Why Are High Altitude Natives So Strong at High Altitude? Nature vs. Nurture: Genetic Factors vs. Growth and Development

Journal of Experimental Biology

Velotta

et al. 2017

We examined the circulatory mechanisms underlying adaptive increases in thermogenic capacity in deer mice () native to the cold hypoxic environment at high altitudes. Deer mice from high- and low-altitude populations were born and raised in captivity to adulthood, and then acclimated to normoxia or hypobaric hypoxia (simulating hypoxia at ∼4300 m). Thermogenic capacity [maximal O consumption (), during cold exposure] was measured in hypoxia, along with arterial O saturation (a ) and heart rate (). Hypoxia acclimation increased by a greater magnitude in highlanders than in lowlanders. Highlanders also had highera and extracted more O from the blood per heartbeat (O pulse=/). Hypoxia acclimation increased , O pulse and capillary density in the left ventricle of the heart. Our results suggest that adaptive increases in thermogenic capacity involve integrated functional changes across the O cascade that augment O circulation and extraction from the blood.

Section: Resultssupporting

confidence: 67%

Circulatory mechanisms underlying adaptive increases in thermogenic capacity in high-altitude deer mice

Tate

Journal of Experimental Biology

Velotta

et al. 2017

“…It has been difficult to determine whether these patterns of variation result from evolved differences or from environmentally induced plasticity (acclimatization, developmental plasticity, etc.) (Brutsaert, 2016;Laguë, 2017;Moore, 2017). Nevertheless, these intriguing results suggest that there may be convergent mechanisms for coping with hypoxia at high altitude within a given geographic region, but divergent mechanisms between species inhabiting different geographic regions.…”

Section: Introductionmentioning

confidence: 99%

Control of breathing and respiratory gas exchange in ducks native to high altitude in the Andes

Journal of Experimental Biology

Lague

York

et al. 2019

We examined the control of breathing and respiratory gas exchange in six species of high-altitude duck that independently colonized the high Andes. We compared ducks from high-altitude populations in Peru (Lake Titicaca at ∼3800 m above sea level; Chancay River at ∼3000-4100 m) with closely related populations or species from low altitude. Hypoxic ventilatory responses were measured shortly after capture at the native altitude. In general, ducks responded to acute hypoxia with robust increases in total ventilation and pulmonary O 2 extraction. O 2 consumption rates were maintained or increased slightly in acute hypoxia, despite ∼1-2°C reductions in body temperature in most species. Two high-altitude taxayellow-billed pintail and torrent duckexhibited higher total ventilation than their low-altitude counterparts, and yellow-billed pintail exhibited greater increases in pulmonary O 2 extraction in severe hypoxia. In contrast, three other high-altitude taxa-Andean ruddy duck, Andean cinnamon teal and speckled tealhad similar or slightly reduced total ventilation and pulmonary O 2 extraction compared with low-altitude relatives. Arterial O 2 saturation (S aO2) was elevated in yellow-billed pintails at moderate levels of hypoxia, but there were no differences in S aO2 in other high-altitude taxa compared with their close relatives. This finding suggests that improvements in S aO2 in hypoxia can require increases in both breathing and haemoglobin-O 2 affinity, because the yellow-billed pintail was the only high-altitude duck with concurrent increases in both traits compared with its low-altitude relative. Overall, our results suggest that distinct physiological strategies for coping with hypoxia can exist across different high-altitude lineages, even among those inhabiting very similar high-altitude habitats.

“…4; Scott and Milsom 2007). This distinction between Andean geese and bar-headed geese is surprisingly similar to that between high-altitude human populations from South America and Asia: Andean humans have a blunted HVR, whereas Tibetans have an enhanced HVR compared with their lowland counterparts (Wu and Kayser 2006;Brutsaert 2016). The reason for this intriguing result is unclear, but it suggests that the selective advantage of the hypoxia response may differ between lineages or between distinct highaltitude regions.…”

Section: Milsom 2009)mentioning

confidence: 69%

Validation of a Pulse Oximetry System for High-Altitude Waterfowl by Examining the Hypoxia Responses of the Andean Goose (Chloephaga melanoptera)

Physiological and Biochemical Zoology

York

Lague

et al. 2018

Hypoxia at high altitudes constrains O supply to support metabolism, thermoregulation in the cold, and exercise. High-altitude natives that somehow overcome this challenge-who live, reproduce, and sometimes perform impressive feats of exercise at high altitudes-are a powerful group in which to study the evolution of physiological systems underlying hypoxia resistance. Here, we sought to determine whether a common pulse oximetry system for rodents (MouseOx Plus) can be used reliably in studies of high-altitude birds by examining the hypoxia responses of the Andean goose. We compared concurrent measurements of heart rate obtained using pulse oximetry versus electrocardiography. We also compared our measurements of peripheral arterial O saturation (SaO) in uncannulated birds with published data collected from blood samples in birds that were surgically implanted arterial cannulae. Responses to acute hypoxia were measured during stepwise reductions in inspired partial pressure of O. Andean geese exhibited very modest breathing and heart rate responses to hypoxia but were nevertheless able to maintain normal O consumption rates during severe hypoxia exposure down to 5 kPa O. There were some minor quantitative differences between uncannulated and cannulated birds, which suggest that surgery, cannulation, and/or other sources of variability between studies had modest effects on the hypoxic ventilatory response, heart rate, blood hemoglobin, and hematocrit. Nevertheless, measurements of heart rate and SaO by pulse oximetry had small standard errors and were generally concordant and well correlated with measurements using other techniques. We conclude that the MouseOx Plus pulse oximetry system can be a valuable tool for studying the cardiorespiratory physiology of waterfowl without the deleterious effects of surgery/cannulation.