R7 [FBbt_00004225]

R7

ID: FBbt_00004225

Inner photoreceptor cell of the ommatidium whose rhabdomere is located distally, directly above that of R8 (Wernet and Desplan, 2004). It has a single axon that extends through a single column of the lamina without making synapses (Fischbach and Dittrich, 1989). This axon crosses the first optic chiasm and extends through a single column of the medulla where it makes pre-synaptic contacts, mainly in medulla layers M1 and M5 (Takemura et al., 2008), before terminating in M6 (Gao et al., 2008; Sancer et al., 2019). It forms reciprocal inhibitory histaminergic synapses with the R8 photoreceptor of the same optic column (Schnaitmann et al., 2018), with a large proportion in the first optic chiasm (Kind et al., 2021).

This term refers to a type of adult eye photoreceptor cell, defined based on the position of its rhabdomere within each ommatidium - see figure 4 in Wolff and Ready (1993). It does not refer to Rh7-expressing photoreceptors.