Collaborative Research: Segment development in select trilobite species - glimpses into the evolution of body organization in an early arthropod clade

合作研究：部分三叶虫物种的体节发育“瞥见了早期节肢动物分支中身体组织的进化。Hughes，U.加州滨江，邮编0616574 H。大卫席，卡尼修斯学院，剑桥-0616726摘要最近在发育遗传学和细胞生物学的进展是革命性的理解的发展基础上的动物形式。身体部分，模块，节肢动物的身体构造，指定和分化的机制，成为已知的冠组Euarthropoda，其中包含所有活的节肢动物群体的成员。已灭绝的三叶虫分支也属于真节肢动物，但就其身体模式的控制而言，与祖先的真节肢动物状态没有明显的区别。因此，保存完好的记录三叶虫的个体发育和发育记录在早古生代岩石承担特殊意义的早期真节肢动物实验中的身体图案的编年史。志留纪Aulacopleurakonincki三叶虫Aulacopleurakonincki已被证明是一个特殊的模式系统，探索三叶虫如何控制分配给躯干区域的节数，以及控制它们将躯干节分配给胸部或臀板（由相连的节组成的终末盾）。Aulacopleura konincki显示不寻常的变化，在成熟的，节不变的生长阶段的胸段的数量。 PI Hughes先前的工作已经测试了关于控制成熟体节数量的假设，结果支持早期决定假说（EDH），其中体节的最终数量在个体发育早期就被确定。这表明早期节肢动物的发育控制受到高度调节，即使是那些在身体构造方面明显具有可塑性的节肢动物。然而，确定一个4.35亿年前的物种的发育控制是一个严峻的挑战。该项目将探索骨片形状变化的个体发育轨迹，以提供EDH的额外测试，主要基于独立于躯干分割的头部（头部）区域的形状变化模式。还将通过地球化学代用方法探讨分段变化的古环境背景。该项目将涉及研究生培训和与捷克共和国、意大利和加拿大科学家的广泛合作，并将涉及开发新的统计软件，免费提供给科学界。

Collaborative Research: Segment development in select trilobite species"glimpses into the evolution of body organization in an early arthropod cladeNigel C. Hughes, U. California Riverside, EAR-0616574H. David Sheets, Canisius College, EAR-0616726ABSTRACTRecent advances in development genetics and cell biology are revolutionizing understanding of the developmental basis of animal form. The mechanisms by which body segments, the modules from which arthropod bodies are constructed, are specified and differentiated are becoming known across members of the crown group Euarthropoda, which contains all living arthropod groups. The extinct clade Trilobita also belonged to the Euarthropoda but with respect to the control of its body patterning did not depart markedly from what was apparently the ancestral euarthropod condition. Hence the exceptionally well-preserved record of trilobite ontogeny and phylogeny recorded in early Paleozoic rocks assumes special significance as a chronicle of early euarthropod experiments in body patterning. The Silurian aulacopleurid trilobite Aulacopleura konincki has proved to be an exceptional model system for exploring how trilobites controlled the number of segments assigned to the trunk region and the controls on their allocation of trunk segments to the thorax or to the pygidium - the terminal shield consisting of conjoined segments. Aulacopleura konincki shows unusual variation in the number of thoracic segments during the mature, segment-invariant growth phase. Previous work by the PI Hughes has tested hypotheses concerning control of the mature segment number, with results favoring the Early Determination Hypothesis (EDH), in which the ultimate number of segments was determined early in ontogeny. This suggests highly regulated developmental control among early arthropods, even those apparently plastic in aspects of body construction. However, determining the controls of development in a species 435 million years old presents a severe challenge. This project will explore ontogenetic trajectories of sclerite shape change to provide additional tests of the EDH, based primarily on the pattern of shape change in the cephalic (head) region that is independent of trunk segmentation. The paleoenvironmental context of changes in segmentation will also be explored through a geochemical proxy approach. The project will involve graduate student training and extensive collaboration with scientists in the Czech Republic, Italy, and Canada, and will involve the development of new statistical software that will be made freely available to the scientific community.