In animals at least as complex as an earthworm, the embryo forms a dent on one side, the blastopore, which deepens to become the archenteron, the first phase in the growth of the gut. In deuterostomes, the original dent becomes the anus while the gut eventually tunnels through to make another opening, which forms the mouth. The protostomes were so named because it used to be thought that in their embryos the dent formed the mouth while the anus was formed later, at the opening made by the other end of the gut. More recent research, however, shows that in protostomes the edges of the dent close up in the middle, leaving openings at the ends which become the mouth and anus.
There are other significant differences between the protostome and deuterostome patterns of development:
Current molecular data suggest that protostome animals can be divided into three major groups:
as well as a number of minor taxa of basal or ambiguous affinity.
The evolution of protostome GATA factors: Molecular phylogenetics, synteny, and intron/ exon structure reveal orthologous relationships.(Research article)
Apr 15, 2008; Authors: William Q Gillis ; Bruce A Bowerman ; Stephan Q Schneider (corresponding author) BackgroundGATA transcription...