Comparative Respiratory Physiology in Cetaceans

Fahlman, Andreas; Borque‐Espinosa, Alicia; Facchin, Federico; Fernandez, Diana Ferrero; Caballero, Paola Muñoz; Haulena, Martin; Rocho‐Levine, Julie

doi:10.3389/fphys.2020.00142

Cited by 72 publications

(27 citation statements)

References 38 publications

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“…V T values presented here are about half of the mean mass‐relative V T values reported for captive Tursiops (Ridgway et al, 1969; Fahlman et al, 2016) or Orcinus (Kreite, 1995), but 60%–80% higher than that predicted by Stahl's (1967) allometric relationship for terrestrial mammals. These results generally agree with Fahlman et al (2020), who reported consistently higher V T higher in marine mammals than in terrestrial mammals. Fahlman et al (2016) found that both V T and f v increased with exercise, but did not report how simultaneous measures of additional variables, such as t E , might have reduced the observed large variability in V T .…”

Section: Discussionsupporting

confidence: 92%

Why Baja? A bioenergetic model for comparing metabolic rates and thermoregulatory costs of gray whale calves (Eschrichtius robustus)

Sumich

2021

Marine Mammal Science

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A bioenergetic model is developed from empirically derived equations of morphometric, ventilatory and thermoregulatory variables to compare estimated field metabolic rates (FMR) of gray whale calves to estimates of unregulated body heat losses and consequent required thermogenesis at birth, natal lagoon departure, and weaning. Estimates of FMR are based on rates of oxygen consumption. Body surface and ventilatory heat fluxes are evaluated separately, then combined to estimate minimum total heat losses from birth to weaning at three ambient water temperature regimes typical of winter natal lagoons and Oregon coastal waters and arctic conditions during summer. Modeled heat losses of neonates in winter lagoons are half their estimated mean FMR. Neonates in good body condition appear to be capable of tolerating heat losses experienced in 10°C water without additional thermogenic activities above their estimated resting metabolic rates. This study provides new evidence that no thermoregulatory advantage accrues to neonates or to their mothers by being born in warm winter natal lagoons or by remaining there several weeks longer than other gray whales. Consequently, avoidance or reduced risk of killer whale predation seems a more likely candidate than reduced heat loss as the principal fitness benefit of low‐latitude winter migrations.

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Section: Discussionsupporting

confidence: 92%

Why Baja? A bioenergetic model for comparing metabolic rates and thermoregulatory costs of gray whale calves (Eschrichtius robustus)

Sumich

2021

Marine Mammal Science

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“…That is, smaller aquatic and terrestrial mammals take similar-sized breaths, whereas large aquatic mammals take larger breaths than large terrestrial mammals. Comprehensively, the aquatic breathing (Stahl, 1967), breathing frequency aquatic = 33•body mass −0.42 (Mortola & Limoges, 2006), (e) tidal volume terrestrial = 7.69•body mass 1.04 (Stahl, 1967), tidal volume aquatic = 0.0372•body mass 0.92 (Fahlman et al, 2020), (f) cardiac output = 187•body mass 0.81 (Stahl, 1967), and (g) minute ventilation = 379•body mass 0.80 (Stahl, 1967). In panels a-d, dots are observed data points and colored lines with shaded regions are population-average model predictions with 95% confidence intervals.…”

Section: Higher Bmrs In Small Aquatic Mammalsmentioning

confidence: 99%

Allometric scaling of metabolic rate and cardiorespiratory variables in aquatic and terrestrial mammals

He,

De Ruiter,

Westover

et al. 2023

Physiological Reports

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While basal metabolic rate (BMR) scales proportionally with body mass (Mb), it remains unclear whether the relationship differs between mammals from aquatic and terrestrial habitats. We hypothesized that differences in BMR allometry would be reflected in similar differences in scaling of O2 delivery pathways through the cardiorespiratory system. We performed a comparative analysis of BMR across 63 mammalian species (20 aquatic, 43 terrestrial) with a Mb range from 10 kg to 5318 kg. Our results revealed elevated BMRs in small (>10 kg and <100 kg) aquatic mammals compared to small terrestrial mammals. The results demonstrated that minute ventilation, that is, tidal volume (VT)·breathing frequency (fR), as well as cardiac output, that is, stroke volume·heart rate, do not differ between the two habitats. We found that the “aquatic breathing strategy”, characterized by higher VT and lower fR resulting in a more effective gas exchange, and by elevated blood hemoglobin concentrations resulting in a higher volume of O2 for the same volume of blood, supported elevated metabolic requirements in aquatic mammals. The results from this study provide a possible explanation of how differences in gas exchange may serve energy demands in aquatic versus terrestrial mammals.

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“…R. Soc. B 376: 20200223 in small-and medium-sized cetaceans [60]. The start of a breath was determined from the flow signal and the f R was determined from the duration between successive breaths.…”

Section: (B) Data Collectionmentioning

confidence: 99%

Scaling of heart rate with breathing frequency and body mass in cetaceans

Blawas

Nowacek

Rocho‐Levine³

et al. 2021

Phil. Trans. R. Soc. B

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Plasticity in the cardiac function of a marine mammal facilitates rapid adjustments to the contrasting metabolic demands of breathing at the surface and diving during an extended apnea. By matching their heart rate ( f H ) to their immediate physiological needs, a marine mammal can improve its metabolic efficiency and maximize the proportion of time spent underwater. Respiratory sinus arrhythmia (RSA) is a known modulation of f H that is driven by respiration and has been suggested to increase cardiorespiratory efficiency. To investigate the presence of RSA in cetaceans and the relationship between f H , breathing rate ( f R ) and body mass ( M b ), we measured simultaneous f H and f R in five cetacean species in human care. We found that a higher f R was associated with a higher mean instantaneous f H (i f H ) and minimum i f H of the RSA. By contrast, f H scaled inversely with M b such that larger animals had lower mean and minimum i f H s of the RSA. There was a significant allometric relationship between maximum i f H of the RSA and M b , but not f R , which may indicate that this parameter is set by physical laws and not adjusted dynamically with physiological needs. RSA was significantly affected by f R and was greatly reduced with small increases in f R . Ultimately, these data show that surface f H s of cetaceans are complex and the f H patterns we observed are controlled by several factors. We suggest the importance of considering RSA when interpreting f H measurements and particularly how f R may drive f H changes that are important for efficient gas exchange. This article is part of the theme issue ‘Measuring physiology in free-living animals (Part I)’.

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Comparative Respiratory Physiology in Cetaceans

Cited by 72 publications

References 38 publications

Why Baja? A bioenergetic model for comparing metabolic rates and thermoregulatory costs of gray whale calves (Eschrichtius robustus)

Why Baja? A bioenergetic model for comparing metabolic rates and thermoregulatory costs of gray whale calves (Eschrichtius robustus)

Allometric scaling of metabolic rate and cardiorespiratory variables in aquatic and terrestrial mammals

Scaling of heart rate with breathing frequency and body mass in cetaceans

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