Sommer R J
Max-Planck Instutut für Entwicklungsbiologie, Abteilung Zellbiologie, Tübingen, Germany.
Development. 1997 Jan;124(1):243-51. doi: 10.1242/dev.124.1.243.
The origin of novelty is one of the least understood evolutionary phenomena. One approach to study evolutionary novelty comes from developmental biology. During developmental cell fate specification of the nematode Pristionchus pacificus (Diplogastridae), five cell fates can be distinguished within a group of twelve ventral epidermal cells. The differentiation pattern of individual cells includes programmed cell death, cell fusion and vulval differentiation after induction by the gonad. A cell lineage comparison among species of seven different genera of the Diplogastridae indicates that the differentiation pattern of ventral epidermal cells is highly conserved. Despite this morphological conservation, cell ablation experiments indicate many independent alterations of underlying mechanisms of cell fate specification. Cell fusion and individual cell competence change during evolution as well as the differentiation property in response to inductive signaling. These results suggest that developmental mechanisms, some of which are redundantly involved in vulval fate specification of the genetic model organism Caenorhabditis elegans, can evolve without concomitant morphological change.
新奇性的起源是最不为人所理解的进化现象之一。一种研究进化新奇性的方法来自发育生物学。在太平洋小杆线虫（双胃线虫科）的发育细胞命运特化过程中，在一组十二个腹侧表皮细胞中可以区分出五种细胞命运。单个细胞的分化模式包括程序性细胞死亡、细胞融合以及性腺诱导后的外阴分化。对双胃线虫科七个不同属的物种进行细胞谱系比较表明，腹侧表皮细胞的分化模式高度保守。尽管有这种形态学上的保守性，但细胞消融实验表明细胞命运特化的潜在机制发生了许多独立的改变。细胞融合和个体细胞能力在进化过程中发生变化，以及对诱导信号的分化特性也发生变化。这些结果表明，发育机制，其中一些在遗传模式生物秀丽隐杆线虫的外阴命运特化中冗余参与，可以在没有伴随形态变化的情况下进化。
