Gabriel Willow N, McNuff Robert, Patel Sapna K, Gregory T Ryan, Jeck William R, Jones Corbin D, Goldstein Bob
Biology Department, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Dev Biol. 2007 Dec 15;312(2):545-59. doi: 10.1016/j.ydbio.2007.09.055. Epub 2007 Oct 6.
Studying development in diverse taxa can address a central issue in evolutionary biology: how morphological diversity arises through the evolution of developmental mechanisms. Two of the best-studied developmental model organisms, the arthropod Drosophila and the nematode Caenorhabditis elegans, have been found to belong to a single protostome superclade, the Ecdysozoa. This finding suggests that a closely related ecdysozoan phylum could serve as a valuable model for studying how developmental mechanisms evolve in ways that can produce diverse body plans. Tardigrades, also called water bears, make up a phylum of microscopic ecdysozoan animals. Tardigrades share many characteristics with C. elegans and Drosophila that could make them useful laboratory models, but long-term culturing of tardigrades historically has been a challenge, and there have been few studies of tardigrade development. Here, we show that the tardigrade Hypsibius dujardini can be cultured continuously for decades and can be cryopreserved. We report that H. dujardini has a compact genome, a little smaller than that of C. elegans or Drosophila, and that sequence evolution has occurred at a typical rate. H. dujardini has a short generation time, 13-14 days at room temperature. We have found that the embryos of H. dujardini have a stereotyped cleavage pattern with asymmetric cell divisions, nuclear migrations, and cell migrations occurring in reproducible patterns. We present a cell lineage of the early embryo and an embryonic staging series. We expect that these data can serve as a platform for using H. dujardini as a model for studying the evolution of developmental mechanisms.
形态多样性是如何通过发育机制的进化产生的。两种研究得最为透彻的发育模式生物，节肢动物果蝇和线虫秀丽隐杆线虫，已被发现属于一个单一的原口动物超类群，即蜕皮动物总门。这一发现表明，一个与之亲缘关系较近的蜕皮动物门可以作为一个有价值的模型，用于研究发育机制是如何以能够产生多样化身体结构的方式进化的。缓步动物，也被称为水熊虫，是一类微小的蜕皮动物门动物。缓步动物与秀丽隐杆线虫和果蝇有许多共同特征，这可能使它们成为有用的实验室模型，但长期培养缓步动物在历史上一直是一项挑战，并且对缓步动物发育的研究很少。在这里，我们表明，缓步动物杜氏高生熊虫可以连续培养数十年，并且可以进行冷冻保存。我们报告称，杜氏高生熊虫有一个紧凑的基因组，比秀丽隐杆线虫或果蝇的基因组略小，并且序列进化以典型的速率发生。杜氏高生熊虫的世代时间较短，在室温下为13 - 14天。我们发现，杜氏高生熊虫的胚胎具有一种定型的卵裂模式，伴随着不对称细胞分裂、核迁移和细胞迁移以可重复的模式发生。我们展示了早期胚胎的细胞谱系和一个胚胎分期系列。我们期望这些数据能够作为一个平台，用于将杜氏高生熊虫作为研究发育机制进化的模型。
