Chromosome number within the class Ascidiacea

Abstract

Additional evidence has been obtained that demonstrates the low capacity of ascidians to polyploidize. The evolution of ascidians appears to have been accompanied by a decrease of chromosome number within the Phlebobranchiata, and by both a decrease and increase of chromosome number in the other two suborders, Aplousobranchiata and Stolidobranchiata. There are indications that the basic chromosome number, 2n=32, of Stolidobranchiata is of very early origin within the class Ascidiacea.