High-Throughput Analysis of Stimulus-Evoked Behaviors in Drosophila Larva Reveals Multiple Modality-Specific Escape Strategies

Abstract

All organisms react to noxious and mechanical stimuli but we still lack a complete understanding of cellular and molecular mechanisms by which somatosensory information is transformed into appropriate motor outputs. The small number of neurons and excellent genetic tools make Drosophila larva an especially tractable model system in which to address this problem. We developed high throughput assays with which we can simultaneously expose more than 1,000 larvae per man-hour to precisely timed noxious heat, vibration, air current, or optogenetic stimuli. Using this hardware in combination with custom software we characterized larval reactions to somatosensory stimuli in far greater detail than possible previously. Each stimulus evoked a distinctive escape strategy that consisted of multiple actions. The escape strategy was context-dependent. Using our system we confirmed that the nociceptive class IV multidendritic neurons were involved in the reactions to noxious heat. Chordotonal (ch) neurons were necessary for normal modulation of head casting, crawling and hunching, in response to mechanical stimuli. Consistent with this we observed increases in calcium transients in response to vibration in ch neurons. Optogenetic activation of ch neurons was sufficient to evoke head casting and crawling. These studies significantly increase our understanding of the functional roles of larval ch neurons. More generally, our system and the detailed description of wild type reactions to somatosensory stimuli provide a basis for systematic identification of neurons and genes underlying these behaviors.

The impact of odor–reward memory on chemotaxis in larval Drosophila

“…From these, we calculated additional time-series variables (Supplemental Table S2) that allowed us to determine the distance of larvae from the odor source when turning, and the orientation and bearing of larvae before and after a turn (Supplemental Tables S3): † Turns were identified according to a method adapted from Gomez-Marin et al (2011), relying primarily on changes in reorientation speed during turning. For a turn to be identified, reorientation speed needed to pass a set of Schmitt-trigger thresholds determined empirically (Supplemental Table S4; Ohyama et al 2013). As larvae must bend to perform a turn, the Choreography variables of head angle, kink, and curve (Supplemental Table S1) were used on those path segments identified as turns.…”

A Group of Segmental Premotor Interneurons Regulates the Speed of Axial Locomotion in Drosophila Larvae

“…In normal conditions at room temperature (w25 C), the speed of forward peristalsis is remarkably stereotypic (w1 s/cycle), suggesting that it is rigorously regulated. However, the larvae move much faster at high temperatures (e.g., w32 C), when deprived of food or in response to noxious sensory stimuli, and crawl more slowly at low temperatures (e.g., w18 C), indicating that the speed can be adjusted to meet internal and external demands [32,33]. Although much work has been done on the role of motor neurons and sensory neurons [34][35][36][37], little is known about the identities of interneurons that regulate larval locomotion.…”

Identification of Ppk26, a DEG/ENaC Channel Functioning with Ppk1 in a Mutually Dependent Manner to Guide Locomotion Behavior in Drosophila

“…Interestingly, Ppk1 also plays an essential role in mechanical nociception behavior (Zhong et al, 2010), suggesting that these neurons can process multiple stimulus modalities. Class IV da neurons resemble mammalian nociceptors morphologically (Caterina and Julius, 1999; Tracey et al, 2003) and in their polymodal sensitivity to a variety of sensory stimuli (Ohyama et al, 2013). In addition to sensing mechanical nociception and coordinating locomotion, Class IV da neurons are also sensitive to temperature (Hwang et al, 2012), light (Xiang et al, 2010), and chemical stimuli (Kang et al, 2010; Xiang et al, 2010).…”