[icehog3]

Originally Posted by forgop

Anatomy lecture on the axial musculature system. Good stuff.

I found it most interesting that axial muscles used for oscillatory swimming are found not only in fish and other vertebrates but also in some protochordates and invertebrates. Chaetognaths have unsegmented locomotor musculature with some unusual features, but larvacean tunicates and the tadpole larvae of ascidians show the simplest variant of the chordate segmented axial muscle arrangement for flexing a notochordal column, where all muscle cells along one side are electrically coupled. With amphioxus, the basic fish myotomal layout is established, with two main fibre types probably used for different patterns of swimming (as in fish).