Pheromones induce visuomotor arousal in jumping spiders
Perception in one sensory modality can be influenced by stimulation in another modality. Such cross-modal effects may arise from multiple underlying processes. For example, animals may be primed by exposure to a cue in one sensory modality and attend to congruent cues in a separate modality. In contrast, input from one sensory modality may result in a general increase in arousal, which in turn influences behavior. Jumping spiders (Salticidae) are famously visual animals but they also respond to pheromones. Here, we test whether pheromones influence visual attention in Phidippus jumping spiders and, if so, whether we see evidence of priming to relevant stimuli or simply an increase in arousal. In Experiment 1, male spiders exposed to female pheromones increased their movements in an arena, a sign of physiological arousal associated with mate searching, whereas females decreased their movements in response to male pheromones. In Experiment 2, freely moving male spiders exposed to female pheromones were more likely to detect and court an image of a female. In Experiment 3, male spiders were shown a series of images of conspecifics, crickets, and abstract shapes as we visualized the gaze direction of their principal eyes using a specialized eyetracker. When pheromones were present, retinal movement markedly increased, but this effect did not differ by stimulus category. Spiders showed greater retinal movement during presentations of crickets and front-facing female conspecifics than during presentations of side-view male conspecifics, regardless of pheromone exposure. In Experiment 4, spiders were shown an array of stimuli, but spiders did not preferentially look at a conspecific stimulus with pheromone exposure. In a second iteration of Experiment 4 with male spiders tested in both control and pheromone conditions, however, pheromone-exposed males looked longer at a front-facing female than at an abstract shape. In Experiment 5, spiders were presented with a salient image of a conspecific of the opposite sex. With pheromone exposure, males were more likely to divert their gaze away from the initial stimulus to an oval distractor, while females were less likely to divert their gaze than controls, mirroring sex-specific shifts in activity from Experiment 1. Increased male movement may enhance encounters, whereas reduced female movement may facilitate being found and evaluating male displays. While we found only limited evidence that spiders were primed to direct their attention toward congruent stimuli, our results show pheromones influence vision, specifically by affecting the spiders' propensity to move their bodies and eyes.