All animals develop from a single-celled zygote into a complex multicellular organism through a series of precisely orchestrated processes^1,2. Despite the remarkable conservation of early embryogenesis across animals, the evolutionary origins of how and when this process first emerged remain elusive. Here, by combining time-resolved imaging and transcriptomic profiling, we show that single cells of the ichthyosporean Chromosphaera perkinsii—a close relative that diverged from animals about 1 billion years ago^3,4—undergo symmetry breaking and develop through cleavage divisions to produce a prolonged multicellular colony with distinct co-existing cell types. Our findings about the autonomous and palintomic developmental program of C. perkinsii hint that such multicellular development either is much older than previously thought or evolved convergently in ichthyosporeans.

所有动物都通过一系列精确编排的过程从单细胞受精卵发育成复杂的多细胞生物^1,2。尽管早期胚胎发生在动物中显着保存，但这个过程如何以及何时首次出现的进化起源仍然难以捉摸。在这里，通过结合时间分辨成像和转录组学分析，我们表明鱼孢子菌 Chromosphaera perkinsii 的单个细胞——大约 10 亿年前与动物分化的近亲^3,4——经历对称性破坏并通过切割分裂发育，产生具有不同共存细胞类型的延长多细胞集落。我们对 C. perkinsii 的自主和回文发育程序的发现表明，这种多细胞发育要么比以前认为的要古老得多，要么在鱼孢子虫中趋同进化。