchers constantly had to reduce their estimate for how many genes we awesome, complicated, advanced humans have. It turned out we only have about 25 000, about the same as mice. (Fruit flies have about 14 000, rice has 60 000!) They were at this point really realizing that complexity does not only stem from the amount of genetic material.

So, these ants are social insects, which implies that they have complex social behavior, and when this discovery was made in 1986, it was one of the first clues that genetic material and complexity are not as correlated as we would like to think.

As far as I could tell, not much research has been done on this variant of the species (it is apparently part of a species complex of very similar sibling species with varying chromosome numbers).

Given this fact, I have to mention that when I took one of the introductory courses in Molecular Biology at Uni.of.Oslo, one of the lecturers mentioned this species and the original article published in 1986. He claimed that he had found the research som interesting and surprising, that he immediately had contacted the people who found them and asked for some specimens. And he got some. A short while after, there was apparently a fire at the original research institute and all the original specimens had vanished. They had gone into the field again, but had been unable to localize the original one-chromosome population.

All this means that there is a researcher at the University of Oslo that has the only specimens left of this species, and he is keeping them hidden in one of his offices. He claimed he would get to them eventually, and that he was quite secretive about it, to be sure that he was still the only one with access to them. He's getting older, and I only hope he has confided in someone as to their whereabouts. Or that he can get crackin on his research!

That little digression serves to tell about how weird and haphazard research can be and develop, and also how weird some scientists are. I mean really; he's held on to those specimens for 20 years now!

Also, one can wonder why the number of chromosomes has been reduced so drastically. In general, choromosome number should increase, as this gives more room dealing with harmful mutations, and more room for variation.

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