RESPIRATORY CHANGES IN STRANDED BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS).

Lung function (breath duration, respiratory flow [V̇], and tidal volume [VT]), and end-expiratory O2 were measured in 19 adult bottlenose dolphins (Tursiops spp.) while at rest in water or beached for up to 10 min. The results show that inspiratory VT, expiratory VT, or inspiratory V̇ did not differ on land or in water. The average expiratory V̇ for all dolphins on land decreased by 16%, and the expiratory and total breath durations increased by 5% and 4%, respectively, compared with in water. There were temporal changes observed during beaching, where expired and inspired VT and inspired V̇ decreased by 13%, 16%, and 9%, respectively, after 10 min on land. These data suggest that dolphins compensate for the effect of gravity by adjusting respiration to maintain alveolar ventilation and gas exchange, but during extended durations, the increased work of breathing may impede ventilation and gas exchange. Continuous monitoring of lung function and gas exchange may help prevent long-term damage during out-of-water medical procedures, optimize animal transport conditions, and improve survival during stranding events.

Ventilation and gas exchange before and after voluntary static surface breath-holds in clinically healthy bottlenose dolphins, Tursiops truncatus.

We measured respiratory flow (V̇), breathing frequency (fR), tidal volume (VT), breath duration and end-expired O2 content in bottlenose dolphins (Tursiops truncatus) before and after static surface breath-holds ranging from 34 to 292 s. There was considerable variation in the end-expired O2, VT and fR following a breath-hold. The analysis suggests that the dolphins attempt to minimize recovery following a dive by altering VT and fR to rapidly replenish the O2 stores. For the first breath following a surface breath-hold, the end-expired O2 decreased with dive duration, while VT and fR increased. Throughout the recovery period, end-expired O2 increased while the respiratory effort (VT, fR) decreased. We propose that the dolphins alter respiratory effort following a breath-hold according to the reduction in end-expired O2 levels, allowing almost complete recovery after 1.2 min.

Characterizing respiratory capacity in belugas (Delphinapterus leucas).

We measured respiratory flow, breath duration, and calculated tidal volume (VT) in nine belugas (Delphinapterus leucas, mean measured body mass: 628 ± 151 kg, n = 5) housed in managed care facilities. Both spontaneous (resting at station) and trained maximal respirations (chuffs) were measured. The mean (±s.d.) inspiratory VT for spontaneous breaths (16.7 ± 4.7 l, range: 7.5-18.7 l) was larger than those predicted based on respiratory scaling equations from terrestrial mammals and was 32 ± 10% of estimated total lung capacity (TLCest) based on an equation from static measurements made on a range of cetaceans and pinniped lungs, and 52 ± 18% of estimated vital capacities (VC, mean: 27.7 ± 8.9 l, range: 16.7-40.3 l) based on respiratory measurements obtained during trained maximal respirations. Expiratory flow (V˙exp, spontaneous: 26.1 ± 5.5 l s-1, chuff: 66.8 ± 22.5 l s-1) was significantly higher as compared with inspiratory flow (V˙insp, spontaneous: 22.3 ± 4.6 l s-1, chuff: 30.1 ± 8.4 l s-1), and the maximal expiratory flow recorded was 212 l s-1. The breath duration was shorter for forced breaths (Expiration: 518 ± 101 ms; Inspiration: 905 ± 170 ms; Total: 1423 ± 227 ms) as compared with spontaneous breaths (Expiration: 995 ± 176 ms; Inspiration: 1098 ± 219 ms; Total: 2093 ± 302 ms). These data provide baseline estimates of the respiratory capacity of belugas.

Partial Redundancy and Morphological Homeostasis: Reliable Development through Overlapping Mechanisms.

How might organisms grow into their desired physical forms in spite of environmental and genetic variation? How do they maintain this form in spite of physical insults? This article presents a case study in simulated morphogenesis, using a physics-based model for embryonic epithelial tissue. The challenges of the underlying physics force the introduction of closed-loop controllers for both spatial patterning and geometric structure. Reliable development is achieved not through elaborate control procedures or exact solutions, but through crude layering of independent, overlapping mechanisms. As a consequence, development and regeneration together become one process, morphological homeostasis, which, owing to its internal feedbacks and partially redundant architecture, is remarkably robust to both knockout damage and environmental variation. The incomplete nature of such redundancy furnishes an evolutionary rationale for its preservation, in spite of individual knockout experiments that may suggest it has little purpose.

Lung mechanics and pulmonary function testing in cetaceans.

