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Session Schedule & Abstracts

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Friday 1st July, 2016

Plenary Session 3: Zerina Johanson

Room: Salon D–E   8:15 am–9:30 am

Moderator(s): A. P. Summers
PLN3-1  8:15 am  Developmental origin of the synarcual in jawed vertebrates: implications for vertebral development and fusion . Johanson Z*, Natural History Museum; Boisvert CA, Curtin University; Trinajstic K, Curtin University
Abstract: The vertebrate axial skeleton is composed of vertebrae developing antero-posteriorly, comprising dorsal, central, and ventral elements in various combinations. Dorsal and ventral vertebral elements occur in jawless vertebrates (e.g., lamprey, hagfish), although axial skeleton fusion appears restricted to jawed vertebrates. This fusion can occur normally during development, or abnormally, as in certain human disorders, or due to external factors like high temperatures or stress. Examples of fusion during regular development include the tetrapod sacrum, the synsacrum in birds, and the fusion of the anterior vertebral column known as the synarcual. The synarcual forms immediately posterior to the cranium and occurs convergently in jawed vertebrates like fossil placoderms and chondrichthyans. Comparable fusion in the neck region in human disorders can be due to failure of somites to segment properly during development (Klippel-Feil syndrome) or to transformation of tissues between the vertebrae into cartilage and bone (FOP), the latter also characterizing vertebral fusion in farmed fishes (salmon). Here, vertebral fusion has important implications for human health and food production, but cannot be examined experimentally (humans) or results from often variable and non-standardized conditions (farmed salmon). In the chondrichthyan Callorhinchus, the synarcual forms consistently in normal development. Regular vertebral segmentation occurs, with subsequent fusion into the synarcual. Vertebrae directly behind the synarcual continue to be incorporated through growth. This appears to be a common pattern, occurring in three major groups of early jawed vertebrates; fusion involves transformation of intervertebral tissues into cartilage and bone/mineralised cartilage. We suggest chondrichthyans have potential as ideal extant models to better understand fundamentals of vertebral fusion for application to abnormal fusion in humans and important food animals such as the salmon.

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