Neurobiology of the Fruit Fly

Posted at: October 23, 2003 09:20 AM | Comments (0) | Edit

The Fruit Fly:
The fruit fly, scientific name Drosophila Melanogaster, is a small insect with red compound eyes and is about 3mm in length (see photo right). Its name comes from its tendency to accumulate around spoiled fruit.

This insect is one of the most studied organisms in biology. It has been used as a model system in genetics research for over 100 years. In March 2000 sequencing of its entire genome was completed. It is particularly suited to genetic study due to its ease of breeding and its relatively short life cycle of 2 weeks.

Due to the huge amount of knowledge about this organism it has more recently also become a model system in brain research. The fly can be genetically modified to bring about changes in behaviour. Specific gene activities are related to single brain structures. This can be used to shed light on the function of these various parts of the brain.

The Drosophila egg starts off at 0.5mm in length. The lava then hatches 1 day after fertilisation and moults a total of 3 times (1,2 and 4 days after hatching). This lava will then pupate for another 4 days before emerging as an adult fly. The genome contains 12,000 genes on 4 chromosomes, and is made up from a total of 165 million base pairs.

The Fruit Fly Brain:
The brain of the fruit fly is made up from some 250,000 cells. Despite this small number of cells the brain is still capable of relatively complex behaviour including orientation, learning, and memory.

The brain consists of two large optic lobes which process visual input. Between these lobes is the central brain which receives pre-processed visual and chemosensory inputs. The central brain consists of antennal lobes, mushroom bodies, and a central complex.

The antennal lobes are a part of the olfactory system. These globular structures are each built from about 35 glomeruli and are positioned at the front of the brain near the midline. The mushroom bodies contain 2500 intrinsic neurons each. These structures are correlated to several conditioning and learning effects of the fly's brain. The central complex consists of noduli, the ellipsoid body, the fanshaped body, and the protocerebral bridge.

The Flybrain Project:
The Flybrain project is an international collaboration aiming to understand the development and complete function the the Drosophila brain. The project started at the University of Freiburg in Germany under the leadership of Professor Karl-Friedrich Fischbach. This laboratory has since teamed up with scientists at the University of Arizona in the USA and the Japanese National Institute for Basic Biology in Okazaki.

Together these scientists are using confocal microscopy with fluorescent labelling to generate 3D renderings of the fly brain in VRML format. The confocal microscopy is able to give a resolution down to less than 1m. The generated 3D renderings can be seen on the Flybrain website (URL below).

Links:
The Flybrain Project: www.flybrain.org