Facultative thermogenesis during brooding is not the norm among pythons

Abstract

Facultative thermogenesis is often attributed to pythons in general despite limited comparative data available for the family. While all species within Pythonidae brood their eggs, only two species are known to produce heat to enhance embryonic thermal regulation. By contrast, a few python species have been reported to have insignificant thermogenic capabilities. To provide insight into potential phylogenetic, morphological, and ecological factors influencing thermogenic capability among pythons, we measured metabolic rates and clutch-environment temperature differentials at two environmental temperatures-python preferred brooding temperature (31.5 °C) and a sub-optimal temperature (25.5 °C)-in six species of pythons, including members of two major phylogenetic branches currently devoid of data on the subject. We found no evidence of facultative thermogenesis in five species: Aspidites melanocephalus, A. ramsayi, Morelia viridis, M. spilota cheynei, and Python regius. However, we found that Bothrochilus boa had a thermal metabolic sensitivity indicative of facultative thermogenesis (i.e., a higher metabolic rate at the lower temperature). However, its metabolic rate was quite low and technical challenges prevented us from measuring temperature differential to make conclusions about facultative endothermy in this species. Regardless, our data combined with existing literature demonstrate that facultative thermogenesis is not as widespread among pythons as previously thought.

In situcardiac perfusion reveals interspecific variation of intraventricular flow separation in reptiles

“…It has further been suggested that the intracardiac separation may support the increased metabolism associated with reproductive thermogenesis in pythons (Wang et al, 2003). However, thermogenesis is not ubiquitous within the python phylogeny (Brashears and DeNardo, 2015) and indeed, is absent in the subject of this study, Python sebae (Vinegar et al, 1970). Conversely, pressure separation has been established in all pythons investigated, including evolutionarily divergent species ; T.W., unpublished results).…”

Reproductive biology and maternal care of neonates in southern African python (Python natalensis)

“…This finding is further supported by Alexander () who found that mother T b approached T chamber (~23°C) when brooding mothers were prevented from basking. This is in agreement with Brashears & DeNardo's () conclusions that facultative thermogenesis is not the norm in python species. The lack of facultative thermogenesis in southern African python is significant since P. natalensis is a large‐bodied species with a range that extends into the cooler parts of South Africa.…”

“…The lack of facultative thermogenesis in southern African python is significant since P. natalensis is a large‐bodied species with a range that extends into the cooler parts of South Africa. This supports the hypothesis that facultative thermogenesis has arisen in Python and Morelia independently (see Stahlschmidt et al ., and Brashears & DeNardo, ).…”

The activity pattern of overwintering Indian Rock Pythons, Python molurus (Linnaeus 1758) in a semi-arid region of India

“…Studies of activity patterns have focused primarily on diurnal lizards; consequently, data on the activity of tropical snakes is lacking (Reed and Rodda 2009), although extensive studies on brooding python thermal biology are available (Ramesh and Bhupathy 2010;Stahlschmidt and Denardo 2010;Stahlschmidt et al 2012;Brashears and Denardo 2015). Snakes generally exhibit seasonal variations in movement and activity patterns (Slip and Shine 1988;Heard et al 2004).…”