Showing posts with label Fruit Flies. Show all posts
Showing posts with label Fruit Flies. Show all posts

Flies Flying-By


Flying about in a crowded airspace is difficult enough, but the biggest problem is landing. Not just anywhere mark you, but on a precise spot that is coming up fast and is often moving. Of course, birds do it and bees do it, but so do fruit flies.

Fruit flies aren’t very large and have to rely on their in-built guidance systems to reliably work on the fly.  Van Breugel and Dickinson, in the current edition of the Journal Of Experimental Biology have been scrutinizing the success and failure of fruit fly landing sequences with a combination of high-speed photographs and 3-D tracking software (1).

The touchdown sequence commences with a sharp turn towards the target and a deceleration that the authors explain is governed by the growth of the image size on the fly’s retina. The go/no-go decision is made at the point that the target image takes up an include angle of about 33 degrees of the fly’s vision field.

If the decision is go – the deceleration sequence continues until the target image angle has increased to about 60 degrees and then the landing gear is deployed. On touch down the feet grasp the target. From gear deployment to touchdown was about 50 ms – pretty fast reactions are a must.

If the no-go decision is called for, the fly’s fly-by procedure is a sharp turn away and off to another target. This occurred in 1065 attempts out of 1242-recorded measurements.

Flies flying-by may have been due to too fast an approach or maybe just the fickleness of the fly. They did record some crash landings when flies came in too fast and failed to abort, but none included any fatalities.

  1. http://jeb.biologists.org/content/215/11/1783


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Alcoholic Fruit Flies


There have been several papers in recent months on alcohol consumption by one of our smaller neighbors – the fruit fly. Before we rush off and criticize their drinking behavior we need to keep in mind that there are medicinal benefits from supping a wee dram.

Fruit flies start their drinking early on in their lives. The larvae eat the yeast on rotting fruit and develop a tolerance to alcohol when very young. A paper in Current Biology last month by Milan et al from Emory U brings out the medical benefits of their self-medication by killing parasites in their blood (1).

Endoparasitoid wasps inject their eggs into fruit fly larvae to provide a live meal for their offspring. Firstly, an alcoholic larva is repellent to the wasps, and secondly, the alcohol in the blood kills off the parasites. If a larva gets infected, it is aware of what happened and goes off to find some alcohol to sort itself out.

Of course, it’s not only parasites that fruit flies have to worry about. Their busy lives can, like ours, be quite stressful. Male fruit flies spend a deal of their time finding mates and if successful, the levels of neuropeptide F are enhanced. If their love life is going badly the levels are reduced.

For the bio-geeks among us, neuropeptide F controls the feeding response in the larvae and when it is reduced in older larvae they get into burrowing mode. It is the analogue of neuropeptide Y that we mammals make use of to regulate our feeding habits. Neuropeptide Y deficient mice overeat and end up with a severe obesity problem.

Now Shohat-Ophir et al from U Cal. SF reported on their experiments with groups of male fruit flies and their drinking habits in the current edition of Science (2). They took some males (fruit flies, that is) and introduced them to a large group of eager females and checked out their alcohol consumption. They then compared that to another group of males after introducing them to a group of pregnant females who had no interest in amorous males.

They noted that the alcohol consumption was markedly higher in the group of males who had been put under stress by universal rejections. Of course, they weren’t just allowed to drown their sorrows in peace, but, like their successful colleagues, were thrown into the blender and the levels of neuropeptide F measured. A successful love life led to high levels and rejection led to low levels and loss of control on the alcohol.

  1. http://www.sciencedirect.com/science/article/pii/S0960982212000759
  2. G.Shohat-Ophir, K.R.Kaun, R.Azanchi and U.Huberlin, Science, 335, 1351, (2012)



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Aging Gracefully


Fruit flies in your kitchen are annoying little critters as they are telling all your visitors that you have over ripe (that is, rotting or fermenting) fruit available. They have a short life cycle; egg to adult takes a week, so your fruit fly restaurant gets crowded very quickly. The other side of the coin is that they make a good model system for scientists to study population behavior and change

In a paper published on Tuesday, Zou et al (1) described a detailed video study of their behavior, minute by minute throughout their lifetime. There was no privacy here. They were monitored as they rested, walked, flew, fed, drank or just scratched themselves.  The study showed that fly activity increased as the flies grew to their prime and then slowed down as they went past middle age and became elderly. Elderly flies spent much more time hanging around in cluster at the top of their cage complaining about the state of their world, the pushy exuberance of the younger guys etc.

A good healthy diet for fruit flies is a sugar and yeast smoothy. This keeps them up and flying well. As we all know (I think), a poor diet can lead to premature aging. A bad diet for fruit flies is to leave their vitamin B on the side of their plates and just drink the sugar water.

Using their tendency to laze around gossiping in clusters instead of getting around to their daily flying tasks as the indicator for reaching middle age, the team showed that middle and old age arrived much earlier when the flies were eating just junk food. A poor diet made the flies relatively hyperactive and increased their tendency after lights-out to stay hanging around bemoaning the state of their world. Rushing about, hustling on a poor diet had them middle aged in half the time of those living on a better diet and having a more relaxed well balanced lifestyle.

        1.  http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0018151