Sam H. Ridgway

Respiration and Deep Diving in the Bottlenose Porpoise

A bottlenose porpoise was trained to dive untethered in the open ocean and to exhale into an underwater collecting funnel before surfacing from prescribed depths down to 300 meters. The animal was also taught to hold its breath for periods up to 4 minutes at the surface and then blow in the funnel. Alveolar collapse is probably complete at around 100 meters, and little pulmonary respiratory exchange occurs below that depth. Thoracic collapse was observ visually at 10 to 50 meters and by underwater television to 300 meters.

Blood Oxygen and Ecology of Porpoises of Three Genera

Blood volumes, hemoglobin concentrations, packed-cell volumes, and heart weights were determined in three genera of propoises which differ from one another in behavior and ecology. The estimate for the total blood-oxygen content of the highly active, deep-diving, pelagic species Phocoenoides dalli was almost three times greater than that for the coastaldwelling species Tursiops truncatus, and about 70 percent greater than for the less active pelagic species, Lagenorhynchus obliquidens. Heart weights of Phocoenoides dalli were about 140 percent greater than in Tursiops truncatus and 55 percent greater than in Logenorhynchus obliquidens.

Molecular cloning and characterization of CD4 in an aquatic mammal, the white whale Delphinapterus leucas

Abstractu2002Given the importance of the cell surface recognition protein, CD4, in immune function, the cloning and characterization of CD4 at the molecular level from an odontocete cetacean, the white whale (Delphinapterus leucas), was carried out. Whale CD4 cDNA contains 2662 base pairs and translates into a protein containing 455 amino acids. Whale CD4 shares 64% and 51% identity with the human and mouse CD4 protein, respectively, and is organized in a similar manner. Unlike human and mouse, however, the cytoplasmic domain, which is highly conserved, contains amino acid substitutions unique to whale. Moreover, only one of the seven potential N-linked glycosylation sites present in whale is shared with human and mouse. Evolutionarily, the whale CD4 sequence is most similar to pig and structurally similar to dog and cat, in that all lack the cysteine pair in the V2 domain. These differences suggest that CD4 may have a different secondary structure in these species, which may affect binding of class II and subsequent T-cell activation, as well as binding of viral pathogens. Interestingly, as a group, species with these CD4 characteristics all have high constituitive expression of class II molecules on T lymphocytes, suggesting potential uniqueness in the interaction of CD4, class II molecules, and the immune response. Molecular characterization of CD4 in an aquatic mammal provides information on the CD4 molecule itself and may provide insight into adaptive evolutionary changes of the immune system.

Sound Reception in the Porpoise as it Relates to Echolocation

Previous to the work of our group which was published in 1970 (McCormick, et al., 1970), all theories of hearing in Cetacea were based on dissections and experiments with dead specimens. Such experiments continue to be published in the literature to this day, and just as the earlier studies of dead material did, they only serve to confound the many students and investigators of Cetacean hearing, especially those who have little formal training in the science of physiological acoustics.

Respiratory Water Exchange in Two Species of Porpoise

Measurements of the respiratory water exchanges of Tursiops truncatus and Lagenorhynchus obli-quidens indicate that these species lose, respectively, only 30 and 77 percent as much water through evaporation as would terrestrial mammals of the same body weight. Control of temperature and pressure within the respiratory system and a lower ventilation rate account for this relatively small loss of water.

Anesthetization of Porpoises for Major Surgery

Comparison of three porpoises (Tursiops truncatus and Lagenorhynchus obliquidens) given nitrous oxide with 18 given halothane, with complete documentation of reflexes and comprehensive physiological monitoring, showed halothane to be a suitable anesthetic for major surgery while nitrous oxide was found to be inadequate. In addition, sodium thiopental administered intravenously was successfully used to facilitate intubation procedures. This development eliminated the need to intubate awake porpoises.

Brain-spinal cord ratios in porpoises: Possible correlations with intelligence and ecology'

As a rough measure of intelligence, brain weight: cord weight ratios in small delphinids compared favorably with, but were slightly less than, this ratio in man. Not all delphinids studied were found to achieve the minimum 1000 gm brain weight correlate of language development in the human child. The average adult brain size in some small pelagic cetaceans was found to be about 800 gm, while the average for Tursiops truncatus, an estuarine species, was found to be about 1450 gm.