Tomorrow Today
Shared Hearing: what can humans learn from fruit flies?
Fruit flies are bothersome pests that can infest and ruin fruit. Professor Martin Göpfert is one of the small group of people who like them. For the biologist, they're a big help because they're perfect subjects for carrying out his scientific research.
Bildunterschrift: Großansicht des Bildes mit der Bildunterschrift: Everyone has seen at least one of these. Fruit flies are pests that prey on our fruit. But Martin Göpfert loves the tiny insects. He is a biologist and fruit flies - also known as Drosophila - are his research objects.
The winged critters are being used in a study of hearing, one of our five senses. The fruit fly's hearing organ is located on a antenna between its eyes, but it works in a way very similar to the sensory cells of the human ear.
Biologist Peter Berthold explains his work: "The really astounding thing about our research is that we're finding more and more parallels; the similarities are really very great. We're finding all the really sophisticated features of our ears in those of the fly."
Bildunterschrift: Großansicht des Bildes mit der Bildunterschrift: Sound waves cause the antenna to oscillate, stimulating the auditory nerve just like the movement of these tiny hairs, or cilia, in the human inner ear. Flies don't have the coiled bony cochlea typical of the human ear, and its middle ear doesn't have the three tiny bones that transmit sound vibrations from the eardrum but the way the auditory nerve is stimulated is the same. That is why Martin Göpfert is using the insect as a model for the biology of the human ear. This research subject can be simply immobilized using a drop of wax. But there's more to the fruit fly than just the ease of working with it that makes it an ideal model for humans.
There's hardly any organism that has been studied more than Drosophila melanogaster, the common fruit fly. Its genetic makeup is known in detail. And the similarity of the flies' genetic code to that of humans could provide a key to curing human hearing disorders. Göpfert thinks it is interestingly: "at the moment, there are attempts to introduce genetic therapy for some hearing disorders. In our ears, the hair cells die off as time passes and they are not regenerated. And the flies have a gene that initiates the development of hearing cells in their ears. The same gene does that in our ear and in mice. At the moment, experiments are being carried out on using the gene to regenerate the hair cells in the ear."
Regenerating the hair cells would be an enormous breakthrough in the fight against hearing damage - because they are a highly important element in the transmission of sound waves to the brain. These sounds are also heard by other insects as well. The mosquito is using its antenna to perceive sound, just the way the fruit fly does. And these ears are hearing the chirping of another grasshopper. The sound is picked up by a tiny slit on the insect's legs. From there, it moves as a nerve impulse into the head of the grasshopper.
Bildunterschrift: Großansicht des Bildes mit der Bildunterschrift: For moths, hearing is vital. Without it, they would not be able to hear the whistles made by bats, and have a chance to avoid the predators. That's something our flies don't have to worry about here in the lab. On the other hand, they do have to submit to having tests done on them. In order to analyze exactly how their ears work, the prepared flies are used as specimens in hearing tests.
Electrodes directly measure the auditory nerve impulses. Now, it's a matter of exposing the insect to a precisely defined sound wave. A laser is used to assess how much the sound caused the antenna to move. An oscillation of 20 Millionths of a millimeter is registered by this very sensitive receiver. By studying the hearing cells of flies, Martin Göpfert's team has got a better idea of how human hearing works. Their results might even lead to an exciting medical application of this research.
The scientist is excited: "Two years ago, we found certain genes in the ear of the fly. If they're not working properly, the fly has a buzzing in its ear. It produces sounds. That happens in the human ear as well: when our ears produce these tones, it's called tinnitus."
It remains to be seen whether tinnitus in flies will lead to a cure for tinnitus in humans. But Martin Göpfert is convinced that fruit flies still have much to tell us about themselves - and about the bipeds who so enthusiastically study them.
