Meeting Abstract
For holometabelous insects, low larval feeding results in small but otherwise normal adults. In fruit flies, this results in conspecifics with small eyes that sacrifice contrast sensitivity optically but recover that sensitivity by sacrificing temporal acuity neurally. However, forward optic flow generates peripheral motion that offers crucial information about flight speed and orientation. Normally, this difference is resolved optically: many fast moving insects have greater inter-ommatidial angles and larger ommatidial apertures in lateral regions of the eye. But fruit flies have a nearly homogeneous eye structure and the temporal summation used by small flies in their central vision would cause substantial motion blur in the periphery. Do small flies process motion differently between central and peripheral visual regions? To address this, we used a flight simulation arena and measured contrast sensitivity and spatial and temporal acuity by displaying moving sinusoidal gratings and measuring their turning behavior with a wingbeat analyzer. Then, using a microscope, we measured the flies’ eye size, ommatidial count, and average ommatidial area. As before, we found that smaller eyes temporally summate when motion is in their central vision. But when motion was displayed in their periphery, small and large flies responded nearly equally. In fact, aside from a small difference in peripheral spatial acuity likely due to differences in acceptance angle, small flies demonstrated little loss in peripheral visual ability. Alternatively, it seems large flies can afford a central region of high temporal acuity not found in smaller flies.
