ARTHROPOD EVOLUTION - GREAT BRAINS, BEAUTIFUL BODIES

While arthropod phytogeny remains controversial, comparative studies o f the genetic control of segmentation and of the nervous system have b egun to throw light on how mandibulate arthropods (myriapods, crustace ans and insects) reached their current level of morphological and beha vioural complexity. Insects and crustaceans show remarkable similariti es in the construction of their brains, suggesting that their common a ncestor had typically arthropod behaviour, while developmental genetic studies are consistent with this ancestor having had distinct head, t runk and tail regions. This conclusion contrasts with the influential view, drawn from comparative embryology and functional anatomy, that i nsects and crustaceans evolved independently from a simple worm-like o rganism, perhaps resembling an annelid.