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Tag: drosophila
Friendly bacteria protect flies from sterilising worms
Animals must wage a never-ending war against parasites, constantly evolving new ways of resisting these threats. Resistance comes in many forms, including genes that allow their owners to shrug off infections. But one species of fly has developed a far more radical solution – it has formed a partnership with a bacterium that lives in its body and defends it against a parasitic worm. So successful is this microscopic bodyguard that it’s spreading like wildfire across America’s besieged flies.
The fly Drosophila neotestacea is plagued by a nematode worm called Howardula. Around a quarter of adults are infected and they don’t fare well. The worm produces thousands of young in the body of its hapless host, and the little worms make their way into the outside world via the fly’s ovaries. Not only does this severely slash the fly’s lifespan, it also always sterilises her. But according to John Jaenike from the University of Rochester, the fly is fighting back.
An entire bacterial genome discovered inside that of a fruit fly
This article is reposted from the old WordPress incarnation of Not Exactly Rocket Science.
A humble species of fruit fly is the genetic equivalent of a Russian doll – peer inside its DNA and you will see the entire genome of a species of bacteria hidden within.
The bacteria in question is Wolbachia, the most successful parasite on earth and infects about 20% of the world’s species of insects. It’s a poster child for selfishness. To further its own dynasty, it has evolved a series of remarkable techniques for ensuring that it gets passed on from host to host. Sometimes it gives infected individuals the ability to reproduce asexually; at other times, it does away with an entire gender.
Now, Julie Dunning-Hotopp from the J. Craig Venter Institute and Michael Clark from the University of Rochester have found an even more drastic strategy used by Wolbachia to preserve its own immortality – inserting its entire genome wholesale into that of another living thing.
Among bacteria, such gene swaps are run-of-the-mill. Humans and other multi-celled creatures must (mostly) contend ourselves with passing our genes to our young but bacteria have no such limits. They can exchange genes as easily as we exchange emails and this free trade in DNA, formally known as ‘horizontal gene transfer’, allows them to swap beneficial adaptations such as drug resistance genes.
Gene transfer between bacteria and eukaryotes is rare but if any bacteria was well placed to do it, it would be Wolbachia. It infects the developing sex cells of its hosts and gets passed on from mother to child in the egg itself – a prime location for integrating its genes into those of the next generation.
Other labs had already managed to detect traces of Wolbachia genes in a species of beetle and a nematode worm. To discover the full extent of its genetic infiltration, Dunning-Hotopp and Clark decided to search for Wolbachia genes in a wide range of invertebrates.
Fruit flies have a taste for fizzy drinks
This article is reposted from the old WordPress incarnation of Not Exactly Rocket Science.
Fizzy drinks like Perrier and Coca-Cola are targeted at a huge range of social groups, but if fruit flies had any capital to spend, they’d be at the top of the list. Unlike posh diners or hyperactive kids, flies have taste sensors that are specially tuned to the flavour of carbonated water.
Humans can pick up five basic tastes – sweet, salty, sour, bitter and umami (savoury). But other animals, with very different diets, can probably expand on this set. And what better place to start looking for these unusual senses than the fruit fly Drosophila, a firm favourite of geneticists worldwide, and an animal with very different taste in food to our own.
Drosophila‘s tongue contains structures that are the equivalent of our own taste buds. They are loaded with taste-sensitive neurons and the activity of specific genes gives these neurons the ability to recognise different tastes.
Other researchers have already isolated the genes that allow Drosophila to tell sweet from bitter. But when Walter Fischler found a group of taste cells that didn’t have either of these genes and connected to a different part of the fly’s brain, he knew he was on to something new.
Flies get the buzz on sexy mates from each other
We get a lot of information from watching other people. We read reviews, we follow links to recommended websites and we listen when our friends vouch for strangers. The opinions of strangers may even be a better guide to the things that make us happy than our own predictions. But humans aren’t the only species to make decisions based on information gleaned from our peers – even animals as supposedly simple as flies can do the same.
Frederic Mery from LEGS (the Laboratory of Evolution, Genomes and Speciation) studied the fly Drosophila melanogaster and found that females have a tendency to follow the crowd. They are more attracted to male flies if other females crowd around him.
Following the crowd makes evolutionary sense; faced with uncertainty over the best males to mate with, females could do worse than to look at who their peers find sexiest. Female fish, birds, rats and possibly even humans are influenced in this way, but this is the first time that anyone has found the same behaviour among invertebrates.
Mery created two lines of male flies – a high-quality lineage raised on a nutritious diet, and a poor-quality one that grew up on much less food. Female flies were placed in a box along with one male from either group, each housed in his own transparent container. The female couldn’t touch the males, but she could see, smell and hear him. Based on that information alone, she could tell the studs from the weaklings and spent twice as much time buzzing over the high-quality male.
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