As my work ultrastructural on retinal degeneration progressed, my interests came to include the receptors and their first order synaptic connections in the visual system. Developmental aspects of structure and function of ectopic eyes from transplanted imaginal disks in flies were pursued in collaboration with P. Sivasubramanian in New Brunswick. The development, structure and function of extra eyes in the extra eye mutant of Drosophila was pursued with David Marcey, then a graduate student at the University of Utah. Some unique attributes of the first order synaptic area in Drosophila's compound eye, the capitate projections, were investigated with the late Prof Stanley D Carlson (Department of Entomology and Neuroscience Program, University of Wisconsin- Madison). A major electron micrographic investigation of the simple eyes (ocelli) of Drosophila was undertaken in my laboratory with my electron microscope technician, Mr. Randall Sapp. Several visual transduction mutants, as well as several ocellar structural mutants were investigated; the latter class included rdo (reduced ocelli), ocelliless and glass (gl being called none = no ocelli narrow eyes at that time). An interesting observation was the feedback synapse of the ocellar ganglion. Work with Prof Wendi Neckameyer and Prof Janis O’Donnell shows that dopamine, best known as a neurotransmitter, is important in development of functional first order visual synapses in Drosophila.

Selected publications on receptor-synaptic function and development:

Sivasubramanian, P. and Stark, W.S. Photoreceptor properties of an ectopic eye in the fleshfly, Sarcophaga bullata. Experientia, 1980, 36, 993-994.

Sivasubramanian, P. and Stark, W. S. Development of visual sensitivity in the fly Sarcophaga bullata. Experientia, 1983, 39, 318-320.

Marcey, D. and Stark, W.S. The morphology, physiology and neural projections of supernumerary compound eyes in Drosophila melanogaster. Developmental Biology, l985, l07, l80-l97. PubMed

Stark, W.S. and Carlson, S.D. Ultrastructure and functional evaluation of capitate projections in dipteran optic neuropil.
Cell and Tissue Research, 1986, 246, 481-486. PubMed

Stark, W.S., Sapp, R. and Carlson, S.D. Ultrastructure of the ocellar visual system in normal and mutant Drosophila melanogaster. Journal of Neurogenetics, 1989a, 5, 127-153. PubMed

Stark, W.S., Sapp, R., and Carlson, S.D. Photoreceptor maintenance and degeneration in the norpA (no receptor potential-A) mutant of Drosophila melanogaster. Journal of Neurogenetics, 1989b, 5, 49-59. PubMed

Zinkl, G., Maier, L., Studer, K., Sapp, R., Chen, D.-M., Stark, W. S. Microphotometric, ultrastructural and electrophysiological analyses of light dependent processes on visual receptors in white-eyed wild-type and norpA (no receptor potential) mutant Drosophila. Visual Neuroscience, 1990, 5, 429-439. PubMed


Stark, W.S. and Carlson, S. D. Comparison of the surfaces of glnone's ocelli and compound eyes with those of several other glass alleles. Drosophila Information Service 1991, 70, 217-219.


Neckameyer, W., O'Donnell, J., Huang, Z., Stark, W. Dopamine and sensory tissue development in Drosophila melanogaster. J. Neurobiology, 2001, 47, 280-294. PubMed. View the pdf file


A relevant research note:


Juang, J.-L., Stark, W. S., Carlson, S. D. Scanning electron microscopy of the retina of Drosophila. Drosophila Information Service 1994, 75, 104-105



A distal TEM section of an ommatidium showing R1-6 and R7.


TEM showing proximal retina with underlying basement membrane, monopolar neurons of lamina ganglionaris (first optic neuropil) (bottom), and two pseudocartridges (axons from individual ommatidia) (between).


Low power TEM of lamina ganglionaris (first optic neuropil). Proximal retina (top). Chiasm to medulla (second optic neuropil, bottom). Lamina is distinctly subdivided into optic cartridges. Note the second order monopolar neurons distal to the neuropil.


Serial section analysis was used for the Stark and Carlson 1986 studies. The top shows an SEM of a formvar-coated slot grid with a ribbon of fly head sections while the bottom shows a higher power phase contrast light micrograph of a few sections in the ribbon


A plate showing lack of photoreceptors in glass compound eye, fairly normal distal optics, but some receptor axons and synapses (Stark et al., 1989a, c.f. Stark and Carlson 1991)

A high power scanning electron micrograph (SEM) of the surface of the Drosophila compound eye. Note that each facet is rough because of "corneal nipples" that serve as an antireflection coating.

A micrograph from Stark et al., 1989a, showing feed-forward and feedback synapses between receptor and interneuron in the ocellar visual system

A scanning electron micrograph (SEM) of a fracture through the Drosophila compound eye showing basement membrane through which axons project to lamina ganglionaris (see Juang et al.)

Light micrograph (left) and scanning electron micrograph (right) of extra eye (ee) (related to Marcey and Stark, 1985)


An electron micrograph showing normal T-bar synapses in norpA (from Stark et al., 1989b); the evidence that these synapses work is discussed elsewhere (Zinkl et al., 1990)

This page was last updated on July 12, 2012

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