Topic: chicken embryo

Vertebrate embryos form repeated body-axis segments, yet the segmentation-clock period does not always match the timing of somite formation. Real-time clock imaging combined with pharmacological and surgical perturbations identifies two timers: a clock that establishes an initial commitment and a subsequent self-organizing hourglass process. Hourglass duration scales with somite size and depends on cytoskeletal regulation. Changing this timer can turn regular zebrafish segmentation into irregular patterns resembling the anterior chicken embryo and alter the number of predetermined compartments