A <em>Caenorhabditis elegans</em> Nutritional-status Based Copper Aversion Assay

Abstract

To ensure survival, organisms must be capable of avoiding unfavorable habitats while ensuring a consistent food source. Caenorhabditis elegans alter their locomotory patterns upon detection of diverse environmental stimuli and can modulate their suite of behavioral responses in response to starvation conditions. Nematodes typically exhibit a decreased aversive response when removed from a food source for over 30 min. Observation of behavioral changes in response to a changing nutritional status can provide insight into the mechanisms that regulate the transition from a well-fed to starved state. We have developed an assay that measures a nematode's ability to cross an aversive barrier (i.e. copper) then reach a food source over a prolonged period of time. This protocol builds upon previous work by integrating multiple variables in a manner that allows for continued data collection as the organisms shift towards an increasingly starved condition. Moreover, this assay permits an increased sample size so that larger populations of nematodes can be simultaneously evaluated. Organisms defective for the ability to detect or respond to copper immediately cross the chemical barrier, while wild type nematodes are initially repelled. As wild type worms are increasingly starved, they begin to cross the barrier and reach the food source. We designed this assay to evaluate a mutant that is incapable of responding to diverse environmental cues, including food sensation or detection of aversive chemicals. When evaluated via this protocol, the defective organisms immediately crossed the barrier, but were also incapable of detecting a food source. Hence, these mutants repeatedly cross the chemical barrier despite temporarily reaching a food source. This assay can straightforwardly test populations of worms to evaluate potential pathway defects related to aversion and starvation.

Intestine-to-neuronal signaling alters risk-taking behaviors in food-deprived Caenorhabditis elegans

“…Collectively, these data suggest that multiple food-associated volatile attractants can promote repellent barrier crossing in food-deprived animals. Consistently, a previous study showed that food-deprived animals are more likely to cross the repellent barrier when paired with a bacterial lawn [ 31 ]. To test whether food-deprivation differentially affected copper or diacetyl responses, we analyzed responses of these animals to varying concentrations of copper or diacetyl alone.…”

Distinct neural circuits establish the same chemosensory behavior in C. elegans

“…Starved adults: Young adults were washed in a watch glass as described above, and then starved on a 10 cm 2% NGM plate without bacterial food for 3 h as previously described . Animals were placed within an annular ring of filter paper soaked in 20 mM copper chloride (CuCl 2 ) solution to keep them from crawling off the edges of plates, since copper is aversive to C. elegans (Campbell et al 2017). After 3 h of starvation, the CuCl 2 ring was removed, and the animals were collected from the plate and washed twice in M9 and once in ddH 2 O in a watch glass.…”

Neuronal mTORC1 inhibition promotes longevity without suppressing anabolic growth and reproduction in C. elegans

“…The copper aversion starvation protocol was adapted from Campbell et al [ 55 ]. Three days before the experiment, animals were synchronized by performing an egg lay on either control or auxin plates.…”