Meeting Abstract
The evolutionary reduction of brain and body size presents a major challenge for animals. At extremely small sizes, neurons become so small and so few in number that they risk losing proper functionality. As a result, tiny animals are expected to be constrained in their cognitive abilities, including memory. Because the central nervous system controls behavior, behavioral assays are useful tools for evaluating the quantity and quality of information an animal retains as well as how an animal uses information to make decisions. For example, when a web-building spider loses captured prey, it searches for the prey by tugging on silk threads while moving about its web until it either finds the prey or gives up. Spiders search longer for larger, more valuable prey, suggesting that prey evaluation and memory are involved in decisions made about searching behavior. In this study, I measured prey-searching behavior of long-bodied cellar spiders (Pholcus phalangioides) to test the hypothesis that miniaturization limits the duration and quality of memory. I gave prey of different sizes to large and tiny spiders, which I then induced to search by stealing the prey. I compared time and effort invested in searching across trials to determine the effects that brain size has on a spider’s ability to evaluate prey and to use memory to make foraging decisions. Search behavior of small spiders differed from that of large spiders in several ways, including the amount of time it took for them to begin searching and the rate at which they tugged while searching. Results from this experiment suggest that brain size imposes limitations on an animal’s ability to acquire, store and use information. I discuss these results within the context of brain size constraints on cognition, and I describe the future directions of this ongoing project.
