Current neuromuscular systems in vertebrates are the descendants of previously existing systems, modified to serve new functions. The ancestral condition and the details of modification are important aspects of their function. The goal of this project is to study the neuromuscular basis for functional shifts during the evolution of feeding behavior in frogs. This is an excellent model system because: 1) evolutionary relationships of frogs are well understood and the behavioral diversity among species is high; and 2) sensory processing associated with feeding behavior has been well studied in frogs, but motor output has received less attention. The experiments to be performed by Dr. Kiisa Nishikawa focus on seven species chosen to permit phylogenetic analysis of functional shifts in the feeding system. Musculoskeletal anatomy, innervation, organization of motor nuclei, and cytoarchitecture of motor neurons will be studied. Kinematic analysis will be used to study the sequence and duration of neuromuscular events. Muscle function will be studied using denervation experiments. In total, these experiments will identify evolutionary changes in the neuromuscular system during phylogeny, and elucidate their anatomical and physiological basis.
