BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Talks.cam//talks.cam.ac.uk// X-WR-CALNAME:Talks.cam BEGIN:VEVENT SUMMARY:The evolutionary and embryonic origins of the gnathostome axial sk eleton - Kate Criswell (University of Cambridge) DTSTART:20170222T130000Z DTEND:20170222T140000Z UID:TALK70491@talks.cam.ac.uk CONTACT:Olivia Tidswell DESCRIPTION:The vertebral column is a defining feature of vertebrates\, bu t it varies widely in its components and tissue types. Ancestral character estimations indicate that there is substantial convergence in the evoluti on of the axial column complex. Specifically\, centra have originated inde pendently numerous times in different gnathostome groups\, and the develop mental processes contributing to centrum formation vary accordingly. There is evidence that teleost centra can form through secretions of bone matri x from the notochord\, while amniote centra develop exclusively from the s clerotome. To test which mode of development is general for jawed vertebra tes\, I studied embryonic development in a cartilaginous fish\, the little skate _(Leucoraja erinacea)_. MicroCT scans of a series of skate embryos show a continuous condensation of tissue around the notochord and neural t ube before the cells differentiate into cartilage and subdivide. Centra co nsist of three layers of tissue: an inner hyaline cartilage\, a middle are olar calcification\, and an outer hyaline cartilage. To investigate the em bryonic origin of skate centra\, I performed complementary somite and noto chord fate mapping experiments. I labeled the ventral somite and early not ochord progenitors with CM-DiI. DiI-labeled somite cells were subsequently identified both in all layers of the centrum\, as well as the arches. Not ochord progenitor cells gave rise to only the notochord and its epithelium . These results suggest that sclerotome ancestrally contributed to the dev elopment of all components of gnathostome vertebrae. LOCATION:Part II Lecture Theatre\, Department of Zoology END:VEVENT END:VCALENDAR