Meeting Abstract

21.3  Thursday, Jan. 3  Saccadic turns in walking and flying Stalk-eyed flies: The behavior and kinematics of turning a wide head. RIBAK, G.*; EGGE, A.R; SWALLOW, J.G.; Univ. of South Dakota gribak@usd.edu

While turning flies typically perform short bursts of body and head rotations (�saccades�) to orient the body with the new direction of motion. The saccades are believed to minimize the duration of eye rotation, a period when visual sensory input is impaired. The eyes of stalk-eyed flies (Diopsidae) are positioned at the end of rigid peduncles projecting laterally from the head. As a result of extreme sexual selection in some species, such as Cyrtodiopsis dalmanni, eye-stalks length, measured as the lateral distance between the eyes, can exceeds body length. The unique shape of the head in stalk-eyed flies makes them an interesting organism for the study of saccades and head kinematics during locomotion. We previously showed that flight trajectories in C. dalmanni suggest a low aerial turning rate in this species. Here we report the actual rotations of the body and head while performing turns during both walking and flying based on high speed video. Male and female flies performed similar rotations of the head and body despite a 1.46 fold difference in eye span (mean � sd of eye span in males: 8.23 � 0.414; females: 5.65 � 0.264 mm, n=20 per sex). While walking, C. dalmanni rotated the head faster than the rest of the body. The change in direction of the head in one smooth turn is limited by the freedom to yaw the head relative to the thorax. During aerial turns, the motion of the head is more synchronized with the rotation of the thorax allowing to rotate the head in one smooth turn. A possible explanation for the differences in head turning between walking and flying may involve the difference in body posture between walking and flying. Funded by NSF IOB 0448060