We measured esophageal pressures, respiratory flow rates, and expired O2 and CO2 in six adult bottlenose dolphins (Tursiops truncatus) during voluntary breaths and maximal (chuff) respiratory efforts. The data were used to estimate the dynamic specific lung compliance (sCL), the O2 consumption rate (V̇O2 ) and CO2 production rates (V̇CO2 ) during rest. Our results indicate that bottlenose dolphins have the capacity to generate respiratory flow rates that exceed 130 l s(-1) and 30 l s(-1) during expiration and inspiration, respectively. The esophageal pressures indicated that expiration is passive during voluntary breaths, but active during maximal efforts, whereas inspiration is active for all breaths. The average sCL of dolphins was 0.31±0.04 cmH2O(-1), which is considerably higher than that of humans (0.08 cmH2O(-1)) and that previously measured in a pilot whale (0.13 cmH2O(-1)). The average estimated V̇O2  and V̇CO2  using our breath-by-breath respirometry system ranged from 0.857 to 1.185 l O2 min(-1) and 0.589 to 0.851 l CO2 min(-1), respectively, which is similar to previously published metabolic measurements from the same animals using conventional flow-through respirometry. In addition, our custom-made system allows us to approximate end tidal gas composition. Our measurements provide novel data for respiratory physiology in cetaceans, which may be important for clinical medicine and conservation efforts.

Hearing threshold measurements of five stranded short-finned pilot whales (Globicephala macrorhynchus).

On May 5, 2011, 23 short-finned pilot whales, Globicephala macrorhynchus, were stranded along the coastline near Cudjoe Key, FL. Five animals (two adult females, two juvenile females, and an adult male) were transported to a rehabilitation facility in Key Largo, FL. Auditory evoked potentials (AEPs) were recorded in response to amplitude modulated tone pips modulated at 1000 Hz. AEP thresholds were determined at 10, 20, 40, 80, and 120 kHz for the four females. However, the adult male was euthanized prior to testing. Short-finned pilot whales had peak sensitivity at lower frequencies than other odontocetes such as bottlenose dolphins. Greatest sensitivity was around 40 kHz for all whales, while thresholds for the two adult females were 25-61 dB higher at 80 kHz than the juveniles. Click evoked potentials were similar between the four whales and comparable to other echolocating odontocetes. Click evoked potential data from a fifth short-finned pilot whale that had stranded in Curacao showed no response. These findings add to the limited database of pilot whale (short- and long-finned) hearing studies, of which there are only two others [Schlundt et al. (2011). J. Acoust. Soc. Am. 129, 1111-1116 and Pacini et al. (2010). J. Exp. Biol. 213, 3138-3143].

Clonally related methicillin-resistant Staphylococcus aureus isolated from short-finned pilot whales (Globicephala macrorhynchus), human volunteers, and a bayfront cetacean rehabilitation facility.

In May of 2011, a live mass stranding of 26 short-finned pilot whales (Globicephala macrorhynchus) occurred in the lower Florida Keys. Five surviving whales were transferred from the original stranding site to a nearby marine mammal rehabilitation facility where they were constantly attended to by a team of volunteers. Bacteria cultured during the routine clinical care of the whales and necropsy of a deceased whale included methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MSSA and MRSA). In order to investigate potential sources or reservoirs of MSSA and MRSA, samples were obtained from human volunteers, whales, seawater, and sand from multiple sites at the facility, nearby recreational beaches, and a canal. Samples were collected on 3 days. The second collection day was 2 weeks after the first, and the third collection day was 2 months after the last animal was removed from the facility. MRSA and MSSA were isolated on each day from the facility when animals and volunteers were present. MSSA was found at an adjacent beach on all three collection days. Isolates were characterized by utilizing a combination of quantitative real-time PCR to determine the presence of mecA and genes associated with virulence, staphylococcal protein A typing, staphylococcal cassette chromosome mec typing, multilocus sequence typing, and pulsed field gel electrophoresis (PFGE). Using these methods, clonally related MRSA were isolated from multiple environmental locations as well as from humans and animals. Non-identical but genetically similar MSSA and MRSA were also identified from distinct sources within this sample pool. PFGE indicated that the majority of MRSA isolates were clonally related to the prototype human strain USA300. These studies support the notion that S. aureus may be shed into an environment by humans or pilot whales and subsequently colonize or infect exposed new hosts.

Hearing loss in stranded odontocete dolphins and whales.

The causes of dolphin and whale stranding can often be difficult to determine. Because toothed whales rely on echolocation for orientation and feeding, hearing deficits could lead to stranding. We report on the results of auditory evoked potential measurements from eight species of odontocete cetaceans that were found stranded or severely entangled in fishing gear during the period 2004 through 2009. Approximately 57% of the bottlenose dolphins and 36% of the rough-toothed dolphins had significant hearing deficits with a reduction in sensitivity equivalent to severe (70-90 dB) or profound (>90 dB) hearing loss in humans. The only stranded short-finned pilot whale examined had profound hearing loss. No impairments were detected in seven Risso's dolphins from three different stranding events, two pygmy killer whales, one Atlantic spotted dolphin, one spinner dolphin, or a juvenile Gervais' beaked whale. Hearing impairment could play a significant role in some cetacean stranding events, and the hearing of all cetaceans in rehabilitation should be tested.