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1. Argentine ant extract induces an osm-9 dependent chemotaxis response in C. elegans

   Alfonso, SA; Arango Sumano, D; Bhatt, DA; Cullen, AB; Hajian, CM; Huang, W; Jaeger, EL; Li, E; Maske, AK; Offenberg, EG; et al (March 2023, microPublication biology)

   Many ant species are equipped with chemical defenses, although how these compounds impact nervous system function is unclear. Here, we examined the utility of Caenorhabditis elegans chemotaxis assays for investigating how ant chemical defense compounds are detected by heterospecific nervous systems. We found that C. elegans respond to extracts from the invasive Argentine Ant (Linepithema humile) and the osm-9 ion channel is required for this response. Divergent strains varied in their response to L. humile extracts, suggesting genetic variation underlying chemotactic responses. These experiments were conducted by an undergraduate laboratory course, highlighting how C. elegans chemotaxis assays in a classroom setting can provide genuine research experiences and reveal new insights into interspecies interactions. 

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2. Argentine ant extract induces an osm-9 dependent chemotaxis response in C. elegans

   Alfonso, Sebastian A.; Arango Sumano1, Daniel; Bhatt, Dhruv A.; Cullen, Aidan B.; Hajian, Cyrus M.; Huang, Winnie; Jaeger, Emma L.; Li, Emily; Maske, A. Kaile; Offenberg, Emma G.; et al (March 2023, microPublication biology)

   Many ant species are equipped with chemical defenses, although how these compounds impact nervous system function is unclear. Here, we examined the utility of Caenorhabditis elegans chemotaxis assays for investigating how ant chemical defense compounds are detected by heterospecific nervous systems. We found that C. elegans respond to extracts from the invasive Argentine Ant (Linepithema humile) and the osm-9 ion channel is required for this response. Divergent strains varied in their response to L. humile extracts, suggesting genetic variation underlying chemotactic responses. These experiments were conducted by an undergraduate laboratory course, highlighting how C. elegans chemotaxis assays in a classroom setting can provide genuine research experiences and reveal new insights into interspecies interactions. 

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3. Pavement ant extract is a chemotaxis repellent for C. elegans

   https://doi.org/10.17912/micropub.biology.001146  

   Lopez, Jayela S; Ali, Saif; Asher, Malcom; Benjamin, Christina A; Brennan, Ryan T; Burke, Mai_Ly T; Civantos, Joseph M; DeJesus, Emilia A; Geller, Ana; Guo, Michaela Y; et al (March 2024, microPublication Biology)

   Ant behavior relies on a collection of natural products, from following trail pheromones during foraging to warding off potential predators. How nervous systems sense these compounds to initiate a behavioral response remains unclear. Here, we used Caenorhabditis elegans chemotaxis assays to investigate how ant compounds are detected by heterospecific nervous systems. We found that C. elegans avoid extracts of the pavement ant (Tetramorium immigrans) and either osm-9 or tax-4 ion channels are required for this response. These experiments were conducted in an undergraduate laboratory course, demonstrating that new insights into interspecies interactions can be generated through genuine research experiences in a classroom setting. 

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4. Temporal processing and context dependency in Caenorhabditis elegans response to mechanosensation

   https://doi.org/10.7554/eLife.36419  

   Liu, Mochi; Sharma, Anuj K; Shaevitz, Joshua W; Leifer, Andrew M (June 2018, eLife)

   A worm called Caenorhabditis elegans has a nervous system made up of only 302 neurons, far fewer than the billions of cells that comprise our own brains. And yet these few hundred neurons are enough for these worms to detect and respond to their surroundings. C. elegans is thus a popular choice for studying how nervous systems process sensory information and use it to control behavior. Yet, most experiments to date have used only simple stimuli, such as taps or pokes, and studied a handful of behaviors, such as whether or not a worm stops moving or backs up. This limits the conclusions it has been possible to draw. Liu et al. therefore set out to determine how the worm’s nervous system responds to more complex stimuli. These included physical stimuli, such as taps on the side of the dish containing the worms, as well as simulated stimuli. To generate the latter, Liu et al. used a technique called optogenetics to directly activate the neurons in the worm’s body that would normally detect information from the senses, by simply shining a light on the worms. Doing so gives the worm the sensation of a physical stimulus, even though none was present. Liu et al. then used mathematics to examine the relationships between the stimuli and the worms’ responses. The results confirmed that worms usually respond to simple stimuli, such as taps on the side of their dish, by backing up. But they also revealed more advanced forms of stimulus processing. The worms responded differently to stimuli that increased over time versus decreased, for example. A worm's response to a stimulus also varied depending on what the worm was doing at the time. Worms that were in the middle of turns, for instance, ignored stimuli to which they would normally respond. This suggests that an animal’s current behavior influences how its nervous system interprets sensory information. The discovery of relatively sophisticated responses to sensory stimuli in C. elegans indicates that even simple nervous systems are capable of flexible sensory processing. This lays a foundation for understanding how neural circuits interpret sensory signals. Building on this work will ultimately help us understand how more complicated nervous systems interpret and respond to the world. 

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5. The nematode worm C. elegans chooses between bacterial foods as if maximizing economic utility

   https://doi.org/10.7554/eLife.69779  

   Katzen, Abraham; Chung, Hui-Kuan; Harbaugh, William T; Della_Iacono, Christina; Jackson, Nicholas; Glater, Elizabeth E; Taylor, Charles J; Yu, Stephanie K; Flavell, Steven W; Glimcher, Paul W; et al (April 2023, eLife)

   na (Ed.)

   In value-based decision making, options are selected according to subjective values assigned by the individual to available goods and actions. Despite the importance of this faculty of the mind, the neural mechanisms of value assignments, and how choices are directed by them, remain obscure. To investigate this problem, we used a classic measure of utility maximization, the Generalized Axiom of Revealed Preference, to quantify internal consistency of food preferences in Caenorhabditis elegans, a nematode worm with a nervous system of only 302 neurons. Using a novel combination of microfluidics and electrophysiology, we found that C. elegans food choices fulfill the necessary and sufficient conditions for utility maximization, indicating that nematodes behave as if they maintain, and attempt to maximize, an underlying representation of subjective value. Food choices are well-fit by a utility function widely used to model human consumers. Moreover, as in many other animals, subjective values in C. elegans are learned, a process we find requires intact dopamine signaling. Differential responses of identified chemosensory neurons to foods with distinct growth potentials are amplified by prior consumption of these foods, suggesting that these neurons may be part of a value-assignment system. The demonstration of utility maximization in an organism with a very small nervous system sets a new lower bound on the computational requirements for utility maximization and offers the prospect of an essentially complete explanation of value-based decision making at single neuron resolution in this organism. 

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