I had the great privilege to attend the Pan-American EvoDevo conference last week and learn from world experts on some of the most interesting life forms on the planet! This list of interesting life forms definitely includes the common fruit fly Drosophila melanogaster, a common guest in kitchens and compost piles around the world. While you may not even give it a second glance while brushing it away from your food, the fruit fly has allowed scientists to learn fundamental developmental processes that have direct connections to human health through the shared genes that control how our bodies know how to arrange everything from head to foot in the right position.
If you would like to see for yourself what Christiane Nusslein-Volhard and Eric Wieschaus, the researchers who were awarded the Nobel Prize for these discoveries, were looking at when they discovered the genes with names like Giant, Hedgehog, and Gooseberry, all you need to do is find some slightly rotten fruit. Preferably fruit that has started to smell like it is fermenting because this means that there are yeast present, a larva’s favorite food. Maru and I found a strawberry that had gone bad and looked closely for small larva or tiny white eggs in the mushy section. If you have a time-lapse camera, you might be able to see things moving after letting your camera image the fruit for a few minutes.
You can see what the larva look like while they are moving on the strawberry here:
If find something that is moving your fruit, use a toothpick, a small stick, or the edge of a slide to gently pick it off and transfer it to your slide. Make sure to cover it so the larva does not crawl into the Foldscope because they are surprisingly fast!
Fruit flies and people are both segmented animals and when looking at the larva segments you might see some small black dots on the top and bottom of the animal. These little dots called denticles are how the larva grip and move around! Each segment of the larva has a different pattern of denticles and Drs. Nusslein-Volhard and Wieschaus looked for mutant flies that had changes in these patterns.
This larva was around one day old and we can tell by looking at how developed the internal structures are. If the long tubes that run the length of the larva end at the head side without a branching structure then it is in the first larval stage. Other things to look for are the mouth hooks that start as black dots and become more complex as the larva grows.
There are over 1579 Drosophila species found world wide and they often will prefer slightly different rotting fruits or leafs but if you look closely, I’m sure you can find them! The eggs are much smaller than the larva and some flies will lay them right next to the rotting parts while others will lay them right in the softest sections. Keep looking!