The organization of perpendicular fibre pathways in the insect optic lobe
Open Access
- 20 July 1976
- journal article
- Published by The Royal Society in Philosophical Transactions of the Royal Society of London. B, Biological Sciences
- Vol. 274 (935) , 555-594
- https://doi.org/10.1098/rstb.1976.0064
Abstract
High resolution serial photomicrography has been used to plot the axonal projection patterns between retina, lamina and medulla in the optic lobes of various insects with differing ommatidial receptor arrangements. Observations are reported on the cabbage white and skipper butterflies, the bee, locust, fly, backswimmer and waterbug. The patterns of these fibre pathways have previously eluded non-rigorous analyses primarily because of their physical dimensions but are revealed in this study to have striking precision and uniformity between species when examined at the level of individually identifiable cells. Axon bundles of the tractsbetweenretina and lamina or lamina and medulla project between a single ommatidium and its corresponding lamina cartridge or between corresponding lamina and medulla cartridges. Lateral interweaving of axons between adjacent bundles is absent. The bundles preserve the retinotopic order within their total array, so transferring the pattern of retinulae directly upon the lamina and thence after horizontal inversion in the chiasma upon the medulla.Withinthe lamina neuropile on the other hand the trajectories of the individual terminals from a bundle have patterns which are species-specific, sometimes involving lateral divergences. In species with open-rhabdomere ommatidia the terminals distribute to a group of lamina cartridges with a pattern which resembles the receptor pattern in the overlying ommatidium. In species with fused-rhabdome ommatidia the terminals of a single retinula behave less interestingly and all enter the same cartridge, within which, again, each occupies a position related to its cell body position within the retinula. Long visual fibres in both eye types penetrate the lamina and terminate in the particular medulla cartridge that connects with the lamina cartridge underlying their ommatidium. The perpendicular fibre pathways therefore project the visual field exactly upon the medulla in all species while the lack of interweaving between adjacent fibre bundles precludes their involvement in lateral interactions between pathways with differing visual axes. Uniformity of these projection patterns between cell layers and species differences in retinular terminal locations in the lamina can be correlated with different modes of axon growth between and within neuropile layers during optic lobe neurogenesis. Further discussion surrounds the question of which particular receptors give rise to which type of axon, for which no clear generalization has yet emerged.Keywords
This publication has 58 references indexed in Scilit:
- Butterfly glowPublished by Elsevier ,2004
- Retinal resistance barriers and electrical lateral inhibitionNature, 1975
- Axonal wiring and polarisation sensitivity in eye of the rock lobsterNature, 1975
- Die Anordnung der Ommatidien in der Retina der Biene (Apis mellifica L.)Cell and tissue research, 1973
- The development of the retina-lamina complex in muscoid fliesJournal of Ultrastructure Research, 1973
- Fine structure of the visual system of the honeybee (Apis mellifera): I. The retinaJournal of Ultrastructure Research, 1969
- Some aspects of the structural organization of the medulla in muscoid fliesJournal of Ultrastructure Research, 1969
- The fine structure of the central cells in the ommatidia of dipteransJournal of Ultrastructure Research, 1967
- Compound eye of dipterans: Anatomical basis for integration — An electron microscope studyJournal of Ultrastructure Research, 1966
- Some aspects of the structural organization of the intermediate retina of dipteransJournal of Ultrastructure Research, 1965