Influence of pregnancy on the thermal biology of the lizard, Sceloporus jarrovi: why do pregnant females exhibit low body temperatures?

Abstract

Summary1. Selected body temperatures of female lizards, Sceloporus jarrovi, were measured on a photothermal gradient during late pregnancy and again when postpartum, and pregnant females were subjected to one of three fluctuating temperature regimes that simulated body temperatures of (1) pregnant females, (2) postpartum females or (3) allowed normal thermoregulation. 2. Overall, females selected lower body temperatures when pregnant (mean = 32·0°C) than when postpartum (mean = 33·5°C). 3. Females regulated body temperature more precisely when pregnant than when postpartum as judged by their smaller variances in body temperature throughout the day. 4. When pregnant, females selected a lower mean maximum body temperature (mean: pregnant = 32·8°C; postpartum = 34·5°C) than when postpartum, but selected mean minimum body temperatures did not differ. 5. None of the experimental temperature treatments was detrimental to pregnant females. Female body length increased during pregnancy but the rate of increase did not differ among treatments. Moreover, length-adjusted body mass of postpartum females did not differ among treatments. 6. Pregnant females that experienced postpartum body temperatures produced neonates that were smaller in body mass and length than pregnant females that experienced pregnant body temperatures and females that were allowed to thermoregulate. 7. For neonates resulting from the postpartum body temperature treatment, the disparity in the body length, but not mass, was still observed at 9 days of age, although survival and growth of neonates was high and did not differ among treatments. 8. The results demonstrate that pregnant females could maintain higher postpartum body temperatures without compromising their physical condition, but select relatively low body temperatures, presumably to avoid decrements in offspring fitness.

Impacts of temperature on performance in two species of South African dwarf chameleons,Bradypodion pumilumandB. occidentale

“…Consequently, B. occidentale is faced with more extreme conditions compared with B. pumilum, which may explain the observed shift towards higher temperatures. It should be noted, however, that most of the B. occidentale chameleons tested in our study were gravid females and it is known that the physiological state of these females may affect their performance (Bauwens and Thoen, 1981;Cooper et al, 1990;Garland, 1985;Qualls and Shine, 1997;Schwarzkopf and Shine, 1992;Shine, 1980), behavior (Garland and Losos, 1994;Schwarzkopf and Shine, 1992) and thermal preference (Braña, 1993;Daut and Andrews, 1993;Le Galliard et al, 2003;Mathies and Andrews, 1997), which can introduce a bias in our results for this species. Furthermore, B. occidentale tested in our study were collected in the extreme southern part of their distribution area.…”

Decreased precision contributes to the hypoxic thermoregulatory response in lizards

“…Other stress stimuli (that in one way or another increase the costs of thermoregulation), such as low environmental thermal quality, risk of predation, territorial defence, or water or food availability have been shown to evoke similar decreases in T b and/or thermoregulatory precision (Cabanac, 1985;Dewitt, 1967;Huey and Slatkin, 1976;Ladyman and Bradshaw, 2003;Lorenzon et al, 1999;Mathies and Andrews, 1997), suggesting conserved thermoregulatory mechanisms in response to costly conditions. Discovering how these stressors alter the sensation of temperature and the underlying neurophysiological control of T b remains a challenge for future studies.…”

<b>Influência do ciclo reprodutivo na biologia termal de <i>Crotalus durissus </i>neotropical (Serpentes, Viperidae) em cativeiro</b>

“…The dataloggers were intraperitoneally implanted, and the incision was sutured. In pregnant females, a portion of the uterus was everted to expose a developing embryo (adapted from Mathies and Andrews, 1997). We then determined the embryonic developmental stage following criteria by Hubert and Dufaure (1968) for Vipera aspis.…”

“…Changes in body temperature (Tb) as a function of female reproductive status are well documented in squamate reptiles (Beuchat, 1986;Charland, 1995;Mathies and Andrews, 1997;Chiaraviglio, 2006;Gardner-Santana and Beaupre, 2009;Tattersall et al, 2016). However, the direction of these changes varies among species.…”

“…However, the direction of these changes varies among species. In some species, pregnant females exhibit lower body temperatures than nonpregnant females and/or males (Beuchat, 1986;Mathies and Andrews, 1997). On the other hand, pregnant females of some species exhibit higher and/or less variable body temperatures than nonpregnant females or males (Charland and Gregory, 1990;Chiaraviglio, 2006).…”