Electromyography of the buccal musculature of octopus (Octopus bimaculoides): a test of the function of the muscle articulation in support and movement

SUMMARY The buccal mass musculature of the octopus (Octopus bimaculoides) was studied with electromyography to test the predictions of a previous morphological study in which we suggested that the muscles of the buccal mass serve as both the effectors of movement and as the joint itself, forming a new category of flexible joint termed a `muscle articulation9. The predictions of muscle function were tested by correlating muscle electrical activity in isolated buccal masses with spontaneous beak movements. Bipolar electromyography electrodes were implanted in the various beak muscles and beak position was recorded simultaneously with an electronic movement monitor (N=14). The results are consistent with the hypothesis that the lateral mandibular muscles produce opening movements of the beaks and provide the first definitive explanation of the opening mechanism. The results are also consistent with the hypothesis that the superior mandibular muscle functions primarily in closing. Co-contraction of the lateral mandibular muscles and the superior mandibular muscles was also observed, suggesting that these muscles may also stabilize the beaks during movement or provide a means of controlling the location of the pivot between the beaks. This study provides an important first test of the predictions of the role of the complex musculature found in muscle articulations such as the cephalopod buccal mass

Modeling How Shoreline Shape Affects Tides and How Underwater Structures Attenuate Wave Energy: An Example of the Georgia Bight

Two demonstrations are presented that lead students to a greater understanding of ocean tides and wave energy, using the unique tidal range and wave action of the Georgia Bight as an example. The goal is to explain how varying geological features in coastal regions create different wave energies and how the shape of a coastline affects the magnitude of the tidal range. These mechanisms were demonstrated to students in an upper-division college course prior to attending a field trip, in which they would evaluate real-world examples of coastlines with high and low wave energy, and regions with large and small tidal magnitudes. Here, the method of applied learning proved to be successful in guiding students to better comprehension of concepts when relating demonstrations to firsthand observations in the field