the eye contains 800 photoreceptor sensory units called ommatidia, these contain 22 cells, 8 of which are photosensitive and have been called R cells, currently 8 types have been described that are listed from 1 to 8 with the letter R, during the development of the ommatidia is expressed by the B088 proteins and through a reaction with the RTKs ligand of R8 induction occurs to the formation of the R7 precursor
All single-celled organisms contain everything they need to survive within their one cell. These cells are able to get energy from complex molecules, to move, and to sense their environment. The ability to perform these and other functions is part of their organization.
