Biology subjects

Quach, K. T.

Publications and source records attributed to Quach, K. T..

3 recordsLinked to original sources

bioRxiv2024

Evolution of lateralized gustation in nematodes

Animals with small nervous systems have a limited number of sensory neurons that must encode information from a changing environment. This problem is particularly exacerbated in nematodes that populate a wide variety of distinct ecological niches but only have a few sensory neurons available to encode multiple modalities. How does sensory diversity prevail within this constraint in neuron number? To identify the genetic basis for patterning different nervous systems, we demonstrate that sensory neurons in Pristionchus pacificus respond to various salt sensory cues in a manner that is partially distinct from that of the distantly related nematode Caenorhabditis elegans. By visualizing neuronal activity patterns, we show that contrary to previous expectations based on its genome sequence, the salt responses of P. pacificus are encoded in a left/right asymmetric manner in the bilateral ASE neuron pair. Our study illustrates patterns of evolutionary stability and change in the gustatory system of nematodes. Animals with small nervous systems have evolved left and right asymmetry in their neurons to process various salts at different concentrations.

neuroscience↗

bioRxiv2024

Interdependence between SEB-3 and NLP-49 peptides shifts across predator-induced defensive behavioral modes in Caenorhabditis elegans

Prey must balance the need to avoid predators with the need to feed, a dilemma central to prey refuge theory. Additionally, prey must also assess predatory imminence, or how close predator threats are in space and time. Predatory imminence theory classifies defensive behaviors into three defense modes--pre-encounter, post-encounter, and circa-strike--each corresponding to increasing levels of predatory imminence--suspecting a predator, detecting a predator, and contact with a predatory attack. Although prey often simultaneously face variations in predatory imminence and spatial distribution of predation risks, research on how these factors intersect to influence defensive behaviors has been limited. Integrating these factors into a complex, naturalistic environment could enable comprehensive analysis of multiple defense modes in consistent conditions within the same study, unlike laboratory tests designed to examine only one mode at a time. Here, we combine prey refuge and predatory imminence theories to develop a model system of nematode defensive behaviors, with Caenorhabditis elegans as prey and Pristionchus pacificus as predator. We show that C. elegans innately exhibits circa-strike behaviors in a foraging environment comprised of a food-rich, high-risk patch and a food-poor, predator-free refuge. However, after extended experience in this environment, C. elegans acquires post- and pre-encounter behaviors that proactively anticipate threats rather than merely reacting to attacks. We also demonstrate that these defense modes are potentiated by increasingly harmful predators, with only life-threatening predators capable of eliciting all three defense modes. Finally, our model system reveals that SEB-3 receptors and NLP-49 peptides, key to stress response regulation, vary in their impact and interdependence across defense modes. We find that SEB-3 has a greater impact on the highest-imminence defense mode, while NLP-49 peptides have a stronger effect on the lowest-imminence defense mode. Overall, our model system reveals detailed and comprehensive insights into how stress-related molecular signaling affects behavioral responses to threats.

animal behavior and cognition↗

bioRxiv2021

Distinct foraging strategies generated by single-action behavioural flexibility

Animals with diverse diets must adapt their food priorities to a wide variety of environmental conditions. This diet optimization problem is especially complex for predators that compete with prey for food. Although predator-prey competition is widespread and ecologically critical, it remains difficult to disentangle predatory and competitive motivations for attacking competing prey. Here, we dissect the foraging decisions of the omnivorous nematode Pristionchus pacificus to reveal that its seemingly failed predatory attempts against Caenorhabditis elegans are actually motivated acts of efficacious territorial aggression. While P. pacificus easily kills and eats larval C. elegans with a single bite, adult C. elegans typically survives and escapes from bites. However, nonfatal biting can provide competitive benefits by reducing access of adult C. elegans and its progeny to bacterial food that P. pacificus also eats. We show that P. pacificus considers costs and benefits of both predatory and territorial outcomes to decide which food goal, prey or bacteria, should guide its motivation for biting. These predatory and territorial motivations impose different sets of rules for adjusting willingness to bite in response to changes in bacterial abundance. In addition to biting, predatory and territorial motivations also influence which search tactic P. pacificus uses to increase encounters with C. elegans. When treated with an octopamine receptor antagonist, P. pacificus switches from territorial to predatory motivation for both biting and search. Overall, we demonstrate that P. pacificus assesses alternate outcomes of attacking C. elegans and flexibly reprograms its foraging strategy to prioritize either prey or bacterial food.

neuroscience↗