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

Fahlman, Andreas; Brodsky, Micah; Miedler, Stefan; Dennison, Sophie; Ivančić, Marina; Levine, Gregg; Rocho‐Levine, Julie; Manley, Mercy; Rocabert, Joan; Borque‐Espinosa, Alicia

doi:10.1242/jeb.192211

Cited by 26 publications

(23 citation statements)

References 52 publications

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“…2A–C). This agrees with a previous study showing that the O 2 stores had recovered after approximately 1.2 min following a surface apnea of up to 5 min 52 . Consequently, for an actively diving dolphin we would expect the recovery f H , SV and CO to reach higher values and/or increase for a longer duration as higher activity would increase the O 2 debt.…”

Section: Discussionsupporting

confidence: 93%

Re-evaluating the significance of the dive response during voluntary surface apneas in the bottlenose dolphin, Tursiops truncatus

Fahlman

Miedler

Rocho‐Levine³

et al. 2019

Sci Rep

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The dive response is well documented for marine mammals, and includes a significant reduction in heart rate ( f H ) during submersion as compared while breathing at the surface. In the current study we assessed the influence of the Respiratory Sinus Arrhythmia (RSA) while estimating the resting f H while breathing. Using transthoracic echocardiography we measured f H , and stroke volume (SV) during voluntary surface apneas at rest up to 255 s, and during recovery from apnea in 11 adult bottlenose dolphins ( Tursiops truncatus , 9 males and 2 females, body mass range: 140–235 kg). The dolphins exhibited a significant post-respiratory tachycardia and increased SV. Therefore, only data after this RSA had stabilized were used for analysis and comparison. The average (±s.d.) f H , SV, and cardiac output (CO) after spontaneous breaths while resting at the surface were 44 ± 6 beats min −1 , 179 ± 31 ml, and 7909 ± 1814 l min −1 , respectively. During the apnea the f H , SV, and CO decreased proportionally with the breath-hold duration, and after 255 s they, respectively, had decreased by an average of 18%, 1–21%, and 12–37%. During recovery, the f H , SV, and CO rapidly increased by as much as 117%, 34%, and 190%, respectively. Next, f H , SV and CO rapidly decreased to resting values between 90–110 s following the surface apnea. These data highlight the necessity to define how the resting f H is estimated at the surface, and separating it from the RSA associated with each breath to evaluate the significance of cardiorespiratory matching during diving.

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Section: Discussionsupporting

confidence: 93%

Re-evaluating the significance of the dive response during voluntary surface apneas in the bottlenose dolphin, Tursiops truncatus

Fahlman

Miedler

Rocho‐Levine³

et al. 2019

Sci Rep

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“…We show that a 5 min period was sufficient to fully recover from a 2-min breath-hold, as the RMR during apnea was very similar to pre-apnea metabolic rates. This is further corroborated by recent experimental evidence, showing that 1.2 min is sufficient for a bottlenose dolphin to recover from a 159 s breath-hold (Fahlman et al, 2019). Failing to account for such extraneous factors, as may be the case in Holt et al (2015), has occurred before: high costs of bird song (with 2.7-to 8.7-fold increases above basal metabolic rate) were initially reported for a small passerine bird, the Carolina wren (Eberhardt, 1994).…”

Section: Discussionsupporting

confidence: 54%

“…The signal was integrated, and the flow was determined assuming a linear response between differential pressure and flow (Fahlman et al, 2015). Breath-by-breath respiratory flow analysis using a pneumotachometer provides very similar results to conventional flow-through respirometry (Fahlman et al, 2015), and is capable of detecting both transient and cumulative increases in oxygen consumption rates (Fahlman et al, 2019;van der Hoop et al, 2018).…”

Section: Respiratory Flow Analysismentioning

confidence: 99%

Whistling is metabolically cheap for communicating bottlenose dolphins (Tursiops truncatus)

