FB2025_05 , released December 11, 2025
FB2025_05 , released December 11, 2025
CV Term Report
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General Information
Term photoreceptor cell R2 ID (Ontology) FBbt:00004215 (Fly Anatomy)
Definition Outer photoreceptor cell of the adult eye whose rhabdomere is located in the middle of the longer of the 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).[ FlyBase:FBrf0049410 FlyBase:FBrf0064798 FlyBase:FBrf0216925 ]
Also Known As "lamina receptor cell R2" ; "R2"
Comment The name photoreceptor cell R2 is occasionally, mistakenly assumed to refer to any Rh2 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 R2 (presynaptic/postsynaptic) in a single lamina cartridge with each cell type was the following: L1 (43/-), L2 (45/1), L3 (10/-), L4 (-/1), Lai (39/-), T1 (2/-), Lawf (-/3), epithelial glia (13/-) and surface glia (1/-) (Rivera-Alba et al., 2011).
Links to External Ontologies
VFB:FBbt_00004215
Annotations
Records annotated with this term OR any of its CHILD TERMS
Records annotated with this exact term (annotations to child terms are NOT included)
Data Class Field Records
Alleles (FBal)  PHENOTYPE_MANIFEST_IN      99
Insertions (FBti)  EXPRESSION_STAGE_TISSUE_POSITION      31
Insertions (FBti)  PHENOTYPE_MANIFEST_IN      17
Constructs (FBtp)  PHENOTYPE_MANIFEST_IN      26
show Full annotation statements including this term (annotations to child terms are NOT included), and relevant FlyBase records
 Full annotation statements 
Relevant FlyBase reports
 Alleles Genes Insertions Constructs
 photoreceptor cell R2 (all annotations which use CV term, excluding "NOT" statements)     105     18     48     31
     photoreceptor cell R2 | cell non-autonomous | third instar larval stage       3       --       --       2
     photoreceptor cell R2 | ectopic       6       --       2      3
     photoreceptor cell R2 | increased number       2       --       --       --
     photoreceptor cell R2 | precursor       1       --       1       --
     photoreceptor cell R2 | somatic clone      20       --       6      3
     photoreceptor cell R2 | somatic clone | increased number       1       --       --       --
     photoreceptor cell R2 | somatic clone | third instar larval stage       2       --       --       --
     photoreceptor cell R2 | third instar larval stage       3       --       1       --
Spanning Tree (Parents/Children)
Only view relationship:
  eye photoreceptor cell
   |__outer photoreceptor cell
       |__photoreceptor cell R2  246 rec.
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Is a outer photoreceptor cell
Develops from photoreceptor R2 precursor cell
Part of
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Synonyms
  • "lamina receptor cell R2" EXACT
    "R2" EXACT VFB_SYMBOL[ FlyBase:FBrf0247762 ]
    "receptor cell R2" RELATED
Secondary IDs
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CL:0000690
VFB:FBbt_00004215