Fig. 1. Anatomy of intrinsic caudal muscles, overlaid on a computer microtomography (µCT) scan of a bluegill sunfish tail. Arrows in the bottom diagram indicate the direction of movement of fin components caused by muscle contraction as determined from electrical stimulation experiments. FD, flexor dorsalis; FV flexor ventralis; HL, hypochordal longitudinalis; IC, infracarinalis; IR, interradialis, designated by fin ray position; SC, supracarinalis. The fin rays are numbered dorsal to ventral. Not depicted in this diagram are the lateralis superficialis (LS) and lateral muscle band of the axial myomeres, which lie superficially to the intrinsic caudal muscles pictured above.