Discussion Draft

The lateral motion data suggests that mako sharks are kinematically closer to tuna than other sharks. As supported by sonomicrometry recordings, during active swimming mako sharks detach their red muscles from the neighbouring tissues and focus their motion towards the posterior region of their body. Such mechanism has been found to be reciprocal in tunas, which recruit their deep red muscles in a similar fashion to power their caudal region. Nonetheless, mako sharks rely on their hypaxial lateral tendon for producing such movement, while in tuna the tendons that perform this task are found in the horizontal septum. Thus the researchers conclude that the locomotion systems of lamnid sharks and tunas arose independently by convergent evolution.