Fig. 1

T. marmoratus larvae have two high-resolution image-forming principal camera eyes on each side of the head (E1 and E2). A Both E1 and E2 are highly pigmented and tubular in shape, as illustrated by a freshly emerged larva in which the head cuticle is still transparent, scale bar = 100 µm. B DAPI staining highlights the nuclei of the support cells (SupCs) that form the distal region of the eye tubes, scale bar = 100 µm. C Schematic of a principal eye, illustrating its division into distally situated SupCs (green) and a proximal tiered retina (purple). D These camera eyes and D. melanogaster compound eyes share similar developmental plans [29]. Based on their organization, it has been hypothesized that the outer SupCs in T. marmoratus camera eyes are related to D. melanogaster interommatidial pigment cells (yellow) and the inner SupCs to D. melanogaster primary pigment and Semper cells (green). E As SupCs and photoreceptor cells are anatomically distinct, they can be dissected into separate regions for tissue-specific transcriptomics