Meeting Abstract

76.4  Sunday, Jan. 6  An analysis of neuromuscular control in the pelvic fin of African lungfish (Protopterus annectens). AIELLO, B.A.*; KING, H.M.; HALE, M.E.; Univ. of Chicago; Univ. of Chicago; Univ. of Chicago braiello@uchicago.edu

African lungfish (Protopterus annectens) and tetrapods share fundamental features of their limbed locomotion. Previous study of pelvic fin kinematics emphasized the fish’s ability to produce rotational movements around the joint between the fin and the pelvis, as well as the ability to lift the body from the substrate, undeterred by the lack of a sacrum and digited limbs. Despite similarities in limb movement, which for sprawling tetrapods, can require nine muscles, the lungfish uses only two muscles that surround the femur and lateral pelvis. These muscles called the pelvic fin protractor and retractor muscle are separated by ventro-medial and dorso-medial running connective tissues. They originate on the medial margin of the pelvis and insert on the distal femur of the fin. The modest morphology of P. annectens is strikingly different from the muscles surrounding the pelvic girdle in terrestrial terapods, where they are often robust and span multiple joints. Here we examine the muscular control of lungfish pelvic fin movement via EMG and fin kinematics to explore specific functions of the protractor and retractor muscles. We hypothesized that these muscles are functionally subdivided and activate synergistically to generate the range of movements observed. EMG records indicate solitary activation of localized regions of both the retractor and the protractor as well as coordinated activation of regions within these muscles to produce a full range of pelvic fin rotation. Our data suggest that functional subdivision within these muscles is fundamental to pelvic fin rotation, which allows lungfish to produce limb coordination similar to those of tetrapods utilizing only two muscles.