Meeting Abstract
P2.67 Jan. 5 Gross morphology of the respiratory muscles in bottlenose dolphins (Tursiops truncatus) COTTEN, P.B.**; PISCITELLI, M.A.*; MCLELLAN, W.A.; ROMMEL, S.A.; PABST, D.A.; UNC Wilmington; UNC Wilmington; UNC Wilmington; UNC Wilmington; UNC Wilmington pbc7783@uncw.edu
Bottlenose dolphins (Tursiops truncatus) possess locomotor stamina; however, the dolphin�s locomotor-respiratory systems are decoupled while swimming on a breath-hold. During their brief surfacing event, locomotion and respiration appear to be mechanically coupled and they respire explosively (exchange 90% of total lung volume in 0.3s). Unlike terrestrial mammals, bottlenose dolphins likely do not have the respiratory assistance provided by the visceral piston as they are not subjected to ground reaction forces. The predominantly slow-twitch fiber profile of their diaphragm suggests that this muscle also does not likely produce the force required for rapid inhalation. Based upon Bramble�s (1989) model of mammalian locomotor-respiratory coupling, we hypothesized that muscles located within the cranial-cervical and lumbo-pelvic units, which both act upon the thoracic unit, function to power respiration in bottlenose dolphins. We investigated the gross morphology of cervical muscles (sternomastoid, sternohyoid, scalenes) and abdominal muscles (rectus abdominis, abdominal obliques) and conducted physical manipulations of the thorax in stranded dolphins. Results suggest that contraction of the scalenes draws the vertebral ribs cranially, which flares the ribs laterally and increases thoracic volume. Contraction of the sternohyoid and sternomastoid appears to draw the sternum and attached ribs cranio-dorsally, which also increases thoracic volume. Contraction of the abdominal muscles draws the sternum caudally and compresses the caudal thorax and abdominal cavity, which decreases thoracic cavity volume. These results suggest that dolphins utilize muscles similar to those in locomoting terrestrial mammals to power respiration.
