Meeting Abstract

57.3  Tuesday, Jan. 5  Structural Organization and Ontogeny of the Lateral Line System in Embryos of the Little Skate, Leucoraja erinacea HACISKI, S. Insley*; WEBB, Jacqueline F.; University of Rhode Island; University of Rhode Island haciski@mail.uri.edu

The mechanosensory lateral line system of elasmobranchiomorph and osteichthyan fishes differs with respect to certain aspects of the canal morphology and distribution. In batoids (skates and rays), the lateral line system is composed of a set of canals similar to those in sharks, but includes additional canals (with uncertain homologies) that extend onto their laterally expanded, wing-like pectoral fins. We took advantage of the availability of eggs/embryos of the little skate, Leucoraja erinacea, to analyze the structural organization of its lateral line system as a representative batoid and elasmobranchiomorph. We mapped canal distribution on the dorsal and ventral surfaces of the body, canal diameter, tubule length and diameter, and the size and distribution of the canal neuromasts in embryos (37-80 mm total length [TL]) using histological analysis and vital fluorescent staining. Preliminary data indicate that the lateral line canals on the head and pectoral fins start forming in embryos less than 50 mm TL, as the pectoral fins are fusing to the head. The tubular lateral line canals (~50-75 µm diameter in a 65 mm TL specimen) have epithelial walls, sit in soft tissue (not cartilage), and are connected to the environment via tubules (~30-35 µm diameter in a 65 mm TL specimen) with terminal pores. Vital fluorescent staining clearly shows that multiple canal neuromasts sit between adjacent tubules and that their size and distribution are unlike that which has been described previously in elasmobranchiomorphs. Further analysis will determine the timing and pattern of canal morphogenesis, which we hypothesized will be distinct from that observed in osteichthyan fishes.