Resting Metabolic Rate and Lung Function in Wild Offshore Common Bottlenose Dolphins, Tursiops truncatus, Near Bermuda.

Diving mammals have evolved a suite of physiological adaptations to manage respiratory gases during extended breath-hold dives. To test the hypothesis that offshore bottlenose dolphins have evolved physiological adaptations to improve their ability for extended deep dives and as protection for lung barotrauma, we investigated the lung function and respiratory physiology of four wild common bottlenose dolphins (Tursiops truncatus) near the island of Bermuda. We measured blood hematocrit (Hct, %), resting metabolic rate (RMR, l O2 ⋅ min-1), tidal volume (VT, l), respiratory frequency (fR, breaths ⋅ min-1), respiratory flow (l ⋅ min-1), and dynamic lung compliance (CL, l ⋅ cmH2O-1) in air and in water, and compared measurements with published results from coastal, shallow-diving dolphins. We found that offshore dolphins had greater Hct (56 ± 2%) compared to shallow-diving bottlenose dolphins (range: 30-49%), thus resulting in a greater O2 storage capacity and longer aerobic diving duration. Contrary to our hypothesis, the specific CL (sCL, 0.30 ± 0.12 cmH2O-1) was not different between populations. Neither the mass-specific RMR (3.0 ± 1.7 ml O2 ⋅ min-1 ⋅ kg-1) nor VT (23.0 ± 3.7 ml ⋅ kg-1) were different from coastal ecotype bottlenose dolphins, both in the wild and under managed care, suggesting that deep-diving dolphins do not have metabolic or respiratory adaptations that differ from the shallow-diving ecotypes. The lack of respiratory adaptations for deep diving further support the recently developed hypothesis that gas management in cetaceans is not entirely passive but governed by alteration in the ventilation-perfusion matching, which allows for selective gas exchange to protect against diving related problems such as decompression sickness.

Acute phase protein quantitation in serum samples from healthy Atlantic bottlenose dolphins (Tursiops truncatus).

Acute phase proteins (APPs) have been studied in many companion and large animals and have been reported to have a differential sensitivity to traditional markers of inflammation. Studies have been performed indicating the conservation of these proteins as well as the application and cross-reactivity of automated assays among different species, but few reports have detailed APPs in marine mammal species. In the present study, automated assays were utilized to generate reference intervals for C-reactive protein, haptoglobin, and serum amyloid A using 44 serum samples from healthy Atlantic bottlenose dolphins (Tursiops truncatus). A total of 25 samples were obtained from dolphins under human care and 19 samples were obtained from free-ranging dolphins. Mild yet statistically significant differences were observed in levels of haptoglobin and serum amyloid A between these groups. The reference intervals from the combined groups were as follows: C-reactive protein 3.1-19.7 mg/l, haptoglobin 0-0.37 mg/ml, and serum amyloid A 17.5-42.9 mg/l. These baseline data should provide an important foundation for future studies of the application of APP quantitation in monitoring the health and stressors of dolphins under human care and with live capture of free-ranging dolphins.

Fetal echocardiographic evaluation of the bottlenose dolphin (Tursiops truncatus).

In humans, fetal echocardiography represents the most important tool for the assessment of the cardiovascular well-being of the fetus. However, because of logistic, anatomic, and behavioral challenges, detailed fetal echocardiographic evaluation of marine mammals has not been previously described. Because the application of fetal echocardiography to cetaceans could have both clinical and academic importance, an approach to evaluating the fetal dolphin's cardiovascular status was developed with conventional, fetal echocardiographic techniques developed in humans. Eight singleton fetal bottlenose dolphins (Tursiops truncatus) were evaluated, each between 6 and 11 mo gestation; six fetuses underwent two fetal echocardiographic evaluations each, four at 3-mo intervals, and two at 0.5-mo intervals. Evaluations were performed without sedation, using conventional, portable ultrasound systems. Multiple transducers, probes, and maternal dolphin positions were used to optimize image quality. Fetal echocardiography included two-dimensional imaging and color flow mapping of the heart and great arteries, as well as pulsed Doppler evaluation of the umbilical artery and vein. Thorough evaluations of the fetal dolphins' cardiovascular status were performed, with the greatest resolution between 8 and 9 mo gestation. With the use of published human fetal echocardiographic findings for comparison, fetal echocardiography demonstrated normal structure and function of the heart and great arteries, including the pulmonary veins, inferior vena cava, right and left atria, foramen ovale, tricuspid and mitral valves, right and left ventricles, ventricular septum, pulmonary and aortic valves, main pulmonary artery and ascending aorta, and ductus arteriosus. Pulsed Doppler techniques demonstrated normal umbilical arterial and venous waveforms, and color flow mapping demonstrated absence of significant valvar regurgitation. Fetal echocardiography, particularly between 8 and 9 mo gestation, can provide a safe and detailed assessment of the cardiovascular status of the fetal bottlenose dolphin.

Echocardiographic evaluation of the bottlenose dolphin (Tursiops truncatus).

Safe and effective echocardiography would represent a valuable tool for marine mammal veterinarians and physiologists evaluating the dolphin heart. Unfortunately, conventional ultrasound technology (transthoracic echocardiography) has been limited by logistic, anatomic, and behavioral challenges. Five mature male Atlantic bottlenose dolphins (Tursiops truncatus) were trained for echocardiographic imaging (four for both transthoracic and transesophageal imaging, and one for only transthoracic imaging). It was noted that transesophageal image quality transiently improved when the dolphins spontaneously exhaled. Subsequently, dolphins were conditioned to hold their breath following forced exhalation, and imaging proceeded during such behavioral breath holds. Over 25 transthoracic and 100 transesophageal echocardiographic studies were performed, including both two-dimensional imaging and color flow mapping. Transthoracic imaging yielded poor-quality images of only small portions of the heart. In contrast, transesophageal imaging, which improved dramatically with behavioral breath holding following exhalation, yielded consistently high-quality images of the entire heart (mitral, tricuspid, aortic, and pulmonary valves, atrial and ventricular septa, left and right atria, left and right ventricles, and ascending aorta and main pulmonary artery). Color flow mapping demonstrated mild tricuspid regurgitation in all dolphins, and mild aortic regurgitation in one dolphin found to have a pedunculated mass arising from the sinutubular junction just above the aortic valve. There were no complications in nonsedated dolphins. The heart of the bottlenose dolphin can be safely, effectively, and reproducibly evaluated with the use of transesophageal echocardiography in conjunction with behavioral breath holding following forced exhalation. This approach, and the normative echocardiographic data generated from this work, lays the foundation for future echocardiographic studies of cetaceans.