Serotoninergic Modulation of Phototactic Variability Underpins a Bet-Hedging Strategy in Drosophila melanogaster

• Main Authors: Indrikis A. Krams, Tatjana Krama, Ronalds Krams, Giedrius Trakimas, Sergejs Popovs, Priit Jõers, Maris Munkevics, Didzis Elferts, Markus J. Rantala, Jānis Makņa, Benjamin L. de Bivort
• Format: Article
• Language: English
• Published: Frontiers Media S.A. 2021-04-01
• Series: Frontiers in Behavioral Neuroscience
• Subjects: adaptive strategies; Drosophila melanogaster; phototaxis; serotonin; variation
• Online Access: https://www.frontiersin.org/articles/10.3389/fnbeh.2021.659331/full

When organisms’ environmental conditions vary unpredictably in time, it can be advantageous for individuals to hedge their phenotypic bets. It has been shown that a bet-hedging strategy possibly underlies the high inter-individual diversity of phototactic choice in Drosophila melanogaster. This study shows that fruit flies from a population living in a boreal and relatively unpredictable climate have more variable variable phototactic biases than fruit flies from a more stable tropical climate, consistent with bet-hedging theory. We experimentally show that phototactic variability of D. melanogaster is regulated by the neurotransmitter serotonin (5-HT), which acts as a suppressor of the variability of phototactic choices. When fed 5-HT precursor, boreal flies exhibited lower variability, and they were insensitive to 5-HT inhibitor. The opposite pattern was seen in the tropical flies. Thus, the reduction of 5-HT in fruit flies’ brains may be the mechanistic basis of an adaptive bet-hedging strategy in a less predictable boreal climate.