Fig. 2. eyc¹ R cells inappropriately retain apical adhesions of rhabdomere extension. (A, left) In 37% p.d. wild-type ommatidia, actin-rich R cell apices face each other in a trapped pocket. Bright ‘bars’ of Armadillo staining highlight zonula adherens (z.a.) junctions delimiting R cell apical surfaces. At lesser intensity, Armadillo is detected across the entire apical membrane. Crumbs, an apical membrane protein (Tepass, 1996), is also distributed across R cell apical membranes. R cell apices are relatively small at this stage; the trapped apical pocket is approximately 5 µm deep. By 50% p.d. (A, center), definitive, actin-rich rhabdomere primordia are established and have extended to the retinal floor, a depth of approximately 15 µm. The stereotyped pattern of contacts prefiguring the adult trapezoid is evident along the planes of separation opening the IRS. Armadillo has largely retreated to the z.a. junctions. Light apical face staining is often encountered in R7. Crumbs remains across the entire apical surface. (A, right) In 50% p.d. eyc¹ eyes, inappropriate contacts between R cells are evident. Contacts between photoreceptors R2, R4 and R7 are prominent. R5 and R6 often establish strong face to face contact. Arm staining typically marks adhesions (arrowheads). Crumbs staining is normal in the mutant at this stage. (The more open mesh of the pigment cells results from removal of the cornea during dissection.). (B, top) In 55% p.d. wild-type eyes, DE- Cadherin and Armadillo are largely absent from R cell apical surfaces. (bottom) In 55% p.d. eyc¹ ommatidia, bars of colocalized Armadillo and DE-cadherin mark sites of contact. Anterior is towards the right, polar is towards the top. Scale bar: 4 µm.