A big step in the neurobiology of Drosophila would be to establish a standard for brain anatomy to which to relate morphological, developmental and genetic data. We propose that only an average brain and its variance would be a biologically meaningful reference and have developed an averaging procedure. Here, we present a brief outline of this method and apply it to the optic lobes of Drosophila melanogaster wild-type Canton S. Whole adult brains are stained with a fluorescent neuropil marker and scanned with the confocal microscope. The resulting three-dimensional data sets are automatically aligned into a common coordinate system and intensity averages calculated. We use effect-size maps for the fast detection of differences between averages. For morphometric analysis, neuropil structures are labelled and superimposed to give a three-dimensional probabilistic map. In the present study, the method was applied to 66 optic lobes. We found their size, shape and position to be highly conserved between animals. Similarity was even higher between left and right optic lobes of the same animal. Sex differences were more pronounced. Female optic lobes were 6% larger than those of males. This value corresponds well with the higher number of ommatidia in females. As females have their additional ommatidia dorsally and ventrally, the additional neuropil in the medulla, lobula and lobula plate, accordingly, was found preferentially at these locations. For males, additional neuropil was found only at the posterior margin of the lobula. This finding supports the notion of male-specific neural processing in the lobula as described for muscid and calliphorid flies.
[1]
Jacob Cohen.
Statistical Power Analysis for the Behavioral Sciences
,
1969,
The SAGE Encyclopedia of Research Design.
[2]
I A Meinertzhagen,et al.
Experience-Dependent Developmental Plasticity in the Optic Lobe of Drosophila melanogaster
,
1997,
The Journal of Neuroscience.
[3]
M. Heisenberg,et al.
Conditioned visual flight orientation in Drosophila: dependence on age, practice, and diet.
,
1996,
Learning & memory.
[4]
P. Lachenbruch.
Statistical Power Analysis for the Behavioral Sciences (2nd ed.)
,
1989
.
[5]
N. J. Strausfeld,et al.
Male and female visual neurones in dipterous insects
,
1980,
Nature.
[6]
Michael Ashburner,et al.
Drosophila: A laboratory handbook
,
1990
.
[7]
M. Heisenberg,et al.
Isolation of Anatomical Brain Mutants of Drosophila by Histological Means
,
1979
.
[8]
Michael Ashburner,et al.
A Laboratory handbook
,
1989
.
[9]
D. Collins,et al.
Automatic 3D Intersubject Registration of MR Volumetric Data in Standardized Talairach Space
,
1994,
Journal of computer assisted tomography.
[10]
M Heisenberg,et al.
Structural plasticity in the Drosophila brain
,
1995,
The Journal of neuroscience : the official journal of the Society for Neuroscience.