Meeting Abstract
Sensory input from the limbs to the central nervous system provides important feedback during motor behaviors. Here we investigate the sensory structure of the larval pectoral fins, which have been shown to beat rhythmically and contribute to respiratory fluid flow during early post-hatching life stages. Sensory input from the larval zebrafish pectoral fins comes from two populations of neurons: hindbrain neurons (HBs) and spinal Rohon Beard neurons (RBs). HBs are believed to persist through ontogeny while RBs die off in later juvenile stages. Using islet2b transgenic lines, we found that an individual pectoral fin is innervated by three to five sensory HBs located in the caudal hindbrain. The extensive arborization of RB dendrites made single cell tracing difficult in transgenic lines, however the Gal4/UAS system allowed single cell labeling and precise 3D reconstructions of individual cells. In a sample of 21 fish with labeling of individual pectoral fin sensory neurons, only four cells were RBs. This information, in combination with broader imaging of the RB pool, suggests that between zero and two RBs innervate the fin at this stage of development. We analyzed a range of morphological parameters encompassing neuronal features from soma location to branching angles. There is high morphological variability among cells innervating the pectoral fins, regardless of soma location. Unexpectedly, all of the cells that innervate the pectoral fin had substantial innervation of the axial body wall as well, indicating that the CNS may not receive spatially precise sensory input from the pectoral fin. Future work will examine the possible chemosensory and mechanosensory functions of these neurons and investigate how this sensory innervation changes through ontogeny.
