Structural and functional imaging of the bottlenose dolphins (Tursiops truncatus)

University of California, San Diego, San Diego, California, United States
Journal of Experimental Biology (Impact Factor: 2.9). 11/2004; 207(Pt 21):3657-65. DOI: 10.1242/jeb.01207
Source: PubMed


Bottlenose dolphins were submitted to structural (CT) and functional (SPECT/PET) scans to investigate their in vivo anatomy and physiology with respect to structures important to hearing and echolocation. The spatial arrangement of the nasal passage and sinus air spaces to the auditory bullae and phonic lips was studied in two dolphins via CT. Air volume of the sinuses and nasal passages ranged from 267.4 to 380.9 ml. Relationships of air spaces to the auditory bullae and phonic lips support previous hypotheses that air protects the ears from echolocation clicks generated by the dolphin and contributes to dolphin hearing capabilities (e.g. minimum angular resolution, inter-aural intensity differences). Lung air may replenish reductions in sinus and nasal passage air volume via the palatopharyngeal sphincter, thus permitting the echolocation mechanism to operate at depth. To determine the relative extent of regional blood flow within the head of the dolphin, two dolphins were scanned with SPECT after an intravenous dose of 1850 MBq 99mTc-bicisate. A single dolphin received 740 MBq of 18F-2-fluoro-2-deoxyglucose (FDG) to identify the relative metabolic activity of head tissues. Substantial blood flow was noted across the dorsoanterior curvature of the melon and within the posterior region of the lower jaw fats. Metabolism of these tissues relative to others within the head was nominal. It is suggested that blood flow in these fat bodies serves to thermoregulate lipid density of the melon and jaw canal. Sound velocity is inversely related to the temperature of acoustic lipids (decreasing lipid density), and changes in lipid temperature are likely to impact the wave guide properties of the sound projection and reception pathways. Thermoregulation of lipid density may maintain sound velocity gradients of the acoustic lipid complexes, particularly in the outer shell of the melon, which otherwise might vary in response to changing environmental temperatures.

Download full-text


Available from: Sam H Ridgway, May 26, 2015
  • Source
    • "64-bit version (Rosset et al. 2004). Anatomical structures were identified using a head atlas of the bottlenose dolphin (Houser et al. 2004) and beaked whale, Ziphius cavirostris (Cranford et al. 2008). Briefly, 3-D reconstructions were completed for the skull, mandibles, brain, tympanoperiotic complex, outer core of the mandibular fat body, inner core of the mandibular fat body, and cranial air spaces, which consisted of the nasal passages and laryngeal air, pterygoid sinus and peribullary sinus. "
    [Show abstract] [Hide abstract]
    ABSTRACT: While odontocetes do not have an external pinna that guides sound to the middle ear, they are considered to receive sound through specialized regions of the head and lower jaw. Yet odontocetes differ in the shape of the lower jaw suggesting that hearing pathways may vary between species, potentially influencing hearing directionality and noise impacts. This work measured the audiogram and received sensitivity of a Risso's dolphin (Grampus griseus) in an effort to comparatively examine how this species receives sound. Jaw hearing thresholds were lowest (most sensitive) at two locations along the anterior, midline region of the lower jaw (the lower jaw tip and anterior part of the throat). Responses were similarly low along a more posterior region of the lower mandible, considered the area of best hearing in bottlenose dolphins. Left- and right-side differences were also noted suggesting possible left-right asymmetries in sound reception or differences in ear sensitivities. The results indicate best hearing pathways may vary between the Risso's dolphin and other odontocetes measured. This animal received sound well, supporting a proposed throat pathway. For Risso's dolphins in particular, good ventral hearing would support their acoustic ecology by facilitating echo-detection from their proposed downward oriented echolocation beam.
    Full-text · Article · Apr 2015 · Journal of Comparative Physiology
  • Source
    • "I = 5.29 Live; Open flow meter, gas analyzer Reed et al., 2000 28.3 E = 0.42, I = 0.49 4.7 0.97 E = 4.91, I = 3.97 Live; Open flow meter, gas analyzer Reed et al., 2000 Bottlenose dolphin (Tursiops truncatus) 200* 2.26 -3.2 0.33 2.6 to 3 (neonate 3.8) 10 (90% TLC) 26.4 11* 55 0.38* E =162 (6.08-5.03 VC/s), I = 70 Trained, unrestrained Kleinenberg, 1956; Slijper, 1958; Ridgway et al., 1969; Kooyman and Cornell, 1981; Kooyman and Ponganis, 1998; Wartzok, 2002; Houser et al., 2004; Piscitelli et al., 2010 "
    [Show abstract] [Hide abstract]
    ABSTRACT: Cetaceans possess diverse adaptations in respiratory structure and mechanics that are highly specialized for an array of surfacing and diving behaviors. Some of these adaptations and air management strategies are still not completely understood despite over a century of study. We have compiled the historical and contemporary knowledge of cetacean lung anatomy and mechanics in regards to normal lung function during ventilation and air management while diving. New techniques are emerging utilizing pulmonary mechanics to measure lung function in live cetaceans. Given the diversity of respiratory adaptations in cetaceans, interpretations of these results should consider species-specific anatomy, mechanics, and behavior. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.
    Full-text · Article · Dec 2013 · Journal of Morphology
  • Source
    • "Unfortunately, CT evaluation on live, free-ranging dolphins is not logistically feasible, as animals would have to be temporarily taken from the wild and transported to a CT scan facility with a wide-bore gantry to allow for the size of an adult bottlenose dolphin. CT has been utilized for the evaluation of health and physiology in live, managed dolphins cared for by the MMP in San Diego, where animals are accustomed to human handling and transport (30–32). Therefore, CT is a feasible option for validation of the US detection of stones in live, managed dolphins. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In humans, ammonium urate (AU) nephrolithiasis is rare in the Western hemisphere and more common in Japan and developing countries. Among a variety of risk factors, insulin resistance has been associated with urate nephrolithiasis in people. Bottlenose dolphins (Tursiops truncatus) are susceptible to AU nephrolithiasis, and it is believed that some populations are more likely to develop nephrolithiasis compared to others. In an effort to better understand population-based risk factors for AU nephrolithiasis in dolphins and their comparative value to humans, sonographic evaluation was performed on dolphins from a managed collection in San Diego Bay, CA (n = 40) and dolphins from a free-ranging, nearshore population in Sarasota Bay, FL (n = 39) to look for evidence of nephrolithiasis. While 14 (35%) of San Diego Bay dolphins evaluated for the study had sonographic evidence of nephrolithiasis, none of the Sarasota Bay dolphins had evidence of disease. Presence or absence of stones was confirmed by computed tomography in a subset of the San Diego collection (n = 10; four dolphins with stones, six without stones). Age was identified as a risk factor, as dolphins with stones in the San Diego collection were significantly older than dolphins without stones (25.4 vs. 19.1 years, respectively; P = 0.04). Additionally, San Diego dolphins included in the study were significantly older than Sarasota Bay dolphins (21.3 vs. 13.8 years, respectively; P = 0.008). In addition to the previously reported risk factors of hypocitraturia and hyperinsulinemia in bottlenose dolphins, other potential factors include geographic location, managed vs. free-ranging status, prey species, and feeding schedules.
    Full-text · Article · Oct 2013 · Frontiers in Endocrinology
Show more