Thereby, gastrulation in the conservatively evolving protostome P. caudatus follows strictly a deuterostomic pattern. We show that the blastopore gives rise to the anus at the vegetal pole and that the hindgut markers brachyury and caudal are expressed in the blastopore and anus, whereas the foregut markers foxA and goosecoid are expressed in the mouth in the animal hemisphere. The blastopore is the first opening of the digestive cavity that is formed during the gastrulation stage of embryonic development, as shown in Figure below. Here, we characterize gastrulation and the embryonic expression of genes involved in bilaterian foregut and hindgut patterning in Priapulus caudatus. During maturation of some animals it evolves into the anus or the mouth in others it is covered over and contributes to the canal joining the primitive gut. What does the blastopore become in echinoderms In deuterostomes, the blastopore becomes the anus, and another opening generated later in development produces the mouth. Priapulids have a conservative morphology, an abundant Cambrian fossil record, and a phylogenetic position that make them a key group in understanding protostome evolution. The blastopore fate of the bilaterian ancestor plays a crucial role in understanding the transition from radial to bilateral symmetric organisms. This variability, combined with an absence of information from key taxa, hampers the reconstruction of the ancestral developmental mode of the Protostomia and the Bilateria.
In deuterostomes, the blastopore forms the anus, but its fate in protostome groups is variable. The fate of the blastopore during development in the bilaterian ancestor is currently not well understood.
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