The gross morphology and histochemistry of respiratory muscles in bottlenose dolphins (Tursiops truncatus)
- UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
- Pamela B. Cotten (Creator)
- Institution
- The University of North Carolina Wilmington (UNCW )
- Web Site: http://library.uncw.edu/
- Advisor
- Heather Koopman
Abstract: Most mammals possess stamina because their locomotor and respiratory (i.e.
ventilatory) systems are mechanically coupled. These systems are decoupled, however,
in bottlenose dolphins (Tursiops truncatus) as they swim on a breath-hold. Locomotion
and ventilation appear to be coupled only during their brief surfacing event, when they
respire explosively (up to 90% of total lung volume in approximately 0.3s) (Ridgway et
al., 1969). The predominantly slow-twitch fiber profile of their diaphragm (Dearolf,
2003) suggests that this muscle does not likely power their rapid ventilatory event. Based
upon Bramble’s (1989) biomechanical model of locomotor-respiratory coupling in
galloping mammals, I hypothesized that muscles located within the cranial-cervical and
lumbo-pelvic units, which act upon the thoracic unit, function to power ventilation in
bottlenose dolphins. I also hypothesized that these muscles would be composed
predominantly of fast-twitch fibers to facilitate the bottlenose dolphin’s rapid ventilation.
The gross morphology (n=6) of cranio-cervical (sternomastoid, sternohyoid, scalenes),
thoracic (intercostals), and lumbo-pelvic (rectus abdominis, abdominal obliques,
hypaxialis) muscles and the fiber-type profiles (n=6) of selected muscles (sternohyoid,
sternomastoid, and rectus abdominis) of bottlenose dolphins were investigated. Physical
manipulations of excised thoracic units were carried out to investigate potential actions of
these muscles. Results suggest that the cranio-cervical muscles act to draw the sternum
and associated ribs cranio-dorsally, which flares the ribs laterally, and increases thoracic
cavity volume required for inspiration. The thoracic muscles physically link the ribs to
create a single functional unit; these muscles can also act to control the size of the
intercostal space. The lumbo-pelvic muscles act to draw the sternum and caudal ribs caudally, which decreases the volume of the thoracic and abdominal cavities required for
expiration. All muscles investigated were composed predominantly of fast-twitch fibers
(range 72-88% by area) and appear histochemically poised for rapid contraction. These
combined results suggest that dolphins utilize muscles, similar to those used by galloping
mammals, to power their explosive ventilation. However, the mechanisms that permit
dolphins to selectively couple and uncouple their locomotor and ventilatory systems,
depending upon whether they are respiring at the surface or swimming on a breath-hold,
remain unknown.
The gross morphology and histochemistry of respiratory muscles in bottlenose dolphins (Tursiops truncatus)
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Created on 1/1/2009
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Additional Information
- Publication
- Thesis
- A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment of the Requirement for the Degree of Masters of Science
- Language: English
- Date: 2009
- Keywords
- Bottlenose dolphin--Physiology, Bottlenose dolphin--Morphology, Bottlenose dolphin--Research, Bottlenose dolphin--Respiration
- Subjects
- Bottlenose dolphin -- Morphology
- Bottlenose dolphin -- Physiology
- Bottlenose dolphin -- Respiration
- Bottlenose dolphin -- Research