Anatomia Cerebri Insecti: Drosophila Brain Serial Sections

Kei Ito August 1994

Institute of Genetics, University of Mainz Saarstr. 21, D55122 Mainz, GERMANY email:

from October 1994: ERATO project, Mitsubishi-Kasei Institute of Life Sciences, Minami-Ooya 11, Machida-shi, Tokyo 194, JAPAN email: should be reachable with the above address

Drosophila is a good model system for studying various aspects of brain development and brain function. Unfortunately, however, no convenient atlas has been published for the brain of the fruit fly. Although such an atlas would be extremely helpful, publishing one is of course not an easy task. This situation makes it difficult for novice people to quickly learn the complicated structure of the fly brain.

When I started working with Drosophila, I made serial sections of wild-type fly heads in three directions and have used the pictures privately for a reference purpose. Recently I scanned the pictures so that I can carry and see the images with my laptop computer (which was stolen after that, though...). Since such pictures would also be helpful for other fellow Drosophila researchers, I added a few annotations and decided to make them publicly available. The Flybase kindly allowed me to put the data into one of its directory.

This is by no means a real atlas, but it would be helpful as a quick reference as well as for educational purpose. This is also an exploration to see how one can share information using electronic media. For this matter it is an experimental version. Since the original pictures were not prepared for serious publication, the sections were not carefully aligned. The scanning resolution was kept minimum to keep the data size relatively small, thus saving the hard disk space and the network traffic. Though it was possible to make a better version with precisely aligned high-resolution images and detailed documents, I was not sure whether it is worth the extra effort.

I would appreciate any comments and suggestions, negative or positive, about this version. Please contact me if you have any idea to make it more useful.

General notes:

1. The following files are provided in this version.

00ReadMe.Doc This document.

Frontal.GIF A folder/directory with 12 frontal sections (F01-F12).

Horizont.GIF A folder/directory with 17 horizontal sections (H01-H17).

Sagittal.GIF A folder/directory with 16 sagittal sections (S01-S16).

Frontal.idx An index picture for the frontal sections (thumbnails).

Horizont.idx An index picture for the horizontal sections (thumbnails).

Sagittal.idx An index picture for the sagittal sections (thumbnails).

All the pictures are saved as 6-bit GIF format data. They are pixel graphics; you cannot remove arrows and characters from the background photographs (see section 11).

2. Seven-micrometer serial sections were prepared from five-day old adult flies of the Canton-S strain. They are stained with silver nitrate (Bodian) and photographed using Zeiss 40x Nomarski optics. When scanning, I skipped every other section to keep the total volume not too large. Only one in four pictures was scanned for the sagittal sections of the optic lobe region (S12-S16).

3. I put the coordinate origin to the posterior end of the center opening of the ellipsoid body. This is close to, but not identical with, the coordinate origin used by Strausfeld for Musca domestica (1976). The distance from the origin is shown in the file name and at the top-left corner of each picture. The distance simply reflects the number of sections from the coordinate origin (hence 14 or 28-micrometer increments). The shrinkage of the specimen was not taken into account.

4. Several names of brain structures were annotated in the figure. The names should be consistent with the description of the Musca brain (Strausfeld, 1976). The names of the cervical fascicles were taken from Power (1948), the muscles and tracheae from Miller (1950).

5. No figure legends are available. Please refer to the articles listed at the end of this document.

Legal notes:

Since the digital image data can easily be duplicated and modified without losing quality, I will make the following notes:

6. You can freely view the pictures with your computer. You can print the pictures at your will. I am also happy if you use them in your talks and posters or distribute them to your students and colleagues. Please contact me if you want to use the pictures for other purposes.

7. You are not allowed to alter the content of the image. Please contact me if you need it.

8. You can freely, and you are encouraged to, distribute the data using network, floppy disks, and other media. Please do not forget to include this document when copying the data. The image data are free but not "public domain"; I reserve all the copyrights.

Technical notes:

9. Those who can afford photo-grade printers should have no problem in getting good hard copies of the pictures. Some of the recent laser printers can also generate good print outs. People with only an old 300- DPI laser printer (or inkjet printer) can still print acceptable copies in the following way, if an image manipulation software is available. The idea is 1: make the picture very bright on the screen, 2: increase the resolution four times (from 72 DPI to 300 DPI, or from 388 pixels to 1552 pixels, for example), 3: dither the gray scale to 1-bit bitmap that is printable with a normal printer. The diffusion dither method works better than the pattern dither.

