Meeting Abstract

LBS1.1  Thursday, Jan. 3  Pros and cons of electromyography in an integrative experimental context KONOW, Nicolai*; SANFORD, Christopher/PJ; Hofstra University nicolai.konow@hofstra.edu

Synchronising measurements of muscle activity and strain-generation, with external and internal kinematics may yield unparalleled insights into musculoskeletal function. In the case of serially-arranged, synergistic/antagonistic muscle-arrays, integrated approaches have distinct advantages over stand-alone EMG, given the uncertain relationship between muscle activity and contractile shortening. In the osteoglossomorph and salmonid tongue-bite apparatus (TBA), a convergently derived muscle-activity pattern (MAP) is linked with functional shifts from basal feeding behaviours into a novel raking behaviour. Synchronised EMG, high-speed video and sonomicrometry was used to test TBA biomechanical models in six taxa. Raking relies on sequential preparatory and power-stroke phase kinematics of the basihyal, suspended in a muscle sling between the mandible and pectoral girdle. Overlap of raking phase-specific MAPs only occurred in osteoglossomorphs, providing avenues for behavioural modulation, and a departure from basal shearing to a crushing power-stroke. Additional TBA functional complexity results from a novel cleithrobranchial ligament (CBL), capable of strain-transmission from the hypaxialis muscle. We investigated how inter-specific and inter-lineage raking MAP differences interplay with subtle changes in CBL morphology. Strong trends were detected, with basal taxa from both lineages showing pronounced MAP stereotypy, while crown-taxa had more complex MAPs. Both convergent and divergent basihyal raking kinematic patterns were identified among sequentially derived taxa within a lineage, and between the lineages. These results are discussed relative to the pros and cons of techniques utilised in quantifying them. Integrated studies of this type provide direct evidence of the relationships between evolutionary changes in biomechanics and MAPs and associated functional shifts.