Blood system formation in the urochordate Ciona intestinalis requires the variable receptor vCRL1.

Sommer F, Awazu S, Anton-Erxleben F, Jiang D, Klimovich A V, Klimovich B V, Samoilovich M P, Satou Y, Krüss M, Gelhaus C, Kürn U, Bosch T C, Khalturin K (2012); Mol Biol Evol., 29(10): 3081-3093. doi: 10.1093/molbev/mss120