Meeting Abstract
Swimming on a breathhold is known to decouple ventilation and locomotion in cetaceans (whales, dolphins, and porpoises). However, the mechanisms underlying this unique behavior are not fully understood. The fiber-type profile of the bottlenose dolphin (Tursiops truncatus) diaphragm suggests that this muscle might act as a barrier against the cranial movement of its abdominal organs during flexion of its tailstock, thereby serving as a modulator of the visceral piston. Characterizing the fiber-type profile of the diaphragms of other dolphin species can help us discern if this potential role of the diaphragm is consistent among cetaceans. In this study, we determined the fiber-type profile of six Atlantic spotted dolphin (Stenella frontalis) diaphragms. We cut sections using a cryostat, stained them for their myosin ATPase activity after basic pre-incubation, and tested for their reaction to myosin heavy chain antibodies (A4840 – slow myosin; SC71 – fast IIa myosin). The ATPase stained sections were imaged, and the fibers were counted and placed into one of three categories (dark, intermediate, or light). In addition, antibody stains were used to confirm the classification of these fibers as either fast- or slow-twitch fibers, as well as examine the expression of intermediately staining fibers. These data were used to calculate the average fiber-type profile of the diaphragm. Diameters of fibers in each of the three categories were also measured using ImageJ. The fiber-type profile and fiber diameters of the diaphragm of Atlantic spotted dolphins will be compared to these features of the bottlenose dolphin muscle in order to identify any similarities or differences. These comparisons will enable us to better understand the unique role of cetacean diaphragms in their ventilation.
