Octopamine levels relate to male mating tactic expression in the wolf spider Rabidosa punctulata

In the wolf spider Rabidosa punctulata, upon encountering a female, males use one of two distinct strategies: (1) they court the female in an attempt to elicit a mating, or (2) they engage in a direct-mount tactic that involves extensive grappling with the female until a mating is achieved. The latter tactic appears more sexually aggressive, and both tactics come with the risk of being cannibalized. We explored the physiological mechanisms underlying this behavioural variation by assessing the relationship between circulating levels of the biogenic amine octopamine (OA), a neuromodulator suggested to play a role in 'fight or flight' responses of arthropods and male mating tactic expression. We predicted, and found support for, a relationship between OA levels and tactic expression, with males adopting the direct-mount tactic expressing higher OA levels than courting males. Male mating tactic and mass also showed a significant interaction, with a negative trend in direct-mounting males and no relationship in courting males. Males had considerably higher levels of OA circulating in their haemolymph than females and female OA level increased with female mass. Our experimental design cannot disentangle cause from effect, but our results are consistent with the hypothesis that OA plays a role in regulating mating tactic expression in R. punctulata. (C) 2014 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd.