Strong expression is first observed in prechordal plate at the stage of 50% epiboly, l the stained cells then migrate to the proctodeum. 整胚原位杂交结果显示该基因最早主要在50%25外包期的前脊索盘中表达，既而迁移到原肛处。
In the course of development, the invagination of stomodeum occurs earlier than that of proctodeum at the third and the sixth nauplius stages respectively. 在发育过程中,口凹是在第三期无节幼虫时内陷形成,而原肛是在第六期无节幼虫时内陷形成的,所以口凹的发生早于原肛的发生。