Open the image file with Adobe Photoshop (or an equivalent software) To make the picture brighter:

Select the Photoshop submenu "Image" - "Adjust" - "Levels" Move the central triangle to the left so that the central number of the "input level" changes from 1.0 to about 3.0. Change the "Mode" to "Bitmap": (Photoshop does the step 2 and 3 at once) Make the output to 300-DPI resolution (not 72-DPI). Select "diffusion dither" method.

Select the page orientation to the landscape mode, and print.

10. Although you can access the images using Mosaic, you may find it easier to navigate if you keep all the picture files in your local computer. For the Macintosh computer there is a good free viewer software called "ImageCatalog". (written by Tom Bereiter, You select the icons of all the picture files and drag them onto the ImageCatalog icon. The program will ask you the size of the thumbnail image. Make the cell size 66 x 44 and the window size 8 x 6 cells. The program will generate a file that consists of the thumbnail image.

11. The image data are saved with 6-bit GIF format. The picture size is about 586 x 388 for the frontal and horizontal sections and 380 x 388 for the sagittal. They are all in the same magnification. The size was chosen so that the image fits in a 640 x 400 pixel-LCD display of a laptop computer.

To save the data size, pictures have only 6 bit per pixel (64 shades of gray) instead of 8bit (256 shades of gray). Since tonality is not very important in this kind of pictures, there was no noticeable difference between the 8 bit and 6 bit versions. GIF and JPEG formats are the two popular formats that can be used with various computer systems such as MS-DOS/Windows, OS2, Macintosh, and Unix. Both formats also compress the files when saved. I chose GIF since it allows users to reduce the data size by decreasing the bit depth. Since JPEG does not allow the bit-depth reduction, I have to choose higher data compression rate to get the comparable file size. This resulted in noticeable artifacts around sharp edges in the pictures. (This does not necessarily mean that JPEG is a bad format. Pictures rich in color and tonality may have better results with the JPEG format than with GIF.)

The original figures were made with a Macintosh computer and saved as PICT format data, with which the arrows and characters can be kept editable and separate from the scanned photographs. The PICT format, however, is not common in other computer systems.


Detailed atlas of a fly brain, though not Drosophila.

Strausfeld, N. J. (1976). Atlas of an Insect Brain. Springer-Verlag, Berlin/Heidelberg/New York/Tokyo.

A classic. Written in German.

Hertweck, H. (1931). Anatomie und Variabilitaet des Nervensystems und der Sinnesorgane von Drosophila melanogaster (Meigen). Z. wiss. Zool. 139, 559-663.

Description of the adult ventral nerve cord.

Power, M. E. (1948). The thoracico-abdominal nervous system of an adult insect, Drosophila melanogaster. J. Comp. Neurol. 88, 347-409.

Description of the adult internal organs.

Miller, A. (1950). The internal anatomy and histology of the imago of Drosophila melanogaster. In "Biology of Drosophila" (M. Demerec, Ed.), pp. 420-534. J. Wiley and Sons, New York.

Anatomical and developmental analysis of the Drosophila brain.

Hanesch, U., Fischbach, K. F., and Heisenberg, M. (1989). Neuronal architecture of the central complex in Drosophila melanogaster. Cell Tissue Res. 257, 343-366.

Stocker, R. F., Lienhard, M. C., Borst, A., and Fischbach, K. F. (1990). Neuronal architecture of the antennal lobe in Drosophila melanogaster. Cell Tissue Res. 262, 9-34.

Bausenwein, B., Dittrich, A., and Fischbach, K. F. (1992). The optic lobe of Drosophila melanogaster. Cell Tissue Res. 267, 17-28.

Meinertzhagen, I. A., and Hanson, T. E. (1993). The Development of the Optic Lobe. In "The Development of Drosophila melanogaster" (M. Bate, and A. Martinez-Arias, Ed.), Vol. II, pp. 1363-1491. Cold Spring Harbor Laboratory Press, Cold Spring Harbor.