collared lizards
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Herpetologica ◽  
2020 ◽  
Vol 76 (1) ◽  
pp. 27 ◽  
Author(s):  
Jodie M. Wiggins ◽  
Enrique Santoyo-Brito ◽  
Jon B. Scales ◽  
Stanley F. Fox


2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Casey L Brewster ◽  
Jason Ortega ◽  
Steven J Beaupre

Abstract Information on bioenergetics can provide valuable insight into the ecology, life history and population dynamics of organisms. For ectothermic animals, thermal sensitivity of digestion is an important determinant of net assimilated energy budgets. A recent study in the Ozark Mountains indicated that eastern collared lizards (Crotaphytus collaris) restricted to encroached glades (characterized by woody vegetation encroachment) experience reduced environmental heat loads and have reduced age-specific growth and reproductive rates compared to populations in intact glades. To assess the potential impact of reduced body temperatures on assimilation rates of C. collaris in encroached glades, we conducted feeding trials across four temperature treatments (28, 31, 34 and 37°C). We tested for temperature effects on voluntary feeding rates, passage times, apparent assimilated energy (AE) and metabolizable energy (ME). Passage times decreased and voluntary feeding rates increased significantly with increasing temperature. Consumption explained the majority of variance in AE and ME, followed by the effect of temperature treatments. Using data on voluntary feeding rates, passage times and ME as a function of temperature, we estimated over a 10-fold increase in predicted daily assimilated energy across temperature treatments (28°C = 0.58 kJ/day, 31°C = 1.20 kJ/day, 34°C = 4.30 kJ/day, 37°C = 7.95 kJ/day). Thus, lower heat loads in encroached glades may cause reduced body temperature and result in restricted energy assimilation rates. Our study provides a novel approach to the integration of bioenergetics and conservation and shows the efficacy of using information on digestive performance to investigate underlying mechanisms in a conservation context.



2019 ◽  
Vol 128 (4) ◽  
pp. 936-943 ◽  
Author(s):  
Melissa Plasman ◽  
Estela Sandoval-Zapotitla ◽  
Roxana Torres

Abstract The immune system allows animals to survive the constant attacks of pathogens. Although it is essential for survival and fitness, the performance of the immune system can decline with age (a process known as immunosenescence), which may be responsible for the increased mortality of older individuals. Only a few studies have investigated the effect of age on the immune system in reptiles, and no evidence of immunosenescence has yet been reported in lizards. In a wild population of Dickerson’s collared lizards (Crotaphytus dickersonae), we evaluated the effect of age (estimated by skeletochronology) on the male’s immune response to a novel antigen (phytohaemagglutinin). We found a strong negative relationship between immune response and age, the first evidence of immunosenescence in a lizard. Our results show that immunosenescence can occur even in relatively short-lived reptiles and underline the importance of age on performance in fitness-related traits.



2019 ◽  
Vol 63 (4) ◽  
pp. 209
Author(s):  
Timothy B. Garrett ◽  
Wade A. Ryberg ◽  
Connor S. Adams ◽  
Tyler A. Campbell ◽  
Toby J. Hibbitts
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