P34-6 Sat Jan 2 Role of visual stabilization in home vector memory during path integration in fiddler crabs, Uca pugilator Chatterji, R*; Layne, JE; University of Cincinnati, Department of Biological Sciences, Cincinnati, OH; University of Cincinnati, Department of Biological Sciences, Cincinnati, OH chattera@mail.uc.edu
Animal survival depends on the ability to orient and navigate in space while executing complex behaviors. One such spatial navigation mechanism is path integration, an innate process by which animals construct a memory of a location they have visited by encoding the distance and direction of their body movements, and summing them as vectors in an internal coordinate system to produce a single ‘home vector’. This home vector can be based in either a geocentric or an egocentric frame of reference. A geocentric reference seems intuitively clear, so here we asked, what is the egocentric reference? Where is, in animal spatial perception, front-and-center? Is it the longitudinal body axis? Fiddler crabs make an excellent model to study the nature of this spatial frame of reference, since they tend to align the transverse axis of the body with the direction of home, and so it has been proposed that their home vector is identical with the body axis. However, this cannot be strictly true since body axis is often not aligned with home. An alternative reference for the home vector, especially since it explicitly reflects the deviation of the body axis from home direction, is eye position. Optokinetic eye movements stabilize the eyes against body rotation. Thus, the hypothesis was that crabs remember the home direction as the body orientation plus the eye-body angle. To test this, the eye-body, eye-burrow, and body-burrow angles were analyzed in the presence and absence of visual structure in the surround. Since eyes were better stabilized in the presence of visual structure, the homing error was smaller compared to absence of visual stabilization, indicating the crabs’ home vector is a combination of the body orientation and eye-body angle.