Morphology of control and MyBPC morphants. (A–D) Microscopy of 4-dpf control-injected (A) larva and larvae injected with splicing blocking MOs for mybpc-1 (B), mybpc-2a (C), and mybpc-2b (D). (E and F) Confocal microscopy of preparations fixed at optimal length for active force development and stained for F-actin (rhodamine phalloidin) from a control and an MyBPC-2B morphant, respectively. Bars: (A–D) 1.0 mm; (E and F) 20 µm. (G) The relative distribution of sarcomere length at optimal length determined in four fixed preparations from each group (controls: open bars, mybpc-2b morphants: black bars). Measurements were grouped and plotted against sarcomere length.