Cartridge of the first optic neuropile (lamina)

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The cross section of a cartridge, the unit module of the first optic neuropile, or lamina, of the optic lobe. This particular cartridge is in the ventral half of the left lamina, seven rows from the equator and eight rows from the posterior eye margin, and is photographed as if viewing the eye from the outside looking in.

The cartridge is innervated by terminals of photoreceptors R1-R6, which are distinguishable by capitate projections (arrowheads in R2) and by membrane invaginations (arrowheads in R1). Two monopolar cells, L1 and L2, share the cartridge core with a terminal of a medulla cell, C3, at this level. A second medulla cell C2 occupies a peripheral position, with L5, between R4 and R5; L3 and L4 define the position of R5 and R6. Arrowheads in R5 indicate presynaptic ribbons of tetrad synapses, the chief input synapse, one a longitudinal section of the ribbon platform. Plaque contacts are visible as densities between beta (T1) profiles and the terminals of R2 (double arrowhead) and R3 (arrowhead).

The group of slender profiles (dots) are presumed ascending fibres of amacrine cell(s). Other unidentified elements are denoted by remaining symbols. Scale bar 1.0 micron. Inset: amacrine feedback synapse upon R4, enlarged from the area shown in the main micrograph; scale bar 0.2 micron.

Meinertzhagen, I 27 Apr 1995

Reference

Flybrain    Atlas    Sagittal Silver Sections    Sagittal Section x=+22.0    Cartridge of the Optic Lobe

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