Ultrastructure of the First Optic Neuropil, the Lamina in the Fruit Fly, Drosophila melanogaster
Abstract: Insect compound eye comprises a unit called ommatidium, which houses 7-8 photoreceptors. Visual signals perceived by photoreceptors are processed in the underlying optic lobe, which consists of three discrete neuropils (from the distal, the lamina, the medulla and the lobula complex). The first visual neuropil, the lamina is located beneath the retina, and composed of an array of units termed cartridges. After the lamina, visual information is conveyed to the central brain through the medulla and the lobula complex. In the optic lobe, several tens of thousands of neurons exist, and they form neural connections (synapses) each other to build neural circuits, where several feature of objects such as motion, color, shape and contrast is extracted. The lamina of the fruit fly, Drosophila melanogaster is one of insect neuropils, whose cellular components and synaptic partnerships in which are most well characterized. Here, we overview its ultrastructure.
Key words: photoreceptor, lamina, cartridge, tetrad synapse, capitate projection