Pedersen

Fahlman²,

Borque‐Espinosa

et al. 2019

Journal of Experimental Biology

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Toothed whales depend on sound for communication and foraging, making them potentially vulnerable to acoustic masking from increasing anthropogenic noise. Masking effects may be ameliorated by higher amplitudes or rates of calling, but such acoustic compensation mechanisms may incur energetic costs if sound production is expensive. The costs of whistling in bottlenose dolphins (Tursiops truncatus) have been reported to be much higher (20% of resting metabolic rate, RMR) than theoretical predictions (0.5-1% of RMR). Here, we address this dichotomy by measuring the change in the resting O 2 consumption rate (V O2), a proxy for RMR, in three post-absorptive bottlenose dolphins during whistling and silent trials, concurrent with simultaneous measurement of acoustic output using a calibrated hydrophone array. The experimental protocol consisted of a 2-min baseline period to establish RMR, followed by a 2-min voluntary resting surface apnea, with or without whistling as cued by the trainers, and then a 5-min resting period to measure recovery costs. Daily fluctuations in V O2 were accounted for by subtracting the baseline RMR from the recovery costs to estimate the cost of apnea with and without whistles relative to RMR. Analysis of 52 sessions containing 1162 whistles showed that whistling did not increase metabolic cost (P>0.1, +4.2±6.9%) as compared with control trials (−0.5±5.9%; means±s.e.m.). Thus, we reject the hypothesis that whistling is costly for bottlenose dolphins, and conclude that vocal adjustments such as the Lombard response to noise do not represent large direct energetic costs for communicating toothed whales.

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“…If true, this would result in lower estimates of mass-specific lung O 2 stores in the present study and thereby lead to relatively larger impacts of muscle and blood O 2 store reductions on estimates of aerobic dive limits. In addition, the end-expired O 2 content of the first breath after a dive has been measured to decrease with breath-hold duration in bottlenose dolphins (13.2% to 5.4%: Ridgway et al, 1969;15.5% to 4.2%: Fahlman et al, 2019b), which suggests there are errors associated with assuming a static O 2 exchange fraction (Fahlman et al, 2019b). More precise physiological measurements on beluga whales may show similar variation in end-expired O 2 content that is associated with dive duration and allow more precise estimates of maximal usable lung O 2 stores.…”

Section: Discussionmentioning

confidence: 99%

Body condition impacts blood and muscle oxygen storage capacity of free-living beluga whales (Delphinapterus leucas)

Choy

Campbell

Berenbrink

et al. 2019

Journal of Experimental Biology

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Arctic marine ecosystems are currently undergoing rapid environmental changes. Over the past 20 years, individual growth rates of beluga whales (Delphinapterus leucas) have declined, which may be a response to climate change; however, the scarcity of physiological data makes it difficult to gauge the adaptive capacity and resilience of the species. We explored relationships between body condition and physiological parameters pertaining to oxygen (O 2 ) storage capacity in 77 beluga whales in the eastern Beaufort Sea. Muscle myoglobin concentrations averaged 77.9 mg g −1 , one of the highest values reported among mammals. Importantly, blood haematocrit, haemoglobin and muscle myoglobin concentrations correlated positively to indices of body condition, including maximum half-girth to length ratios. Thus, a whale with the lowest body condition index would have ∼27% lower blood (26.0 versus 35.7 ml kg −1 ) and 12% lower muscle (15.6 versus 17.7 ml kg −1 ) O 2 stores than a whale of equivalent mass with the highest body condition index; with the conservative assumption that underwater O 2 consumption rates are unaffected by body condition, this equates to a >3 min difference in maximal aerobic dive time between the two extremes (14.3 versus 17.4 min). Consequently, environmental changes that negatively impact body condition may hinder the ability of whales to reach preferred prey sources, evade predators and escape ice entrapments. The relationship between body condition and O 2 storage capacity may represent a vicious cycle, in which environmental changes resulting in decreased body condition impair foraging, leading to further reductions in condition through diminished prey acquisition and/or increased foraging efforts.

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

Cited by 26 publications

References 52 publications

Re-evaluating the significance of the dive response during voluntary surface apneas in the bottlenose dolphin, Tursiops truncatus

Re-evaluating the significance of the dive response during voluntary surface apneas in the bottlenose dolphin, Tursiops truncatus

Whistling is metabolically cheap for communicating bottlenose dolphins (Tursiops truncatus)

Body condition impacts blood and muscle oxygen storage capacity of free-living beluga whales (Delphinapterus leucas)

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