Meeting Abstract

34.6  Friday, Jan. 4  Dermal Bone Remodeling in the Cranial Lateral Line Canals of Zebrafish: The Role of Osteoclasts WEBB, Jacqueline F. *; MOORE, Margaret E.; University of Rhode Island; Villanova University jacqueline_webb@mail.uri.edu

The cranial lateral line canals of bony fishes are developmentally integrated into a subset of dermatocranial bones, and this integration is maintained as body size increases and the canals increase in diameter throughout life. We hypothesize that canal diameter increase occurs as the result of bone resorption by osteoclast activity on the inside surface of the canals and the addition of bone on the outside of the canal by osteoblasts. We examined osteoclast activity using a histochemical assay for tartrate-resistant acid phosphatase (TRAP) in the supraorbital, mandibular and infraorbital canals in 6 age classes (32-100 dpf) of zebrafish. Results show that osteoclasts are present in all three canals in all age classes indicating that bone remodeling starts soon after initial ossification, but that osteoclast number decreased in individuals > 81 dpf suggesting a slowing of the process of bone resorption in sexually mature individuals. The distribution of TRAP-positive osteoclasts and extracellular TRAP, occurs around the entire inner surface of the canals, with no consistent pattern among canals or among age classes. Osteoclasts and TRAP were found less often on the outer canal surface (only 10-28% of 3887 osteoclasts), but are also found at the edges of nerve foramina and canal pores, providing a mechanism to account for their ontogenetic increases in size. This work is the first to specifically analyze the pattern of osteoclast-mediated bone resorption in the lateral line canals of a bony fish, and as such it provides insights into the ways in which developmental integration of the lateral line canal system in the dermatocranium is maintained.