PATEL, Nipam H.; University of California, Berkeley: The Evolution of Segmentation – Mechanisms of Terminal Addition

Pattern formation is particularly well understood in the model species, Drosophila melanogaster. Arthropods, however, display remarkably diverse modes of early embryogenesis and striking variations in morphology. I will present our efforts to examine early events of pattern formation in the amphipod crustacean, Parhyale hawaiensis, focusing on segmentation and the mechanisms of terminal growth. Three modes of terminal growth have been characterized in crustaceans: 1) growth through the orderly division of a defined set of ectoteloblasts 2) growth through the seemingly unorganized division of an unpatterned growth zone, and 3) growth through the orderly division of an unpatterned growth zone. I will present our recent work on the similarities and differences between these three modes of terminal addition at the morphological and molecular levels, and how they relate to what is seen in insects and other arthropods.