Rosales, K. | bioRxiv Science

bioRxiv2022

Dopamine signaling regulates predator-driven behavioral changes in Caenorhabditis elegans

Prey respond to predators by altering their behavior to optimize their own fitness and survival. Specifically, prey are known to avoid predator-occupied territories to reduce their risk of harm or injury to themselves and their progeny. We probe the interactions between Caenorhabditis elegans and its naturally cohabiting predator Pristionchus uniformis to reveal the pathways driving changes in prey behavior. While C. elegans prefers to lay its eggs on a bacteria food lawn, the presence of a predator inside a lawn induces C. elegans to lays more eggs away from that lawn. We confirm that this change in egg laying is in response to bites from predators, rather than to predatory secretions. Moreover, predator-exposed prey continue to lay their eggs away from the dense lawn even after the predator is removed, indicating a form of learning. Next, we find that mutants in dopamine synthesis significantly reduce egg laying behavior off the lawn in both predator-free and predator-inhabited lawns, which we can rescue by transgenic complementation or supplementation with exogenous dopamine. Moreover, we find that dopamine is likely released from multiple dopaminergic neurons and requires combinations of both D1-(DOP-1), and D2-like (DOP-2 and DOP-3) dopamine receptors to alter predator-induced egg laying behavior, whereas other combinations modify baseline levels of egg laying behavior. Together, we show that dopamine signaling can alter both predator-free and predator-induced foraging strategies, implying a role for this pathway in defensive behaviors.

neuroscience↗

bioRxiv2019

A many-to-one sensory circuit encodes oxygen levels and drives respiratory behaviour in Danio rerio

Zebrafish larvae respond to hypoxia by increasing a number of ventilatory behaviors. During development, these animals switch from skin-resident to gill-resident neuroendocrine cells around 7 days post fertilization (d.p.f.) to detect hypoxia and drive adaptive behaviors. Here, we probe the neural pathways that receive inputs from skin-resident neuroendocrine cells and alter pectoral fin movements. We first show that a 5 d.p.f. larva increases its pectoral fin movements and heart activity upon hypoxia exposure. Next, we map the downstream neural circuitry and show that individual vagal sensory neurons receive inputs from multiple oxygen-sensing neuroendocrine cells. We then use calcium imaging to show that neurons in the second, but not third, vagal sensory ganglia show increases in the magnitude of their hypoxia-evoked responses. Finally, we link purinergic signaling between neuroendocrine cells and second vagal sensory neurons to increases in pectoral fin movements. Collectively, we suggest that vagal sensory neurons transform hypoxic stimuli into respiratory behaviors.

neuroscience↗