E-Prints Complutense

Abstract

Proper orientation is one of the most important skills in the repertoire of an organism. Many different strategies are used in the animal kingdom to fi nd resources like food, nesting sites, a comfortable environment, or mating partners. Optimizing the ability of fi nding places of interest surely has a great impact on the fi tness of the organism. A way to optimize orientation is analyzed here, shown representatively in visual object approach and in temperature gradient orientation of fruit fl ies. This orientation strategy is called “memotaxis”. It benefi ts from the integration of past events, leading to a robust path towards the desired goal. Although memotaxis is perfectly suited for noisy environments, its existence is conveniently proven in situations with low noise. In landmark approach experiments, fruit fl ies show that the longer they approach a particular target, the longer it takes for them to abandon it after its disappearance. This holds true even in the presence of a distracting landmark that comes on only after disappearance of the fi rst-visited target. The strategy was found again in temperature orientation, in which fl ies are over-running a temperature optimum: distances travelled after crossing the optimum scale with the distances walked towards the optimum. Memotaxis is assumed to exist in many animals, but the genetic tools available in Drosophila melanogaster allow localizing the relevant brain centers and pathways. Memotaxis as an orientation strategy proves useful also for autonomously roving robots.