LOCOMOTORY BEHAVIOR IN THE HAWKMOTH MANDUCA-SEXTA - KINEMATIC AND ELECTROMYOGRAPHIC ANALYSES OF THE THORACIC LEGS IN LARVAE AND ADULTS

During metamorphosis in Manduca sexta, muscles and most sensory struct ures of the thoracic legs undergo extensive changes while the motor ne urons that are present in the larva persist into the adult. The main g oal of this work was to identify similarities and dissimilarities in t horacic leg movements during crawling in larvae and walking in adults. This information provides a foundation for understanding the extent t o which centrally located neural elements are reorganized during metam orphosis to accommodate changes in locomotion, Analysis of electromyog raphic activity from leg muscles synchronized with video-taped recordi ngs of the leg movements during larval crawling and adult walking reve aled differences in cycle periods as well as intersegmental and intras egmental patterns of coordination. Larval crawling was characterized b y synchronous movements of segmental pairs of legs as activity proceed ed slowly from the more posterior to the more anterior segments. Durin g crawling, antagonistic muscles maintained a strict reciprocity. In c ontrast, walking in adults was characterized by fast, alternating move ments of the left and right prothoracic legs and more variable coordin ation patterns in the mesothoracic and metathoracic legs (ranging from synchrony to alternation), In adults, sensory information, possibly a ssociated with the weight-bearing or postural demands of walking on an incline, contributed to a strong dependence between the duration of m uscle activity and cycle period and to the extent that the muscle acti vity overlapped during walking.