Behavior without synapses

Arjen Boender, a Ramon y Cajal Fellow and IKERBASQUE researcher of the Laboratory of Comparative Neuroscience published a Journal Club article in Nature Reviews Neuroscience. In this format, scientists are invited to comment on a previously published study that has had special significance for their field.

Dr. Boender chose to highlight a paper by Senatore et al., which examines a tiny, brainless animal found in shallow, tidal marine environments: Trichoplax adhaerens. This animal is remarkable because, despite lacking a brain, neurons, and synapses, it exhibits complex behaviors such as social feeding and coordinated movements.

The study shows that these behaviors are regulated by neuropeptides, which are small signaling molecules composed of only a few amino acids. Because Trichoplax are thought to be among the earliest of animals, this provided compelling evidence that this form of communication predates synaptic signaling. As peptidergic signaling has been conserved throughout evolution and is present in all mammals, these findings offer important insights into the ancient biological roots of behavioral coordination and challenge neuron-centric views of how behavior is controlled.

For a visual introduction to this fascinating creature and its behavior, you can watch this short explainer video.

More information:

• Boender AJ. Behaviour without synapses: peptidergic signalling as a mode of behavioural coordination. Nat Rev Neurosci. 2026 Jan 16. doi: 10.1038/s41583-026-01022-8. Epub ahead of print. PMID: 41545674.
• Senatore A, Reese TS, Smith CL. Neuropeptidergic integration of behavior in Trichoplax adhaerens, an animal without synapses. J Exp Biol. 2017 Sep 15;220(Pt 18):3381-3390. doi: 10.1242/jeb.162396. PMID: 28931721; PMCID: PMC5612019.