The simple fly larval visual system can process complex images

Abstract

Animals that have simple eyes are thought to only detect crude visual detail such as light level. However, predatory insect larvae using a small number of visual inputs seem to distinguish complex image targets. Here we show that Drosophila melanogaster larvae, which have 12 photoreceptor cells per hemisphere, are attracted to distinct motions of other, tethered larvae and that this recognition requires the visual system but not the olfactory system. In addition, attraction to tethered larvae still occurs across a clear plastic barrier, does not occur significantly in the dark and attraction occurs to a computer screen movie of larval motion. By altering the artificial attractant movie, we conclude that visual recognition involves both spatial and temporal components. Our results demonstrate that a simple but experimentally tractable visual system can distinguish complex images and that processing in the relatively large central brain may compensate for the simple input.

Visual attraction in Drosophila larvae develops during a critical period and is modulated by crowding conditions

“…The behavioral assay is essentially the same as described (Justice et al 2012). For larval targets, 4-5 L3F Canton S larvae are super-glue tethered at their rear segments to one spot positioned 1 cm in from the edge of the underside of a 100-mm plastic Petri dish.…”

“…Drosophila larvae can be tested for visual attraction to the movements of other larvae, using a simple Petri dish assay (Justice et al 2012), (Fig. 1a).…”

“…Vision may also play a role (Justice et al 2012). While larvae possess a rudimentary visual system, consisting of only 12 photoreceptors per side (Keene and Sprecher 2012), they can nevertheless visually distinguish moving larvae from dead ones (Justice et al 2012). This is based on the measured attraction of one test larva to moving, tethered larvae on the other side of clear plastic.…”

“…Species-specific cuticular hydrocarbons serve an important role in recognition and clustering (Mast et al 2014). Vision may also play a role (Justice et al 2012). While larvae possess a rudimentary visual system, consisting of only 12 photoreceptors per side (Keene and Sprecher 2012), they can nevertheless visually distinguish moving larvae from dead ones (Justice et al 2012).…”

Can Bees See at a Glance?

“…There might be a simple explanation: if visual perception depends on active visual probing of the environment by means of self-generated movement, then tethered bees (which cannot move their heads to scan visual patterns) are constrained to fail in any but the most simple discrimination tasks . Insects might simply rely on active vision to perform more complex discriminations (Justice et al, 2012) and therefore fail when scanning is not possible, for example as a result of the short presentation durations in our experiment.…”