Abstract
Mate-copying is a form of social learning in which the mate-choice decision of an individual (often a female) is influenced by the mate-choice of conspecifics. Drosophila melanogaster females are known to perform such social learning, and in particular, to mate-copy after a single observation of one conspecific female mating with a male of one phenotype, while the other male phenotype is rejected. Here, we show that this form of social learning is dependent on serotonin and dopamine. Using a pharmacological approach, we reduced dopamine or serotonin synthesis in adult virgin females with 3-iodotyrosine (3-IY) and DL-para-chlorophenylalanine (PCPA), respectively, and then tested their mate-copying performance. We found that, while control females without drug treatment copied the choice of the demonstrator, drug-treated females with reduced dopamine or serotonin chose randomly. To ensure the specificity of the drugs, the direct precursors of the neurotransmitters, either the dopamine precursor L-3,4-dihydroxyphenylalanine (L-DOPA) or the serotonin precursor 5-L-hydroxytryptophan (5-HTP) were given together with the drug, (respectively 3-IY and PCPA) resulting in a full rescue of the mate-copying defects. This indicates that dopamine and serotonin are both required for mate-copying. These results give a first insight into the mechanistic pathway underlying this form of social learning in D. melanogaster.
Highlights
Many animal species from a vast array of taxa can learn from others, in the context of mate-choice (Avital and Jablonka, 2000; Danchin et al, 2004; Galef and Laland, 2005)
We compared the three groups and found a significant difference (GLMM, N = 241, X2 = 7.26, P = 0.027), which we found when comparing PCPA- or 3-IY-treated flies to the vehicle (Figure 1 and Supplementary Table S1)
We found that dopamine and serotonin are both required in learning during mate-copying
Summary
Many animal species from a vast array of taxa can learn from others (i.e., social learning), in the context of mate-choice (Avital and Jablonka, 2000; Danchin et al, 2004; Galef and Laland, 2005). Such observational learning can lead to mate-copying (Pruett-Jones, 1992), when females mate preferentially with a male showing similar characteristics as the male they saw being chosen by another female (trait-based copying, Bowers et al, 2012). Based on the fact that visual and olfactory learning share common neurotransmitters and neural structures (Vogt et al, 2014), we hypothesized that our model of observational social learning, mate-copying, involves the same two neurotransmitters. To ensure specificity of the drugs, we had two rescue treatments in which the female received the drug (3-IY or PCPA) together with the immediate precursor of the neurotransmitter (L-DOPA or 5-HTP, respectively), so that the level of dopamine or serotonin was less reduced than with 3-IY or PCPA alone
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