Two cholinesterase activities and genes are present in amphioxus.
Sutherland D, McClellan JS, Milner D, Soong W, Axon N, Sanders M, Hester A, Kao YH, Poczatek T, Routt S, Pezzementi L. Two cholinesterase activities and genes are present in amphioxus. J Exp Zool. 1997 Feb 15; 277(3):213-29.