Table 1.

Evidence of muscle-based non-shivering thermogenesis in vertebrates.

Taxon	Species	Evidence for muscle NST	References
Fish	Billfish, butterfly mackerel	No BAT, no thermogenic function of UCP1. Heater organ- release of sequestered Ca2+ from the SR via ryanodine receptors. SERCA1a pumps it back into the organelle, leading to Ca2+ cycling and heat production.	Block, 1994; Jastroch et al., 2005
Amphibia	NA	Not yet investigated.
Reptilia	Potentially tegu lizards	No BAT, no thermogenic function of UCP1. Tegu lizards maintain a Tb of 5–6°C above ambient during the reproductive season and even during the colder night hours, when an increase of Tb via basking is not possible.	Tattersall et al., 2016
Birds	Several species	No BAT, no UCP1. A release of sequestered Ca2+ from the SR via ryanodine receptors. SERCA1a pumps it back into the organelle, leading to Ca2+ cycling and heat production.	Dumonteil et al., 1995
Mammals
Monotremata	Anecdotal evidence for echidnas	No BAT, no evidence for thermogenic UCP1; Speculations about alternative rewarming mechanism from torpid states.	e.g., Grigg et al., 1992, 2004; Nicol et al., 1992
Marsupialia	NA	No BAT, no thermogenic function of UCP1; speculations about alternative rewarming mechanism from torpid states.	e.g., Nicol et al., 1992; Grigg et al., 2004
Placentalia	Found in rodents, lagomorpha; strong evidence for pigs	BAT and thermogenic function of UCP1 in most species; Evidence of sarcolipin-regulated muscle NST in mice and rats (in addition to UCP1/BAT); Downregulated sarcolipin gene expression in thirteen-lined ground squirrels. Muscle NST via SERCA found in rabbits; Likely in piglets- increasing thermogenic capacity in piglets, while at the same time shivering is decreasing.	Berthon et al., 1994, 1996; de Meis, 2001a,b; de Meis et al., 2005b; Babu et al., 2007; Bal et al., 2012, 2016; Anderson, 2016; Anderson et al., 2016; Pant et al., 2016