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

High-altitude organisms exhibit hematological adaptations to augment blood transport of oxygen. One common mechanism is through increased values of blood traits such as erythrocyte count, hematocrit, and hemoglobin concentration. However, a positive relationship between altitude and blood traits is not observed in all high-altitude systems. To understand how organisms adapt to high altitudes, it is important to document physiological patterns related to hypoxia gradients from a greater variety of species. Here, we present an extensive hematological description for three populations of Sceloporus grammicus living at 2,500, 3,400, and 4,300 m. We did not find a linear increase with altitude for any of the blood traits we measured. Instead, we found nonlinear relationships between altitude and the blood traits erythrocyte number, erythrocyte size, hematocrit, and hemoglobin concentration. Erythrocyte number and hematocrit leveled off as altitude increased, whereas hemoglobin concentration and erythrocyte size were highest at intermediate altitude. Additionally, lizards from our three study populations are similar in blood pH, serum electrolytes, glucose, and lactate. Given that the highest-altitude population did not show the highest levels of the variables we measured, we suggest these lizards may be using different adaptations to cope with hypoxia than lizards at low or intermediate altitudes. We discuss future directions that research could take to investigate such potential adaptations.

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Body temperature is important in determining individual performance in ectotherms such as lizards. Environmental temperature decreases with increasing altitude, but nevertheless many lizards inhabit high-altitude environments. The ‘thermal melanism hypothesis’ proposes that a dark dorsal coloration enables darker individuals to heat up faster because they absorb more solar radiation and thus being darker may be advantageous in cold habitats. The aim of the present study is to evaluate how heating rate, cooling rate and net heat gain vary with body size and dorsal skin coloration in Sceloporus grammicus lizards along an altitudinal gradient. We measured these traits multiple times in the same individuals with a radiation heat source and spectrophotometry under laboratory conditions. Our results showed that S. grammicus lizards are smaller and darker at high elevations than at low elevations. In addition, the smallest and darkest lizards showed the greatest heating rate and net heat gain. Therefore, in S. grammicus, we suggest that small body size and dark dorsal coloration provide thermoregulatory benefits in high-altitude environments. Hence, this study supports the thermal melanism hypothesis in a lizard species under varied thermal environments.

Amputations of a traumatic origin are very frequent in developing countries, in the case of Guatemala these are a result of work accidents very closely related to poor work conditions existing for manual workers, as well as social violence and the lack of security that governs society. The present case shows a patient that suffered a left hand amputation at wrist level. Amputated hand was transported swiftly and in adequate conditions, maintaining cold chain at all times until arrival at Hospital for replantation. After 14 months, patient has evolved satisfactorily and obtained functional result of the hand.

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ARREDONDO, J.; GONZÁLEZ-MORALES, J. C.; RODRÍGUEZ-ANTOLÍN, J.; BASTIAANS, E.; MONROY-VILCHIS, O.; MANJARREZ, J. & FAJARDO, V.Histological characteristics of gills and dorsal skin in Ambystoma leorae and Ambystoma rivulare: morphological changes for living at high altitude. Int. J. Morphol., 35(4):1590Morphol., 35(4): -1596Morphol., 35(4): , 2017. SUMMARY:Vertebrates exhibit structural changes in their cardiovascular and gas exchange systems in response to hypoxic conditions in high altitude environments. In highland neotenic mole salamanders, as other amphibians, the majority of gases exchange is carried out for skin and gills. But, in high altitude environments, the available oxygen is lower than it is in the air thus, the scarcity of oxygen limits the survival of organisms. Many studies on this subject have focused on understanding the hematological mechanisms that amphibians exhibit in response to hypoxia. However, little is known about possible morphological changes in respiratory structures that may permit increased gas exchange during respiration in high altitude amphibians like Ambystoma leorae and A. rivulare, two threatened Mexican salamander species. The aim of the present study was to describe and compare the histological characteristics of the gills and dorsal skin of A. leorae and A. rivulare from populations at low and high altitudes. We found that, in comparison to lowland organisms, highland ones exhibited more pronounced skin folds, greater numbers of secondary branches in the gills, thinner dorsal and gill epidermises, and greater quantity of melanin surrounding the gill blood vessels. These differences permit a greater capacity for gas exchange and also increase thermoregulatory capacity in high altitude environments.