Fig. 6. Adult phenotypes of hnt mutants. (A) Scanning electron micrograph (SEM) of part of an eye from a hnt^peb/hnt^peb fly. Some of the facets do not have the stereotypical hexagonal shape, others are fused. The sensory bristles are sometimes mispositioned and show a variation in size never seen in wild type. (B) Apical tangential section through a wild-type eye, showing each ommatidium with a trapezoidal arrangement of the seven photoreceptor (R) cells. All the ommatidia in this half of the eye have the same polarity. (C) In an eye from a hnt^peb/Y fly raised at the restrictive temperature, 40% of the ommatidia are missing outer or central R cells (black arrowheads), 12% have extra R cells (white arrowhead) and some of the ommatidia are fused (yellow arrows point to a pair of fused ommatidia). The ommatidia also have variable polarity. (D) SEM of an eye with a scar caused by a clone of hnt^XO01 tissue. Clones mutant for three different hnt alleles (hnt^XE81, hnt^EH704a and hnt^XO01) form scars. (E) An apical tangential section through a hnt^XE81 scar (to right of red dots) reveals that the interior of the clone contains no R cells but that pigment cells are still present. (F) A cross section through another hnt^XE81 scar, shows that some of the R cells (arrowheads) have fallen out of the retinal epithelium. The R cells come to reside on the optic lobe of the brain and the basal, fenestrated membrane of the retina, which is assembled after the R cells fall out of the epithelium (see Fig. 7 and Results), separates these R cells from the retina.

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