R3 [FBbt_00004217]

R3

ID: FBbt_00004217

Outer photoreceptor cell of the adult eye whose rhabdomere is located at the non-right angled vertex of the longer of two parallel sides of the trapezoid of rhabdomeres in each ommatidium. It has a single axon that projects along a single lamina optic cartridge (Fischbach and Dittrich, 1989; Wolff and Ready, 1993).

The name photoreceptor cell R3 is occasionally, mistakenly assumed to refer to any Rh3 expressing photoreceptor cell. This is incorrect. This term only refers to a type of adult eye photoreceptor cell. The name is based simply on the position of the cell and its rhabdomere within each ommatidium - see figure 4 in Wolff and Ready, 1993. Cell connectivity was determined by analysis of semi-automated EM reconstruction of 749 serial sections of 21 complete lamina cartridges. The number of synaptic connections for R3 (presynaptic/postsynaptic) in a single lamina cartridge with each cell type was the following: L1 (37/-), L2 (39/-), L3 (4/-), L4 (-/3), Lai (39/-), T1 (2/-), C3 (2/1), Lawf (-/1) and epithelial glia (7/-) (Rivera-Alba et al., 2011).