Kinetics of proliferation and differentiation of an EYFP-marked mnc cluster. Time-lapse series taken from full-somite, three-channel confocal stacks of a single Musclebow2 marked fish after heat-shock at 24 hpf. (A) Full somite stack mip of tile scan of somites 9-18 showing five clusters of EYFP-marked mncs (brackets) at 3 dpf. Note the large areas lacking marked mncs and the more numerous marked fibres in anterior somites. (B) Time-lapse confocal mips showing development of the mnc cluster in somite 14 of panel A. Boxes shown magnified at right. Note the early presence and later absence of EYFP-marked mncs on the vertical myoseptum (arrows), the increase in numbers of marked mncs, nascent fibres (blue arrowheads) and large fibres (white arrowheads) in the body of the myotome and the lack of increase in marked fibres in the adjacent region of somite 15 that also lacked marked mncs (asterisks). Scale bars: 50 µm.