Fig. 4
From: Cilia are required for asymmetric nodal induction in the sea urchin embryo
The ciliated Left-Right Organizer: a synapomorphy of the deuterostomes. a–c Schematic drawings of sea urchin (a), amphioxus (b) and Xenopus (c) gastrula/neurula stage embryos (anterior to the left). In all cases the archenteron harbors cells of mesodermal fate (SM, red), which in frog and sea urchin are ciliated and function as LROs. The position of mesodermal LROs is indicated by an arrowhead. d nodal is evolutionary conserved among metazoans except for the ecdysozoa. Deuterostomes share a ciliated LRO as a common synapomorphy. Drawings adapted in parts from Blum et al. 2014 [3]