Berná L, D'Onofrio G, Alvarez-Valin F.

Mol Phylogenet Evol. 2012 Feb;62(2):708-17. doi:10.1016/j.ympev.2011.11.013

Peculiar patterns of amino acid substitution and conservation in the fast evolving tunicate Oikopleura dioica.

Faster evolution for regulatory genes. High and even mutation rates for every aminoacid suggest a relaxation of functional constraints. This is particularly surpising for cystein, which is highly conserved in other fast-evolving species such as Ciona. The frequency of C is reduced of 10% compared with Ciona.