Fig. 6. Expression and function of Esg in late-stage differentiation of interommatidial pigment cells. (A-C') Flat mounted pupal retinas of 42 hour APF. (A,A') Wild-type pupal retina stained for Escargot (green), Elav (red) and Cut (blue), showing the selective expression of Escargot in the pigment cells surrounding the ommatidia. (B-B'') Pupal retina containing a dsh[V26] clone marked by the absence of GFP (green) stained for Escargot (red). Escargot expression is not perturbed in the interior interommatidial pigment cells. (C,C') Pupal retina containing a clone mutant for escargot (marked by the absence of green) is stained for Armadillo (red) that outlines the cellular profiles. The mutant pigment cells fail to undergo apical constriction. (D) Section through an adult eye in which escargot clones have been induced (marked by the lack of pigmentation). Interommatidial pigment cells are absent or defective, causing vacuolar structures (arrowheads) and ommatidial fusion (not shown).