Changes in partial pressures of respiratory gases during submerged voluntary breath hold across odontocetes: is body mass important?

Little is known about the postnatal development of the physiological characteristics that support breath-hold in cetaceans, despite their need to swim and dive at birth. Arctic species have the additional demand of avoiding entrapment while navigating under sea ice, where breathing holes are patchily distributed and ephemeral. This is the first investigation of the ontogeny of the biochemistry of the locomotor muscle in a year-round Arctic-dwelling cetacean (beluga whale, Delphinapterus leucas). Compared with what we know about other cetaceans, belugas are born with high myoglobin content (1.56±0.02 g 100 g −1 wet muscle mass, N=2) that matures rapidly. Myoglobin increased by 452% during the first year after birth and achieved adult levels (6.91±0.35 g 100 g −1 wet muscle mass, N=9) by 14 months postpartum. Buffering capacity was 48.88±0.69 slykes (N=2) at birth; adult levels (84.31±1.38 slykes, N=9) were also achieved by 14 months postpartum. As the oxygen stores matured, calculated aerobic dive limit more than doubled over the first year of life, undoubtedly facilitating the movements of calves under sea ice. Nonetheless, small body size theoretically continues to constrain the diving ability of newly weaned 2 year olds, as they only had 74% and 69% of the aerobic breath-hold capacity of larger adult female and male counterparts. These assessments enhance our knowledge of the biology of cetaceans and provide insight into age-specific flexibility to alter underwater behaviors, as may be required with the ongoing alterations in the Arctic marine ecosystem associated with climate change and increased anthropogenic activities.

Section: Modeling Breath-hold Limitsmentioning

confidence: 99%

Navigating under sea ice promotes rapid maturation of diving physiology and performance in beluga whales

Noren

Suydam

2016

“…For walruses, there is no evidence of resource partitioning between sexes when they overlap in distribution during the winter. Thus, inter-sexual competition could be problematic for female walruses if prey availability decreases in the Arctic because the typical response of pinnipeds to low prey availability is to increase dive duration (Feldkamp et al, 1989;Crocker et al, 2006;Melin et al, 2008), and breeding females will be most at risk as they have elevated energetic requirements because of the costs of lactation (Noren et al, 2012(Noren et al, , 2014b. In addition, maternal foraging behaviors could be constrained by the physiological limits of their progeny.…”

Section: Diving Capacity Of Walrusesmentioning

confidence: 99%

“…The number of walruses converging on coastal haul-outs is expected to increase as summer sea ice continues to decline (Jay et al, 2011), but the ability of localized food supplies in these coastal regions to support large numbers of walruses over the long term is unknown (Ovsyanikov et al, 2008). Thus, these changes in behavior could affect the ability of walruses to meet daily energetic requirements (Noren et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Rapid maturation of the muscle biochemistry that supports diving in Pacific walruses (Odobenus rosmarus divergens)

Noren

Jay

Burns

et al. 2015

Physiological constraints dictate animals' ability to exploit habitats. For marine mammals, it is important to quantify physiological limits that influence diving and their ability to alter foraging behaviors. We characterized age-specific dive limits of walruses by measuring anaerobic (acid-buffering capacity) and aerobic (myoglobin content) capacities of the muscles that power hind (longissimus dorsi) and fore (supraspinatus) flipper propulsion. Mean buffering capacities were similar across muscles and age classes (a fetus, five neonatal calves, a 3 month old and 20 adults), ranging from 41.31 to 54.14 slykes and 42.00 to 46.93 slykes in the longissimus and supraspinatus, respectively. Mean myoglobin in the fetus and neonatal calves fell within a narrow range (longissimus: 0.92-1.68 g 100 g −1 wet muscle mass; supraspinatus: 0.88-1.64 g 100 g −1 wet muscle mass). By 3 months post-partum, myoglobin in the longissimus increased by 79%, but levels in the supraspinatus remained unaltered. From 3 months post-partum to adulthood, myoglobin increased by an additional 26% in the longissimus and increased by 126% in the supraspinatus; myoglobin remained greater in the longissimus compared with the supraspinatus. Walruses are unique among marine mammals because they are born with a mature muscle acid-buffering capacity and attain mature myoglobin content early in life. Despite rapid physiological development, small body size limits the diving capacity of immature walruses and extreme sexual dimorphism reduces the diving capacity of adult females compared with adult males. Thus, free-ranging immature walruses likely exhibit the shortest foraging dives while adult males are capable of the longest foraging dives.

“…Note that maximum total body O 2 store and maximum O 2 uptake for a male killer whale were set at 137.3 and 25.52 l, respectively. Noren et al (2012) concluded that apnoea of 13.3 min in an adult male killer whale did not cause a rise in blood lactate levels. The maximum apnoea durations observed in our study were 6.1 and 5.3 min for males and females, respectively; it was assumed that lactate accumulation was not an issue.…”

Section: Influences Of Sex and Activity Level On Respiration Behaviourmentioning

confidence: 98%

The significance of respiration timing in the energetics estimates of free-ranging killer whales (Orcinus orca)

Roos

Miller

2016

Respiration rate has been used as an indicator of metabolic rate and associated cost of transport (COT) of free-ranging cetaceans, discounting potential respiration-by-respiration variation in O 2 uptake. To investigate the influence of respiration timing on O 2 uptake, we developed a dynamic model of O 2 exchange and storage. Individual respiration events were revealed from kinematic data from 10 adult Norwegian herring-feeding killer whales (Orcinus orca) recorded with high-resolution tags (DTAGs). We compared fixed O 2 uptake per respiration models with O 2 uptake per respiration estimated through a simple 'broken-stick' O 2 -uptake function, in which O 2 uptake was assumed to be the maximum possible O 2 uptake when stores are depleted or maximum total body O 2 store minus existing O 2 store when stores are close to saturated. In contrast to findings assuming fixed O 2 uptake per respiration, uptake from the broken-stick model yielded a high correlation (r 2 >0.9) between O 2 uptake and activity level. Moreover, we found that respiration intervals increased and became less variable at higher swimming speeds, possibly to increase O 2 uptake efficiency per respiration. As found in previous studies, COT decreased monotonically versus speed using the fixed O 2 uptake per respiration models. However, the broken-stick uptake model yielded a curvilinear COT curve with a clear minimum at typical swimming speeds of 1.7-2.4 m s −1. Our results showed that respiration-by-respiration variation in O 2 uptake is expected to be significant. And though O 2 consumption measurements of COT for free-ranging cetaceans remain impractical, accounting for the influence of respiration timing on O 2 uptake will lead to more consistent predictions of field metabolic rates than using respiration rate alone.