Meeting Abstract
94.1 Sunday, Jan. 6 Lateral Line Morphogenesis in Chondrichthyan vs. Osteichthyan Fishes: New Perspectives on an Old Problem WEBB, JF*; GILLIS, JA; University of Rhode Island and MBL, Woods Hole; Dalhousie University and MBL, Woods Hole jacqueline_webb@mail.uri.edu
The morphology of the lateral line system (LL) differs significantly in chondrichthyan and osteichthyan fishes, so we hypothesized that the pattern of its development would also be distinct in these two gnathostome lineages. We have shown that in the little skate (Leucoraja erinacea), migration/elongation of LL placode-derived primordia, differentiation of neuromasts, and morphogenesis of LL canals are not discrete, sequential processes as in bony fishes. SEM revealed that the surface of the shallow grooves that define the paths of the migrating/elongating LL primordia on the head and trunk is characterized by small epithelial cells with dense apical microvilli. We used CM-DiI to trace the fate of LL placode-derived cells (from the anterodorsal and posterior placodes) to clarify the relationship between the LL primordium, microvillous epithelial cells, and the unique longitudinal pocket associated with LL development on the trunk (Johnson, 1917). DiI+ placode-derived cells were found below the microvillous epithelial cells found in the cranial grooves and rostral to the entrance to the pocket and below the epithelial cells that line the pocket on the trunk. Gillis et al. (2012) had shown that LL placode-derived cells contribute to neuromasts and canal walls in older embryos. Thus, we hypothesize that placode-derived cells found below the epithelium subsequently intercalate among the microvillous cells and differentiate into the hair cells of the canal neuromasts and the cells of the walls of the lateral line canals. An on-going analysis with finer temporal resolution will allow an accurate description of the processes of neuromast differentiation and canal morphogenesis in chondrichthyan fishes. Supported by URI (JFW) and a Allen/Bang/Colwin Summer Research Fellowship from the MBL, Woods Hole (JAG).
