The Development of Arthropod Segmentation Across the Embryonic/Post-embryonic Divide – An Evolutionary Perspective

In many arthropods, the appearance of new segments and their differentiation are not completed by end embryogenesis but continue, in different form degree, well after hatching, some cases up to last post-embryonic molt. Focusing on segmentation process currently described as segment addition (or, anamorphosis), we revise here current knowledge discuss it an evolutionary framework which involves data from fossils, comparative morphology extant taxa gene expression. We advise that for a better understanding developmental changes underlying evolution arthropod segmentation, key concepts should be applied critical way. These include notion body block idea hatching represents well-defined divide, shared all between two contrasting phases, embryonic vs. post-embryonic. This eventually reveals complexity processes occurring across can evolve directions with pace, creating observed vagueness embryonic/post-embryonic divide.