Alteration of size perception: serotonin has opposite effects on the aggressiveness of crayfish confronting either a smaller or a larger rival

Julien Bacqué-Cazenave (1) , Daniel Cattaert (2) , Jean Paul Delbecque , Pascal Fossat (3)

1 INCIA - Institut de Neurosciences cognitives et intégratives d'Aquitaine
2 LNR - Laboratoire de neurobiologie des réseaux
3 LTDS - Laboratoire de Tribologie et Dynamique des Systèmes

We injected serotonin (5-HT) into adult male crayfish before pairing them with size-matched non-injected competitors, and observed dyadic agonistic interactions. Paradoxically, 5-HT elicited opposite behavioral responses if the injected animal was opposed by a smaller or larger rival: the level of aggressiveness of the injected crayfish was higher when facing a larger rival but lower when facing a smaller rival. Our results indicate that the effects of 5-HT on aggressiveness are dependent on the perception of the relative size difference of the opponent. In both cases, however, 5-HT significantly delayed the decision to retreat. We conclude that 5-HT does not primarily act on aggressiveness but rather on the brain centers that integrate risk assessment and/or decision making, which then modulate the aggressive response. Our findings support a reinterpretation of the role of 5-HT in crustacean agonistic behavior that may be of interest for studies of other animals.

Mots clés: Aggression; Agonistic context; Opponent perception; 5-HT

Domaines: Psychologie et comportements

Julien Bacqué-Cazenave, Daniel Cattaert, Jean Paul Delbecque, Pascal Fossat. Alteration of size perception: serotonin has opposite effects on the aggressiveness of crayfish confronting either a smaller or a larger rival. Journal of Experimental Biology, 2018, 221 (12), pp.jeb177840. ⟨10.1242/jeb.177840⟩. ⟨hal-02333018⟩