Is erythrocyte size a strategy to avoid hypoxia in Wiegmann’s Torquate Lizards (Sceloporus torquatus)? Field evidence

Abstract

Is erythrocyte size a strategy to avoid hypoxia in Sceloporus torquatus? Field evidence 4 5 Abstract 6 This study examined changes of some different hematological parameters in a reptilian model 7 naturally exposed to altitude-associated hypoxia. Four populations of the Mexican lizard Sceloporus 8 torquatus (Wiegmann 1828) from different altitudes were sampled to evaluate erythrocyte count 9 (Erc), hematocrit (Hct), mean corpuscular hemoglobin concentration (MCHC) and erythrocyte size 10 (Ers). Blood was also assayed to determine hemoglobin ([Hb]), glucose, lactate and electrolytes 11 concentration. Erc was performed using a Neubauer hemocytometer. Hct was calculated as per cent 12 packed cell volume by centrifuging blood samples. [Hb] was determined using a Bausch and Lomb 13 Spectronic Colorimeter. MCHC was calculated with 100 x [Hb]/Hct. Erythrocyte size (Ers) was 14 calculated from blood smear micro-photographs analyzed with the Sigma Scan Pro software. Serum 15 electrolytes (Na + , K + and Ca 2+ ), pH, glucose, and lactate values from blood samples were obtained 16 through a blood electrolyte analyzer. Highland populations of Sceloporus torquatus exhibited a 17 significant increase in erythrocyte count, hematocrit, erythrocyte size, and hemoglobin 18 concentration. In contrast, MCHC showed no correlation with altitude. Additionally, significant 19differences in lactate, sodium, potassium and calcium were observed in highland populations. In 20 general, we found that most hematological parameters were significantly different among lizard 21 populations from different altitudes. This is the first study to report changes in erythrocyte size in 22 relation to altitude, which could be a physiological response to hypoxia. 23 24

Lizards at the Peak: Physiological Plasticity Does Not Maintain Performance in Lizards Transplanted to High Altitude

“…Two important parameters related to blood-oxygen capacity-hematocrit and hemoglobin concentration-were correlated and increased within the first 3 wk of the experiment (increases of 12% and 4%, respectively). This response is concordant with numerous studies demonstrating that lizards from high-altitude populations have higher hemoglobin concentration and hematocrit compared to lowland populations (Vinegar and Hillyard 1972;Weathers and White 1972;Newlin and Ballinger 1976;González-Morales et al 2015;Lu et al 2015). Lowland lizards acclimated to simulated high-altitude hypoxia increased hemoglobin concentration and hematocrit and changed other parameters related to oxygen transport and use, but these responses were not identical to those in lizards native to highaltitude populations (Weathers and McGrath 1972;He et al 2013).…”

Haematology and biochemistry of the San Cristóbal Lava Lizard (Microlophus bivittatus)

“…For lactate values, we found higher levels than reported by González-Morales et al (2015) in Sceloporus torquatus , González-Morales et al (2017) in S. grammicus , and Lewbart et al (2015) for marine iguanas ( Amblyrhynchus cristatus) . Very few studies have reported lactate levels in squamate reptiles ( Lewbart et al , 2015 ; González-Morales et al , 2015 , 2017 ), and most evaluated lactate production after exercise in diving reptiles ( Bartholomew et al , 1976 ; Seymour, 1979 ; Harms et al , 2003 ; Warren and Jackson, 2008 ). In squamates, blood lactate levels may be affected by altitude ( González-Morales et al , 2015 , 2017 ), exercise ( Bennett et al , 1981 ; Gleeson and Dalessio, 1989 ; Schuett and Grober, 2000 ) and handling ( Lewbart et al , 2015 ).…”

“…Very few studies have reported lactate levels in squamate reptiles ( Lewbart et al , 2015 ; González-Morales et al , 2015 , 2017 ), and most evaluated lactate production after exercise in diving reptiles ( Bartholomew et al , 1976 ; Seymour, 1979 ; Harms et al , 2003 ; Warren and Jackson, 2008 ). In squamates, blood lactate levels may be affected by altitude ( González-Morales et al , 2015 , 2017 ), exercise ( Bennett et al , 1981 ; Gleeson and Dalessio, 1989 ; Schuett and Grober, 2000 ) and handling ( Lewbart et al , 2015 ). Lactate levels may also be influenced by glucose and oxygen levels ( Gleeson and Dalessio, 1989 ; Bennett, 1973 ), but apparently there is little dependence on body temperature ( Bennett and Litch, 1972 ).…”

“…For example, low haematocrit may be due to anaemic processes (haemorrhagic, haemolytic or decreased red cell production), but a higher than normal value may be due to haemoconcentration, usually as a result of dehydration. Haemoconcentration also sometimes involves altitude ( He et al , 2013 ; González-Morales, 2015 , 2017 ) or body size and age ( Dunlap, 2006 ). Anaemia has been reported in free-living birds and mammals, but is also often associated with traumatic events or ill health (e.g.…”

Resting metabolic rates increase with elevation in a mountain‐dwelling lizard

“…2013; Gonzáles‐Morales et al . 2015), resulting in a higher affinity for oxygen. Individuals can exhibit changes in these variables within weeks (Gangloff et al .…”