Continuous, long-term crawling behavior characterized by a robotic transport system

Abstract

Detailed descriptions of behavior provide critical insight into the structure and function of nervous systems. In Drosophila larvae and many other systems, short behavioral experiments have been successful in characterizing rapid responses to a range of stimuli at the population level. However, the lack of long-term continuous observation makes it difficult to dissect comprehensive behavioral dynamics of individual animals and how behavior (and therefore the nervous system) develops over time. To allow for long-term continuous observations in individual fly larvae, we have engineered a robotic instrument that automatically tracks and transports larvae throughout an arena. The flexibility and reliability of its design enables controlled stimulus delivery and continuous measurement over developmental time scales, yielding an unprecedented level of detailed locomotion data. We utilize the new system’s capabilities to perform continuous observation of exploratory search behavior over a duration of 6 hr with and without a thermal gradient present, and in a single larva for over 30 hr. Long-term free-roaming behavior and analogous short-term experiments show similar dynamics that take place at the beginning of each experiment. Finally, characterization of larval thermotaxis in individuals reveals a bimodal distribution in navigation efficiency, identifying distinct phenotypes that are obfuscated when only analyzing population averages.

Accelerated hermaphrodite maturation on male pheromones suggests a general principle of coordination between larval behavior and development

“…High-resolution long-term monitoring promises to expand our understanding of behavior ( Elliott et al, 2021 ). In Drosophila , continuous monitoring of larval crawling on timescales comparable with the duration of one larval instar revealed apparent epochs of faster directional movement with fewer turns followed by prolonged periods of slower movement with more turns ( Yu et al, 2023 ), a pattern strikingly similar to the one observed during long-term monitoring of C. elegans larvae ( Stern et al, 2017 ) ( Fig. 4C ).…”

Temperature sensitivity and temperature response across development in the Drosophila larva

“…Although the adjacent bins do not show statistically significance differences, this could be a legitimate effect. Recent results (Yu et al, 2023 ) with long time scale larva thermotaxis experiments (up to 6 h) suggest two distinct groups of larvae, one group strongly navigating and the other more neutral. The neutral crawlers would be more likely to crawl in strong-cooling directions (because strong navigators turn away quickly), so perhaps they become more prevalent in the overall averaging for those conditions, leading to a reduced average turning rate.…”