Conspicuous visual ornaments are frequently incorporated into complex courtship displays that integrate signal components from multiple sensory modalities. Mature male Schizocosa crassipes (Walckenaer, 1837) wolf spiders wave, arch, and tap their ornamented forelegs in a visual courtship display that simultaneously incorporates seismic components. To determine the importance of modality-specific signal components in female mate choice, we used a signal ablation design and compared the mating frequency of female-male pairs across signaling environments with manipulated modality-specific transmission properties. We found that the successful transmission of isolated visual or seismic signaling was sufficient for mating success; neither signaling modality was necessary. Additionally, the environment enabling the successful transmission of composite, multimodal displays yielded the highest mating frequencies. Our results indicate the presence of selection from S. crassipes females for multimodal courtship and suggest that multimodal signaling may facilitate mating across variable signaling environments. We next explored the influence of ornamentation per se on female choice by phenotypically manipulating males into two groups: (i) intact (brushes present) and (ii) shaved (brushes absent). We compared the mating frequencies of intact versus shaved males in the presence versus absence of seismic signaling. Males with brushes intact had higher mating frequencies than shaved males, but only under specific signaling conditions -in the presence of seismic signaling. Female choice for male brushes then appears dependent on the signaling background, making brushes themselves an unlikely target of direct selection. Our results emphasize the complex nature of female choice, highlighting the potential for both trait interactions and environment-dependent selection [Current Zoology 59 (2): 200-209, 2013].

The interplay between an animal’s environmental niche and its behavior can influence the evolutionary form and function of its sensory systems. While intraspecific variation in sensory systems has been documented across distant taxa, fewer studies have investigated how changes in behavior might relate to plasticity in sensory systems across developmental time. To investigate the relationships among behavior, peripheral sensory structures, and central processing regions in the brain, we take advantage of a dramatic within-species shift of behavior in a nocturnal, net-casting spider (Deinopis spinosa), where males cease visually-mediated foraging upon maturation. We compared eye diameters and brain region volumes across sex and life stage, the latter through micro-computed X-ray tomography. We show that mature males possess altered peripheral visual morphology when compared to their juvenile counterparts, as well as juvenile and mature females. Matching peripheral sensory structure modifications, we uncovered differences in relative investment in both lower-order and higher-order processing regions in the brain responsible for visual processing. Our study provides evidence for sensory system plasticity when individuals dramatically change behavior across life stages, uncovering new avenues of inquiry focusing on altered reliance of specific sensory information when entering a new behavioral niche.

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Animals that possess extreme sensory structures are predicted to have a related extreme behavioural function. This study focuses on one such extreme sensory structure-the posterior median eyes of the net-casting spider Deinopis spinosa. Although past research has implicated the importance of vision in the nocturnal foraging habits of Deinopis, no direct link between vision in the enlarged eyes and nocturnal foraging has yet been made. To directly test the hypothesis that the enlarged posterior median eyes facilitate visually based nocturnal prey capture, we conducted repeated-measures, visual occlusion trials in both natural and laboratory settings. Our results indicate that D. spinosa relies heavily on visual cues detected by the posterior median eyes to capture cursorial prey items. We suggest that the enlarged posterior median eyes benefit D. spinosa not only through increased diet breadth, but also by allowing spiders to remain active solely at night, thus evading predation by diurnal animals.