Gastrulation - Laser Ablation of Secondary Mesenchyme

A direct test to determine whether secondary mesenchyme cells are actually needed for archenteron elongation involves killing them using a laser microbeam. Hardin (1988) performed this experiment, and found that the archenteron can elongate to 2/3 of its normal, final length in the absence of functional SMC filopodia. This shows that the archenteron can elongate on its own, but that it requires intact SMCs for complete elongation This result can be quantified, by correlating the rate of migration with the number of intact SMCs, as shown in the graph below (from Hardin, 1988).

This graph shows that there is a quantitative relationship between rate of extension in late gastrulae and the number of intact SMCs.