Patterning of Mesenchyme - Secondary Mesenchyme

We can prevent SMCs from touching the animal pole region by sucking embryos into capillary tubes to elongate them along the animal-vegetal axis, as shown here. When this is done, the exploratory behavior of the SMCs continues for abnormally long periods of time. Eventually, in some cases the SMCs detach from the tip of the archenteron and those that migrate near the animal pole aggregate there (arrow). This provides further evidence that contact with this region results in the change of behavior of SMCs.