Thermoregulation and Cold Tolerance of the Mexican Lizard Barisia Imbricata (Anguidae), With Implica

Fierro-Estrada, Natalia

Posgrado en Ciencias Biológicas, Instituto de Biología, Universidad Nacional Autónoma de México, A. P. 70-153, C.P. 04510 Ciudad de México, México Laboratorio de Herpetología, Departamento de Zoología, Instituto de Biología, Universidad Nacional Autónoma de México, A. P. 70515, C.P. 04510 Ciudad de México, México.

natalia_fierro@hotmail.com

Méndez de la Cruz, Fausto R.

Laboratorio de Herpetología, Departamento de Zoología, Instituto de Biología, Universidad Nacional Autónoma de México, A. P. 70515, C.P. 04510 Ciudad de México, México.

We evaluated and compared the thermal efficiency of two populations of the viviparous lizard Barisia imbricata distributed in two contrasting elevations (2,200m and 3,700m), through the four seasons of the year. The thermal efficiency index was calculated using the body temperature, preferred temperature (in a thermal gradient) and operative temperatures (according to null models). We also recorded substrate and air temperature at the time of capture. We investigated the freezing point of B. imbricata, for that we took glucose levels in all the captured individuals and measured the crystallization temperature of organisms inside a chiller's bath with ethylene-glycol. Finally we calculated performance curve, activity hours and restriction hours to project the probability of presence of the species under three scenarios from the Intergovernmental Panel on Climate Change (RCP 2.6, 4.5 and 8.5) to the year 2050 and 2070. The body temperature of both populations showed positive and significant correlation with environmental temperatures, with higher ratio between body and air temperature. Both populations showed significant seasonal differences in body temperature. There was also a significant difference between the body temperatures of the two populations. The efficiency index also differed between populations. The low altitude population appears to be a thermo-conformer, whereas the thermal quality of the environment of the high altitude population was lower and the organisms actively thermoregulate. The organisms presented high levels of glucose and survived to experimental freezing. The projections show that almost all populations will present higher extinction risk due to climate change. Results show that B. imbricata is an eurythermic organism that can be active at low temperatures.


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