Ascidian larva reveals ancient origin of vertebrate-skeletal-muscle troponin I characteristics in chordate locomotory muscle.

Ascidians are protochordates related to vertebrate ancestors. The ascidian larval tail, with its notochord, dorsal nerve cord, and flanking rows of sarcomeric muscle cells, exhibits the basic chordate body plan. Molecular characterization of ascidian larval tail muscle may provide insight into molecular aspects of vertebrate skeletal muscle evolution.