Acuity and summation strategies differ in vinegar and desert fruit flies

Abstract

Summary An animal's vision depends on terrain features that limit the amount and distribution of available light. Approximately 10,000 years ago, vinegar flies ( Drosophila melanogaster ) transitioned from a single plant specialist into a cosmopolitan generalist. Much earlier, desert flies ( D. mojavensis ) colonized the New World, specializing on rotting cactuses in southwest North America. Their desert habitats are characteristically flat, bright, and barren, implying environmental differences in light availability. Here, we demonstrate differences in eye morphology and visual motion perception under three ambient light levels. Reducing ambient light from 35 to 18 cd/m 2 causes sensitivity loss in desert but not vinegar flies. However, at 3 cd/m 2 , desert flies sacrifice spatial and temporal acuity more severely than vinegar flies to maintain contrast sensitivity. These visual differences help vinegar flies navigate under variably lit habitats around the world and desert flies brave the harsh desert while accommodating their crepuscular lifestyle.

Evolution of compound eye morphology underlies differences in vision between closely related Drosophila species

“…The complexity of the visual system overall, incorporating mechanisms of neural summation and hyperacuity, further highlights the importance of using behavioural measurements of acuity and sensitivity and reinforces the conceptual distinction between optical and contrast sensitivity. Neural summation could have reversed these differences as it did for D. mojavensis due to darkness adaptation [ 55 ] or facultatively within D. melanogaster individuals in response to forward optical flow [ 56 ]. An assessment of the optics alone would have ignored the difference in temporal acuity and overestimated the difference in contrast sensitivity between D. mauritiana and D. simulans based on differences in optical sensitivity .…”

“…S7c). Stimuli were generated by a computer using a custom open-source graphics library and projected onto the front panel of the arena at 120 Hz by a high-speed projector (technical information can be found in Currea, Smith and Theobald [ 41 ] and Currea et al [ 55 ]. An IR light cast the shadow of each wing onto photodiodes below the fly designed to output the amplitude of each wingbeat shadow as a 1000-Hz voltage signal.…”

Measuring compound eye optics with microscope and microCT images

“…Further, progress in understanding fruit fly (D. melanogaster) eye development 7,9,10,13 , makes compound eyes ideal for assessing principles of eye development across different taxa 10,12,14 . And because optics are the first limit to incoming visual information 18,30 , they inform electrophysiological and behavioral data to infer intermediate neural processing 6,11,44,46,[52][53][54][55] .…”

Measuring Compound Eye Optics with Microscope and MicroCT Images

“…Further, progress in understanding fruit fly eye development ( D. melanogaster; Callier and Nijhout 2013; Casares and McGregor 2020; Gaspar et al 2019; Ready et al 1976), makes compound eyes ideal for assessing principles of eye development across different taxa (Casares and McGregor 2020; Friedrich 2003; Harzsch and Hafner 2006). And because optics are the first limit to incoming visual information (Land 1997; Stavenga 1979), they inform electrophysiological and behavioral data to infer intermediate neural processing (Currea et al 2022, 2018; Gonzalez-Bellido et al 2011; Juusola et al 2017; Land and Nilsson 2012a; Theobald et al 2010; Wardill et al 2017; Warrant 1999).…”