Browsing by Autor "Jordi Altimiras"

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Aerobic performance in tinamous is limited by their small heart. A novel hypothesis in the evolution of avian flight
(Nature Portfolio, 2017) Jordi Altimiras; Isa Lindgren; Lina M. Giraldo‐Deck; Alberto Matthei; Álvaro Garitano‐Zavala
Aerobic power and flight capacity in birds: a phylogenetic test of the heart-size hypothesis
(The Company of Biologists, 2017) Roberto F. Nespolo; César González‐Lagos; Jaiber J. Solano‐Iguaran; Magnus Elfwing; Álvaro Garitano‐Zavala; Santi Mañosa; Juan Carlos Alonso; Jordi Altimiras
Flight capacity is one of the most important innovations in animal evolution; it only evolved in insects, birds, mammals and the extinct pterodactyls. Given that powered flight represents a demanding aerobic activity, an efficient cardiovascular system is essential for the continuous delivery of oxygen to the pectoral muscles during flight. It is well known that the limiting step in the circulation is stroke volume (the volume of blood pumped from the ventricle to the body during each beat), which is determined by the size of the ventricle. Thus, the fresh mass of the heart represents a simple and repeatable anatomical measure of the aerobic power of an animal. Although several authors have compared heart masses across bird species, a phylogenetic comparative analysis is still lacking. By compiling heart sizes for 915 species and applying several statistical procedures controlling for body size and/or testing for adaptive trends in the dataset (e.g. model selection approaches, phylogenetic generalized linear models), we found that (residuals of) heart size is consistently associated with four categories of flight capacity. In general, our results indicate that species exhibiting continuous hovering flight (i.e. hummingbirds) have substantially larger hearts than other groups, species that use flapping flight and gliding show intermediate values, and that species categorized as poor flyers show the smallest values. Our study reveals that on a broad scale, routine flight modes seem to have shaped the energetic requirements of birds sufficiently to be anatomically detected at the comparative level.
Myocardial gene expression of the tinamou reflects the physiological challenges of having a small heart
(Wiley, 2013) Hanna Österman; Andreas Ekström; Álvaro Garitano‐Zavala; Jordi Altimiras
Tinamous are an ancient family of neotropical flying birds that occupy diverse habitats from lowland jungle forests to the Andean high plateaus. Tinamous have a very small heart, closer to that of non‐avian reptiles than to birds with similar living styles. Even though tinamous are endothermic, the small heart size compromises oxygen transport, aerobic metabolism and thermoregulation. This led us to hypothesize that gene expression in the heart of tinamous would reflect the basal scenario from which neognate birds, with larger hearts and higher aerobic capacity, evolved. A microarray analysis was performed to determine differences in gene expression between tinamou and chicken myocardium. Key genes involved in cardiac remodeling and hypertrophy were up regulated in tinamous, including PI3Kα, TGFβII, TAK1, FGF and PDGFRα. This indicates elevated activity in hypertrophic pathways and is consistent with previous indications of left ventricular hypertrophy in N.ornata . Up regulation of key glycolytic enzymes was also observed, namely PFK‐1, FBPase‐2 and ALDOB, indicating an increase in cardiac glycolytic metabolism in N.ornata compared to high altitude chickens. These gene expression differences reflect the physiological challenges of being endothermic while having a small heart. Supported by FORMAS Centre of Excellence in Animal Welfare Science and career grant from Linköpings universitet to JA.
The small heart of the Ornate Tinamou is compatible with endothermy and flight but compromises aerobic metabolism and thermoregulation during recovery from exhaustive activity
(Wiley, 2013) Jordi Altimiras; Lina Maria Giraldo Deck; Álvaro Garitano‐Zavala
Tinamous are an ancient family of neotropical flying birds. Scant data from a few species show that they have a small heart so our aim was to characterize relative heart size of two species of the genus Nothoprocta and assess the physiological limitations associated with a small heart size. Relative heart size (0.24% for the Ornate Tinamou OT, a highland species and 0.28% for the Chilean Tinamou CT, a lowland species) was significantly smaller than high and lowland chickens (0.54% and 0.42% respectively), without evidence of right ventricular hypertrophy. Resting aerobic metabolism was 31% lower in OT than in highland chickens. When subjected to exhaustive activity, OT had elevated glucose and lactate levels suggesting a severe oxygen debt when exhausted. This was further shown as a significant drop in body temperature after an exhaustive bout. Finally heart rate while running on a treadmill at 3 km h −1 was 5% lower in OT, indicating that tinamous cannot compensate for the reduction in heart size with a faster heart rate. Altogether, we provide evidence that heart size is a phylogenetically conserved trait among tinamous and that the Ornate Tinamou cannot compensate aerobically for its small heart. Instead, it relies on anaerobic metabolism incurring in a large oxygen debt while exhausted. Supported by FORMAS Centre of Excellence in Animal Welfare Science and career grant from Linköpings universitet to JA.