Hibernating arctic ground squirrels, Spermophilus parryii, were able to adopt and spontaneously arouse from core body temperatures as low as -2.9 degrees C without freezing. Abdominal body temperatures of ground squirrels hibernating in outdoor burrows were recorded with temperature-sensitive radiotransmitter implants. Body temperatures and soil temperatures at hibernaculum depth reached average minima during February of -1.9 degrees and -6 degrees C, respectively. Laboratory-housed ground squirrels hibernating in ambient temperatures of -4.3 degrees C maintained above 0 degree C thoracic temperatures but decreased colonic temperatures to as low as -1.3 degrees C. Plasma sampled from animals with below 0 degree C body temperatures had normal solute concentrations and showed no evidence of containing antifreeze molecules.

https://science.sciencemag.org/content/sci/244/4912/1593.full.pdf

Freeze avoidance in a mammal: body temperatures below 0 degree C in an Arctic hibernator

The ability to synthesize ascorbic acid is absent in the insects, invertebrates, and fishes. The biosynthetic capacity started in the kidney of amphibians, resided in the kidney of reptiles, became transferred to the liver of mammals, and finally disappeared from the guinea pig, the flying mammals, monkey, and man. A similar transition in the biosynthetic ability was observed in the branched evolution of the birds.

https://science.sciencemag.org/content/sci/182/4118/1271.full.pdf

Evolution and the biosynthesis of ascorbic acid

Inflammatory cells of teleostean fish: A review focusing on mast cells/eosinophilic granule cells and rodlet cells

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1096-0031.1986.tb00462.x

Heads and tails: a chordate phylogeny

Bats are often thought to have poor temperature regulation, to feed on insects, and to enter hibernation. This combination of characteristics is typical only of temperate species. In the last two decades intensive work in the tropics, especially in the New World, has shown the great ecological diversity existing among bats, which in turn permits us to place temperate species in their appropriate ecological and evolutionary perspective and to examine some of the physiological and ecological alternatives available to bats when living in a physically benign environment.

Evolutionary Alternatives in the Physiological Ecology of Bats

1. Responses to upward and downward changes in ambient temperature from 5° C. were studied in dormant bats of the species E. fuscus, P. subflavus, M. sodalis, M. lucifugus and L. borealis. Rectal temperatures and heart rates were recorded.2. Except for L. borealis which did not arouse until ambient temperature reached about 20° C., all species responded by arousal from dormancy when the temperature was increased to 15° C.3. The effects of decreasing ambient temperature varied considerably among species. E. fuscus invariably aroused from dormancy. L. borealis never aroused but showed a thermoregulatory response by increasing its metabolism to compensate for the increase in heat loss. The responses of the other species depended upon the abruptness of the temperature change. Abrupt lowering of ambient temperature tended to induce arousal in M. lucifugus and M. sodalis, whereas these species responded similarly to L. borealis when exposed to gradually decreasing temperature. P. subflavus usually aroused in re...

Responses of bats from temperate regions to changes in ambient temperature

A phylogenetical approach to the functional significance of tissue mast cell histamine.

SummaryHeart rates and rectal temperatures (Tr) were recorded from inactive bats exposed to stepwise changes in ambient temperature (Tn) in the range between —5°C and 10°C. An increase in heart rate and in the difference (ΔT) between rectal and ambient temperature (ΔT — Tr — Tu) with decreasing ambient temperature below 5°C was found. The bats remained in the dormant state but were able to arouse from dormancy in response to mechanical stimuli. The results indicate that the species of bats studied possess thermoregulatory ability during dormancy and that this ability is a homeostatic mechanism and thus different from the process of arousal.We thank Dr. Loren D. Carlson for suggestions and criticism during preparation of the manuscript.

Thermoregulation in Bats Exposed to Low Ambient Temperatureis

Systematic studies on the vascular smooth muscle responses to histamine and 5-hydroxytryptamine, similar to those previously accomplished in jawless vertebrates and fish, were performed in amphibians (frogs, toads and salamanders). Both intact animals and artificially perfused preparations were studied. The effects were recorded as changes in systemic arterial blood pressure after intravascular administration of drugs or as changes in vascular resistance after introduction of drugs into the perfusion fluid during perfusion at constant flow rate. Responses to adrenaline, noradrenaline and acetylcholine were studied for comparison. The direct or indirect nature of actions produced by the different drugs were evaluated by means of pharmacological blocking agents. The outcome of the studies may be summarized as follows: Marked and specific inhibitory actions of 5-hydroxytryptamine on vascular smooth muscle, manifest as vasodilatation, are present in all studied species, displaying a feature which has not been demonstrated in jawless vertebrates and fish. In addition, the blood vessels of some amphibians occasionally show a constrictor response to 5-hydroxytryptamine. The nature of the latter response remains uncertain. Histamine apparently has but negligible influence on amphibian vascular smooth muscle. The inhibitory and stimulatory actions of adrenaline and noradrenaline and the stimulatory action of acetylcholine, pharmacological characteristics of vascular smooth muscle also in more primitive vertebrates, are retained in the amphibians, while the inhibitory action of acetylcholine, like the inhibitory action of 5-hydroxytryptamine, appears as a new feature.

The Evolution of Vascular Smooth Muscle Responses to Histamine and 5-Hydroxytryptamine: II. Appearance of inhibitory actions of 5-hydroxytryptamine in amphibians1

Ola Bodvar Reite

Papers

Responses of bats from temperate regions to changes in ambient temperature

A phylogenetical approach to the functional significance of tissue mast cell histamine.

Thermoregulation in Bats Exposed to Low Ambient Temperatureis

The Evolution of Vascular Smooth Muscle Responses to Histamine and 5-Hydroxytryptamine: II. Appearance of inhibitory actions of 5-hydroxytryptamine in amphibians1