Meeting Abstract

P2.81  Jan. 5  Motor Control of the Zebrafish Pectoral Fin THORSEN, DH*; GREEN, MH; HALE, ME; Univ. of Chicago; Univ. of Chicago; Univ. of Chicago mhale@uchicago.edu

Limb movement has been a major focus of work in motor control. We describe innervation of the pectoral fin of the zebrafish (Danio rerio) through development from larval to adult stages. We used immunocytological and gross histological techniques with confocal microscopy to label and characterize fin innervation. We also retrograde labeled and characterized the motor neuron populations servicing the pectoral fin. At 5 days post fertilization, the first four spinal nerves innervate the pectoral fin musculature that is composed of two fan-shaped muscles, each one muscle fiber thick. The first three spinal nerves enter the fin from the dorsal fin base and service the dorsal and middle fin regions. The fourth spinal nerve enters the fin from the ventral fin base and innervates the ventral region. Within the larval spinal cord we found no mediolateral spatial segregation between adductor and abductor cell bodies suggesting that motoneuron pools are not organized into spatially distinct half-centers. As the skeleton and muscles expand and differentiate through post-larval development, there are major changes in fin innervation including extensive elaboration to the developing muscles and concentration of innervation to specific nerves and fin regions. The pattern of larval fin innervation recorded is associated with later muscle subdivision suggesting that fin muscles may be functionally subdivided before they are morphologically subdivided. Changes in fin innervation were correlated with changes in fin propulsion in which pectoral fins serve as propulsors in juveniles and in an accessory maneuvering role in adults. Funded by NIH NS043977 to MEH and NSF graduate research fellowship to DHT.