Is SEX worth it?
Let’s be honest. It’s not always worth it to put up the effort for sex. Because mating is so cumbersome for many species, going it alone and reproducing asexually is the best alternative.
However, as attractive as it may appear, evolution imposes a high price on a population that foregoes sex for an extended period of time. A eukaryotic species will either have to swap chromosomes in a DNA shake-up that enhances genetic variation or risk extinction, sooner or later.
This Beetle is Odd
At least, that’s the rule, but the beetle mite (Oppiella nova) isn’t having it. A team of European researchers discovered that this micrometer-sized insect had been living a chaste lifestyle for millions of years by comparing its DNA to that of its sexually active cousin, O. subpectinata.
These little mites, like us, contain two copies of each chromosome in their DNA, making them a diploid organism.
When disaster strikes – be it a plague, a temperature change, or the introduction of a new predator – swapping chromosomes and subjecting them to some mix-and-match helps give a population a diverse choice of genetic combinations, ensuring that when disaster strikes – be it a plague, a temperature change, or the introduction of a new predator – at least a few individuals will be able to cope.
Take away all the frills, and you’ve got sex in a nutshell. Unfortunately, all of those bells and whistles (looking for mates, competing with them, generating all that sperm, the entire pregnancy thing) take a toll on genetic diversity maximisation.
Various than sexual reproduction, there are other means to retain a degree of variation. These processes allow mutations to accumulate in different ways in different types of the same gene (or allele), giving asexual organisms’ genes a distinct signature.
This mutation pattern, known as the Meselson effect after Harvard geneticist Matthew Meselson, might theoretically be used to designate a diploid creature as a true long-term asexual species.
The main issue is that none of the evidence for this effect has been conclusive, leaving a lot of opportunity for speculation. Some long-thought-to-be asexual species have now been discovered to have just recently converted, or – as scandalous as it may seem – to have sprinkled their genes with the occasional licentious tryst over the aeons.
Researchers required a clear, unmistakable evidence of gene variation in an animal suspected of having abandoned sex long ago and never looked back.
Which leads us back to O. nova, a little mite with sublineages that split between 6 and 16 million years ago, indicating that it’s a long-lived species.
More crucially, it’s an asexual species, unlike others on its branch of the family tree, making it an ideal candidate for research into the Meselson effect.
The challenge of collecting and sequencing the DNA of an animal that could build a conga-line inside a single millimetre was not easy, as one might expect of an animal that could form a conga-line inside a single millimetre.
How easy it is to Recognize?
According to reproductive biologist Jens Bast of the University of Lausanne in Switzerland, “these mites are only one-fifth of a millimetre in size and difficult to recognise.”
To read the genomes, the scientists needed sophisticated computer algorithms, but it was all worth it in the end.
Bast states, “Our findings clearly suggest that O. nova reproduces entirely asexually. These beetle mites could still surprise us when it comes to understanding how evolution works without sex.”
This is not to claim that asexual reproduction is without flaws. The beetle mite appears to be an outlier in a biological rule that is otherwise pretty consistent.
However, the finding of a mammal that has managed to live without sex for millions of years shows that it is possible to flourish without it.
This study was published in the journal PNAS.