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Sensory Ecology of the Net-Casting Spider, Deinopis spinosa
Sensory systems are both highly beneficial and highly costly. The balance between these benefits and costs is what shapes the sensory systems of animals. A better understanding of how sensory systems evolve can illustrate how the environment might shape animal behavior, morphology, and ecology. This dissertation examines the sensory ecology of a nocturnal, visual specialist predator, the net-casting spider, Deinopis spinosa. An integrative approach, I provide insight into the benefits of specific sensory systems in foraging and mating contexts, as well as potential constraints for sensory system development in D. spinosa. First, I used field and laboratory visual occlusion trials to decipher potential benefits of possessing the enlarged posterior median eyes (PMEs) of D. spinosa. I found that spiders without PME vision seemed unable to capture cursorial prey items walking beneath their web. These prey items tended to be larger than prey captured from the air. Thus, PME vision benefits D. spinosa specifically in the ability to capture cursorial prey items that might be of greater nutritional quality. Second, I investigated potential plasticity of peripheral (e.g. eyes) and central ( e.g. brain) structures related to vision. I compared absolute and relative eye diameters of principal and secondary eyes in D. spinosa and found that mature males had smaller secondary eyes, but larger principal eyes when compared to penultimate males. Relative investment in central brain structures mirrored peripheral investment. Such adaptations likely enhance mate-searching efforts, as well as longevity. Lastly, I investigated the role of olfaction in male mate-searching behavior. I found that mature males were sensitive to airborne cues given by mature females, and preferred to associate with female odor over conspecific penultimate males’ odor, and thus likely use airborne cues in mate-searching. Taken together, I utilized field and laboratory based behavioral assays in conjunction with quantifications of external and internal sensory morphology to gain a better understanding of sensory system benefits and constraints within an enigmatic, sensory specialist, the net-casting spider. Future studies within this family of spiders have great potential for further elucidating how sensory systems are shaped through time.
Evolution and Development
Stafstrom, Jay A, "Sensory Ecology of the Net-Casting Spider, Deinopis spinosa" (2017). ETD collection for University of Nebraska - Lincoln. AAI10272487.