Behavior ofCaenorhabditis elegansin a nicotine gradient modulated by food

Abstract

Nicotine decreases food intake, and smokers often report that they smoke to control their weight. To see whether similar phenomena could be observed in the model organism Caenorhabditis elegans, we challenged drug-naïve nematodes with a chronic low (0.01 mM) and high (1 mM) nicotine concentration for 55 h (from hatching to adulthood). After that, we recorded changes in their behavior in a nicotine gradient, where they could choose a desired nicotine concentration. By using a combination of behavioral and morphometric methods, we found that both nicotine and food modulate worm behavior. In the presence of food (E. coli OP50) the nematodes adapted to the low nicotine concentration, when placed in the gradient, chose a similar nicotine concentration like C. elegans adapted to the high nicotine concentration. However, in the absence of food, the nematodes adapted to the low nicotine concentration, when placed in the gradient of this alkaloid, chose a similar nicotine concentration like naïve worms. The nematodes growing up in the presence of high concentrations of nicotine had a statistically smaller body size, compared to the control condition, and the presence of food did not cause any enhanced slowing movement. These results provide a platform for more detailed molecular and cellular studies of nicotine addiction and food intake in this model organism.

News & Views

“…A recent study reported the use of the nematode Caenorhabditis elegans as a model organism to investigate the effects of nicotine addiction and food intake. Sobkowiak et al 1 habituated C. elegans worms to low and high nicotine concentrations (0.01 mM and 1 mM, respectively) for 55 hours (from hatching to adulthood, at least ¾ of their life cycle). Then, the worms were transferred to Petri dishes with a nicotine gradient and allowed to move freely.…”

Chemoreception of botanical nematicides byMeloidogyne incognitaandCaenorhabditis elegans

“…To study the behavior of worms, we used an automated tracking system to follow individual young adults crawling on NGM plates. [22,23] Single young adults (C. elegans aged ~ 55 h) or freshly hatched (24 h) M. incognita second-stage juveniles (J2) were manually picked off a plate and placed using a platinum pick in a 1 μL droplet of water on the agar surface of the gradient assay plate, 15 mm from the plate center (Fig. 1).…”

“…Custom worm tracker software (WormSpy) was used to move the camera automatically to re-center the worm under the field of view during recording. [22,23] The automated tracking system comprises . CC-BY-NC-ND 4.0 International license a certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.…”

“…We reduced the variation in sampling rate as a consequence of the small differences in the time it took to re-center the worm and the need to take data only when the stage was stationary by developing a simultaneous localization and tracking method for a worm tracking system. [22,23] The spatiotemporal track of each worm was reconstructed from the record of centroid locations and camera displacements. The instantaneous speed and trajectory were computed using the displacement of the centroid in successive samples.…”