Neurophylogeny: Architecture of the nervous system and a fresh view on arthropod phyologeny

The phylogenetic relationships within the Arthropoda have beencontroversial for more than a century. Today, comparative studieson the structure and development of the nervous system contributeimportant arguments to this discussion, so that the term "neurophylogeny"was coined for this discipline. The large number of recent studieson the nervous system in various nonmodel arthropods indicatesthat we are far advanced in the process of analyzing the cellulararchitecture of the arthropod nervous system in a depth thatwill ultimately provide characters at a level of resolutionequal or even superior to that of characters traditionally usedin morphological phylogenetic studies. This article sets outto summarize the current state of the discussion on arthropodphylogeny and briefly evaluates the morphological charactersthat have been used as arguments in favor of the traditionalTracheata hypothesis. Then, a thorough overview is given ofcharacters derived from structure and development of the arthropodbrain and the ventral nerve cord from the cellular level tothe level of larger neuropil systems. These characters supportthe new Tetraconata hypothesis suggested by Dohle and provideevidence for a clade that unites malacostracan and remipedecrustaceans with the Hexapoda.