A central question in chordate evolution is the origin of sessility in adult ascidians, and whether the appendicularian complete free-living style represents a primitive or derived condition among tunicates¹. According to the ‘a new heart for a new head’ hypothesis, the evolution of the cardiopharyngeal gene regulatory network appears as a pivotal aspect to understand the evolution of the lifestyles of chordates^2,3,4. Here we show that appendicularians experienced massive ancestral losses of cardiopharyngeal genes and subfunctions, leading to the ‘deconstruction’ of two ancestral modules of the tunicate cardiopharyngeal gene regulatory network. In ascidians, these modules are related to early and late multipotency, which is involved in lineage cell-fate determination towards the first and second heart fields and siphon muscles. Our work shows that the deconstruction of the cardiopharyngeal gene regulatory network involved the regressive loss of the siphon muscle, supporting an evolutionary scenario in which ancestral tunicates had a sessile ascidian-like adult lifestyle. In agreement with this scenario, our findings also suggest that this deconstruction contributed to the acceleration of cardiogenesis and the redesign of the heart into an open-wide laminar structure in appendicularians as evolutionary adaptations during their transition to a complete pelagic free-living style upon the innovation of the food-filtering house⁵.

脊索动物进化的一个核心问题是成年海鞘无生命力的起源，以及附肢完全自由生活的方式是否代表被囊动物的原始或衍生条件¹。根据“新头换新心”假说，心咽基因调控网络的进化似乎是理解脊索动物生活方式进化的关键方面^2,3,4. 在这里，我们表明阑尾动物经历了心咽基因和亚功能的大量祖先损失，导致被囊动物心咽基因调控网络的两个祖先模块的“解构”。在海鞘中，这些模块与早期和晚期多能性有关，后者参与第一和第二心脏区域和虹吸肌的谱系细胞命运决定。我们的工作表明，心咽基因调控网络的解构涉及虹吸肌的退行性丧失，支持一种进化情景，在这种情景中，被囊类动物的祖先具有类似海鞘的无柄成年生活方式。同意这种情况，⁵ .