Serotonin promotes exploitation in complex environments by accelerating decision-making

Shachar Iwanir, Adam S. Brown, Stanislav Nagy, Dana Najjar, Alexander Kazakov, Kyung Suk Lee, Alon Zaslaver, Erel Levine, David Biron*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


Background: Fast responses can provide a competitive advantage when resources are inhomogeneously distributed. The nematode Caenorhabditis elegans was shown to modulate locomotion on a lawn of bacterial food in serotonin (5-HT)-dependent manners. However, potential roles for serotonergic signaling in responding to food discovery are poorly understood. Results: We found that 5-HT signaling in C. elegans facilitates efficient exploitation in complex environments by mediating a rapid response upon encountering food. Genetic or cellular manipulations leading to deficient serotonergic signaling resulted in gradual responses and defective exploitation of a patchy foraging landscape. Physiological imaging revealed that the NSM serotonergic neurons responded acutely upon encounter with newly discovered food and were key to rapid responses. In contrast, the onset of responses of ADF serotonergic neurons preceded the physical encounter with the food. The serotonin-gated chloride channel MOD-1 and the ortholog of mammalian 5-HT1 metabotropic serotonin receptors SER-4 acted in synergy to accelerate decision-making. The relevance of responding rapidly was demonstrated in patchy environments, where the absence of 5-HT signaling was detrimental to exploitation. Conclusions: Our results implicate 5-HT in a novel form of decision-making, demonstrate its fitness consequences, suggest that NSM and ADF act in concert to modulate locomotion in complex environments, and identify the synergistic action of a channel and a metabotropic receptor in accelerating C. elegans decision-making.

Original languageAmerican English
Article number9
JournalBMC Biology
Issue number1
StatePublished - 4 Feb 2016

Bibliographical note

Funding Information:
Some strains were provided by the Caenorhabditis Genetics Center (CGC), which is funded by National Institutes of Health (NIH) Office of Research Infrastructure Programs (P40 OD010440). Additional strains were kindly provided by the Horvitz Laboratory at the Massachusetts Institute of Technology, the Komuniecki laboratory at the University of Toledo, the Ringstad laboratory at the New York University School of Medicine, and the Bargmann laboratory at Rockefeller University. We thank Vera Hapiak and Richard Komuniecki for useful discussions. This work was supported by the Burroughs Wellcome Fund Career Awards at the Scientific Interface (DB), the Searle Scholars Program (DB), the National Science Foundation (IOS 1256989, DB), I-core (AZ), and the European Research Council (ERC Starting Grant 336803, AZ).

Publisher Copyright:
© 2016 Iwanir et al.


  • 5-HT
  • C. elegans
  • Decision-making
  • Foraging
  • Foraging systems
  • Patchy environments
  • Re-feeding
  • Resource distribution
  • Serotonin
  • Serotonin (5-HT)
  • Slowdown


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