Sex-limited diversification of the eye in Heliconius butterflies

Butterflies have evolved an immense diversity in eye organization to support a range of vision-based behaviors, including courtship, oviposition, and foraging. This diversity has been surveyed extensively across the butterfly phylogeny, and here we take a complementary approach to characterize the eye within a group of closely related Heliconius butterflies. Using a combination of immunostaining for different opsins and eyeshine for determining the distribution of light-filtering screening pigments, we identified several sexually dimorphic features of eye organization where male eyes varied and female eyes did not. Ultraviolet (UV) sensitive photoreceptors varied in which of two UV opsins were expressed, including co-expression of both within single photoreceptors, and these differences were consistent with a role in courtship and conspecific identification. Additional differences across species and sex included the distribution of three ommatidial types defined by the expression pattern of UV and blue opsins, the distribution of screening pigments, and the relationship between ommatidial type and screening pigment. We hypothesize that female eyes are optimized for a dimorphic behavior such as oviposition, while male eyes more freely adapt to their natural light environment.

Methods
This dataset includes a MATLAB file that includes all of the original eyeshine images that were taken along with the analyzed counts. A second MATLAB file includes immunostaining data for all animals included in the study. The original .czi files for each tissue section is also included. See the README.txt for additional details.