A Computerized Goniometer Instrument for Rapid Evaluation of Regional Compound Eye Specializations

Abstract

Event Abstract Back to Event A Computerized Goniometer Instrument for Rapid Evaluation of Regional Compound Eye Specializations John K. Douglass1* 1 National Academies of Science, United States Previous studies (e.g. 1-3) have shown how much can be learned about regional specializations of compound eyes by taking advantage of in vivo optical phenomena such as pseudopupils, deep pseudopupils, and visual pigment fluorescence, as well as by measuring ommatidial facet dimensions and arrangements. Many flying insects are known to have high spatial resolution acute zones; “bright zones” with high absolute sensitivity may also afford improvements in temporal resolution. But among insects as a whole, studies to date are phylogenetically sparse, perhaps in part because manual measurements from entire visual fields at high sampling densities can be very time-consuming and tedious. I am developing a computer-controlled instrument that is designed to facilitate rapid positioning, data collection, and analyses of this kind. The custom- built goniometer potentially can be interfaced with various microscope arrangements. The current configuration includes a programmable digital camera on an epi-illumination microscope, motorized positioners for focusing, orienting and positioning the subject, manual positioners for aligning axes, and a user-friendly graphical interface written in Matlab. While continuing software development, I have begun to investigate regional ommatidial variations in some locally available insects. Data examples to be presented may include maps comparing distributions of interommatidial angles, facet sizes, and facet geometry. In nearly all insects whose eyes have been described in any detail, the facet geometry is predominantly hexagonal. Exceptions are two subfamilies of the Ephemeroptera (4) and a vertical transitional zone noted in some calliphorid and muscid flies (5). Preliminary data suggest an additional exception, in what otherwise appear to be typical apposition, open-rhabdom dipteran eyes: across significant portions of the eye, facet arrays in Stratiomyids and some close relatives are more square than hexagonal. With improved capabilities for rapid data acquisition, computerized ommatidial analyses offer new opportunities for broadly comparative and evolutionary studies of visual field specializations. (Cleared for Public Release 96ABW-2013-0159) Acknowledgements Supported by a research associateship from the U.S. National Research Council, and with facilities and funding of the AFRL Bio-Sensors Lab, Eglin Air Force Base, Florida. I thank Martin F. Wehling for encouragement and many fruitful discussions. Numerous other Eglin personnel have also been very helpful, including Ben Dickinson, Eric Glattke, Jimmy Touma, and Eglin Model Shop staff.