Meeting Abstract
Wild adult fruit flies vary in size due to variable food availability during early development, but how this variation impacts their eye size, vision, and flight behavior remains largely unknown. For holometabolous insects like the fruit fly, growth is almost entirely restricted to the larval stages and lower larval feeding results in smaller adult flies. Smaller adult flies possess smaller eyes that, in principle, must sacrifice spatial acuity or contrast sensitivity due to smaller optics. Such small eyes are common in nature where larval nutrition is limited and ephemeral. However, because fruit fly vision is currently understood from uniformly large, lab-reared adults, how their visual development copes with small optics is unknown. Do smaller eyes sacrifice spatial acuity, by increasing their inter-ommatidial angle, or contrast sensitivity, by decreasing their ommatidial diameter? Further, might the visual system neurally adapt to these optical constraints via temporal or spatial pooling? To address these questions, we generate a broad distribution of eye sizes by removing larvae from their food during their third instar and measure the optical and functional effects of small eyes on their vision. Using a digital recording microscope, an immersive visual arena, and psychophysical paradigm, we show that small eyes maintain spatial acuity by sacrificing contrast sensitivity at the optical level, but recover contrast sensitivity by sacrificing temporal acuity at the neural level. Therefore, we find that smaller flies, due to limited larval feeding, have smaller and slower but otherwise normal eyes. [NIH/NIGMS grant R25 GM061347 to JPC]
