Welcome to the next episode of the WOrM Podcast 🪱Today we're talking about a worm with teeth.And a nervous system that has been rewired — by evolution — to become aggressive.⸻🧬 The central ideaPristionchus pacificus is a predatory nematode.It kills C. elegans larvae.Sometimes for food.Sometimes just to remove a competitor.But how does its brain decide to attack?⸻🔬 What's actually going on?This is not just predation.It is a distinct behavioural state — aggression —driven by a specific neurochemical system.The researchers used machine learning to identify six distinct behavioural states:roaming and dwelling — shared with C. eleganspredatory search, predatory biting, predatory feeding — unique to a predatory contextThe worm doesn't attack randomly.It switches modes.⸻⚡ Two chemicals. Opposite effects.The key twist is this:Octopamine pushes the worm into aggressive, predatory statesTyramine pulls it back into passive, docile statesThey act antagonistically — like a switch.Remove octopamine → the worm stops attacking.Remove tyramine as well → aggression returns.⸻🧠 The receptors tell the storyTwo octopamine receptors are required: Ppa-ser-3 and Ppa-ser-6.One tyramine receptor mediates the passive state: Ppa-lgc-55.Crucially — these receptors are expressed in sensory neurons at the worm's nose.Specifically, the IL2 neurons.These are the first point of contact between predator and prey.Silence the IL2 neurons → aggression drops.⸻🧠 A rewired circuitIn C. elegans, octopamine and tyramine do completely different things — fasting signals, escape responses.In P. pacificus, evolution has repurposed these same molecules to regulate aggression.The neurons producing them are conserved.The function has diverged.This is circuit-level evolutionary innovation.⸻🧠 Ancient and widespreadThe same octopamine-aggression link was found in Allodiplogaster sudhausi —a distant relative in the Diplogastridae family.So this adaptation is not unique to P. pacificus.It emerged early, in the predatory lineage — and stuck.⸻🌍 The bigger pictureThis paper shows that:new behaviours can evolve through repurposing of existing neurochemical systemsthe same molecules can serve completely different functions in closely related speciessensory neurons are a key site of neuromodulatory innovationEvolution doesn't always build from scratch.Sometimes it just rewires what's already there.⸻🧠 The take-home messageA predatory worm evolved aggressionnot through new neurons,but through new ways of using old chemistry.Octopamine and tyramine — present across invertebrates —were redeployed to gate an entirely new behavioural state.That is elegant. And slightly terrifying.⸻📄 Paper discussedEren, G. G.; Böger, L.; Roca, M.; Hiramatsu, F.; Liu, J.; Alvarez, L.; Goetting, D. L.; Cockram, L. A.; Zorn, N.; Han, Z.; Okumura, M.; Scholz, M.; Lightfoot, J. W. (2026)Predatory aggression evolved through adaptations to noradrenergic circuitsNature, Vol 651https://doi.org/10.1038/s41586-025-10009-xIf you enjoyed this episode, please like, follow, and subscribe wherever you listen to the WOrM Podcast ⭐🎧 It really helps others in the community find the show.This podcast is generated with artificial intelligence and curated by Veeren. If you'd like your publication or product featured on the show, please get in touch.📩 More info:🔗 www.veerenchauhan.com📧 [email protected]

Ask this episode

“What did the council decide on item 42?” — answered with the speaker and the moment.

Transcript

Related